Centimeter-scale fullerene-free tin-based perovskite solar cells achieving over 14% efficiency

Centimeter-scale fullerene-free tin-based perovskite solar cells achieving over 14% efficiency | 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 Centimeter-scale fullerene-free tin-based perovskite solar cells achieving over 14% efficiency Jia Liang, Tianpeng Li, Feifei He, Tao Shen, Dongsheng Yan, Zuoming Jin, and 11 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6079304/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Fullerene-based materials have traditionally served as the primary electron transport layers (ETLs) in environmentally friendly tin-based perovskite solar cells (TPSCs) due to their suitable band structures. However, they suffer from limitations such as high cost, complex synthetic process, low electron mobilities, limited interactions with Sn-based perovskites, and challenges in tuning their chemical and electrical structures, which have hindered further improvements in power conversion efficiency (PCE) of TPSCs. To tackle these issues, we propose a fullerene-free TPSC architecture and introduce a series of low-cost non-fullerene materials, i.e. fluorinated triple-acceptor polymers (named as P1 , P2 , and P3 ), as alternative ETLs. Compared to fullerene-based ETL, such as indene-C 60 bisadduct (ICBA), these non-fullerene ETLs exhibit facile synthetic process, three orders of magnitude higher electron mobilities, and high structural flexibility. Additionally, these non-fullerene ETLs form continuous and conformal interfaces with Sn-based perovskite layers, enabling stronger and more uniform interactions over large-area Sn-based perovskite layers. In 1-cm 2 TPSCs, particularly those using the P3 ETL, we achieve a remarkable PCE of 14.39%, surpassing the PCE of 10.61% observed in 1-cm 2 TPSCs with the ICBA ETL. Notably, TPSCs with the P3 ETL achieved a record PCE of 16.06% for small area of 0.04-cm 2 (certified at 15.90%). Furthermore, the fullerene-free TPSC with the P3 ETL demonstrates exceptional stability, showing no significant degradation over 1200 hours of shelf storage and maintaining nearly 86% of its initial PCE after 550 h of maximum power point tracking under continuous 1-sun illumination. This enhanced stability is attributed to the robust hydrophobicity conferred by the long alkyl side chains. Overall, this study substantiates the substantial potential of fullerene-free TPSCs using non-fullerene ETLs in advancing both the photovoltaic performance and stability of large-area TPSCs. Physical sciences/Materials science/Materials for energy and catalysis/Solar cells Physical sciences/Materials science/Nanoscale materials/Carbon nanotubes and fullerenes Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Tin-based perovskite solar cells (TPSCs) are attracting increasing attention from the research community as a promising next-generation perovskite-based photovoltaic technology because of their competitive advantages such as environmental friendliness, ideal bandgaps, low cost, ease of growth, and high power conversion efficiencies (PCEs). [ 1 – 4 ] Currently, fullerene-based materials, such as fullerene (C 60 ), [ 5 – 7 ] phenyl-C 60 -butyric acid methyl ester (PC 60 BM), [ 8 – 10 ] and indene-C 60 bisadduct (ICBA), [ 11 – 14 ] have been the dominant electron transport layers (ETLs) used in TPSCs. Despite several advancements, persistent issues and limitations with TPSCs necessitate the replacement of these outdated ETLs. Scientifically, fullerene-based materials exhibit low electron mobilities, limited interactions with Sn-based perovskites, poor resistance to moisture penetration, thermal instability, and photochemical instability, all of which are detrimental to TPSC performance. [ 15 – 17 ] Moreover, chemical modifications of fullerenes are challenging, leading to low structural flexibility and difficulty in tuning electronic properties. From an engineering perspective, fullerene-based materials are hindered by high-cost precursors, complex synthetic processes, and the need for time-consuming purification. Therefore, exploring new ETLs to enhance TPSCs is imperative. [ 18 – 20 ] Non-fullerene materials present a promising solution to these challenges and may emerge as optimal ETLs for TPSCs due to several distinct advantages. On one hand, non-fullerene materials benefit from a vast molecular design space, enabling excellent synthetic flexibility with utilizing more readily available source materials [ 21 – 23 ] . This flexibility allows for easily tunable electronic properties and improved solubility, facilitating their integration into TPSC architectures. On the other hand, non-fullerene materials can be specifically tailored to work with Sn-based perovskites in terms of both high electron mobilities, strong interaction with Sn-based perovskites, and protection from moisture in the air [ 24 – 26 ] . Additionally, the