Single-Crystal Growth of Complex Non-fullerene Acceptor Molecules via Cocrystallization

Single-Crystal Growth of Complex Non-fullerene Acceptor Molecules via Cocrystallization | 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 Single-Crystal Growth of Complex Non-fullerene Acceptor Molecules via Cocrystallization Liang-Sheng Liao, Zhuhua Xu, Haocheng Tang, Wenxing Luo, Yuan Li, and 17 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7423857/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Feb, 2026 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract The growth of high-quality organic single crystals is essential for probing intrinsic optoelectronic properties and molecular packing especially in the field of organic photovoltaic (OPV). However, the conventional vapor- and liquid-phase methods fail for structurally complex molecules like the non-fullerene acceptor (NFA) Y6, where thermal instability and steric hindrance from branched sidechains inhibit crystallization. Here, we report an additive-directed cocrystallization strategy to grow Y6-additive cocrystals (YACs) with controlled morphology and tunable thicknesses (18 nm to 341 nm). The single-crystal structure is determined by Micro Electron Diffraction Technology at first time. Growth mechanism studies reveal that additive molecules mitigate sidechain interference by enabling configuration coupling of π-π stacking, yielding YACs with central length of 450 µm and largest lengths of 1.5 mm. Generalizability is demonstrated across 10 kinds of Y6-like NFAs with axial/central symmetry and 2 kinds of effective additives. Single-pixel image is realized based on photodetectors of YACs, meanwhile which exhibits a polarized and helical light response enabling by molecular ordered stacking. Most of YACs exhibit strong second harmonic generation (SHG) response. This work establishes a paradigm of single-crystal growth for structurally hindered complex molecules and provides a crystallographic basis for investigating the optoelectronic properties. Physical sciences/Materials science/Materials for optics/Nonlinear optics Physical sciences/Materials science/Materials for optics/Photonic crystals organic semiconductor molecules single crystal non-fullerene acceptor cocrystal engineering optoelectronics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Organic single crystals with molecularly ordered stacking exhibit superior multidimensional optoelectronic characteristics compared to their amorphous counterparts, demonstrating enhanced carriers’ mobility 1 , 2 , exceptional photo response characteristics 3 , and precise crystal structure determination and analysis 4 , exhibiting promising applications in micro/nano electronic devices 5 , and providing unique platforms for fundamental investigations of light-matter interactions 6 . The growth of organic single crystals primarily relies on liquid- and vapor-phase methods. The liquid-phase approach involves solvent evaporation and molecular supersaturation to induce crystallization. For example, Grzybowski and collaborators reported enhanced single crystal growth methods by polyelectrolyte solutions and shear flow, a process that occurs in a solvent 7 . The vapor-phase method involves high-temperature evaporation and deposition growth. For example, Thomas J. Kempa and collaborators reported the direct growth of high-quality metal-organic framework (MOF) single crystals via chemical vapor deposition (CVD) 8 . In fact, combined liquid- and vapor-phase methods have also been developed to synthesize 2D organic lateral heterojunction crystals 9 . However, for certain complex organic molecules designed to integrate multiple functions, conventional growth methods (including liquid- and vapor-phase) face challenges due to their low decomposition temperatures and long side chains which hinder crystallization. The Y6, a star non-fullerene acceptor (NFA) in photovoltaics, is derived from the TPBT central unit (TPBT refers to 2, 1, 3-benzothiadiazole (BT)-core-based fused-unit dithie-nothiophen [3.2-b]-pyrrolobenzothiadiazole) 10 . The intricate molecular structure of Y6 is designed to integrate multiple functionalities, including a narrow optical gap, high absorption coefficient, and good solubility in common solvents. Inspired by these advantages, numerous Y6-like NFAs have been reported, exhibiting exceptional optoelectronic properties and significantly advancing the field of organic photovoltaics (OPV) 11 . However, the optoelectronic potential of Y6 and Y6-like singles crystals remains unexplored due to challenges in growing high-quality and large-scale single crystals. The conventional methods face two limitations: (i) vapor-phase growth is hindered by thermal decomposition at elevated temperatures 12 , and (ii) liquid-phase growth is impeded by steric interference from long side chains 13 . Meanwhile, in organic photovoltaics (OPV), molecular stacking arrangements within the photoactive layer critically govern device performance metrics such as power conversion efficiency (PCE) 14 . This is because molecular stacking configurations directly modulate intermolecular charge-transfer pathways and kinetics. While current research predominantly relies on macroscopic characterization techniques—notably grazing-incidence wide-angle X-ray scattering (GIWAXS)—to probe ensemble-level ordering in thin films 15 . Crucially, a fundamental gap persists: the exact intermolecular packing geometries remain undetermined due to the absence of structural validation which requires suitable large-scale single crystals. To address this challenge, the cocrystal growth method—mostly used for pharmaceutical crystal engineering—has been employed to facilitate single crystal growth 16 . Cocrystals consist of two or more distinct molecular components, stabilized by supramolecular interactions such as hydrogen bonds and π-π stacking. Cocrystal growth method has emerged as a powerful strategy for growing high-quality and large-scale organic single crystals, particularly for structurally complex molecules such as Y6 and Y6-like NFAs. Key techniques such as solvent evaporation, melt crystallization, and mechanochemical synthesis are widely employed for cocrystallization. For instance, Dominik Cinčić and colleagues demonstrated the growth of cocrystals via halogen bonding to phosphorus, arsenic, and antimony, combining experimental observations with theoretical analysis to elucidate solid-state assembly mechanisms 17 . Xutang Tao and colleagues developed a micro-spacing in-air sublimation method for growing organic cocrystals, enabling precise morphology control and rapid crystal growth 18 , 19 . These successful examples demonstrate that cocrystal growth method is an effective strategy for obtaining organic single crystals with complex structures and multifunctional properties. Building on this approach, a novel strategy for growing Y6 and Y6-like NFAs was raised through engineered cocrystal design. The single crystal structure of Y6-additive cocrystals ((Y6-Additive Cocrystals, named YACs) is determined by Micro Electron Diffraction Technology at first time, forming two distinct morphologies: (ⅰ) elongated strip-like crystals with lengths up to ~ 450 µm (the largest length reaches 1.5 mm) and (ⅱ) ultrathin sheet-like crystals with monolayer thicknesses of ~ 18 nm (tunable from 18 nm to 341 nm). This strategy demonstrates broad applicability, as evidenced by successful extension to additional 10 Y6-like NFAs and 2 kinds of effective additives. Strikingly, the photodetector based on YACs demonstrates exceptional polarized and helical light response and realizing single-pixel imaging. The excellent second harmonic generation (SHG) responses appear on most of YACs. These findings establish a novel pathway for growing organic single crystals of complex molecular architectures and promote the optoelectrical properties research. Results and Discussion Cocrystal Growth Strategy for Non-fullerene Acceptors (NFAs) Y6 ((2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2",3’':4’,5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile)), a prominent NFA in organic photovoltaics, was selected as target molecule for cocrystal growth due to its optimal optical bandgap, low exciton binding energy, and high carriers’ mobility 20 ( Fig. 1 a ) . Using 4,8-Bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene as a structure-directing additive (Fig. 1 b), Y6-based cocrystals were grown successfully to further investigate their optoelectronic properties. This approach differs fundamentally from conventional organic crystal growth methods, as the additive actively participates in crystal formation through π-π stacking interactions at a precise 1:1 molar ratio with Y6 : additive, becoming a component of integral structure, and forming a new class of single crystals (Y6-Additive Cocrystals, named YACs). Conventional single crystal growth of organic materials primarily relies on vapor-phase and liquid-phase methods. However, these approaches face fundamental limitations for NFAs molecules used in photovoltaics, which typically exhibit low thermal decomposition temperatures and sterically hindered long side chains 10 . Vapor-phase growth is precluded by thermal instability, while liquid-phase growth is impeded by disordered molecular packing caused by side chain interference during solvent evaporation and supersaturation. To overcome these challenges, cocrystal growth strategy was developed by introducing a structure-directing additive. This approach establishes new configuration coupling interactions while simultaneously mitigating the hindrance effects of side chains on molecular ordering (Fig. 1 c). Y6 belongs to the A-D-A'-D-A class of NFAs, featuring