Regulating the microstructure of two-dimensional perovskite single-crystals via high-throughput experimentations

Regulating the microstructure of two-dimensional perovskite single-crystals via high-throughput experimentations | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Regulating the microstructure of two-dimensional perovskite single-crystals via high-throughput experimentations Ning Li, Jingyan Qi, Wei Meng, Kang An, Xujie Hui, Liqun Liu, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6431736/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Dec, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Controllable solution-based synthesis of semiconducting micro-structured materials with tailored morphologies and specific properties is crucial for the development of cost-effective microelectronic devices. Here, we present a high-throughput experimental approach that integrates in-situ absorption spectroscopy and molecular dynamics simulations to systematically explore ligand-mediated crystallization dynamics in two-dimensional (2D) perovskite single crystals. We establish a clear correlation between structures of organic ligands and morphology of perovskite single crystals, showing that shorter ligands promote 1D nanowire formation, while longer ligands favor 2D nanosheet growth. In-situ spectroscopy and molecular simulations reveal that larger ligands induce conformational changes within the perovskite lattice, shifting crystallization from direct nucleation to lamellar exfoliation. Transmission electron microscopy (TEM) and density functional theory (DFT) calculations confirm that such transition is driven by enhanced solute–solvent binding energy, which modulates the crystallization pathway of lead halide intermediates. Our findings provide valuable insights into solution-phase crystallization kinetics and offer a rational strategy for designing perovskite materials with tailored optoelectronic properties, facilitating their scalable integration into advanced semiconductor applications. Physical sciences/Materials science/Nanoscale materials/Organic–inorganic nanostructures Physical sciences/Materials science/Nanoscale materials/Synthesis and processing 2D perovskites perovskite single-crystals ligand engineering crystal engineering high-throughput experimentation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The relentless advancement of information technology has propelled the demand for micro- and nanoscale semiconductor electronic devices. Conventional miniaturization techniques face high costs, environmental concerns, and scalability constraints limitations, such as vacuum deposition, epitaxy and etching 1 . Solution-processed mesostructured semiconductors provide a promising alternative, offering cost-effective fabrication with precise control over composition and structural design, making them highly attractive for next-generation optoelectronic and photonic applications. Among solution-processed semiconductors, two-dimensional (2D) layered metal halide perovskites (L 2 A n − 1 M n X 3n+1 ) have garnered significant attention owing to their promising characteristics, such as high charge carrier diffusion length and high defect tolerance. Here, L represents a bulky organic cation, A a small organic cation (e.g., methylammonium, MA), M a metal cation (e.g., Pb or Sn), X a halide anion, and n an integer dictating the inorganic layer thickness, effectively functioning as a quantum well 2 , 3 . The tunability of structural and electronic properties makes them ideal candidates for mesoscopic optoelectronic applications 4 . The dimensionality of perovskites fundamentally influences charge transport and light–matter interactions, thereby determining the optoelectronic performance 5 . For instance, perovskite nanowires, with 1D electron confinement, exhibit ultrahigh carrier mobility and enhanced sensitivity, rendering them suitable for photodetectors and lasers. Conversely, 2D perovskite nanosheets, characterized by large surface areas and strong quantum confinement, enhance light absorption and charge separation, benefiting solar cells and photocatalysis 6 . Therefore achieving precise control over crystallization is critical for tailoring perovskite morphologies to optimize the semiconductor functionality 7 , 8 . Various synthetic methodologies have been developed to fabricate perovskite materials with tailored dimensionalities, including vapor-phase growth, lithographically templated solution-phase growth, ligand-assisted solution-phase growth, and alcoholic solvent-assisted growth 9 – 16 . However, methodologies developed so far largely rely on empirical synthetic experiments, necessitating iterative functional group modifications to organic ligands to regulate crystal morphology. These methods suffer from high processing complexity, elevated costs, and limited scalability, restricting their applicability mainly in specific materials design. A fundamental challenge remains: the lack of generalizable principles governing ligand-induced crystallization in 2D perovskite systems. The complex interplay of multidimensional parameters further complicates precise morphology control, underscoring the need for a deeper understanding of perovskite crystallization kinetics 17 . Here, we present a high-throughput experimental approach integrating in-situ absorption spectroscopy and molecular dynamics simulations to elucidate ligand-mediated crystallization in 2D perovskite single crystals. Our automated system systematically explores 98 synthesis conditions with programmable robotic arms, enabling precise control over crystal morphology. By screening nine alkane ligands, five aromatic hydrocarbon ligands, and varying precursor solution dilutions, we establish a direct correlation between ligand chain length and crystallization behavior: shorter ligands favor 1D nanowire formation, whereas longer ligands promote 2D nanosheet growth. In situ absorption spectroscopy and molecular dynamics simulations reveal that increasing ligand size modulates the ligand conformation within the 2D perovskite lattice, shifting crystallization from direct nucleation to lamellar exfoliation. Transmission electron microscopy (TEM) and density functional theory (DFT) calculations further confirm that morphological transition is driven by enhanced solute-solvent binding energy, governing the crystallization pathway of lead halide intermediates. Our study provides insights into solution-phase dynamics governing perovskite lattice formation and offers a rational strategy to design perovskite materials with tailored optoelectronic properties, advancing their integration into next-generation semiconductor technologies. Discussion High-throughput synthesis of 2D perovskite nanorods and nanoplates Alkylammoniums ranging from tert-butylammonium to dodecyl ammonium, i.e., alkylammoniums with main chains ranging from 2 Cs to 12 Cs, were selected as alkyl ligands; aromatic ammoniums ranging from phenyl ammonium to phenyl butylammonium, i.e., aromatic ammoniums with phenyl-ring side-chain Cs ranging from 0 to 4, were selected as aromatic hydrocarbon ligands, with a total of 14 ligands throughout the high-throughput experiments (Supplementary Fig. 1). The original solution was diluted with a mixture of three antisolvents to reduce the crystal density of the single crystals 18 . 2D perovskite single crystals were prepared by the drop injection method at different solution dilution ratios (Fig. 1 a). We have recently set up a fast and versatile high-throughput experimental platform for the development of optoelectronic materials and devices (Supplementary Fig. 2). The platform employs an 8-channel pipetting robot (FCA, Flexible Channel Arm), in which four pipetting fingers are able to precisely prepare different perovskite precursor solutions in 24-well plates at arbitrary ratios. In addition, a robotic gripper arm (RGA) is responsible for transferring the substrates between the various functional modules of the platform in order to complete the different experimental steps. Since four pipetting tips can simultaneously aspirate and dispense liquids in different volumes, high-throughput automated workstations can increase experimental efficiency by at least fourfold. It can perform 240 drop-coating operations and repeat the entire high-throughput experiment 2 times per hour with prominent reliability and accuracy. For alkyl ligands, tert-butyl ammonium 19 and isopropyl ammonium 20 were chosen, since the molecular size of ethyl ammonium is in the range of 3D perovskites, and it is not able to be used as an intermediate layer to form 2D perovskites 21 . The absorption spectra of the 2D perovskite films prepared with 14 ligands showed that the absorption peaks of the films are located at 300–400 nm and 510 nm (Supplementary Fig. 3a), the peaks of the PL spectra of the films are in the range of 485–555 nm (Supplementary Fig. 3b), and the fitting lifetimes of the TrPL spectra of the films are in the nanosecond order of magnitude (Supplementary Fig. 3c and Supplementary Table 3), indicating that all of the selected organic ligands could form 2D perovskite structures 22 . In the experiment, the dilution ratio of nine alkyl ammonium ligand perovskite precursor solutions was set at seven ratios ranging from 60 to 960 times, and the dilution ratio of five aromatic hydrocarbon ligand perovskite precursor solutions was also set at seven ratios ranging from 30 to 480 times. The two variables, the type of ligand molecule and the dilution ratio of solution, form the variable parameter space, and 98 groups of high-throughput experimental results can be obtained (Fig. 1 b and Supplementary Fig. 4, a – n). Among the 98 sets of crystallization experiments, 14 characteristic crystals were screened based on crystal morphology and single crystal integrity, corresponding to 14 different types and molecular sizes of ligands, as shown in Fig. 1 c. Among the 14 characteristic crystals, with the continuous growth of ligand carbon chain and the gradual increase of ligand volume, the morphology of 2D perovskite single crystals gradually changes from rod-like to sheet, as shown in Fig. 1 d. When the ratio of length to diameter of perovskite crystals is above 1.5, the crystal form is considered to be rod-like, and when the ratio of length to diameter is below 1.5, the crystal form is considered to be sheet 23 , 24 . Among the alkane ligands, the 2D perovskite single crystal morphology formed by tert-butylammonium (t-BA), isopropyl ammonium (i-PA), n-propylammonium (PA) and n-butylammonium (BA) ligands with smaller volume are mainly rod-like morphology. Five large ligands, pentylammonium iodide (PentA), hexylammonium (HA), octylammonium (OA), nonylammonium (NonylA) and dodecylammonium (DDA), were mainly formed in sheet morphology. Among the aromatic hydrocarbon ligands, the 2D perovskites formed by phenylammonium (PhA) and phenylmethylammonium (PMA) are rod-like crystals, while the 2D perovskites formed by phenylethylammonium (PEA), phenylpropylammonium (PPA) and phenylbutylammonium (PBA) show obvious lamellar morphology (Fig. 1 e). Among the 14 ligands, both alkane ligands and aromatic ligands showed a rod to lamellar transition in their perovskite single-crystal morphology with a gradual increase in ligand length. The perovskite single crystals formed by the crystallization of different ligand precursor solutions, whether rod-like or flaky-like, exhibit stable green light emission under the fluorescence field (Fig. 2 , a – d). The length of rod-shaped 2D perovskite single crystal reach 15 µm, and the size of lamellar single crystal reach 10 × 10 µm. Under the electron microscope, the single crystals showed clear rod-like (Fig. 2 , e and g) and flaky (Fig. 2 , f and h) morphology. Meanwhile, the photoluminescence peaks of each 2D perovskite single crystal measured by single crystal PL are 527 nm (Fig. 2 i), 508 nm (Fig. 2 j), 530 nm (Fig. 2 k), 538 nm (Fig. 2 l) respectively, indicating the pure 2D (n = 1) perovskite crystal obtained 25 . In-situ absorption spectroscopy In order to explore the crystallization process of 2D perovskites formed by different ligands, in-situ absorption spectroscopy was used to monitor the evaporation crystallization process of precursor solutions baked at 70 ℃, as shown in Supplementary Fig. 5, A and B. In the process of evaporation and crystallization, the droplet on the Si sheet moves due to the volume contraction of the solution, resulting in a phase of signal absorption disturbance in the test. The duration of this phase varies from 3 to 10 s depending on the type of solution used. Among the 14 ligands, the in-situ spectra of the representative small-site-resistance ligand BA, and the large-site-resistance ligand DDA showed different features. The two stages before and after signal disturbance were divided into Stage I and Stage II, representing solvent evaporation stage and stable crystallization stage respectively, as shown in Fig. 3 , a and d. For BA, the absorbed signal of PbI 2 at 425 nm and the absorbed signal of (BA) 2 PbI 4 at 510 nm both appear at Stage II, as shown in Fig. 3 b. For DDA, the absorption signal of PbI 2 at 425 nm has appeared in Stage I, while the absorption signal of (DDA) 2 PbI 4 at 510 nm does not appear until the time reaches Stage II. As shown in Fig. 3 e, the absorbed signal at 425 nm does not increase, while the absorbed signal at 510 nm increases. Based on the different absorption signal characteristics, we conclude that small-site