use of low-cost cores, coupled with facile synthesis and simplified purification contributes to significant reductions in the production cost of non-fullerene materials [ 22 – 31 ] . Furthermore, achieving high PCEs in small-area devices is critical, but scaling up to centimeter-scale devices is essential for the practical deployment of TPSCs. The transition to larger-scale devices often presents challenges, such as maintaining uniformity and stability across the functional layer, which can significantly impact overall efficiency. Demonstrating high PCEs in centimeter-scale TPSCs thus serves as a crucial benchmark, indicating that the material and device architecture are robust enough for potential commercialization and large-scale manufacturing. Following this line of thoughts, we put forward a fullerene-free TPSC architecture and developed a series of low-cost, n-type semiconducting non-fullerene ETLs (named as P1 , P2 , and P3 ), through molecular design strategies involving fluorination and triple-acceptor modulation. Using Stille-coupling polymerization, these non-fullerene materials can be synthesized in high yield, offering potential for large-scale production. While maintain band structures similar to those of fullerene-based counterpart, these non-fullerene materials demonstrated electron mobilities that were three orders of magnitude higher, making them ideal candidates for ETLs in TPSCs. Moreover, the functional groups present in these non-fullerene materials facilitated the formation of continuous and conformal interfaces with Sn-based perovskite layers, resulting in more uniform and stronger interactions, and enabling efficient electron transfer across the interface. As a result of these advancements, the fullerene-free TPSC with the P3 ETL exhibited record PCEs of 16.06% for small-area devices and 14.39% for large-area devices. Additionally, the enhanced stability of these fullerene-free TPSCs, attributed to their robust hydrophobicity conferred by long alkyl side chains, further underscores their potential. Specifically, the fullerene-free TPSC with the P3 ETL shows no significant change after 1200 h of shelf storage and retains 86% of its initial PCE after 550 h of maximum power point tracking under continuous 1-sun illumination. These results highlight the potential of fullerene-free TPSCs with non-fullerene ETLs to enhance the photovoltaic performance and long-term stability. 2. Results and discussions 2.1 Fullerene-free TPSC design The design of fullerene-free TPSC structure draws inspiration from, yet is distinct from, conventional organic solar cells. Typically, organic solar cells employ a blend of a conjugated polymer and a fullerene derivative as the active layer. However, the PCEs of organic solar cells has historically been capped around 10%, primarily due to several inherent drawbacks of fullerene derivatives. [ 32 – 34 ] These drawbacks include low structural flexibility, weak interaction with conjugated polymer, low charge mobility, high costs, and complex synthetic process. By introducing non-fullerene materials to replace these fullerene derivatives, these issues have been mitigated, resulting in a near doubling of PCEs in organic solar cells over the past decade. [ 35 – 38 ] In inverted TPSCs, similar challenges persist. Figure 1 a shows the widely used structure of inverted TPSCs, typically comprising an ITO/HTL/Sn-based perovskite/ETL/BCP/Ag configuration, where the ETL is often composed of fullerene derivatives, such as C 60 , PC 60 BM, and ICBA. Beyond their intrinsic shortcomings, these fullerene derivative ETLs exhibit weak interactions with the perovskite layer, leading to sluggish electron transfer and severe non-radiative recombination. To overcome these challenges, we aimed to develop a fullerene-free TPSC that integrates several desirable features: (i) low cost and facile synthetic process; (ii) high charge mobility; (iii) high structure flexibility; (iv) hydrophobicity, attributed to long alkyl side chains; and (v) strong interactions with perovskite layers due to the presence of multiple functional groups. As depicted in Fig. 1 b, the strong interaction between the perovskite layer and the non-fullerene ETL, coupled with the high mobility of the non-fullerene ETL, is anticipated to accelerate electron transfer from the Sn-based perovskite layer to the non-fullerene ETL and suppress non-radiative recombination at the interface. We selected Diketopyrrolopyrrole (DPP)-based materials as the non-fullerene ETLs for their planar structure, high crystallinity, acceptable electron-withdrawing properties and superior solubilizing capability via N -alkylation. [ 39 – 41 ] Fig. 1 c outlines the synthesis routes for the novel non-fullerene ETLs based on DPP. First, through a strategic combination of fluorination and triple-acceptor modulation involving DPP and difluorobenzothiadiazole, an electron-deficient