a fused-ring central core with alternating electron-donating (D) and electron-accepting (A/A') units 10 . While the extended π-conjugated system enables multifunctional integration, several intrinsic molecular characteristics impede crystal growth: (ⅰ) bulky side chains that enhance solubility but disrupt ordered packing, and (ⅱ) limited thermal stability (decomposition temperature ~ 300°C). These factors collectively preclude from the formation of high-quality and large-scale single crystals via thermal evaporation methods. The extended alkyl side chains in Y6 introduce significant steric hindrance, disrupting the π-π stacking and long-range molecular ordering required for single crystals growth via liquid-phase crystallization. The 4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene was selected as additive for cocrystallization due to its dual functionality: (ⅰ) a planar benzo ring in site of core that facilitates π-π stacking interactions with Y6 molecule, and (ⅱ) suitable physical state such as oiliness to provide suitable condition of molecular self-assembly. Both Y6 and additive demonstrate excellent mutual solubility in chloroform (CF), forming a homogeneous precursor solution essential for controlled cocrystal growth. ( See section of materials and Methods ). The growth results demonstrate that the additive is indispensable for cocrystal formation, as confirmed by control experiments (Fig. S1 ). Upon determining the crystal structure, it's unexpectedly discovered that the additive actively participates in the crystal lattice, forming a 1:1 cocrystal (YACs) with Y6. This cocrystallization behavior fundamentally differs from conventional organic crystal growth methods. Single crystal structure analysis reveals that the additive serves as a bridging template, directing the ordered stacking of Y6 molecules through a newly formed configuration coupling of Y6-additive π-π stacking. Simultaneously, the additive's participation creates expanded intermolecular spacing which accommodates Y6's long side chains while reducing their steric hindrance effects. Furthermore, the additive's oily nature at both room temperature and 80°C (Growth temperature) constitutes another critical factor, as it provides an optimal dynamic environment that enables Y6 molecules to freely migrate and self-assemble, ultimately facilitating YACs formation. Structural and Morphological Characterizations of YACs Polarized optical microscopy reveals well-defined striated YACs grown on SiO 2 /Si substrates, exhibiting chromatic variations due to anisotropic light scattering 21 (Fig. 2 a). The observed smooth surfaces and straight edges indicate high crystalline quality, with a measured thickness of 327 nm (Fig. 2 b). Statistical analysis shows the length distribution centers at approximately 450 µm (Lorentzian fitting), while the maximum observed length extends to 1500 µm (Fig. 2 c). Additionally, theoretical X-ray Diffraction (XRD) spectra derived from the YACs via analog computation match the experimental data, with the strong (100) diffraction peak indicating preferred orientation along the (100) plane and high crystallinity. (Fig. 2 d). The high-density YACs distribution and regularly oriented growth radiating from a single nucleation point to multiple directions observed in polarized microscopy images demonstrate exceptionally high growth productivity ( See sample movie 1 in Supplementary Materials ). The morphology and shape diversity of YACs can be precisely controlled by adjusting the Y6-to-additive ratio and precursor concentration. The primary morphological evolution follows two main trends: (ⅰ) Increasing the additive proportion transforms shape of YACs from sheet-like to strip-like forms, and (ⅱ) decreasing the precursor concentration reduces the overall thickness (Fig. S2-18) . The YACs’ shapes predominantly manifest as either two-dimensional sheets or one-dimensional strips. The sheets exhibit nm-level thickness through layer-by-layer growth (18 nm to 341 nm), with each monolayer measuring approximately 2.0 nm in thickness. The YACs structure was determined using Micro Electron Diffraction Technology 22 – 24 ( Fig. S20-25, Table S1 -6 ). Data visualization was performed using the REDp program, and processing was conducted using DiffProAnalyze software (developed by ReadCrystal Tech Inc.). The single-crystal structure was determined, belonging to the P \(\:\stackrel{-}{1}\) space group. The diffraction pattern is consistent with the extinction rules of P \(\:\stackrel{-}{1}\) , permitting all reflections without restrictions on h, k, or l indices. Any combination of h, k, and l (positive, negative, or zero) can give rise to a reflection, provided it is structurally feasible based on the crystal's atomic arrangement (Figs. 2 e to 2 i). The analysis confirms that unit lattice parameters of YACs are a = 14.640(3) Å, b = 19.170(4) Å, c = 19.730(4) Å, and angles α (∠ boc ) = 75.00(3)°, β (∠ aoc ) = 70.00(3)°, γ (∠ aob ) = 87.00(3)° ( CIF information of YACs in Supplementary Material ). Y6 and the additive form π-π stacking between the terminal benzene ring attached two fluorine atoms of Y6 and the centrally located benzene ring of the additive, and the distance of π-π stacking is 3.446 Å (Fig. 2 j and 2 k). The YACs possesses an inversion center as its symmetry element (Fig. 2 l). The Y6 and the additive couple to form a basic unit, which then stacks in a back-to-back, step-like fashion ( Fig. 2 m and 2 n ). Growth Mechanism of YACs Our observations reveal that stick YACs exhibit radial growth originating from a central nucleation point, with crystalline domains expanding uniformly in all directions. This growth behavior was characterized through in situ optical microscopy during thermal annealing at 80°C, capturing the complete crystallization process from nucleation (t = 0 s) to crystal development (t = 1040 s) (Fig. 3 a). The time-resolved imaging demonstrates distinct stages of nucleation initiation followed by directional crystal growth. ( See growth movie 2 in Supplementary Material ). In situ imaging identifies molecular aggregation sites as nucleation centers, with both AFM and SEM images revealing subsequent crystal growth emanating from these nucleation sites, and growing layer by layer (Fig. 3 b and Fig. S19 ). Other shape including lamellar and foliate YACs also exhibit radial growth patterns, expanding outward from a single nucleation center (Fig. 3 c) as 1:1 cocrystallization of Y6 and additive molecule growth (Fig. 3 d). To elucidate the Y6-additive interaction mechanism, the additive's influence was investigated systematically through both chemical structure and physical state analyses. A series of derivative additives containing isolated functional groups from the parent additive were designed for controlled experiments, enabling precise determination of each functional group's role. The primary additive was structurally deconvoluted into two key components: 3-methoxyheptane, benzo[1,2-b:4,5-b']dithiophene, and further fragmented into its constituent basic units (benzene, thiophene, and thianaphthene). This systematic fragmentation enabled controlled investigation of individual functional group contributions through comparative experiments. Notably, the extended alkyl side chains were found to substantially enhance molecular solubility and facilitate solid-to-liquid phase transitions in small-molecule systems 25 . Control experiments reveal distinct growth outcomes: (ⅰ) unable to crystallize occurs with benzene, thiophene, and 3-methoxyheptane (all liquids, fast volatility), whereas (ⅱ) small crystal grains form with benzo[1,2-b:4,5-b′]dithiophene and thianaphthene (both solids) (Fig. 3 e). These results demonstrate that effective cocrystal growth requires effective packing sites and optimal physical state. ( Table S7 ) The YACs growth is influenced by physical state of the parent additive and its functional groups critically. The viscous liquid phase (oiliness) of the parent additive creates an optimal environment for crystallization, as evidenced by the growth of YACs under additive-rich conditions ( Fig. S6 ). In contrast, fast-volatility additives fail to support crystallization due to rapid evaporation, which prevents sufficient time for molecular self-assembly. Based on the structural analysis of YACs with molecular dynamics simulations, π-π stacking interactions are identified as the key determinant for growth. The computational results reveal that π-π stacking occurs between the terminal fluorinated benzene ring of Y6 and the central benzene ring of the additive 26 , leading to self-assembly after 20 ns, which is consistent with the observed YACs structure (Fig. 3 f, Fig. S26-32 ). Generalized growth approach of YACs The versatility of this approach is demonstrated through successful YACs growth on diverse substrates, including quartz, glass, ITO-coated glass, polyimide (PI), and aluminum (Al) foil, indicating its potential for device integration and scalable fabrication (Fig. 4 a, Fig. S33 ). The YACs morphology and growth behavior remain consistent across substrates, predominantly forming stick-like and sheet-like structures similar to those observed on SiO 2 /Si substrate, demonstrating excellent substrate compatibility. Notably, YACs also grow conformally along the inner walls of capillary tubes with diameters of 1.12 mm and 0.50 mm, maintaining their crystalline structure even in curved configurations (Fig. 4 b). This behavior demonstrates two key advantages: (i) the ability to grow in confined micro-spaces, and (ii) inherent mechanical flexibility of YACs 27 ( Fig. S34 ). Aligned growth of YACs in parallel arrangements is achieved on Si substrates patterned with parallel nanograting, which direct