resistance ligands and large-site resistance ligands have different crystallization processes. For BA-type small-site-resistant ligands, the PbI 2 absorption signal at 425nm and the (BA) 2 PbI 4 absorption signal at 510 nm both appear at Stage II, indicating that neglectable PbI 2 crystallization occurs during the solvent evaporation process. In the stable crystallization stage, PbI 2 and (BA) 2 PbI 4 crystals begin to appear simultaneously, which is dominated by (BA) 2 PbI 4 direct nucleation mechanism. The growth of (BA) 2 PbI 4 crystal is directly induced by (BA) 2 PbI 4 crystal nuclei in solution 26 , as shown in Fig. 3 c, which is represented by Eq. (1). $$\:\begin{array}{c}{Pb}^{2+}+2{BA}^{-}+2BAI\to\:{\left(BA\right)}_{2}Pb{I}_{4}\#\left(1\right)\end{array}$$ For DDA-type large-site-resistance ligands, the absorption signal of PbI 2 at 425 nm appears first in Stage I, while the absorption signal of (DDA) 2 PbI 4 at 510 nm does not appear until Stage II, indicating that more PbI 2 crystals appear first in the solution during solvent evaporation. (DDA) 2 PbI 4 crystals appear in large quantities during stable crystallization. It is assumed that the process is dominated by the stripping mechanism of PbI 2 crystals. In solution, the first PbI 2 nanocrystals are stratified 27 , and the detached PbI 2 sheets induce the insertion of DDA + into the [PbI 4 ] 2− octahedral structure 28 , and further formation of (DDA) 2 PbI 4 crystals, as shown in Fig. 3 F. The process is represented by Eqs. (2)(3)(4). $$\:\begin{array}{c}{Pb}^{2+}+2{I}^{-}\to\:Pb{I}_{2}\#\left(2\right)\end{array}$$ $$\:\begin{array}{c}\left(2n-1\right)Pb{I}_{2}\to\:\left(n-1\right){\left[Pb{I}_{4}\right]}^{2-}+n{Pb}^{2+}+2{I}^{-}\#\left(3\right)\end{array}$$ $$\:\begin{array}{c}{\left[Pb{I}_{4}\right]}^{2-}+2{DDA}^{+}\to\:{\left(DDA\right)}_{2}Pb{I}_{4}\#\left(4\right)\end{array}$$ where Eq. (2) represents the generation of PbI 2 nanocrystals, Eq. (3) represents the process of layer exfoliation of PbI 2 nanocrystals, and Eq. (4) represents the process of formation of 2D perovskites by DDA + insertion. The in-situ absorption spectra of BA, DDA and 12 other ligands during crystallization are shown in Supplementary Fig. 6, a – n. For the ligands with smaller sizes, such as t-BA, i-PA, PA, BA, PhA, PMA, low PbI 2 signals appeared in the absorption spectra at the evaporation crystallization stage and no obvious calixarene absorption appeared. In the absorption spectra of stable crystallization stage, the absorption intensity of PbI 2 increases, and the perovskite absorption signal appears. However, for larger ligands, such as PentA, HA, OA, NonylA, DDA, PEA, PPA, and PBA, PbI 2 absorption signals appear obviously in the evaporative crystallization stage, and there are no obvious perovskite absorption signals. In the absorption spectra of the stable crystallization stage, the obvious perovskite absorption signal appears on the basis of PbI 2 absorption signal. The variation characteristics of the two absorbed signals correspond to the direct nucleation mechanism and the PbI 2 crystal stripping mechanism respectively 29 . Crystallization mechanism To address the underlying factors that trigger the two crystallization mechanisms, molecular dynamics simulations are used to explore the relationship between different types of ligands and solvent binding energies. The kinetic state of the precursor diluent is simulated at a drop casting temperature of 343 K (Supplementary Table 2). Among the four solvents, DMF with strong solvation energy can dissolve perovskite precursors effectively, but its crystal growth kinetics are slow. Other three antisolvents (CB, ACN, and DCB) have weak solvation energies and limited solubility for precursors, but have the potential for rapid crystallization 30 . Since the antisolvent CB has the largest percentage and plays a dominant role in the evaporative crystallization process, we calculated the interaction energies, i.e., intermolecular binding energies, of the 14 ligand ions in solution with the CB molecules in solution to determine the change of the solution system during the heating process, which is shown in Eq. (5): $$\:\begin{array}{c}{E}_{int}={E}_{AB}-{E}_{A}-{E}_{B}\#\left(5\right)\end{array}$$ where A = t-BA + , i-PA + , PA + , BA + , PentA + , HA + , OA + , NonylA + , DDA + , PhA + , PMA + , PEA + , PPA + , PBA + , and B = CB, with E AB as the overall energy of AB, E A as the energy of A, E B as the energy of B, and E int as the interaction energy between A and B. We obtained the relationship between the binding energy between 14 alkane and aromatic ligands and CB with ligand size (Fig. 3 g), where \(\:{E}_{int({BA}^{+}-CB)}\) is − 16.92×10 3 kcal/mol, and \(\:{E}_{int({DDA}^{+}-CB)}\) is − 17.37×10 3 kcal/mol (Supplementary Table 2). For the small-site resistance ligand represented by BA, the negative value of its binding energy with CB is small, so only a small amount of heat is needed to make CB evaporate quickly from the solution system during solvent evaporation 31 . During the solvent evaporation phase, the percentage of DMF in the total solution rapidly increases. As shown in Fig. 3 h, DMF binds to Pb 2+ and I − in solution to form [PbI m X n ] 2−m (X = DMF) complexes 32 , resulting in the inability to form a large number of PbI 2 crystals, and the ligand ions cannot be induced to insert into the octahedral layer. At the stable crystallization stage, the DMF content decreases to supersaturation and the perovskites begin to nucleate. As for the large-site resistance ligand represented by DDA, due to the large negative value of the binding energy of DDA + with CB, which indicates that CB needs to absorb more heat to detach from the solution, the content of DMF does not undergo a large increase in the solvent evaporation stage, the overall solubility of the solution for PbI 2 is low, and a certain amount of PbI 2 nanocrystals can be formed in the system, and at a later stage, with CB and DMF evaporation, the PbI 2 nanocrystals underwent lamellar exfoliation 33 , and the exfoliated PbI 2 nanosheets continued to induce the crystallization of (DDA) 2 PbI 4 34 , as shown in Fig. 3 I. Influence of crystal structure on the growth process In order to further investigate the factors affecting the initiation of different crystalline morphologies, we established the cell models of perovskites formed by 14 different ligands by taking the cell parameters and the symmetry of the space group of (BA) 2 PbI 4 single crystals as a reference 35 . In addition, we performed functional optimization on all cell models to make the semiconductor bandgap formed by the cells conform to the results measured in PL experiments (Supplementary Fig. 8, and Supplementary Table 7), so as to obtain accurate cell structures as much as possible. The final cell parameters of each 2D perovskite cell are shown in Supplementary Table 4. Since the growth process of the crystals was under the kinetic condition of 70°C, we appropriately expanded the crystal cell into a certain volume of supercells and simulated the kinetic state of the supercells under 343 K conditions (Supplementary Fig. 8, a – n). The interlayer spacing between the layers of 2D perovskite octahedra shows a gradual increasing trend as the size of the ligand molecules increases. However, with the growth of ligand main chains, ligand chains interspersed between layers. The ratio of layer spacing to ligand size of t-BA, i-PA, PA, BA, PhA, PMA and other small hindrance ligands is close to 2, which means that there is no interchain interpenetration. For large-site-resistance ligands such as PentA, HA, OA, NonylA, DDA, PEA, PPA, and PBA, the ratio of layer spacing to ligand size was closer to 1, indicating that ligand chains interspersed in the middle space of inorganic layers (Fig. 4 a). Taking BA and DDA as an example, the small-site-resistance ligand BA does not interweave between inorganic layers, and the methyl group at the end of the main chain between the two layers of butyl ammonium is relatively close, which forms an interaction between the layers and maintains a 2D structure (Fig. 4 b) 36 . Whereas, for the large-site-resistance ligand DDA, the carbon chains of the ligands interpenetrate between the inorganic layers, so the formation of interactions extends to the whole range of the organic layers that interpenetrate each other (Fig. 4 c). Under the kinetic conditions of 343 K, the ligand chains undergo irregular movements between the layers. For (BA) 2 PbI 4 , the butyl chains show a more chaotic structure in the interlayer due to the formation of interactions only between the terminal methyl groups (Fig. 4 d); whereas for (DDA) 2 PbI 4 , the dodecyl chains are more regular and organized in the interlayer as the range of interactions present is the whole range of organic layers (Fig. 4 e). We further calculated the interaction energy of the interlayer ligand molecules according to Eq. (5) (Fig. 4 f). The binding energy between the two layers of ligands in the organic layer increases gradually with the growth of the main carbon chain of the ligand. For two ligands, t-BA and i-PA, because of the presence of branch chains, the number of methyl groups in contact with each other increases, so the binding energy between organic layers increases slightly. The interlayer binding energy of the organic layer of (BA) 2 PbI 4 and (DDA) 2 PbI 4 were calculated to be − 1.85×10 5 and − 2.43×10 5 kcal/mol, respectively (Supplementary Table 6). The greater the negative value of the binding energy, the greater the energy required to separate the two layers, so the more negative the binding energy, the stronger the interlayer binding force. According to the general law of binding energy, when the size of ligand molecules reaches a certain level, cross-overlaps occur between the octahedral layers of perovskite. Due to the limitation of lattice and ligand chain size, the space of molecular chain activity decreases, the degree of interlayer disorder decreases, the degree of order increases, and the degree of distortion to the inorganic octahedron is small. The range of the interlayer van der Waals forces is extended, the energy of each particle in the crystal is lower 37 , as shown in Fig. 4 h. Whereas the effect of van der Waals forces on perovskite crystals formed by small steric ligands is only at the end of the ligand chain, not the whole organic layer, and the inorganic octahedron is distorted to a greater extent 38 , as shown in Fig. 4 g. Crystals tend to grow towards a certain surface with lower energy, and different interlayer stacking configurations lead to different surface energies, resulting in 1D rod crystals and 2D lamellar crystals 39 . The kinetic simulation shows that this law is also applicable to the aromatic hydrocarbon system (Supplementary Fig. 9, a – n). In order to investigate the crystal orientation of solution-grown 2D perovskite single crystals, we have tested the high-resolution physical phases, crystal plane spacing, selected area electron diffraction (SAED) patterns, and energy dispersive x-ray spectroscopy (EDS) of (BA) 2 PbI 4 single crystals as well as (PEA) 2 PbI 4 single crystals under an accelerating voltage of 200 kV. We have successfully revealed the lattice information of solution-grown 2D perovskite lattice information of single crystals. As shown in Fig. 5 a, the continuous lattice stripes of the barred (BA) 2 PbI 4 single crystals and the corresponding Fourier transform information (Fig. 5 a, bottom right) indicate that the lattice spacing of the barred single crystals is 8.05 Å, which corresponds to the (1 0 0) crystallographic plane. The (BA) 2 PbI 4 nanowire cross-section high-resolution microscopy is shown in Supplementary Fig. 10a. High-angle annular dark-field (HAADF) (Supplementary Fig. 10b) as well as energy spectra (Fig. 5 b) show that the 2D perovskite did not undergo decomposition or physical phase changes during the transfer from the Si substrate to the conducting carbon film. For the lamellar (PEA) 2 PbI 4 single crystals, the crystal face spacing in the high-resolution physical phase (Fig. 5 c) is 6.01 Å, which corresponds to the \(\:\text{(1}\text{}\stackrel{\text{-}}{\text{1}}\:\stackrel{\text{-}}{\text{1}}\text{)}\) crystal faces of (PEA) 2 PbI 4 . Its diffraction pattern (Fig. 5 c, bottom right) can be labeled \(\:\text{(1}\text{}\stackrel{\text{-}}{\text{1}}\:\stackrel{\text{-}}{\text{1}}\text{)}\) crystal diffraction spot, corresponding to the band axis [2 1 1]. EDS measurement shows that the major elements such as Pb and I are uniformly distributed in the nanosheets, forming a stable pure 2D perovskite phase (Fig. 5 d). The EDS mapping of element C could not show a clear profile due to the large amount of element C in the solvent CB, and the EDS spectrum of each element are shown in Supplementary Fig. 10, c and d. As shown by the lattice information presented by TEM, the rod-like (BA) 2 PbI 4 single crystals have the lowest surface energy at the (1 0 0) crystallographic plane, which extends along the (1 0 0) crystallographic plane when grown in solution and are stacked in the order of L + -I − -L + , as shown in Fig. 5 e. Taken as a whole, after nucleation of 2D chalcogenides, the area of the inorganic octahedral layer remains at the scale of nucleation without growth. The new ligand and inorganic layers continue to stack in accordance with the (1 0 0) crystallographic direction, eventually forming 1D-scale rod-like single crystals, as shown in Fig. 5 f. For cubic phase chalcogenide