precursor distribution via micro/nanostructure confinement (Fig. 4 c, Fig. S35 ). In addition, the light-controlled growth of YACs has been realized. The experiment results reveal that YACs selectively grow in non-illuminated regions while remaining absent in light-exposed (< about 900 nm which precisely aligns with the edge of Y6 absorption spectrum) areas ( Fig. S36 and S37 ). The controlled growth of patterned arrays can be achieved using a light-masking, where a specific optical array is projected to define the growth pattern. In this process, the illuminated regions correspond to the non-growth zones. To systematically evaluate the general applicability of additive-directed crystallization for NFAs, this growth method was successfully extended to multiple material systems, including: A-D-A’-D-A type of axial symmetry (COTIC-4F, Y6-BO, BTP-eC9, Y7) (Fig. 4 d and Fig. S38 ) and D-A’-D type of central symmetry (ITIC, ITIC-M, ITIC-4F,Y7 ITIC-4Cl, ITIC-Th, IDIC) (Fig. 4 e and Fig. S39 ), which have significantly propelled advancements in the OPV field ( Table S7 ). These crystals exhibit varied morphologies (blocks, strips, and sheets), attributed to distinct molecular packing configurations and intermolecular coupling effects 28 , 29 . According to the above-mentioned principle for the selection of additives, 2,6-dibromo-4,8-bis[(2-butyl-n-octyl)oxy]benzo[1,2-b:4,5-b']dithiophene (A1) and benzo[1,2-b:4,5-b']dithiophene-4,8-dione (A2) are also selected as additives for YACs growth under identical conditions. The A1 exhibits a viscous liquid state at both room temperature and 80°C, and A2 transforms from solid at room temperature to viscous liquid state at 80°C. Both of them have suitable packing sites. The growth results indicate high-quality single crystal of YACs (Fig. 4 f, 4 g and Fig. S40 ). Optoelectronic Performance of YACs The optoelectronic properties of Y6 and YACs were focused on absorption, photoluminescence (PL) spectra, and polarized optoelectronic response. Due to the localized nature of electronic density in organic molecules 30 – 32 , their optoelectronic characteristics at the molecular level remain largely unaffected after crystallization. However, a key consideration here is whether the introduction of the additive in YACs modifies the electronic distribution through charge transfer interactions between the two molecules 33 . The nearly identical absorption and photoluminescence (PL) spectra of Y6 and YACs suggest minimal changes between the amorphous and crystal states ( Fig. S41a and b ). As a hallmark property of organic crystalline, the polarized optoelectronic response has been extensively studied and holds significant promise for applications in multidimensional light detection technologies 34 . The angular-dependent PL spectra were measured under linearly polarized excitation at room temperature. The PL peak intensity exhibits a pronounced angular dependence, demonstrating clear dichroic behavior characteristic of anisotropic optical transitions ( Fig. S41c and d ). To investigate the optoelectronic properties of YACs (Based on Y6), the photodetector was fabricated by growing the YACs directly on Au interdigitated electrodes (Fig. 5 a) exhibiting efficient photo response characteristics (Fig. 5 b). Meanwhile, the angular-dependent photocurrent measurements under 638 nm polarized light demonstrate strong dichroic behavior originated from the well-aligned molecular orientation within the YACs ( Fig. S42a ). Furthermore, the same device exhibits strong optical rotation responses under both left- and right-handed circularly polarized light, highlighting its potential for polarization-sensitive optoelectronics ( Fig. S42b ). Finally, practical application was demonstrated by integrating the device into a single-pixel imaging test system with mask ( Fig. S43a and b ), successfully reconstructing a high-contrast lotus pattern (Fig. 5 c). Organic nonlinear optical (NLO) materials offer advantages like low cost, and ease of synthesis over inorganic counterparts, enabling applications in wavelength conversion and telecom 35 . Second harmonic generation (SHG), a key NLO process doubling incident light frequency, provides efficient frequency conversion and high-power laser generation 36 . Here, Second-order nonlinear optical responses in YACs were characterized using back-reflection SHG measurements. 37 (Fig. 5 d). A strong emission peak appears at 515 nm from the YACs (Based on IT-M) sample when excited by a 1030 nm femtosecond laser (Fig. 5 e). A plot of SHG intensity versus pump power yields a slope of 2.08 ± 0.15 on a log-log scale, confirming the characteristic quadratic dependence of high-quality SHG in YACs (Fig. 5 f). The SHG response also exhibits polarization dependence at 1030 nm and 9.6 µW, attributed to the structural anisotropy of YACs (Fig. 5 g ) . The polarization-dependent SHG response, characterized by four peaks (two strong and two weak) spaced 90° apart, indicates a multicomponent nature of SHG process from YACs. We analyzed this may be related to the crystal structure of organic co-crystals, particularly single crystals composed of two molecules coupling 38 . Strict frequency doubling is observed across a series of fundamental wavelengths from 994 nm to 1030 nm, generating SHG signals from 497 nm to 515 nm. The SHG intensity decreases with blue-shifting fundamental wavelength, due to weakening by intrinsic optical absorption 39 (Fig. 5 h). SHG measurements conducted on all YACs at 1030 nm and 4.6 µW indicate that YACs exhibit standard SHG responses (Fig. 5 i). While non-centrosymmetric crystal structure is a necessary condition for SHG, we note that YACs based on Y6—which belongs to the centrosymmetric space group P \(\:\stackrel{-}{1}\) with centrosymmetric properties—also exhibit strong SHG. According to previous studies, the local disorder in molecular orientation caused by long side chains 40 , along with charge distortion and local dipole chains induced by charge transfer 41 , can break the centrosymmetric properties of YACs, thereby enabling SHG. This proof-of-concept experiment validates the feasibility of YACs-based devices for future optoelectrical technologies. Conclusion In summary, we have developed a generalizable additive-directed cocrystal strategy to grow YACs-a previously unattainable feat due to steric hindrance from long side chains. Structural characterization confirms the formation of YACs in the triclinic P \(\:\stackrel{-}{1}\) space group, where additive molecules enable cocrystallization through π-π stacking via configuration coupling. This approach provides unprecedented control over YACs morphology (stick/sheet) and dimensions (18 nm-341 nm thick; central and longest lengths to 450 µm and 1.5 mm). Through pattern summarization, this growth method can be extended to single-crystal growth of ten NFA molecules and the selection of two novel additives. The optoelectrical properties were focused on photodetectors and SHG response. The photodetector based on YACs (Y6) achieve exceptional polarized, optical rotation light sensitivity, and single-pixel imaging. Most of YACs exhibit strong SHG response including Polarization dependence. Our work establishes a paradigm to single crystal growth for structurally complex functional NFAs molecule, unlocking their potential for advanced optoelectronic applications. Materials and Methods Materials : ITIC-TH, IDIC, Y7, Y6, IT-4CL, ITIC, Y6-BO, COTIC-4F, L8-BO, IT-M, BTP-EC9, IT-4F purchased from Shanghai Weizhu Chemical Technology Co., Ltd., purity 99%. 2,6-Dibromo-4,8-bis[(2-butyl-n-octyl)oxy]benzo[1,2-b:4,5-b']dithiophene (A1) purchased from Shanghai Hao Hong Biological Pharmaceutical Technology Co., LTD., purity ≥ 97%. Benzo[1,2-b:4,5-b']dithiophene-4,8-dione (A2) was purchased from Shanghai Maclin Biochemical Technology Co., LTD. Purity 98%., purity ≥ 99%. Trichloromethane (also known as chloroform, CF, CAS No. 67-66-3, formula: CHCl₃, Analyzable pure) purchased from Shanghai Lingfeng Chemical Reagent Co., LTD.,) Growth methods : Solution preparation: Dissolve 4 mg of the target material (or 3 mg of Y6 in the light control growth test) in 100 µL chloroform and add different volumes of additives The solution was dissolved by magnetic stirring at a speed of 1200 rpm. Spin coating films: Take 10 µL solution and add it to pre-treated SiO 2 /Si substrate (or quartz, glass, grating and other substrates), spin coating for 60 seconds at 4000 rpm to form a uniform film. Solvent annealing: The coated substrate is placed on a constant temperature table at 80℃ to promote solvent volatilization and crystal self-assembly. After growth completely, rinse with ethanol to get clean YACs. Y6 light-controlled growth: After spin coating, the substrate was placed on the heated microscope stage (80℃), and the light source of the microscope was used for local irradiation for 3 hours, and the crystal morphology was observed immediately after the heating was turned off. Y6 multi-substrate adaptability test: Repeat the above steps on quartz, glass, grating and capillary surfaces (capillary tubes are sucked into the inner tube wall by capillary effect and heated directly). YACs growth based on different additives: Y6 and additives A1, A2 were dissolved in chloroform (3 mg/mL) at a mass ratio of 1:1, stirred at room temperature for 2 hours and then spin coated on SiO₂/Si substrate (4000 rpm, 60 seconds). After solvent annealing at 80 ℃ for 18 hours, high-quality single crystals were formed and observed under the microscope with different magnifications. Characterizations and tests : The PL spectra were carried on the Horiba LabRAM HR800. The absorption spectra were carried on the Nicolet is 50. AFM images were carried on Bruker Dimension Ico, Optical and polarized images were carried on OLYMPUS microscope, SEM images were carried on HITACHI SU8010, XRD spectra were carried on D8 Advance. Electrical and photoelectric properties were measured by using a dual-channel digital source meter (Keithley 6482) on a probe station under ambient conditions. The devices were tested with laser sources at 520, 638. Incident light was modulated with a function generator (DG822, RIGOL, 25MHz) combined with light-controlled system of polarized light and optical rotation. SHG measurements were performed using a custom reflection-mode microscope. A tunable femtosecond laser (pulse width: 200 fs; repetition rate: 100 kHz) served as the excitation source. Polarized excitation was achieved using a 1030 nm half-wave plate. Emitted signals were collected via a multimode fiber coupled to a spectrometer. All experiments were conducted at room temperature. Declarations Data availability : Additional data related to this paper may be requested from the corresponding author. Acknowledgments: We thank the ReadCrystal Biotechnology for the organic single crystal test and analysis. This work is supported by National Natural Science Foundation of China: No. 12304334, 12104110, 62205084, 62475057. Author contributions: Conceptualization: Zhuhua Xu；Methodology: Zhuhua Xu；Investigation: Zhuhua Xu, Haochen Tan, Wenxing Luo, Yuang Li；Visualization: Zhuhua Xu，Qiang Lv, Linqing Qiu, Qingsong Tao, Sheng Ni, Chengcheng Wu, Zhanpeng Wang, Zilong Ye, Rui Zhang, Ning Zhou, Changlong Liu, Jing Li, Hongxing Dong, Mingjie Liu；Supervision: Hongxing Dong, Mingjie Liu, Xue-Dong Wang, Zheng Liu, Liang-Sheng Liao, Jingzhou Li, Long Zhang; Writing—original draft: Zhuhua Xu, Writing—review & editing: Zhuhua Xu, Xue-Dong Wang, Zheng Liu, Liang-Sheng Liao, Jingzhou Li. Competing interests : All other authors declare they have no competing interests. Supplementary Information: All supplementary information in the paper is present in Supplementary Materials. References Sokolov AN et al (2011) From computational discovery to experimental characterization of a high hole mobility organic crystal. 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Supplementary Files SupportingInformationYACsY6.cif Dataset 1 SupportingInformationMovie1LargescalesampleofYACs.mp4 Supporting Information-Movie 1-Large-scale sample of YACs SupportingInformationMovie2GrowthprocessofYACs.mp4 Supporting Information-Movie 2-Growth process of YACs SupportingInformationNM.docx Supporting Information Cite Share Download PDF Status: Published Journal Publication published 25 Feb, 2026 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. We do this by developing innovative software and high quality services for the global research community. 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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-7423857","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":513462472,"identity":"a376e9ca-d7f9-4413-b841-38d4b1a9a97e","order_by":0,"name":"Liang-Sheng 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Fine Mechanics","correspondingAuthor":false,"prefix":"","firstName":"Hongxing","middleName":"","lastName":"Dong","suffix":""},{"id":513462492,"identity":"6195ec0d-1475-44cc-9762-9cd0ac80c43e","order_by":20,"name":"Long Zhang","email":"","orcid":"","institution":"Shanghai Institute of Optics and Fine Mechanics","correspondingAuthor":false,"prefix":"","firstName":"Long","middleName":"","lastName":"Zhang","suffix":""},{"id":513462493,"identity":"0fc2f2bb-1557-4784-98f8-5fb2f4fa6783","order_by":21,"name":"Jingzhou Li","email":"","orcid":"https://orcid.org/0000-0002-6428-3172","institution":"Hangzhou Institute for Advanced Study, University of Chinese Academy of Science, Hangzhou 310024, China","correspondingAuthor":false,"prefix":"","firstName":"Jingzhou","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-08-21 08:20:42","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7423857/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7423857/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-026-69997-7","type":"published","date":"2026-02-25T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":91199093,"identity":"9d5ce56f-a369-4644-8207-4d0b70fb6632","added_by":"auto","created_at":"2025-09-12 15:18:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":603748,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic illustration of cocrystal growth strategy for non-fullerene acceptors (NFAs). \u003c/strong\u003eThe molecular structures of Y6 (a) and additive (b).\u003cstrong\u003e \u003c/strong\u003eConventional vapor- and liquid-phase growth methods prove ineffective for Y6 and Y6-like NFA due to their low decomposition temperatures and steric hindrance from long side chains. By employing additive, cocrystal is grown successfully through the establishment of novel configuration coupling interactions, enabling the growth of high-quality organic single crystals (c).\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/1be3555a7d212bc93a0c63c9.png"},{"id":91200484,"identity":"4cca0599-2208-441b-9495-09df8bc9405c","added_by":"auto","created_at":"2025-09-12 15:26:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":594215,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStructural and morphological characterizations of YACs.\u003c/strong\u003e (a) Polarized optical microscopy images of YACs with corresponding enlarged optical and AFM images (b). (c) Statistical length distribution of YACs with Lorentzian fitting. Inset: Schematic illustrating the length measurement methodology. (d) Comparison of experimental and simulated XRD patterns for YACs. (e) TEM image of YACs. (f-i) 3D reciprocal lattice of YACs. (j-k) Stacking mode of Y6 and the additive. (l) Unit cell structure of YACs and corresponding schematic diagram (m). (n) Multi-period crystal schematic diagram of YACs.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/521789c0c4c9297e1bb68a5f.png"},{"id":91199097,"identity":"1419f7b2-3a0e-46b9-b81b-51f7a4d2b498","added_by":"auto","created_at":"2025-09-12 15:18:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":788344,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGrowth mechanism of YACs. \u003c/strong\u003e(a) Time-resolved optical microscopy images tracking YACs growth from 0 s to 1040 s. (b) The AFM image of YACs’ surface. (c) Radial growth pattern of stick YACs from a central nucleation point, with inset showing the 1:1 co-crystallization of Y6 and additive molecules (d). (e) Control experiments evaluating crystal growth with fragmented additive derivatives, demonstrating that only the original additive, benzo[1,2-b:4,5-b']dithiophene and thianaphthene promote crystal growth. (f) Molecular dynamics simulation (Gromacs 2021) shows that π-π stacking appeared between the fluorinated terminal benzene ring of Y6 and the central benzene ring of the additive and driving self-assembly (20 ns).\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/5eb7f33aec3cffd0d47a215f.png"},{"id":91200485,"identity":"c0e543d5-1ded-4033-a119-080b053266ea","added_by":"auto","created_at":"2025-09-12 15:26:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":939970,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGeneralized growth approach of YACs.\u003c/strong\u003e (a) Universal substrate compatibility demonstrated on quartz, glass, ITO, polyimide (PI), and aluminum (Al) foil. (b) Confined growth within capillary tubes. (c) Directed assembly on Si substrates with parallel nanograting. General growth to other NFAs, including typical axially symmetric (A-D-A’-D-A) for COTIC-4F, Y6-BO, BTP-eC9, Y7 (d) and centrally symmetric (D-A’-D) for ITIC, ITIC-M, ITIC-4F, ITIC-4Cl, ITIC-Th, IDIC (e). Co-crystal growth of Y6 molecules via novel additives A1 (f) and A2 (g).\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/8209112e4a19a0362832ed99.png"},{"id":91199099,"identity":"1555102c-88db-4cc0-81f3-19d34d631561","added_by":"auto","created_at":"2025-09-12 15:18:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":323371,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptoelectronic Performance of YACs.\u003c/strong\u003e (a) Optical microscopy images of YACs grown on interdigitated Au electrodes and schematic of the fabricated device. (b) Current-voltage (\u003cem\u003eI-V\u003c/em\u003e) characteristics under 638 nm illumination. (c) The lotus pattern tested by integrating the device into a single-pixel imaging test system with mask. (d) SHG measurement geometry. (e) Pump-power-dependent SHG intensity with linear fit (slope = 2.08 ± 0.15). (f) Polarization-dependent SHG showing high anisotropy. (g) Wavelength-dependent SHG at 8 nW pump power. (h) SHG response in selected YACs.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/0d4eed012bbccb541b8409ff.png"},{"id":106073361,"identity":"3a948bdb-9abf-45d2-b4e6-5f99b6ba8233","added_by":"auto","created_at":"2026-04-03 07:06:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4147373,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/07471723-d5aa-4e8d-a884-4256145ea0e4.pdf"},{"id":91199096,"identity":"df2ce505-a7dc-46a3-bb36-d967de8f595b","added_by":"auto","created_at":"2025-09-12 15:18:43","extension":"cif","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":780371,"visible":true,"origin":"","legend":"Dataset 1","description":"","filename":"SupportingInformationYACsY6.cif","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/63dc190fcd2e431f60f4374e.cif"},{"id":91199102,"identity":"fc437dc0-b013-4416-8072-1b0670f13c14","added_by":"auto","created_at":"2025-09-12 15:18:43","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":4807086,"visible":true,"origin":"","legend":"Supporting Information-Movie 1-Large-scale sample of YACs","description":"","filename":"SupportingInformationMovie1LargescalesampleofYACs.mp4","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/e31d4de13fd718b839f724a6.mp4"},{"id":91199113,"identity":"7a6ba0c0-4ac0-4096-afc1-fa69aec648f0","added_by":"auto","created_at":"2025-09-12 15:18:43","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":10210109,"visible":true,"origin":"","legend":"Supporting Information-Movie 2-Growth process of YACs","description":"","filename":"SupportingInformationMovie2GrowthprocessofYACs.mp4","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/ca7caf1d7cab521836744c52.mp4"},{"id":91199117,"identity":"8a71fe07-c817-404b-b970-5e528dcf489a","added_by":"auto","created_at":"2025-09-12 15:18:45","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":107288668,"visible":true,"origin":"","legend":"Supporting Information","description":"","filename":"SupportingInformationNM.docx","url":"https://assets-eu.researchsquare.com/files/rs-7423857/v1/d52844141c5f51279aafc2c8.