cells, the surface energy of the (1 1 1) crystal surface is higher than that of the (1 0 0) crystal surface. Specifically, the surface energy of the (1 1 1) crystal faces of chalcocite is 0.93 J/m 2 , while the surface energy of the (1 0 0) crystal faces is 0.89 J/m 2 40, 41 . Sheeted (PEA) 2 PbI 4 single crystals grow in solution with the lowest (1 0 0) crystal surface energy due to the stacking conformation of the interlayer organic ligands, which breaks the cubic phase conformation resulting in the (1 0 0) crystal surface energy. In contrast, (PEA) 2 PbI 4 single crystals have the lowest (1 1 1) crystal surface energy. Thus, along the (1 1 1) crystal plane during crystal growth, the stacking follows the Pb 2+ -I − -Pb 2+ order, as shown in Fig. 5 g. As a whole, starting from the nucleation site, the inorganic octahedron undergoes an extended growth with the consequent insertion of long-chain ligands into the inorganic layer, leading to the formation of 2D-scale lamellar single crystals as shown in Fig. 5 h. By modeling the arrangement of organic layer ligands, we have gained a more accurate understanding of the interlayer interactions in layered 2D perovskites. The direction and magnitude of interlayer interactions determine the tendency of cell stacking, which further determines the crystalline form of 2D perovskites formed with different ligands. Our study explains the fundamental reasons affecting the morphology of 2D perovskite single crystals from a molecular perspective. Conclusion In summary, we used 2D perovskite ligands with different molecular sizes and regulated the solution dynamics of precursors by the magnitude of their binding energies with solvent molecules to crystallize 2D perovskites by different mechanisms, finally realized the high-throughput preparation and characterization of 2D perovskite single crystals in the form of rods and flakes. We used in-situ UV-Vis absorption spectroscopy to investigate the crystallization mechanisms of 2D perovskites guided by ligands of different sizes. Contrary to previous reports, the process of 2D perovskite crystallization is not a pure solvent evaporation process. The binding energy between the ligand and the solvent is not negligible for the evaporation process. The fast rate at which solvent molecules in the precursor solution are detached from the overall solution system during evaporative crystallization leads to different changes in the solubility of the solution for PbI 2 as well as perovskite during crystallization. This further leads to a different order of arrival of PbI 2 as well as perovskites at supersaturation, and hence two different crystallization mechanisms. In the growth process after crystal nucleation, due to the different configurations of ligands of different sizes in the perovskite crystal lattice, with the increase of the ligand main chain length, the organic layers appear to be interspersed with each other in the configuration of ligand carbon chains, which further leads to a different range of interactions between the organic layers, resulting in different surface energy. The present study revisits the structure of 2D layered perovskite crystals and corrects the previous understanding of the arrangement of organic cations between layers. A conformational relationship between cell structure and crystal morphology is established, providing a basis for the modulation of layered 2D perovskite single crystals. Solution kinetic modulation of perovskite precursor solutions is an effective strategy universally applicable to the morphology control of various types of layered organic-inorganic 2D perovskites. In this work, we derived a universal law of solute-solvent binding energy regulation of 2D perovskite crystallization, which is applicable to alkane and aromatic hydrocarbon ammonium salt ligands. The regulation of solute-solvent intermolecular binding energy can be realized through molecular polarity, the introduction of special functional groups, etc. The diversity of 2D perovskite ligands signifies that ligand templates are the most effective method for modulating the optoelectronic properties of 2D perovskites. The present study provides universal laws applicable to most of the ligands. Mechanistic studies on the regulation of crystallization processes and crystal morphology have allowed us to regulate the growth of single crystals on a molecular scale, which contributes to further reducing the size of 2D perovskite optoelectronic devices to the micron level using the solution method, providing a strong support for the large-scale application of 2D perovskites. Methods Materials Lead iodide (PbI 2 ), tert-butylammonium iodide (t-BAI), iso-propylammonium iodide (i-PAI), propylammonium iodide (PAI), pentylammonium iodide (PentAI), hexylammonium iodide (HAI), octylammonium iodide (OAI), nonylammonium iodide (NonylAI), dodecylammonium iodide (DDAI), phenylammonium iodide (PhAI), benzylammonium iodide (PMAI), phenylpropylammonium iodide (PPAI), phenylbutylammonium iodide (PBAI) were purchased from Xi’an Yuri Solar Co., Ltd. N-butylammonium iodide (BAI) was purchased from TCI, and phenethylamine hydroiodide (PEAI) was purchased from Sigma-Aldrich. Chlorobenzene (CB) and 1, 2-dichlorobenzene (DCB), were purchased from Thermo Fisher Scientific Inc. Acetonitrile (ACN), N, N-dimethylformamide (DMF) and Poly(methyl methacrylate) (PMMA, MW~35000) were purchased from Aladdin. Single-sided polished high-purity monocrystalline silicon wafers (crystal direction [100], size 15×15 mm, flatness < 1 μm) were purchased from LIGE SCIENCE. 15mm×15mm super white glass substrate purchased from Liaoning You Xuan New Energy Technology Co. Solution-phase synthesis of pure 2D halide perovskite single crystal In this work, 14 pure two-dimensional perovskite micro-sized single crystals have been synthesized using quaternary solvents. 10 μmol PbI 2 was dissolved with 20 μmol LI (L= t-BA, i-PA, PA, BA, PentA, HA, OA, NonylA, DDA, PhA, PMA, PEA, PPA, PBA) in 2 mL of DMF/CB (1:1, v/v) co-solvent to obtain 5 mM of 2D perovskite stock solution. CB/ACN/DCB (9.5:0.1:0.01, v/v) co-solvent was prepared as a dilution solvent. In high-throughput experiments, the dilution factors of alkylamine ligands (t-BA, i-PA, PA, BA, PentA, HA, OA, NonylA, DDA) were set at 60, 120, 240, 480, 560, 640, and 960 times, while those of aromatic amine ligands (PhA, PMA, PEA, PPA, PBA) were set at 30, 60, 120, 180, 240, and 480 times. The Si substrates were preheated to 70 °C and then 50 to 100 μL of perovskite dilute solution was dropped onto them. The single crystal growth time was approximately 1 to 3 minutes. The entire process was carried out in a nitrogen-filled glove box. The high-throughput platform operating procedures are described in the SI. Preparation of two-dimensional perovskite thin films A 1M 2D perovskite precursor solution was prepared by dissolving PbI 2 with LI in DMF at 1:2 (mol: mol). The dissolved solution was filtered with a 0.22 μm PTFE hydrophobic filter tip to remove impurities. The clean and dry glass substrate was placed in a plasma oxygen microwave apparatus for 10 minutes for plasma treatment, with the aim of cleaning the organic matter on the glass substrate and improving the infiltration between the perovskite and the glass substrate. 50 μL of precursor solution was taken and spin-coated on the glass substrate, the speed of the homogenizer was 400 rpm and the spin-coating time was 30s. At the 20th s, 150 μL of CB was taken and added to the substrate in a rapid drop of 1 s or less. After spin-coating, the substrate was heated and annealed at 70 °C for 10 minutes. The entire process was carried out in a nitrogen-filled glove box. The high-throughput platform operating procedures are described in the SI. Preparation of TEM samples Prepare a CB solution of 10 mg/mL PMMA. Filter the PMMA solution using a 0.22 μm hydrophobic PTFE filter tip. The PMMA solution was spin-coated onto the Si substrate. The speed of the homogenizer was 4000 rpm for 30 s. After the spin-coating was finished, the Si substrate was annealed at 70 ℃ for 10 min. 2D perovskite was subsequently grown on the PMMA-covered Si substrate. After the growth was completed, CB was used to dissolve the PMMA on the surface of the Si substrate. The Si substrate containing PMMA and perovskite was placed in a centrifuge tube with CB added to the tube over the Si sheet. The centrifuge tube was placed in an ultrasonic machine for 1h so that PMMA was dissolved by CB while perovskite single crystals were dispersed into CB. The dispersion was added several times dropwise onto a conductive carbon film (EMCN LG14-102 Transmission Electron Microscope Carbon Supported Membrane for Grid Carriers, 200 mesh). Eventually the perovskite single crystals were transferred to the conductive carbon film. Optical imaging Brightfield optical images were acquired using a Mshot metallurgical microscope MJ31. Brightness-adjustable white LEDs are used as light source with an Abbe spotting scope NA1.25 without filter. Brightfield image uniformity is obtained by the long working distance flat field objective L Plan 50X. Photoluminescence imaging Fluorescence field optical images were acquired by a Leica DM4000 automated microscope. The excitation light was modified to the blue band through the use of a filter, and all images were observed and photographed under a dark-field dry 100× objective. SEM imaging Backscatter SEM images were acquired using a Hitachi Regulus 8100 with accelerating voltages of 22 kV, 9 kV, 5 kV, and 15 kV. TEM imaging and spectrum acquisition Transmission electron microscopy (TEM) imaging, energy spectra, and diffraction patterns were acquired by a Talos F200X G2 from Thermo Fisher, USA. The accelerating voltage was 200 kV. STEM imaging and chemical energy spectra of the samples were acquired automatically by Thermo Scientific Maps software (enabled by Thermo Scientific Velox software).The main analysis was performed using GATAN GMS 3 software after the acquisition was completed. CaRIne Grystallography 3.1 was used to assist in the calculation of the crystallographic indices facet spacing and angle. The calibration of the diffraction patterns of the two perovskite samples is shown in Supplementary Table 8. Absorption spectrum and In-situ absorption spectrum The absorption spectra of two-dimensional perovskite thin films were collected by Ocean Optics QE65 Pro scientific grade spectrometer, and the light source was a combination of deuterium-tungsten halogen lamp DT-MINI-2-GS, and the analysis software was BiaoQi Spectrum Analysis Software. The in-situ absorption spectra were collected by an in-house built in-situ test system, in which the spectrometer was an Ocean Optics QE65 Pro scientific grade spectrometer, and the light source was an LS-3 visible-near-infrared halogen lamp with a Y-type optical fiber and a hot bench. The test is performed by preheating the substrate to 70 ℃. The white light fiber is incident perpendicular to the substrate and the solution is dripped from the side, and the test starts when the solution is dripped. The schematic diagram of in situ absorption spectroscopy test is shown in Supplementary Fig. 4. Steady-state photoluminescence spectrum and Time-resolved photoluminescence spectroscopy The 2D perovskite film photoluminescence spectra and time-dependent photoluminescence spectra were collected by Pico Quant FluoTime300 fluorescence lifetime spectrometer. Excitation was performed using PDL 820 LDH-P-C-405 monochromatic picosecond laser diode head. The UV-red detector used a Hybrid PMT with a 425nm LP filter. TrPL measurements were made using a single photon counter ps TCSPC TimeHarp 260 P. Photoluminescence spectra of perovskite single crystals were obtained by focusing the excitation light with an Olympus BX43 microscope and focusing it onto individual single crystals. The PL spectral processing and TrPL data fitting software utilized was EasyTau, while the image capture and processing software was IDS Peak Cockpit. The fitting publics and procedures are illustrated in Supplementary Table 2. Molecular dynamics and DFT simulations For the 2D perovskite solution and cell dynamics and DFT simulations, the solution and cell models were constructed mainly using Material Studio, and geometry optimization was carried out using density functionals. Based on this, the kinetic energy, electrostatic potential and energy band structure were calculated. The solution and crystal models were optimized using the COMPASSIII force field in Forcite and the GGA-PBE general function in CASTEP module. The cell model was used as a reference with the crystal information of (BA) 2 PbI 4 , and the spacer cations were replaced to obtain the rest of the crystal model. The kinetic simulation temperature was set to the experimental temperature (343 K), and binding energy calculations were performed using a script where all kinetic energies were averaged from the output. The molecular electrostatic potential was calculated using the DMol3 module with the GGA-PBE generalization. The 2D perovskite cell energy band structure is calculated using CASTEP module, GGA-PBE generalized function, which ensures the reliability and consistency of the calculation results. The detailed process and parameters of the simulation calculations are shown in SI. Declarations Data availability All data related to this study are available from the corresponding author on reasonable request. Acknowledgements This work was financially supported by the National Natural Science Foundation of China (52394273 and 52373179), the TCL Science and Technology Innovation Fund (20242065). This work was partially supported by High Performance Computing Platform of South China University of Technology. We thank Dr. Yang at Shenzhen HUASUAN Tech. Co., Ltd., for insightful discussions and suggestions. Author contributions J.Q. synthesized and characterized two-dimensional perovskite single crystals and thin films. J.Q. and X.H performed the operation of the high-throughput platform. J.Q. and K.A performed the construction and use of the in-situ absorption test system. J.Q., L.L. and Y.M performed PL mapping testing and data collection. J.Q. performed molecular dynamics simulations, TEM characterization, and data analysis.J.Q., W.M. and N.L. wrote the manuscript; all authors read and revised the manuscript. Competing interests The authors declare no competing interests. Additional information Supplementary information is available for this paper. Correspondence and requests for materials should be addressed to N.L. References Hu, J., Odom, T. W. & Lieber, C. M. Chemistry and Physics in One Dimension: Synthesis and Properties of Nanowires and Nanotubes. Accounts of Chemical Research 32 , 435-445, doi:10.1021/ar9700365 (1999). Ricciardulli, A. G., Yang, S., Smet, J. H. & Saliba, M. Emerging perovskite monolayers. Nature Materials 20 , 1325-1336, doi:10.1038/s41563-021-01029-9 (2021). Leng, K., Fu, W., Liu, Y., Chhowalla, M. & Loh, K. P. From bulk to molecularly thin hybrid perovskites. Nature Reviews Materials 5 , 482-500, doi:10.1038/s41578-020-0185-1 (2020). Fu, Y. Tableet al. 