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Single-Crystal Growth of Complex Non-fullerene Acceptor Molecules via Cocrystallization","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOrganic single crystals with molecularly ordered stacking exhibit superior multidimensional optoelectronic characteristics compared to their amorphous counterparts, demonstrating enhanced carriers\u0026rsquo; mobility\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, exceptional photo response characteristics\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, and precise crystal structure determination and analysis\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, exhibiting promising applications in micro/nano electronic devices\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e, and providing unique platforms for fundamental investigations of light-matter interactions\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. The growth of organic single crystals primarily relies on liquid- and vapor-phase methods. The liquid-phase approach involves solvent evaporation and molecular supersaturation to induce crystallization. For example, Grzybowski and collaborators reported enhanced single crystal growth methods by polyelectrolyte solutions and shear flow, a process that occurs in a solvent\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The vapor-phase method involves high-temperature evaporation and deposition growth. For example, Thomas J. Kempa and collaborators reported the direct growth of high-quality metal-organic framework (MOF) single crystals via chemical vapor deposition (CVD)\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. In fact, combined liquid- and vapor-phase methods have also been developed to synthesize 2D organic lateral heterojunction crystals\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eHowever, for certain complex organic molecules designed to integrate multiple functions, conventional growth methods (including liquid- and vapor-phase) face challenges due to their low decomposition temperatures and long side chains which hinder crystallization. The Y6, a star non-fullerene acceptor (NFA) in photovoltaics, is derived from the TPBT central unit (TPBT refers to 2, 1, 3-benzothiadiazole (BT)-core-based fused-unit dithie-nothiophen [3.2-b]-pyrrolobenzothiadiazole)\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The intricate molecular structure of Y6 is designed to integrate multiple functionalities, including a narrow optical gap, high absorption coefficient, and good solubility in common solvents. Inspired by these advantages, numerous Y6-like NFAs have been reported, exhibiting exceptional optoelectronic properties and significantly advancing the field of organic photovoltaics (OPV)\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. However, the optoelectronic potential of Y6 and Y6-like singles crystals remains unexplored due to challenges in growing high-quality and large-scale single crystals. The conventional methods face two limitations: (i) vapor-phase growth is hindered by thermal decomposition at elevated temperatures\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, and (ii) liquid-phase growth is impeded by steric interference from long side chains\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eMeanwhile, in organic photovoltaics (OPV), molecular stacking arrangements within the photoactive layer critically govern device performance metrics such as power conversion efficiency (PCE)\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. This is because molecular stacking configurations directly modulate intermolecular charge-transfer pathways and kinetics. While current research predominantly relies on macroscopic characterization techniques\u0026mdash;notably grazing-incidence wide-angle X-ray scattering (GIWAXS)\u0026mdash;to probe ensemble-level ordering in thin films\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Crucially, a fundamental gap persists: the exact intermolecular packing geometries remain undetermined due to the absence of structural validation which requires suitable large-scale single crystals.\u003c/p\u003e\u003cp\u003eTo address this challenge, the cocrystal growth method\u0026mdash;mostly used for pharmaceutical crystal engineering\u0026mdash;has been employed to facilitate single crystal growth\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Cocrystals consist of two or more distinct molecular components, stabilized by supramolecular interactions such as hydrogen bonds and π-π stacking. Cocrystal growth method has emerged as a powerful strategy for growing high-quality and large-scale organic single crystals, particularly for structurally complex molecules such as Y6 and Y6-like NFAs. Key techniques such as solvent evaporation, melt crystallization, and mechanochemical synthesis are widely employed for cocrystallization. For instance, Dominik Cinčić and colleagues demonstrated the growth of cocrystals via halogen bonding to phosphorus, arsenic, and antimony, combining experimental observations with theoretical analysis to elucidate solid-state assembly mechanisms\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Xutang Tao and colleagues developed a micro-spacing in-air sublimation method for growing organic cocrystals, enabling precise morphology control and rapid crystal growth\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThese successful examples demonstrate that cocrystal growth method is an effective strategy for obtaining organic single crystals with complex structures and multifunctional properties. Building on this approach, a novel strategy for growing Y6 and Y6-like NFAs was raised through engineered cocrystal design. The single crystal structure of Y6-additive cocrystals ((Y6-Additive Cocrystals, named YACs) is determined by Micro Electron Diffraction Technology at first time, forming two distinct morphologies: (ⅰ) elongated strip-like crystals with lengths up to ~\u0026thinsp;450 \u0026micro;m (the largest length reaches 1.5 mm) and (ⅱ) ultrathin sheet-like crystals with monolayer thicknesses of ~\u0026thinsp;18 nm (tunable from 18 nm to 341 nm). This strategy demonstrates broad applicability, as evidenced by successful extension to additional 10 Y6-like NFAs and 2 kinds of effective additives. Strikingly, the photodetector based on YACs demonstrates exceptional polarized and helical light response and realizing single-pixel imaging. The excellent second harmonic generation (SHG) responses appear on most of YACs. These findings establish a novel pathway for growing organic single crystals of complex molecular architectures and promote the optoelectrical properties research.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eCocrystal Growth Strategy for Non-fullerene Acceptors (NFAs)\u003c/h2\u003e\u003cp\u003eY6 ((2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2\",3\u0026rsquo;':4\u0026rsquo;,5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile)), a prominent NFA in organic photovoltaics, was selected as target molecule for cocrystal growth due to its optimal optical bandgap, low exciton binding energy, and high carriers\u0026rsquo; mobility\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea\u003cb\u003e)\u003c/b\u003e. Using 4,8-Bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene as a structure-directing additive (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), Y6-based cocrystals were grown successfully to further investigate their optoelectronic properties. This approach differs fundamentally from conventional organic crystal growth methods, as the additive actively participates in crystal formation through π-π stacking interactions at a precise 1:1 molar ratio with Y6 : additive, becoming a component of integral structure, and forming a new class of single crystals (Y6-Additive Cocrystals, named YACs).\u003c/p\u003e\u003cp\u003eConventional single crystal growth of organic materials primarily relies on vapor-phase and liquid-phase methods. However, these approaches face fundamental limitations for NFAs molecules used in photovoltaics, which typically exhibit low thermal decomposition temperatures and sterically hindered long side chains\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Vapor-phase growth is precluded by thermal instability, while liquid-phase growth is impeded by disordered molecular packing caused by side chain interference during solvent evaporation and supersaturation. To overcome these challenges, cocrystal growth strategy was developed by introducing a structure-directing additive. This approach establishes new configuration coupling interactions while simultaneously mitigating the hindrance effects of side chains on molecular ordering (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Y6 belongs to the A-D-A'-D-A class of NFAs, featuring a fused-ring central core with alternating electron-donating (D) and electron-accepting (A/A') units\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. While the extended π-conjugated system enables multifunctional integration, several intrinsic molecular characteristics impede crystal growth: (ⅰ) bulky side chains that enhance solubility but disrupt ordered packing, and (ⅱ) limited thermal stability (decomposition temperature\u0026thinsp;~\u0026thinsp;300\u0026deg;C). These factors collectively preclude from the formation of high-quality and large-scale single crystals via thermal evaporation methods. The extended alkyl side chains in Y6 introduce significant steric hindrance, disrupting the π-π stacking and long-range molecular ordering required for single crystals growth via liquid-phase crystallization. The 4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene was selected as additive for cocrystallization due to its dual functionality: (ⅰ) a planar benzo ring in site of core that facilitates π-π stacking interactions with Y6 molecule, and (ⅱ) suitable physical state such as oiliness to provide suitable condition of molecular self-assembly. Both Y6 and additive demonstrate excellent mutual solubility in chloroform (CF), forming a homogeneous precursor solution essential for controlled cocrystal growth. (\u003cb\u003eSee section of materials and Methods\u003c/b\u003e). The growth results demonstrate that the additive is indispensable for cocrystal formation, as confirmed by control experiments \u003cb\u003e(Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e).\u003c/b\u003e Upon determining the crystal structure, it's unexpectedly discovered that the additive actively participates in the crystal lattice, forming a 1:1 cocrystal (YACs) with Y6. This cocrystallization behavior fundamentally differs from conventional organic crystal growth methods. Single crystal structure analysis reveals that the additive serves as a bridging template, directing the ordered stacking of Y6 molecules through a newly formed configuration coupling of Y6-additive π-π stacking. Simultaneously, the additive's participation creates expanded intermolecular spacing which accommodates Y6's long side chains while reducing their steric hindrance effects. Furthermore, the additive's oily nature at both room temperature and 80\u0026deg;C (Growth temperature) constitutes another critical factor, as it provides an optimal dynamic environment that enables Y6 molecules to freely migrate and self-assemble, ultimately facilitating YACs formation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eStructural and Morphological Characterizations of YACs\u003c/h3\u003e\n\u003cp\u003ePolarized optical microscopy reveals well-defined striated YACs grown on SiO\u003csub\u003e2\u003c/sub\u003e/Si substrates, exhibiting chromatic variations due to anisotropic light scattering\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The observed smooth surfaces and straight edges indicate high crystalline quality, with a measured thickness of 327 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Statistical analysis shows the length distribution centers at approximately 450 \u0026micro;m (Lorentzian fitting), while the maximum observed length extends to 1500 \u0026micro;m (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). Additionally, theoretical X-ray Diffraction (XRD) spectra derived from the YACs via analog computation match the experimental data, with the strong (100) diffraction peak indicating preferred orientation along the (100) plane and high crystallinity. (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). The high-density YACs distribution and regularly oriented growth radiating from a single nucleation point to multiple directions observed in polarized microscopy images demonstrate exceptionally high growth productivity (\u003cb\u003eSee sample movie 1 in Supplementary Materials\u003c/b\u003e). The morphology and shape diversity of YACs can be precisely controlled by adjusting the Y6-to-additive ratio and precursor concentration. The primary morphological evolution follows two main trends: (ⅰ) Increasing the additive proportion transforms shape of YACs from sheet-like to strip-like forms, and (ⅱ) decreasing the precursor concentration reduces the overall thickness \u003cb\u003e(Fig. S2-18)\u003c/b\u003e. The YACs\u0026rsquo; shapes predominantly manifest as either two-dimensional sheets or one-dimensional strips. The sheets exhibit nm-level thickness through layer-by-layer growth (18 nm to 341 nm), with each monolayer measuring approximately 2.0 nm in thickness.\u003c/p\u003e\u003cp\u003eThe YACs structure was determined using Micro Electron Diffraction Technology\u003csup\u003e\u003cspan additionalcitationids=\"CR23\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e (\u003cb\u003eFig. S20-25, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e-6\u003c/b\u003e). Data visualization was performed using the REDp program, and processing was conducted using DiffProAnalyze software (developed by ReadCrystal Tech Inc.). The single-crystal structure was determined, belonging to the P\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e space group. The diffraction pattern is consistent with the extinction rules of P\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e, permitting all reflections without restrictions on h, k, or l indices. Any combination of h, k, and l (positive, negative, or zero) can give rise to a reflection, provided it is structurally feasible based on the crystal's atomic arrangement (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee to \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ei). The analysis confirms that unit lattice parameters of YACs are \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;14.640(3) \u0026Aring;, \u003cem\u003eb\u003c/em\u003e\u0026thinsp;=\u0026thinsp;19.170(4) \u0026Aring;, \u003cem\u003ec\u003c/em\u003e\u0026thinsp;=\u0026thinsp;19.730(4) \u0026Aring;, and angles \u003cem\u003eα\u003c/em\u003e (\u0026ang;\u003cem\u003eboc\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;75.00(3)\u0026deg;, \u003cem\u003eβ\u003c/em\u003e (\u0026ang;\u003cem\u003eaoc\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;70.00(3)\u0026deg;, \u003cem\u003eγ\u003c/em\u003e (\u0026ang;\u003cem\u003eaob\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;87.00(3)\u0026deg; (\u003cb\u003eCIF information of YACs in Supplementary Material\u003c/b\u003e). Y6 and the additive form π-π stacking between the terminal benzene ring attached two fluorine atoms of Y6 and the centrally located benzene ring of the additive, and the distance of π-π stacking is 3.446 \u0026Aring; (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ej and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ek). The YACs possesses an inversion center as its symmetry element (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003el). The Y6 and the additive couple to form a basic unit, which then stacks in a back-to-back, step-like fashion \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003em and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003en\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eGrowth Mechanism of YACs\u003c/h3\u003e\n\u003cp\u003eOur observations reveal that stick YACs exhibit radial growth originating from a central nucleation point, with crystalline domains expanding uniformly in all directions. This growth behavior was characterized through in situ optical microscopy during thermal annealing at 80\u0026deg;C, capturing the complete crystallization process from nucleation (t\u0026thinsp;=\u0026thinsp;0 s) to crystal development (t\u0026thinsp;=\u0026thinsp;1040 s) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). The time-resolved imaging demonstrates distinct stages of nucleation initiation followed by directional crystal growth. (\u003cb\u003eSee growth movie 2 in Supplementary Material\u003c/b\u003e). In situ imaging identifies molecular aggregation sites as nucleation centers, with both AFM and SEM images revealing subsequent crystal growth emanating from these nucleation sites, and growing layer by layer (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb and \u003cb\u003eFig. S19\u003c/b\u003e). Other shape including lamellar and foliate YACs also exhibit radial growth patterns, expanding outward from a single nucleation center (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec) as 1:1 cocrystallization of Y6 and additive molecule growth (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). To elucidate the Y6-additive interaction mechanism, the additive's influence was investigated systematically through both chemical structure and physical state analyses. A series of derivative additives containing isolated functional groups from the parent additive were designed for controlled experiments, enabling precise determination of each functional group's role. The primary additive was structurally deconvoluted into two key components: 3-methoxyheptane, benzo[1,2-b:4,5-b']dithiophene, and further fragmented into its constituent basic units (benzene, thiophene, and thianaphthene). This systematic fragmentation enabled controlled investigation of individual functional group contributions through comparative experiments. Notably, the extended alkyl side chains were found to substantially enhance molecular solubility and facilitate solid-to-liquid phase transitions in small-molecule systems\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Control experiments reveal distinct growth outcomes: (ⅰ) unable to crystallize occurs