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Preferred Crystallographic Orientation via Solution Bathing for High‐Performance Inverted Perovskite Photovoltaics. Advanced Functional Materials 34 , doi:10.1002/adfm.202407732 (2024). Xia, M. et al. Kinetic Wulff-shaped heteroepitaxy of phase-pure 2D perovskite heterostructures with deterministic slab thickness. Nature Synthesis , doi:10.1038/s44160-024-00692-5 (2025). Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryImformation.docx Supplementary Information Cite Share Download PDF Status: Published Journal Publication published 12 Dec, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6431736","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":453329387,"identity":"4abbe391-e045-45d1-8dc8-cdce0f628c57","order_by":0,"name":"Ning Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7UlEQVRIiWNgGAWjYDACZiB+YGDDw8/efAAqlECElgSDNDnJnmMgpQZEaIEYe9jY4EaOAXFazNl5D79IKGBObDiQ8/nDz7Y/DPzsQL0/d+DWYtnMl2aRYMCW2Nhwdptkb5sBg2TPGwPG3jO4tRgc5jEzSDDgSWxm7N3GzAjUAnIhkEFQi0RiGzPP488gLfZEaDF+kGBgYMzDxsMgDbZFgghbgIGcICfBw2Ym2XPOmEfizLOCg734tJw/Y/zhw5//PPb3Hz/+8KNMTo6/PXnjg594tAABmwQyjwdEHMCrARj/HwgoGAWjYBSMgpEOALbNTO81MZD8AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-1208-4638","institution":"South China University of Technology","correspondingAuthor":true,"prefix":"","firstName":"Ning","middleName":"","lastName":"Li","suffix":""},{"id":453329388,"identity":"7949ac0c-3716-4028-b456-85d519dfb6b8","order_by":1,"name":"Jingyan Qi","email":"","orcid":"","institution":"South China University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Jingyan","middleName":"","lastName":"Qi","suffix":""},{"id":453329389,"identity":"60ed6c24-00f9-4aac-a780-6f89f9232c18","order_by":2,"name":"Wei Meng","email":"","orcid":"","institution":"South China University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Meng","suffix":""},{"id":453329390,"identity":"1b975396-47a2-4948-af61-0b4bbea50d8b","order_by":3,"name":"Kang An","email":"","orcid":"","institution":"South China Univeristy of Technology","correspondingAuthor":false,"prefix":"","firstName":"Kang","middleName":"","lastName":"An","suffix":""},{"id":453329391,"identity":"76c13c9c-605f-4a7b-8fe6-171dfaf665a4","order_by":4,"name":"Xujie Hui","email":"","orcid":"","institution":"South China University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Xujie","middleName":"","lastName":"Hui","suffix":""},{"id":453329392,"identity":"30182c08-a4d1-4190-ac0f-eadee2d0c9ea","order_by":5,"name":"Liqun Liu","email":"","orcid":"https://orcid.org/0000-0003-1530-9775","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Liqun","middleName":"","lastName":"Liu","suffix":""},{"id":453329393,"identity":"fd594d67-bf9b-4648-baed-85abcd80b224","order_by":6,"name":"Yuguang Ma","email":"","orcid":"","institution":"South China University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yuguang","middleName":"","lastName":"Ma","suffix":""}],"badges":[],"createdAt":"2025-04-12 02:45:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6431736/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6431736/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-025-66505-1","type":"published","date":"2025-12-12T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82570296,"identity":"5eba093c-4a4c-4f1b-b857-fc50bcf2818b","added_by":"auto","created_at":"2025-05-13 04:06:32","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1058917,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHigh-throughput experimental procedures and results. a\u003c/strong\u003e, Flowchart of high-throughput experiments. An automated platform robotic arm was used to draw up the solution and drop-cast it onto a silicon substrate for evaporative crystallization. \u003cstrong\u003eb\u003c/strong\u003e, 98 high-pass experiments were designed with 14 ligand types and 7 precursor solution dilution times as variables. \u003cstrong\u003ec\u003c/strong\u003e, The morphology of two-dimensional perovskite crystals gradually changed from rod-like to lamellar with the increase of the size of ligands in the characteristic crystals of 14 kinds of ligands. \u003cstrong\u003ed\u003c/strong\u003e, The three-dimensional lengths of the ligand molecules used. \u003cstrong\u003ee\u003c/strong\u003e, Rod and flake crystals were defined by calculating the ratio of length to diameter of the crystals. The statistical histogram of the ratio of length to diameter of a single perovskite crystal was prepared by using the coordination system with the limit of 1.5. Scale bars, 10 μm in \u003cstrong\u003ec\u003c/strong\u003e.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6431736/v1/e90d5a7216471dd763171355.png"},{"id":82570297,"identity":"e0ecbc4c-0c08-4f7e-90fc-c0d094e09f70","added_by":"auto","created_at":"2025-05-13 04:06:32","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":810476,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptical characterization of two-dimensional perovskite single crystals.\u003c/strong\u003e \u003cstrong\u003ea – d\u003c/strong\u003e,\u003cstrong\u003e \u003c/strong\u003eFluorescence microscopy images of (\u003cstrong\u003ea\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003eb\u003c/strong\u003e) (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003ec\u003c/strong\u003e) (PMA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003ed\u003c/strong\u003e) (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals. \u003cstrong\u003ee – h\u003c/strong\u003e, SEM images of (\u003cstrong\u003ee\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003ef\u003c/strong\u003e) (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003eg\u003c/strong\u003e) (PMA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003eh\u003c/strong\u003e) (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals. \u003cstrong\u003ei – l\u003c/strong\u003e, PL spectra of (\u003cstrong\u003ei\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003ej\u003c/strong\u003e) (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003ek\u003c/strong\u003e) (PMA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, (\u003cstrong\u003el\u003c/strong\u003e) (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals. Scale bars, 10 μm in (\u003cstrong\u003ea\u003c/strong\u003e) to (\u003cstrong\u003ed\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6431736/v1/87b887ea8f2f765cb2a12891.png"},{"id":82570154,"identity":"06a1659c-4a7a-4073-adf2-cb1c9e9cc4cb","added_by":"auto","created_at":"2025-05-13 03:58:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":970941,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIn situ absorption analysis.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, In-situ absorption spectra of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e crystallization process. The red part is the region with strong absorption signal, representing the appearance of crystallization. The characteristic absorption peak of PbI\u003csub\u003e2\u003c/sub\u003e is around 445 nm, and the characteristic absorption peak of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e perovskites is around 500 nm. Both of the two absorption peaks appeared in Stage II time range. \u003cstrong\u003eb\u003c/strong\u003e, Absorption spectra at 180 s and 200 s after the start of drop casting. These two time nodes are Stage I and Stage II respectively. The PbI\u003csub\u003e2\u003c/sub\u003e signal at 400 – 450 nm and the (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e signal at 480 – 515 nm both increased, indicating that the contents of PbI\u003csub\u003e2\u003c/sub\u003e and (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e increased simultaneously in the later stage, corresponding to the direct nucleation mechanism of perovskite nucleation. \u003cstrong\u003ec\u003c/strong\u003e, Schematic diagram of the direct nucleation mechanism and equation. \u003cstrong\u003ed\u003c/strong\u003e, In-situ absorption spectrum of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e crystallization process. The characteristic absorption peak of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e at 445 nm appeared within the Stage I time range, while the characteristic absorption peak of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e perovskite at 525 nm did not appear until the time reached Stage II. \u003cstrong\u003ee\u003c/strong\u003e, Absorption spectra at 225 s and 255 s after casting, the two time nodes of absorption spectra were Stage I and Stage II, respectively. PbI\u003csub\u003e2\u003c/sub\u003e absorption was evident at 225 s, and there was no significant change in PbI\u003csub\u003e2\u003c/sub\u003e signal strength between 400 and 450 nm in both spectra. The absorption of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e at 445 – 525 nm increased significantly. The results indicated that the content of PbI\u003csub\u003e2\u003c/sub\u003e was high in the early stage, while the content of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e increased in the late stage, which indicated that the stripping mechanism of PbI\u003csub\u003e2\u003c/sub\u003e nanocrystalline dominated the perovskite crystallization. \u003cstrong\u003ef\u003c/strong\u003e, Schematic diagram and equation of the stripping mechanism. \u003cstrong\u003eg\u003c/strong\u003e, Binding energies of 14 ligand ions and CB molecules in precursor solution environments, showing a tendency for the binding energy to increase with ligand size. \u003cstrong\u003eh – i\u003c/strong\u003e, The binding energy properties of (\u003cstrong\u003eh\u003c/strong\u003e) BA and (\u003cstrong\u003ei\u003c/strong\u003e) DDA with CB result in the different rates of CB detachment from the solution system which leads to different solubility of the solution for PbI\u003csub\u003e2\u003c/sub\u003e at a given time, which results in the crystallization of perovskites by different mechanisms. From the electrostatic potential diagram, it can be seen that the amino terminus of the ligand ion as the electrophilic end and the more nucleophilic Cl in the CB molecule can undergo mutual attraction.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6431736/v1/69f52593fe3be6a8189cd13f.png"},{"id":82570299,"identity":"c24331bd-cd73-4465-bcdb-02cbf92948c1","added_by":"auto","created_at":"2025-05-13 04:06:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1126454,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMolecular dynamics simulations of two-dimensional perovskite cells.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, Layer spacing, ligand size and ratio of the alkane ligand. \u003cstrong\u003eb – c\u003c/strong\u003e, Schematic diagrams of the interlayer structures of (\u003cstrong\u003eb\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e and (\u003cstrong\u003ec\u003c/strong\u003e) (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e at 0 K, with the shaded areas showing the extent of the interactions occurring. \u003cstrong\u003ed – e\u003c/strong\u003e,\u003cstrong\u003e \u003c/strong\u003eSchematic diagrams of the supercell structures of (\u003cstrong\u003ed\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e and (\u003cstrong\u003ee\u003c/strong\u003e) (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e at 343 K.\u003cstrong\u003e f\u003c/strong\u003e,\u003cstrong\u003e \u003c/strong\u003eInterlayer binding energy of organic layers of 14 perovskite supercells at 343K. The values of the binding energies increase with the size of the ligand molecules, indicating that the interlayer interactions are getting stronger and stronger. \u003cstrong\u003eg – h\u003c/strong\u003e,\u003cstrong\u003e \u003c/strong\u003eSchematic diagrams of the organic layer configurations of (\u003cstrong\u003eg\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e as well as (\u003cstrong\u003eh\u003c/strong\u003e) (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e (hydrogen atoms have been hidden). ∆d is the difference in bond lengths of the neighboring Pb-I bonds; ∠\u003csub\u003ePb-I-Pb\u003c/sub\u003e represents the octahedral bond angle. The octahedral distortion of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e is larger than that of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, which is due to the structural distortion of the inorganic layer caused by the weak interlayer interaction.