with benzene, thiophene, and 3-methoxyheptane (all liquids, fast volatility), whereas (ⅱ) small crystal grains form with benzo[1,2-b:4,5-b\u0026prime;]dithiophene and thianaphthene (both solids) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). These results demonstrate that effective cocrystal growth requires effective packing sites and optimal physical state. (\u003cb\u003eTable S7\u003c/b\u003e) The YACs growth is influenced by physical state of the parent additive and its functional groups critically. The viscous liquid phase (oiliness) of the parent additive creates an optimal environment for crystallization, as evidenced by the growth of YACs under additive-rich conditions (\u003cb\u003eFig. S6\u003c/b\u003e). In contrast, fast-volatility additives fail to support crystallization due to rapid evaporation, which prevents sufficient time for molecular self-assembly. Based on the structural analysis of YACs with molecular dynamics simulations, π-π stacking interactions are identified as the key determinant for growth. The computational results reveal that π-π stacking occurs between the terminal fluorinated benzene ring of Y6 and the central benzene ring of the additive\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, leading to self-assembly after 20 ns, which is consistent with the observed YACs structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef, \u003cb\u003eFig. S26-32\u003c/b\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eGeneralized growth approach of YACs\u003c/h3\u003e\n\u003cp\u003eThe versatility of this approach is demonstrated through successful YACs growth on diverse substrates, including quartz, glass, ITO-coated glass, polyimide (PI), and aluminum (Al) foil, indicating its potential for device integration and scalable fabrication (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, \u003cb\u003eFig. S33\u003c/b\u003e). The YACs morphology and growth behavior remain consistent across substrates, predominantly forming stick-like and sheet-like structures similar to those observed on SiO\u003csub\u003e2\u003c/sub\u003e/Si substrate, demonstrating excellent substrate compatibility. Notably, YACs also grow conformally along the inner walls of capillary tubes with diameters of 1.12 mm and 0.50 mm, maintaining their crystalline structure even in curved configurations (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). This behavior demonstrates two key advantages: (i) the ability to grow in confined micro-spaces, and (ii) inherent mechanical flexibility of YACs\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e (\u003cb\u003eFig. S34\u003c/b\u003e). Aligned growth of YACs in parallel arrangements is achieved on Si substrates patterned with parallel nanograting, which direct precursor distribution via micro/nanostructure confinement (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec, \u003cb\u003eFig. S35\u003c/b\u003e). In addition, the light-controlled growth of YACs has been realized. The experiment results reveal that YACs selectively grow in non-illuminated regions while remaining absent in light-exposed (\u0026lt;\u0026thinsp;about 900 nm which precisely aligns with the edge of Y6 absorption spectrum) areas (\u003cb\u003eFig. S36 and S37\u003c/b\u003e). The controlled growth of patterned arrays can be achieved using a light-masking, where a specific optical array is projected to define the growth pattern. In this process, the illuminated regions correspond to the non-growth zones.\u003c/p\u003e\u003cp\u003eTo systematically evaluate the general applicability of additive-directed crystallization for NFAs, this growth method was successfully extended to multiple material systems, including: A-D-A\u0026rsquo;-D-A type of axial symmetry (COTIC-4F, Y6-BO, BTP-eC9, Y7) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed \u003cb\u003eand Fig. S38\u003c/b\u003e) and D-A\u0026rsquo;-D type of central symmetry (ITIC, ITIC-M, ITIC-4F,Y7 ITIC-4Cl, ITIC-Th, IDIC) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee \u003cb\u003eand Fig. S39\u003c/b\u003e), which have significantly propelled advancements in the OPV field (\u003cb\u003eTable S7\u003c/b\u003e). These crystals exhibit varied morphologies (blocks, strips, and sheets), attributed to distinct molecular packing configurations and intermolecular coupling effects\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. According to the above-mentioned principle for the selection of additives, 2,6-dibromo-4,8-bis[(2-butyl-n-octyl)oxy]benzo[1,2-b:4,5-b']dithiophene (A1) and benzo[1,2-b:4,5-b']dithiophene-4,8-dione (A2) are also selected as additives for YACs growth under identical conditions. The A1 exhibits a viscous liquid state at both room temperature and 80\u0026deg;C, and A2 transforms from solid at room temperature to viscous liquid state at 80\u0026deg;C. Both of them have suitable packing sites. The growth results indicate high-quality single crystal of YACs (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg \u003cb\u003eand Fig. S40\u003c/b\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eOptoelectronic Performance of YACs\u003c/h3\u003e\n\u003cp\u003eThe optoelectronic properties of Y6 and YACs were focused on absorption, photoluminescence (PL) spectra, and polarized optoelectronic response. Due to the localized nature of electronic density in organic molecules\u003csup\u003e\u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e, their optoelectronic characteristics at the molecular level remain largely unaffected after crystallization. However, a key consideration here is whether the introduction of the additive in YACs modifies the electronic distribution through charge transfer interactions between the two molecules\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. The nearly identical absorption and photoluminescence (PL) spectra of Y6 and YACs suggest minimal changes between the amorphous and crystal states (\u003cb\u003eFig. S41a and b\u003c/b\u003e). As a hallmark property of organic crystalline, the polarized optoelectronic response has been extensively studied and holds significant promise for applications in multidimensional light detection technologies\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. The angular-dependent PL spectra were measured under linearly polarized excitation at room temperature. The PL peak intensity exhibits a pronounced angular dependence, demonstrating clear dichroic behavior characteristic of anisotropic optical transitions (\u003cb\u003eFig. S41c and d\u003c/b\u003e).\u003c/p\u003e\u003cp\u003eTo investigate the optoelectronic properties of YACs (Based on Y6), the photodetector was fabricated by growing the YACs directly on Au interdigitated electrodes (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea) exhibiting efficient photo response characteristics (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). Meanwhile, the angular-dependent photocurrent measurements under 638 nm polarized light demonstrate strong dichroic behavior originated from the well-aligned molecular orientation within the YACs (\u003cb\u003eFig. S42a\u003c/b\u003e). Furthermore, the same device exhibits strong optical rotation responses under both left- and right-handed circularly polarized light, highlighting its potential for polarization-sensitive optoelectronics (\u003cb\u003eFig. S42b\u003c/b\u003e). Finally, practical application was demonstrated by integrating the device into a single-pixel imaging test system with mask (\u003cb\u003eFig. S43a and b\u003c/b\u003e), successfully reconstructing a high-contrast lotus pattern (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec).\u003c/p\u003e\u003cp\u003eOrganic nonlinear optical (NLO) materials offer advantages like low cost, and ease of synthesis over inorganic counterparts, enabling applications in wavelength conversion and telecom\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. Second harmonic generation (SHG), a key NLO process doubling incident light frequency, provides efficient frequency conversion and high-power laser generation\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. Here, Second-order nonlinear optical responses in YACs were characterized using back-reflection SHG measurements. \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed). A strong emission peak appears at 515 nm from the YACs (Based on IT-M) sample when excited by a 1030 nm femtosecond laser (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee). A plot of SHG intensity versus pump power yields a slope of 2.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15 on a log-log scale, confirming the characteristic quadratic dependence of high-quality SHG in YACs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef). The SHG response also exhibits polarization dependence at 1030 nm and 9.6 \u0026micro;W, attributed to the structural anisotropy of YACs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg\u003cb\u003e)\u003c/b\u003e. The polarization-dependent SHG response, characterized by four peaks (two strong and two weak) spaced 90\u0026deg; apart, indicates a multicomponent nature of SHG process from YACs. We analyzed this may be related to the crystal structure of organic co-crystals, particularly single crystals composed of two molecules coupling\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. Strict frequency doubling is observed across a series of fundamental wavelengths from 994 nm to 1030 nm, generating SHG signals from 497 nm to 515 nm. The SHG intensity decreases with blue-shifting fundamental wavelength, due to weakening by intrinsic optical absorption\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh). SHG measurements conducted on all YACs at 1030 nm and 4.6 \u0026micro;W indicate that YACs exhibit standard SHG responses (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ei). While non-centrosymmetric crystal structure is a necessary condition for SHG, we note that YACs based on Y6\u0026mdash;which belongs to the centrosymmetric space group P\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e with centrosymmetric properties\u0026mdash;also exhibit strong SHG. According to previous studies, the local disorder in molecular orientation caused by long side chains\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e, along with charge distortion and local dipole chains induced by charge transfer\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e, can break the centrosymmetric properties of YACs, thereby enabling SHG. This proof-of-concept experiment validates the feasibility of YACs-based devices for future optoelectrical technologies.