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6431736/v1/5146735ee395c211f563b77c.png"},{"id":82570715,"identity":"23770077-5d39-4cdd-9b4c-72c89aa86ddc","added_by":"auto","created_at":"2025-05-13 04:14:32","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1162678,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTEM characterization of (BA)\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003ePbI\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e and (PEA)\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003ePbI\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e single crystals.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e and \u003cstrong\u003ec\u003c/strong\u003e, Lattice fringing and diffraction patterns of (\u003cstrong\u003ea\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e and (\u003cstrong\u003ec\u003c/strong\u003e) (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals. \u003cstrong\u003eb\u003c/strong\u003e and \u003cstrong\u003ed\u003c/strong\u003e,\u003cstrong\u003e \u003c/strong\u003e\u0026nbsp;energy dispersion spectra of (\u003cstrong\u003eb\u003c/strong\u003e) (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e and (\u003cstrong\u003ed\u003c/strong\u003e) (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals, which provided information on single crystal orientation and lattice arrangement. \u003cstrong\u003ee\u003c/strong\u003e, Schematic representation of the (1 0 0) crystal plane of a (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystal that extends as a stack in the ligand direction. \u003cstrong\u003ef\u003c/strong\u003e, (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals have the lowest surface energy at the (1 0 0) crystal face and grow along the c-axis of the cell after nucleation. \u003cstrong\u003eg\u003c/strong\u003e, Schematic of the (1 1 1) crystal plane of (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystal, which extends as a stack in the inorganic octahedral direction. \u003cstrong\u003eh\u003c/strong\u003e, (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals have the lowest (1 1 1) crystalline surface energy, and the inorganic octahedral layer extends laterally after nucleation.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6431736/v1/95cee2f9f2aee666ae055987.png"},{"id":99212974,"identity":"57a994d7-cfa8-4b3c-aef4-d2d1b5ed18cc","added_by":"auto","created_at":"2025-12-30 08:34:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6178180,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6431736/v1/4491cd0a-5a5a-4a4d-b5ba-8c340639b263.pdf"},{"id":82570164,"identity":"33242749-a95d-4799-b8b0-eb58151ef8ba","added_by":"auto","created_at":"2025-05-13 03:58:32","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":10965549,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"SupplementaryImformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6431736/v1/9082b3693af6feb9f005409e.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Regulating the microstructure of two-dimensional perovskite single-crystals via high-throughput experimentations","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe relentless advancement of information technology has propelled the demand for micro- and nanoscale semiconductor electronic devices. Conventional miniaturization techniques face high costs, environmental concerns, and scalability constraints limitations, such as vacuum deposition, epitaxy and etching\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Solution-processed mesostructured semiconductors provide a promising alternative, offering cost-effective fabrication with precise control over composition and structural design, making them highly attractive for next-generation optoelectronic and photonic applications.\u003c/p\u003e \u003cp\u003eAmong solution-processed semiconductors, two-dimensional (2D) layered metal halide perovskites (L\u003csub\u003e2\u003c/sub\u003eA\u003csub\u003en\u0026thinsp;\u0026minus;\u0026thinsp;1\u003c/sub\u003eM\u003csub\u003en\u003c/sub\u003eX\u003csub\u003e3n+1\u003c/sub\u003e) have garnered significant attention owing to their promising characteristics, such as high charge carrier diffusion length and high defect tolerance. Here, L represents a bulky organic cation, A a small organic cation (e.g., methylammonium, MA), M a metal cation (e.g., Pb or Sn), X a halide anion, and n an integer dictating the inorganic layer thickness, effectively functioning as a quantum well\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. The tunability of structural and electronic properties makes them ideal candidates for mesoscopic optoelectronic applications\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. The dimensionality of perovskites fundamentally influences charge transport and light\u0026ndash;matter interactions, thereby determining the optoelectronic performance\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. For instance, perovskite nanowires, with 1D electron confinement, exhibit ultrahigh carrier mobility and enhanced sensitivity, rendering them suitable for photodetectors and lasers. Conversely, 2D perovskite nanosheets, characterized by large surface areas and strong quantum confinement, enhance light absorption and charge separation, benefiting solar cells and photocatalysis\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Therefore achieving precise control over crystallization is critical for tailoring perovskite morphologies to optimize the semiconductor functionality\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eVarious synthetic methodologies have been developed to fabricate perovskite materials with tailored dimensionalities, including vapor-phase growth, lithographically templated solution-phase growth, ligand-assisted solution-phase growth, and alcoholic solvent-assisted growth\u003csup\u003e\u003cspan additionalcitationids=\"CR10 CR11 CR12 CR13 CR14 CR15\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. However, methodologies developed so far largely rely on empirical synthetic experiments, necessitating iterative functional group modifications to organic ligands to regulate crystal morphology. These methods suffer from high processing complexity, elevated costs, and limited scalability, restricting their applicability mainly in specific materials design. A fundamental challenge remains: the lack of generalizable principles governing ligand-induced crystallization in 2D perovskite systems. The complex interplay of multidimensional parameters further complicates precise morphology control, underscoring the need for a deeper understanding of perovskite crystallization kinetics\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHere, we present a high-throughput experimental approach integrating in-situ absorption spectroscopy and molecular dynamics simulations to elucidate ligand-mediated crystallization in 2D perovskite single crystals. Our automated system systematically explores 98 synthesis conditions with programmable robotic arms, enabling precise control over crystal morphology. By screening nine alkane ligands, five aromatic hydrocarbon ligands, and varying precursor solution dilutions, we establish a direct correlation between ligand chain length and crystallization behavior: shorter ligands favor 1D nanowire formation, whereas longer ligands promote 2D nanosheet growth. In situ absorption spectroscopy and molecular dynamics simulations reveal that increasing ligand size modulates the ligand conformation within the 2D perovskite lattice, shifting crystallization from direct nucleation to lamellar exfoliation. Transmission electron microscopy (TEM) and density functional theory (DFT) calculations further confirm that morphological transition is driven by enhanced solute-solvent binding energy, governing the crystallization pathway of lead halide intermediates. Our study provides insights into solution-phase dynamics governing perovskite lattice formation and offers a rational strategy to design perovskite materials with tailored optoelectronic properties, advancing their integration into next-generation semiconductor technologies.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eHigh-throughput synthesis of 2D perovskite nanorods and nanoplates\u003c/h2\u003e \u003cp\u003eAlkylammoniums ranging from tert-butylammonium to dodecyl ammonium, i.e., alkylammoniums with main chains ranging from 2 Cs to 12 Cs, were selected as alkyl ligands; aromatic ammoniums ranging from phenyl ammonium to phenyl butylammonium, i.e., aromatic ammoniums with phenyl-ring side-chain Cs ranging from 0 to 4, were selected as aromatic hydrocarbon ligands, with a total of 14 ligands throughout the high-throughput experiments (Supplementary Fig.\u0026nbsp;1). The original solution was diluted with a mixture of three antisolvents to reduce the crystal density of the single crystals\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. 2D perovskite single crystals were prepared by the drop injection method at different solution dilution ratios (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). We have recently set up a fast and versatile high-throughput experimental platform for the development of optoelectronic materials and devices (Supplementary Fig.\u0026nbsp;2). The platform employs an 8-channel pipetting robot (FCA, Flexible Channel Arm), in which four pipetting fingers are able to precisely prepare different perovskite precursor solutions in 24-well plates at arbitrary ratios. In addition, a robotic gripper arm (RGA) is responsible for transferring the substrates between the various functional modules of the platform in order to complete the different experimental steps. Since four pipetting tips can simultaneously aspirate and dispense liquids in different volumes, high-throughput automated workstations can increase experimental efficiency by at least fourfold. It can perform 240 drop-coating operations and repeat the entire high-throughput experiment 2 times per hour with prominent reliability and accuracy. For alkyl ligands, tert-butyl ammonium\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e and isopropyl ammonium\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e were chosen, since the molecular size of ethyl ammonium is in the range of 3D perovskites, and it is not able to be used as an intermediate layer to form 2D perovskites\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. The absorption spectra of the 2D perovskite films prepared with 14 ligands showed that the absorption peaks of the films are located at 300\u0026ndash;400 nm and 510 nm (Supplementary Fig.\u0026nbsp;3a), the peaks of the PL spectra of the films are in the range of 485\u0026ndash;555 nm (Supplementary Fig.\u0026nbsp;3b), and the fitting lifetimes of the TrPL spectra of the films are in the nanosecond order of magnitude (Supplementary Fig.\u0026nbsp;3c and Supplementary Table\u0026nbsp;3), indicating that all of the selected organic ligands could form 2D perovskite structures\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. In the experiment, the dilution ratio of nine alkyl ammonium ligand perovskite precursor solutions was set at seven ratios ranging from 60 to 960 times, and the dilution ratio of five aromatic hydrocarbon ligand perovskite precursor solutions was also set at seven ratios ranging from 30 to 480 times. The two variables, the type of ligand molecule and the dilution ratio of solution, form the variable parameter space, and 98 groups of high-throughput experimental results can be obtained (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb and Supplementary Fig.\u0026nbsp;4, a \u0026ndash; n). Among the 98 sets of crystallization experiments, 14 characteristic crystals were screened based on crystal morphology and single crystal integrity, corresponding to 14 different types and molecular sizes of ligands, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec.\u003c/p\u003e \u003cp\u003eAmong the 14 characteristic crystals, with the continuous growth of ligand carbon chain and the gradual increase of ligand volume, the morphology of 2D perovskite single crystals gradually changes from rod-like to sheet, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed. When the ratio of length to diameter of perovskite crystals is above 1.5, the crystal form is considered to be rod-like, and when the ratio of length to diameter is below 1.5, the crystal form is considered to be sheet\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Among the alkane ligands, the 2D perovskite single crystal morphology formed by tert-butylammonium (t-BA), isopropyl ammonium (i-PA), n-propylammonium (PA) and n-butylammonium (BA) ligands with smaller volume are mainly rod-like morphology. Five large ligands, pentylammonium iodide (PentA), hexylammonium (HA), octylammonium (OA), nonylammonium (NonylA) and dodecylammonium (DDA), were mainly formed in sheet morphology. Among the aromatic hydrocarbon ligands, the 2D perovskites formed by phenylammonium (PhA) and phenylmethylammonium (PMA) are rod-like crystals, while the 2D perovskites formed by phenylethylammonium (PEA), phenylpropylammonium (PPA) and phenylbutylammonium (PBA) show obvious lamellar morphology (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee). Among the 14 ligands, both alkane ligands and aromatic ligands showed a rod to lamellar transition in their perovskite single-crystal morphology with a gradual increase in ligand length.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe perovskite single crystals formed by the crystallization of different ligand precursor solutions, whether rod-like or flaky-like, exhibit stable green light emission under the fluorescence field (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, a \u0026ndash; d). The length of rod-shaped 2D perovskite single crystal reach 15 \u0026micro;m, and the size of lamellar single crystal reach 10 \u0026times; 10 \u0026micro;m. Under the electron microscope, the single crystals showed clear rod-like (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, e and g) and flaky (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, f and h) morphology. Meanwhile, the photoluminescence peaks of each 2D perovskite single crystal measured by single crystal PL are 527 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ei), 508 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ej), 530 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ek), 538 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003el) respectively, indicating the pure 2D (n\u0026thinsp;=\u0026thinsp;1) perovskite crystal obtained\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eIn-situ absorption spectroscopy\u003c/h3\u003e\n\u003cp\u003eIn order to explore the crystallization process of 2D perovskites formed by different ligands, in-situ absorption spectroscopy was used to monitor the evaporation crystallization process of precursor solutions baked at 70 ℃, as shown in Supplementary Fig.\u0026nbsp;5, A and B. In the process of evaporation and crystallization, the droplet on the Si sheet moves due to the volume contraction of the solution, resulting in a phase of signal absorption disturbance in the test. The duration of this phase varies from 3 to 10 s depending on the type of solution used.\u003c/p\u003e \u003cp\u003eAmong the 14 ligands, the in-situ spectra of the representative small-site-resistance ligand BA, and the large-site-resistance ligand DDA showed different features. The two stages before and after signal disturbance were divided into Stage I and Stage II, representing solvent evaporation stage and stable crystallization stage respectively, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, a and d. For BA, the absorbed signal of PbI\u003csub\u003e2\u003c/sub\u003e at 425 nm and the absorbed signal of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e at 510 nm both appear at Stage II, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb. For DDA, the absorption signal of PbI\u003csub\u003e2\u003c/sub\u003e at 425 nm has appeared in Stage I, while the absorption signal of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e at 510 nm does not appear until the time reaches Stage II. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee, the absorbed signal at 425 nm does not increase, while the absorbed signal at 510 nm increases.\u003c/p\u003e \u003cp\u003eBased on the different absorption signal characteristics, we conclude that small-site resistance ligands and large-site resistance ligands have different crystallization processes. For BA-type small-site-resistant ligands, the PbI\u003csub\u003e2\u003c/sub\u003e absorption signal at 425nm and the (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e absorption signal at 510 nm both appear at Stage II, indicating that neglectable PbI\u003csub\u003e2\u003c/sub\u003e crystallization occurs during the solvent evaporation process. In the stable crystallization stage, PbI\u003csub\u003e2\u003c/sub\u003e and (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e crystals begin to appear simultaneously, which is dominated by (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e direct nucleation mechanism. The growth of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e crystal is directly induced by (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e crystal nuclei in solution\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, which is represented by Eq.\u0026nbsp;(1).\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}{Pb}^{2+}+2{BA}^{-}+2BAI\\to\\:{\\left(BA\\right)}_{2}Pb{I}_{4}\\#\\left(1\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eFor DDA-type large-site-resistance ligands, the absorption signal of PbI\u003csub\u003e2\u003c/sub\u003e at 425 nm appears first in Stage I, while the absorption signal of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e at 510 nm does not appear until Stage II, indicating that more PbI\u003csub\u003e2\u003c/sub\u003e crystals appear first in the solution during solvent evaporation. (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e crystals appear in large quantities during stable crystallization. It is assumed that the process is dominated by the stripping mechanism of PbI\u003csub\u003e2\u003c/sub\u003e crystals. In solution, the first PbI\u003csub\u003e2\u003c/sub\u003e nanocrystals are stratified\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, and the detached PbI\u003csub\u003e2\u003c/sub\u003e sheets induce the insertion of DDA\u003csup\u003e+\u003c/sup\u003e into the [PbI\u003csub\u003e4\u003c/sub\u003e]\u003csup\u003e2\u0026minus;\u003c/sup\u003e octahedral structure\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, and further formation of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e crystals, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eF. The process is represented by Eqs.\u0026nbsp;(2)(3)(4).\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}{Pb}^{2+}+2{I}^{-}\\to\\:Pb{I}_{2}\\#\\left(2\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}\\left(2n-1\\right)Pb{I}_{2}\\to\\:\\left(n-1\\right){\\left[Pb{I}_{4}\\right]}^{2-}+n{Pb}^{2+}+2{I}^{-}\\#\\left(3\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}{\\left[Pb{I}_{4}\\right]}^{2-}+2{DDA}^{+}\\to\\:{\\left(DDA\\right)}_{2}Pb{I}_{4}\\#\\left(4\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere Eq.\u0026nbsp;(2) represents the generation of PbI\u003csub\u003e2\u003c/sub\u003e nanocrystals, Eq.\u0026nbsp;(3) represents the process of layer exfoliation of PbI\u003csub\u003e2\u003c/sub\u003e nanocrystals, and Eq.\u0026nbsp;(4) represents the process of formation of 2D perovskites by DDA\u003csup\u003e+\u003c/sup\u003e insertion.\u003c/p\u003e \u003cp\u003eThe in-situ absorption spectra of BA, DDA and 12 other ligands during crystallization are shown in Supplementary Fig.\u0026nbsp;6, a \u0026ndash; n. For the ligands with smaller sizes, such as t-BA, i-PA, PA, BA, PhA, PMA, low PbI\u003csub\u003e2\u003c/sub\u003e signals appeared in the absorption spectra at the evaporation crystallization stage and no obvious calixarene absorption appeared. In the absorption spectra of stable crystallization stage, the absorption intensity of PbI\u003csub\u003e2\u003c/sub\u003e increases, and the perovskite absorption signal appears. However, for larger ligands, such as PentA, HA, OA, NonylA, DDA, PEA, PPA, and PBA, PbI\u003csub\u003e2\u003c/sub\u003e absorption signals appear obviously in the evaporative crystallization stage, and there are no obvious perovskite absorption signals. In the absorption spectra of the stable crystallization stage, the obvious perovskite absorption signal appears on the basis of PbI\u003csub\u003e2\u003c/sub\u003e absorption signal. The variation characteristics of the two absorbed signals correspond to the direct nucleation mechanism and the PbI\u003csub\u003e2\u003c/sub\u003e crystal stripping mechanism respectively\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003eCrystallization mechanism\u003c/h3\u003e\n\u003cp\u003eTo address the underlying factors that trigger the two crystallization mechanisms, molecular dynamics simulations are used to explore the relationship between different types of ligands and solvent binding energies. The kinetic state of the precursor diluent is simulated at a drop casting temperature of 343 K (Supplementary Table\u0026nbsp;2). Among the four solvents, DMF with strong solvation energy can dissolve perovskite precursors effectively, but its crystal growth kinetics are slow. Other three antisolvents (CB, ACN, and DCB) have weak solvation energies and limited solubility for precursors, but have the potential for rapid crystallization\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Since the antisolvent CB has the largest percentage and plays a dominant role in the evaporative crystallization process, we calculated the interaction energies, i.e., intermolecular binding energies, of the 14 ligand ions in solution with the CB molecules in solution to determine the change of the solution system during the heating process, which is shown in Eq.\u0026nbsp;(5):\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}{E}_{int}={E}_{AB}-{E}_{A}-{E}_{B}\\#\\left(5\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere A\u0026thinsp;=\u0026thinsp;t-BA\u003csup\u003e+\u003c/sup\u003e, i-PA\u003csup\u003e+\u003c/sup\u003e, PA\u003csup\u003e+\u003c/sup\u003e, BA\u003csup\u003e+\u003c/sup\u003e, PentA\u003csup\u003e+\u003c/sup\u003e, HA\u003csup\u003e+\u003c/sup\u003e, OA\u003csup\u003e+\u003c/sup\u003e, NonylA\u003csup\u003e+\u003c/sup\u003e, DDA\u003csup\u003e+\u003c/sup\u003e, PhA\u003csup\u003e+\u003c/sup\u003e, PMA\u003csup\u003e+\u003c/sup\u003e, PEA\u003csup\u003e+\u003c/sup\u003e, PPA\u003csup\u003e+\u003c/sup\u003e, PBA\u003csup\u003e+\u003c/sup\u003e, and B\u0026thinsp;=\u0026thinsp;CB, with E\u003csub\u003eAB\u003c/sub\u003e as the overall energy of AB, E\u003csub\u003eA\u003c/sub\u003e as the energy of A, E\u003csub\u003eB\u003c/sub\u003e as the energy of B, and E\u003csub\u003eint\u003c/sub\u003e as the interaction energy between A and B. We obtained the relationship between the binding energy between 14 alkane and aromatic ligands and CB with ligand size (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg), where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{int({BA}^{+}-CB)}\\)\u003c/span\u003e\u003c/span\u003e is \u0026minus;\u0026thinsp;16.92\u0026times;10\u003csup\u003e3\u003c/sup\u003e kcal/mol, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{int({DDA}^{+}-CB)}\\)\u003c/span\u003e\u003c/span\u003e is \u0026minus;\u0026thinsp;17.37\u0026times;10\u003csup\u003e3\u003c/sup\u003e kcal/mol (Supplementary Table\u0026nbsp;2). For the small-site resistance ligand represented by BA, the negative value of its binding energy with CB is small, so only a small amount of heat is needed to make CB evaporate quickly from the solution system during solvent evaporation\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. During the solvent evaporation phase, the percentage of DMF in the total solution rapidly increases. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eh, DMF binds to Pb\u003csup\u003e2+\u003c/sup\u003e and I\u003csup\u003e\u0026minus;\u003c/sup\u003e in solution to form [PbI\u003csub\u003em\u003c/sub\u003eX\u003csub\u003en\u003c/sub\u003e]\u003csup\u003e2\u0026minus;m\u003c/sup\u003e (X\u0026thinsp;=\u0026thinsp;DMF) complexes\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e, resulting in the inability to form a large number of PbI\u003csub\u003e2\u003c/sub\u003e crystals, and the ligand ions cannot be induced to insert into the octahedral layer. At the stable crystallization stage, the DMF content decreases to supersaturation and the perovskites begin to nucleate. As for the large-site resistance ligand represented by DDA, due to the large negative value of the binding energy of DDA\u003csup\u003e+\u003c/sup\u003e with CB, which indicates that CB needs to absorb more heat to detach from the solution, the content of DMF does not undergo a large increase in the solvent evaporation stage, the overall solubility of the solution for PbI\u003csub\u003e2\u003c/sub\u003e is low, and a certain amount of PbI\u003csub\u003e2\u003c/sub\u003e nanocrystals can be formed in the system, and at a later stage, with CB and DMF evaporation, the PbI\u003csub\u003e2\u003c/sub\u003e nanocrystals underwent lamellar exfoliation\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e, and the exfoliated PbI\u003csub\u003e2\u003c/sub\u003e nanosheets continued to induce the crystallization of (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e34\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eI.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eInfluence of crystal structure on the growth process\u003c/h3\u003e\n\u003cp\u003eIn order to further investigate the factors affecting the initiation of different crystalline morphologies, we established the cell models of perovskites formed by 14 different ligands by taking the cell parameters and the symmetry of the space group of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals as a reference\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. In addition, we performed functional optimization on all cell models to make the semiconductor bandgap formed by the cells conform to the results measured in PL experiments (Supplementary Fig.