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, we have developed a generalizable additive-directed cocrystal strategy to grow YACs-a previously unattainable feat due to steric hindrance from long side chains. Structural characterization confirms the formation of YACs in the triclinic P\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e space group, where additive molecules enable cocrystallization through π-π stacking via configuration coupling. This approach provides unprecedented control over YACs morphology (stick/sheet) and dimensions (18 nm-341 nm thick; central and longest lengths to 450 \u0026micro;m and 1.5 mm). Through pattern summarization, this growth method can be extended to single-crystal growth of ten NFA molecules and the selection of two novel additives. The optoelectrical properties were focused on photodetectors and SHG response. The photodetector based on YACs (Y6) achieve exceptional polarized, optical rotation light sensitivity, and single-pixel imaging. Most of YACs exhibit strong SHG response including Polarization dependence. Our work establishes a paradigm to single crystal growth for structurally complex functional NFAs molecule, unlocking their potential for advanced optoelectronic applications.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003e\u003cb\u003eMaterials\u003c/b\u003e: ITIC-TH, IDIC, Y7, Y6, IT-4CL, ITIC, Y6-BO, COTIC-4F, L8-BO, IT-M, BTP-EC9, IT-4F purchased from Shanghai Weizhu Chemical Technology Co., Ltd., purity 99%. 2,6-Dibromo-4,8-bis[(2-butyl-n-octyl)oxy]benzo[1,2-b:4,5-b']dithiophene (A1) purchased from Shanghai Hao Hong Biological Pharmaceutical Technology Co., LTD., purity\u0026thinsp;\u0026ge;\u0026thinsp;97%. Benzo[1,2-b:4,5-b']dithiophene-4,8-dione (A2) was purchased from Shanghai Maclin Biochemical Technology Co., LTD. Purity 98%., purity\u0026thinsp;\u0026ge;\u0026thinsp;99%. Trichloromethane (also known as chloroform, CF, CAS No. 67-66-3, formula: CHCl₃, Analyzable pure) purchased from Shanghai Lingfeng Chemical Reagent Co., LTD.,)\u003c/p\u003e\u003cp\u003e\u003cb\u003eGrowth methods\u003c/b\u003e: Solution preparation: Dissolve 4 mg of the target material (or 3 mg of Y6 in the light control growth test) in 100 \u0026micro;L chloroform and add different volumes of additives The solution was dissolved by magnetic stirring at a speed of 1200 rpm. Spin coating films: Take 10 \u0026micro;L solution and add it to pre-treated SiO\u003csub\u003e2\u003c/sub\u003e/Si substrate (or quartz, glass, grating and other substrates), spin coating for 60 seconds at 4000 rpm to form a uniform film. Solvent annealing: The coated substrate is placed on a constant temperature table at 80℃ to promote solvent volatilization and crystal self-assembly. After growth completely, rinse with ethanol to get clean YACs. Y6 light-controlled growth: After spin coating, the substrate was placed on the heated microscope stage (80℃), and the light source of the microscope was used for local irradiation for 3 hours, and the crystal morphology was observed immediately after the heating was turned off. Y6 multi-substrate adaptability test: Repeat the above steps on quartz, glass, grating and capillary surfaces (capillary tubes are sucked into the inner tube wall by capillary effect and heated directly). YACs growth based on different additives: Y6 and additives A1, A2 were dissolved in chloroform (3 mg/mL) at a mass ratio of 1:1, stirred at room temperature for 2 hours and then spin coated on SiO₂/Si substrate (4000 rpm, 60 seconds). After solvent annealing at 80 ℃ for 18 hours, high-quality single crystals were formed and observed under the microscope with different magnifications.\u003c/p\u003e\u003cp\u003e\u003cb\u003eCharacterizations and tests\u003c/b\u003e: The PL spectra were carried on the Horiba LabRAM HR800. The absorption spectra were carried on the Nicolet is 50. AFM images were carried on Bruker Dimension Ico, Optical and polarized images were carried on OLYMPUS microscope, SEM images were carried on HITACHI SU8010, XRD spectra were carried on D8 Advance. Electrical and photoelectric properties were measured by using a dual-channel digital source meter (Keithley 6482) on a probe station under ambient conditions. The devices were tested with laser sources at 520, 638. Incident light was modulated with a function generator (DG822, RIGOL, 25MHz) combined with light-controlled system of polarized light and optical rotation. SHG measurements were performed using a custom reflection-mode microscope. A tunable femtosecond laser (pulse width: 200 fs; repetition rate: 100 kHz) served as the excitation source. Polarized excitation was achieved using a 1030 nm half-wave plate. Emitted signals were collected via a multimode fiber coupled to a spectrometer. All experiments were conducted at room temperature.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e: Additional data related to this paper may be requested from the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e We thank the ReadCrystal Biotechnology for the organic single crystal test and analysis. This work is supported by National Natural Science Foundation of China: No. 12304334, 12104110, 62205084, 62475057.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u0026nbsp;\u003c/strong\u003eConceptualization: Zhuhua Xu；Methodology: Zhuhua Xu；Investigation: Zhuhua Xu, Haochen Tan, Wenxing Luo, Yuang Li；Visualization: Zhuhua Xu，Qiang Lv, Linqing Qiu, Qingsong Tao, Sheng Ni, Chengcheng Wu, Zhanpeng Wang, Zilong Ye, Rui Zhang, Ning Zhou, Changlong Liu, Jing Li, Hongxing Dong, Mingjie Liu；Supervision: Hongxing Dong, Mingjie Liu, Xue-Dong Wang, Zheng Liu, Liang-Sheng Liao, Jingzhou Li, Long Zhang; Writing\u0026mdash;original draft: Zhuhua Xu, Writing\u0026mdash;review \u0026amp; editing: Zhuhua Xu, Xue-Dong Wang, Zheng Liu, Liang-Sheng Liao, Jingzhou Li.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e: All other authors declare they have no competing interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary Information:\u0026nbsp;\u003c/strong\u003eAll supplementary information in the paper is present in Supplementary Materials.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSokolov AN et al (2011) From computational discovery to experimental characterization of a high hole mobility organic crystal. 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However, the conventional vapor- and liquid-phase methods fail for structurally complex molecules like the non-fullerene acceptor (NFA) Y6, where thermal instability and steric hindrance from branched sidechains inhibit crystallization. Here, we report an additive-directed cocrystallization strategy to grow Y6-additive cocrystals (YACs) with controlled morphology and tunable thicknesses (18 nm to 341 nm). The single-crystal structure is determined by Micro Electron Diffraction Technology at first time. Growth mechanism studies reveal that additive molecules mitigate sidechain interference by enabling configuration coupling of π-π stacking, yielding YACs with central length of 450 \u0026micro;m and largest lengths of 1.5 mm. Generalizability is demonstrated across 10 kinds of Y6-like NFAs with axial/central symmetry and 2 kinds of effective additives. Single-pixel image is realized based on photodetectors of YACs, meanwhile which exhibits a polarized and helical light response enabling by molecular ordered stacking. Most of YACs exhibit strong second harmonic generation (SHG) response. This work establishes a paradigm of single-crystal growth for structurally hindered complex molecules and provides a crystallographic basis for investigating the optoelectronic properties.\u003c/p\u003e","manuscriptTitle":"Single-Crystal Growth of Complex Non-fullerene Acceptor Molecules via Cocrystallization","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-12 15:18:38","doi":"10.21203/rs.3.rs-7423857/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":"dfeef28d-dde5-4ec2-b499-6db9356886bb","owner":[],"postedDate":"September 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":54545659,"name":"Physical sciences/Materials science/Materials for optics/Nonlinear optics"},{"id":54545660,"name":"Physical sciences/Materials science/Materials for optics/Photonic crystals"}],"tags":[],"updatedAt":"2026-04-03T07:06:15+00:00","versionOfRecord":{"articleIdentity":"rs-7423857","link":"https://doi.org/10.1038/s41467-026-69997-7","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2026-02-25 05:00:00","publishedOnDateReadable":"February 25th, 2026"},"versionCreatedAt":"2025-09-12 15:18:38","video":"","vorDoi":"10.1038/s41467-026-69997-7","vorDoiUrl":"https://doi.org/10.1038/s41467-026-69997-7","workflowStages":[]},"version":"v1","identity":"rs-7423857","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7423857","identity":"rs-7423857","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}