\u0026nbsp;8, and Supplementary Table\u0026nbsp;7), so as to obtain accurate cell structures as much as possible. The final cell parameters of each 2D perovskite cell are shown in Supplementary Table\u0026nbsp;4. Since the growth process of the crystals was under the kinetic condition of 70\u0026deg;C, we appropriately expanded the crystal cell into a certain volume of supercells and simulated the kinetic state of the supercells under 343 K conditions (Supplementary Fig.\u0026nbsp;8, a \u0026ndash; n).\u003c/p\u003e \u003cp\u003eThe interlayer spacing between the layers of 2D perovskite octahedra shows a gradual increasing trend as the size of the ligand molecules increases. However, with the growth of ligand main chains, ligand chains interspersed between layers. The ratio of layer spacing to ligand size of t-BA, i-PA, PA, BA, PhA, PMA and other small hindrance ligands is close to 2, which means that there is no interchain interpenetration. For large-site-resistance ligands such as PentA, HA, OA, NonylA, DDA, PEA, PPA, and PBA, the ratio of layer spacing to ligand size was closer to 1, indicating that ligand chains interspersed in the middle space of inorganic layers (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). Taking BA and DDA as an example, the small-site-resistance ligand BA does not interweave between inorganic layers, and the methyl group at the end of the main chain between the two layers of butyl ammonium is relatively close, which forms an interaction between the layers and maintains a 2D structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb)\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. Whereas, for the large-site-resistance ligand DDA, the carbon chains of the ligands interpenetrate between the inorganic layers, so the formation of interactions extends to the whole range of the organic layers that interpenetrate each other (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). Under the kinetic conditions of 343 K, the ligand chains undergo irregular movements between the layers. For (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, the butyl chains show a more chaotic structure in the interlayer due to the formation of interactions only between the terminal methyl groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed); whereas for (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, the dodecyl chains are more regular and organized in the interlayer as the range of interactions present is the whole range of organic layers (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee).\u003c/p\u003e \u003cp\u003eWe further calculated the interaction energy of the interlayer ligand molecules according to Eq.\u0026nbsp;(5) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef). The binding energy between the two layers of ligands in the organic layer increases gradually with the growth of the main carbon chain of the ligand. For two ligands, t-BA and i-PA, because of the presence of branch chains, the number of methyl groups in contact with each other increases, so the binding energy between organic layers increases slightly. The interlayer binding energy of the organic layer of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e and (DDA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e were calculated to be \u0026minus;\u0026thinsp;1.85\u0026times;10\u003csup\u003e5\u003c/sup\u003e and \u0026minus;\u0026thinsp;2.43\u0026times;10\u003csup\u003e5\u003c/sup\u003e kcal/mol, respectively (Supplementary Table\u0026nbsp;6). The greater the negative value of the binding energy, the greater the energy required to separate the two layers, so the more negative the binding energy, the stronger the interlayer binding force. According to the general law of binding energy, when the size of ligand molecules reaches a certain level, cross-overlaps occur between the octahedral layers of perovskite. Due to the limitation of lattice and ligand chain size, the space of molecular chain activity decreases, the degree of interlayer disorder decreases, the degree of order increases, and the degree of distortion to the inorganic octahedron is small. The range of the interlayer van der Waals forces is extended, the energy of each particle in the crystal is lower\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh. Whereas the effect of van der Waals forces on perovskite crystals formed by small steric ligands is only at the end of the ligand chain, not the whole organic layer, and the inorganic octahedron is distorted to a greater extent\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg. Crystals tend to grow towards a certain surface with lower energy, and different interlayer stacking configurations lead to different surface energies, resulting in 1D rod crystals and 2D lamellar crystals\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e. The kinetic simulation shows that this law is also applicable to the aromatic hydrocarbon system (Supplementary Fig.\u0026nbsp;9, a \u0026ndash; n).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn order to investigate the crystal orientation of solution-grown 2D perovskite single crystals, we have tested the high-resolution physical phases, crystal plane spacing, selected area electron diffraction (SAED) patterns, and energy dispersive x-ray spectroscopy (EDS) of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals as well as (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals under an accelerating voltage of 200 kV. We have successfully revealed the lattice information of solution-grown 2D perovskite lattice information of single crystals. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, the continuous lattice stripes of the barred (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals and the corresponding Fourier transform information (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, bottom right) indicate that the lattice spacing of the barred single crystals is 8.05 \u0026Aring;, which corresponds to the (1 0 0) crystallographic plane. The (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e nanowire cross-section high-resolution microscopy is shown in Supplementary Fig.\u0026nbsp;10a. High-angle annular dark-field (HAADF) (Supplementary Fig.\u0026nbsp;10b) as well as energy spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb) show that the 2D perovskite did not undergo decomposition or physical phase changes during the transfer from the Si substrate to the conducting carbon film. For the lamellar (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals, the crystal face spacing in the high-resolution physical phase (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec) is 6.01 \u0026Aring;, which corresponds to the \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{(1}\\text{}\\stackrel{\\text{-}}{\\text{1}}\\:\\stackrel{\\text{-}}{\\text{1}}\\text{)}\\)\u003c/span\u003e\u003c/span\u003e crystal faces of (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e. Its diffraction pattern (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, bottom right) can be labeled \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{(1}\\text{}\\stackrel{\\text{-}}{\\text{1}}\\:\\stackrel{\\text{-}}{\\text{1}}\\text{)}\\)\u003c/span\u003e\u003c/span\u003e crystal diffraction spot, corresponding to the band axis [2 1 1]. EDS measurement shows that the major elements such as Pb and I are uniformly distributed in the nanosheets, forming a stable pure 2D perovskite phase (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed). The EDS mapping of element C could not show a clear profile due to the large amount of element C in the solvent CB, and the EDS spectrum of each element are shown in Supplementary Fig.\u0026nbsp;10, c and d. As shown by the lattice information presented by TEM, the rod-like (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals have the lowest surface energy at the (1 0 0) crystallographic plane, which extends along the (1 0 0) crystallographic plane when grown in solution and are stacked in the order of L\u003csup\u003e+\u003c/sup\u003e-I\u003csup\u003e\u0026minus;\u003c/sup\u003e-L\u003csup\u003e+\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee. Taken as a whole, after nucleation of 2D chalcogenides, the area of the inorganic octahedral layer remains at the scale of nucleation without growth. The new ligand and inorganic layers continue to stack in accordance with the (1 0 0) crystallographic direction, eventually forming 1D-scale rod-like single crystals, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef. For cubic phase chalcogenide cells, the surface energy of the (1 1 1) crystal surface is higher than that of the (1 0 0) crystal surface. Specifically, the surface energy of the (1 1 1) crystal faces of chalcocite is 0.93 J/m\u003csup\u003e2\u003c/sup\u003e, while the surface energy of the (1 0 0) crystal faces is 0.89 J/m\u003csup\u003e2 40,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Sheeted (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals grow in solution with the lowest (1 0 0) crystal surface energy due to the stacking conformation of the interlayer organic ligands, which breaks the cubic phase conformation resulting in the (1 0 0) crystal surface energy. In contrast, (PEA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e single crystals have the lowest (1 1 1) crystal surface energy. Thus, along the (1 1 1) crystal plane during crystal growth, the stacking follows the Pb\u003csup\u003e2+\u003c/sup\u003e-I\u003csup\u003e\u0026minus;\u003c/sup\u003e-Pb\u003csup\u003e2+\u003c/sup\u003e order, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg. As a whole, starting from the nucleation site, the inorganic octahedron undergoes an extended growth with the consequent insertion of long-chain ligands into the inorganic layer, leading to the formation of 2D-scale lamellar single crystals as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBy modeling the arrangement of organic layer ligands, we have gained a more accurate understanding of the interlayer interactions in layered 2D perovskites. The direction and magnitude of interlayer interactions determine the tendency of cell stacking, which further determines the crystalline form of 2D perovskites formed with different ligands. Our study explains the fundamental reasons affecting the morphology of 2D perovskite single crystals from a molecular perspective.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, we used 2D perovskite ligands with different molecular sizes and regulated the solution dynamics of precursors by the magnitude of their binding energies with solvent molecules to crystallize 2D perovskites by different mechanisms, finally realized the high-throughput preparation and characterization of 2D perovskite single crystals in the form of rods and flakes. We used in-situ UV-Vis absorption spectroscopy to investigate the crystallization mechanisms of 2D perovskites guided by ligands of different sizes. Contrary to previous reports, the process of 2D perovskite crystallization is not a pure solvent evaporation process. The binding energy between the ligand and the solvent is not negligible for the evaporation process. The fast rate at which solvent molecules in the precursor solution are detached from the overall solution system during evaporative crystallization leads to different changes in the solubility of the solution for PbI\u003csub\u003e2\u003c/sub\u003e as well as perovskite during crystallization. This further leads to a different order of arrival of PbI\u003csub\u003e2\u003c/sub\u003e as well as perovskites at supersaturation, and hence two different crystallization mechanisms. In the growth process after crystal nucleation, due to the different configurations of ligands of different sizes in the perovskite crystal lattice, with the increase of the ligand main chain length, the organic layers appear to be interspersed with each other in the configuration of ligand carbon chains, which further leads to a different range of interactions between the organic layers, resulting in different surface energy. The present study revisits the structure of 2D layered perovskite crystals and corrects the previous understanding of the arrangement of organic cations between layers. A conformational relationship between cell structure and crystal morphology is established, providing a basis for the modulation of layered 2D perovskite single crystals.\u003c/p\u003e \u003cp\u003eSolution kinetic modulation of perovskite precursor solutions is an effective strategy universally applicable to the morphology control of various types of layered organic-inorganic 2D perovskites. In this work, we derived a universal law of solute-solvent binding energy regulation of 2D perovskite crystallization, which is applicable to alkane and aromatic hydrocarbon ammonium salt ligands. The regulation of solute-solvent intermolecular binding energy can be realized through molecular polarity, the introduction of special functional groups, etc. The diversity of 2D perovskite ligands signifies that ligand templates are the most effective method for modulating the optoelectronic properties of 2D perovskites. The present study provides universal laws applicable to most of the ligands. Mechanistic studies on the regulation of crystallization processes and crystal morphology have allowed us to regulate the growth of single crystals on a molecular scale, which contributes to further reducing the size of 2D perovskite optoelectronic devices to the micron level using the solution method, providing a strong support for the large-scale application of 2D perovskites.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eMaterials\u003c/p\u003e\n\u003cp\u003eLead iodide (PbI\u003csub\u003e2\u003c/sub\u003e), tert-butylammonium iodide (t-BAI), iso-propylammonium iodide (i-PAI), propylammonium iodide (PAI), pentylammonium iodide (PentAI), hexylammonium iodide (HAI), octylammonium iodide (OAI), nonylammonium iodide (NonylAI), dodecylammonium iodide (DDAI), phenylammonium iodide (PhAI), benzylammonium iodide (PMAI), phenylpropylammonium iodide (PPAI), phenylbutylammonium iodide (PBAI) were purchased from Xi’an Yuri Solar Co., Ltd. N-butylammonium iodide (BAI) was purchased from TCI, and phenethylamine hydroiodide (PEAI) was purchased from Sigma-Aldrich. Chlorobenzene (CB) and 1, 2-dichlorobenzene (DCB), were purchased from Thermo Fisher Scientific Inc. Acetonitrile (ACN), \u0026nbsp;N, N-dimethylformamide (DMF) and Poly(methyl methacrylate) (PMMA, MW~35000) were purchased from Aladdin. Single-sided polished high-purity monocrystalline silicon wafers (crystal direction [100], size 15×15 mm, flatness \u0026lt; 1 μm) were purchased from LIGE SCIENCE. 15mm×15mm super white glass substrate purchased from Liaoning You Xuan New Energy Technology Co.\u003c/p\u003e\n\u003cp\u003eSolution-phase synthesis of pure 2D halide perovskite single crystal\u003c/p\u003e\n\u003cp\u003eIn this work, 14 pure two-dimensional perovskite micro-sized single crystals have been synthesized using quaternary solvents.\u003c/p\u003e\n\u003cp\u003e10 μmol PbI\u003csub\u003e2\u003c/sub\u003e was dissolved with 20 μmol LI (L= t-BA, i-PA, PA, BA, PentA, HA, OA, NonylA, DDA, PhA, PMA, PEA, PPA, PBA) in 2 mL of DMF/CB (1:1, v/v) co-solvent to obtain 5 mM of 2D perovskite stock solution. CB/ACN/DCB (9.5:0.1:0.01, v/v) co-solvent was prepared as a dilution solvent.\u003c/p\u003e\n\u003cp\u003eIn high-throughput experiments, the dilution factors of alkylamine ligands (t-BA, i-PA, PA, BA, PentA, HA, OA, NonylA, DDA) were set at 60, 120, 240, 480, 560, 640, and 960 times, while those of aromatic amine ligands (PhA, PMA, PEA, PPA, PBA) were set at 30, 60, 120, 180, 240, and 480 times. The Si substrates were preheated to 70 °C and then 50 to 100 μL of perovskite dilute solution was dropped onto them. The single crystal growth time was approximately 1 to 3 minutes. The entire process was carried out in a nitrogen-filled glove box. The high-throughput platform operating procedures are described in the SI.\u003c/p\u003e\n\u003cp\u003ePreparation of two-dimensional perovskite thin films\u003c/p\u003e\n\u003cp\u003eA 1M 2D perovskite precursor solution was prepared by dissolving PbI\u003csub\u003e2\u003c/sub\u003e with LI in DMF at 1:2 (mol: mol). The dissolved solution was filtered with a 0.22 μm PTFE hydrophobic filter tip to remove impurities. The clean and dry glass substrate was placed in a plasma oxygen microwave apparatus for 10 minutes for plasma treatment, with the aim of cleaning the organic matter on the glass substrate and improving the infiltration between the perovskite and the glass substrate. 50 μL of precursor solution was taken and spin-coated on the glass substrate, the speed of the homogenizer was 400 rpm and the spin-coating time was 30s. At the 20th s, 150 μL of CB was taken and added to the substrate in a rapid drop of 1 s or less. After spin-coating, the substrate was heated and annealed at 70 °C for 10 minutes.\u0026nbsp;The entire process was carried out in a nitrogen-filled glove box. The high-throughput platform operating procedures are described in the SI.\u003c/p\u003e\n\u003cp\u003ePreparation of TEM samples\u003c/p\u003e\n\u003cp\u003ePrepare a CB solution of 10 mg/mL PMMA. Filter the PMMA solution using a 0.22 μm hydrophobic PTFE filter tip. The PMMA solution was spin-coated onto the Si substrate. The speed of the homogenizer was 4000 rpm for 30 s. After the spin-coating was finished, the Si substrate was annealed at 70 ℃ for 10 min. 2D perovskite was subsequently grown on the PMMA-covered Si substrate. After the growth was completed, CB was used to dissolve the PMMA on the surface of the Si substrate. The Si substrate containing PMMA and perovskite was placed in a centrifuge tube with CB added to the tube over the Si sheet. The centrifuge tube was placed in an ultrasonic machine for 1h so that PMMA was dissolved by CB while perovskite single crystals were dispersed into CB. The dispersion was added several times dropwise onto a conductive carbon film (EMCN LG14-102 Transmission Electron Microscope Carbon Supported Membrane for Grid Carriers, 200 mesh). Eventually the perovskite single crystals were transferred to the conductive carbon film.\u003c/p\u003e\n\u003cp\u003eOptical imaging\u003c/p\u003e\n\u003cp\u003eBrightfield optical images were acquired using a Mshot metallurgical microscope MJ31. Brightness-adjustable white LEDs are used as light source with an Abbe spotting scope NA1.25 without filter. Brightfield image uniformity is obtained by the long working distance flat field objective L Plan 50X.\u003c/p\u003e\n\u003cp\u003ePhotoluminescence imaging\u003c/p\u003e\n\u003cp\u003eFluorescence field optical images were acquired by a Leica DM4000 automated microscope. The excitation light was modified to the blue band through the use of a filter, and all images were observed and photographed under a dark-field dry 100× objective.\u003c/p\u003e\n\u003cp\u003eSEM imaging\u003c/p\u003e\n\u003cp\u003eBackscatter SEM images were acquired using a Hitachi Regulus 8100 with accelerating voltages of 22 kV, 9 kV, 5 kV, and 15 kV.\u003c/p\u003e\n\u003cp\u003eTEM imaging and spectrum acquisition\u003c/p\u003e\n\u003cp\u003eTransmission electron microscopy (TEM) imaging, energy spectra, and diffraction patterns were acquired by a Talos F200X G2 from Thermo Fisher, USA. The accelerating voltage was 200 kV. STEM imaging and chemical energy spectra of the samples were acquired automatically by Thermo Scientific Maps software (enabled by Thermo Scientific Velox software).The main analysis was performed using GATAN GMS 3 software after the acquisition was completed. CaRIne Grystallography 3.1 was used to assist in the calculation of the crystallographic indices facet spacing and angle. The calibration of the diffraction patterns of the two perovskite samples is shown in\u0026nbsp;Supplementary\u0026nbsp;Table 8.\u003c/p\u003e\n\u003cp\u003eAbsorption spectrum and In-situ absorption spectrum\u003c/p\u003e\n\u003cp\u003eThe absorption spectra of two-dimensional perovskite thin films were collected by Ocean Optics QE65 Pro scientific grade spectrometer, and the light source was a combination of deuterium-tungsten halogen lamp DT-MINI-2-GS, and the analysis software was BiaoQi Spectrum Analysis Software. The in-situ absorption spectra were collected by an in-house built in-situ test system, in which the spectrometer was an Ocean Optics QE65 Pro scientific grade spectrometer, and the light source was an LS-3 visible-near-infrared halogen lamp with a Y-type optical fiber and a hot bench. The test is performed by preheating the substrate to 70 ℃. The white light fiber is incident perpendicular to the substrate and the solution is dripped from the side, and the test starts when the solution is dripped. The schematic diagram of in situ absorption spectroscopy test is shown in\u0026nbsp;Supplementary\u0026nbsp;Fig. 4.\u003c/p\u003e\n\u003cp\u003eSteady-state photoluminescence spectrum and Time-resolved photoluminescence spectroscopy\u003c/p\u003e\n\u003cp\u003eThe 2D perovskite film photoluminescence spectra and time-dependent photoluminescence spectra were collected by Pico Quant FluoTime300 fluorescence lifetime spectrometer. Excitation was performed using PDL 820 LDH-P-C-405 monochromatic picosecond laser diode head. The UV-red detector used a Hybrid PMT with a 425nm LP filter. TrPL measurements were made using a single photon counter ps TCSPC TimeHarp 260 P. Photoluminescence spectra of perovskite single crystals were obtained by focusing the excitation light with an Olympus BX43 microscope and focusing it onto individual single crystals. The PL spectral processing and TrPL data fitting software utilized was EasyTau, while the image capture and processing software was IDS Peak Cockpit. The fitting publics and procedures are illustrated in\u0026nbsp;Supplementary\u0026nbsp;Table 2.\u003c/p\u003e\n\u003cp\u003eMolecular dynamics and DFT simulations\u003c/p\u003e\n\u003cp\u003eFor the 2D perovskite solution and cell dynamics and DFT simulations, the solution and cell models were constructed mainly using Material Studio, and geometry optimization was carried out using density functionals. Based on this, the kinetic energy, electrostatic potential and energy band structure were calculated.\u003c/p\u003e\n\u003cp\u003eThe solution and crystal models were optimized using the COMPASSIII force field in Forcite and the GGA-PBE general function in CASTEP module. The cell model was used as a reference with the crystal information of (BA)\u003csub\u003e2\u003c/sub\u003ePbI\u003csub\u003e4\u003c/sub\u003e, and the spacer cations were replaced to obtain the rest of the crystal model. The kinetic simulation temperature was set to the experimental temperature (343 K), and binding energy calculations were performed using a script where all kinetic energies were averaged from the output. The molecular electrostatic potential was calculated using the DMol3 module with the GGA-PBE generalization. The 2D perovskite cell energy band structure is calculated using CASTEP module, GGA-PBE generalized function, which ensures the reliability and consistency of the calculation results. The detailed process and parameters of the simulation calculations are shown in SI.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data related to this study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by the National Natural Science Foundation of China (52394273 and 52373179), the TCL Science and Technology Innovation Fund (20242065). This work was partially supported by High Performance Computing Platform of South China University of Technology. We thank Dr. Yang at Shenzhen HUASUAN Tech. Co., Ltd., for insightful discussions and suggestions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJ.Q. synthesized and characterized two-dimensional perovskite single crystals and thin films. J.Q. and X.H performed the operation of the high-throughput platform. J.Q. and K.A performed the construction and use of the in-situ absorption test system. J.Q., L.L. and Y.M performed PL mapping testing and data collection. J.Q. performed molecular dynamics simulations, TEM characterization, and data analysis.J.Q., W.M. and N.L. wrote the manuscript; all authors read and revised the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary information\u0026nbsp;\u003c/strong\u003eis available for this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence and requests for materials\u0026nbsp;\u003c/strong\u003eshould be addressed to N.L.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHu, J., Odom, T. W. \u0026amp; Lieber, C. M. 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Here, we present a high-throughput experimental approach that integrates in-situ absorption spectroscopy and molecular dynamics simulations to systematically explore ligand-mediated crystallization dynamics in two-dimensional (2D) perovskite single crystals. We establish a clear correlation between structures of organic ligands and morphology of perovskite single crystals, showing that shorter ligands promote 1D nanowire formation, while longer ligands favor 2D nanosheet growth. In-situ spectroscopy and molecular simulations reveal that larger ligands induce conformational changes within the perovskite lattice, shifting crystallization from direct nucleation to lamellar exfoliation. Transmission electron microscopy (TEM) and density functional theory (DFT) calculations confirm that such transition is driven by enhanced solute\u0026ndash;solvent binding energy, which modulates the crystallization pathway of lead halide intermediates. Our findings provide valuable insights into solution-phase crystallization kinetics and offer a rational strategy for designing perovskite materials with tailored optoelectronic properties, facilitating their scalable integration into advanced semiconductor applications.\u003c/p\u003e","manuscriptTitle":"Regulating the microstructure of two-dimensional perovskite single-crystals via high-throughput experimentations","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-13 03:58:27","doi":"10.21203/rs.3.rs-6431736/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c6f48d9a-4494-451b-a227-9d0f0f4b464d","owner":[],"postedDate":"May 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":48209469,"name":"Physical sciences/Materials science/Nanoscale materials/Organic\u0026#x2013;inorganic nanostructures"},{"id":48209470,"name":"Physical sciences/Materials science/Nanoscale materials/Synthesis and processing"}],"tags":[],"updatedAt":"2025-12-30T08:34:45+00:00","versionOfRecord":{"articleIdentity":"rs-6431736","link":"https://doi.org/10.1038/s41467-025-66505-1","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-12-12 05:00:00","publishedOnDateReadable":"December 12th, 2025"},"versionCreatedAt":"2025-05-13 03:58:27","video":"","vorDoi":"10.1038/s41467-025-66505-1","vorDoiUrl":"https://doi.org/10.1038/s41467-025-66505-1","workflowStages":[]},"version":"v1","identity":"rs-6431736","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6431736","identity":"rs-6431736","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}