building block based on DPP-difluorobenzothiadiazole triad, i.e., 6,6′-((5,6-difluorobenzo[ c ][1,2,5]thiadiazole-4,7-diyl)bis(thiophene-5,2-diyl))bis(2,5-bis(2-octyldodecyl)-3-(thiophen-2-yl)-2,5-dihydropyrrolo[3,4- c ]pyrrole-1,4-dione) (DFB), was synthesized. Second, bromination of DFB using N-bromosuccinimide was conducted to obtain the monomer 6,6″-(5,5″-(5,6-difluorobenzo[ c ][1,2,5]thiadiazole-4,7-diyl)bis(thiophene-5,2-diyl))bis(3-(5-bromothiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo[3,4- c ]pyrrole-1,4(2 H ,5 H )-dione) (DFB-Br). Finally, these three non-fullerene materials, designated as P1 , P2 , and P3 , were synthesized using palladium-catalyzed Stille-coupling polymerization with three distinct tin compounds of thiophene donor derivatives. Detailed synthesis details are provided in the supplementary information. The structural and optical characteristics of these non-fullerene ETLs were confirmed through nuclear magnetic resonance (NMR) and Tauc plots ( Supplementary Figs. 1–2 ). 2.2 Characterization of non-fullerene ETLs An ideal ETL for TPSCs should feature a favorable band structure aligned well with Sn-based perovskites and exhibit high mobility [ 13 , 16 ] . To demonstrate the suitability of the three types of non-fullerene materials as ETLs in this regard, their ultraviolet photoelectron spectroscopy (UPS) data of the valence band maximum (VBM) onsets and the secondary electron cutoff energy boundaries were characterized, as shown in Figs. 2 a-b. Utilizing the formula of VBM = 21.22 – ( E cutoff – E onset ) and bandgaps obtained from UV-vis spectra (Fig. 2 c and Supplementary Fig. 2 ), their VBM and conduction band minimum (CBM) energies were calculated, respectively, as shown in Fig. 2 d. Both P1 and P2 ETLs exhibit slightly deeper CBMs compared to Sn-based perovskites, while the P3 ETL shares the same CBM with Sn-based perovskite. Theoretically, the P3 ETL emerges as the most promising ETL candidate for TPSCs as it possesses the shallowest CBM among the three types of non-fullerene ETLs, maximizing the attainable photovoltage determined by the quasi-Fermi level splitting, V OC = ( E Fn – E Fp )/ q . [ 11 ] In addition to band structures, the mobilities of the three types of non-fullerene ETLs, including P1 , P2 , and P3 , were assessed. Figure 2 e shows their space-charge-limited current (SCLC) curves of devices with ITO/Ag/non-fullerene ETLs/Ag structures. Their mobilities ( µ s) were quantitatively evaluated in the trap-free regions using the formula: [ 4 ] $$\:\mu\:=\frac{8{L}^{3}\bullet\:{J}_{D}}{9\epsilon\:{\epsilon\:}_{0}{V}_{h}^{2}}$$ Here, V h and J D represent the voltage and current density at the trap-free region, L is the thickness of the non-fullerene ETLs, ε 0 is the vacuum permittivity, ε denotes the relative dielectric constant of the non-fullerene ETLs. Consequently, the calculated µ s of P1 , P2 , and P3 are 1.98, 3.17, and 1.29 cm 2 V -1 s -1 , respectively ( Supplementary Note 1 ). Notably, these values are three orders of magnitude higher than that of fullerene-based ICBA ETL (6.9 × 10 − 3 cm 2 V -1 s -1 ), which further suggest these non-fullerene ETLs are promising candidates for TPSCs. [ 4 , 13 – 17 ] Moreover, beyond confirming their suitability as novel ETLs in TPSCs, the three types of non-fullerene ETLs exhibited super hydrophobic behavior in water contact angle experiments due to their hydrophobic nature of long-chain alkyl groups. As illustrated in Fig. 2 f, the water contact angles of the non-fullerene P1 , P2 , and P3 ETLs on Sn-based perovskites were measured at 101.8°, 101.9°, and 103.2°, respectively, all significantly surpassing that of the fullerene-based ICBA ETL of 59.9°. This observation underscores the potential advantages of these non-fullerene ETLs in protecting Sn-based perovskites from moisture permeation. 2.3 Interactions between non-fullerene ETLs and Sn-based perovskite layers After identifying the three types of non-fullerene ETLs as ideal candidates for TPSCs, their interactions with Sn-based perovskites were first assessed through calculated electrostatic surface potentials (ESPs), as shown in Fig. 3 a and Supplementary Fig. 3 . For comparison, the ESP of fullerene-based ICBA ETL was also calculated (Fig. 3 b). All three types of non-fullerene ETLs possess electron-rich (red areas) and electron-poor (blue areas) domains, confirming their potentials for effective interaction with Sn-based perovskites. Notably, the P3 ETL shows a higher ESP than P1 and P2 ETLs, suggesting a stronger interaction with the Sn-based perovskite. This was further validated by calculating the calculated adsorption energy ( E ads ). Supplementary Fig. 4 shows that the E ads of ICBA on the Sn-based perovskite surface is -1.26 eV, while the E ads s values for P1 , P2 and P3 ETLs are − 2.95, -2.90 and − 3.22 eV, respectively, indicating the same results with ESPs. These predicted interactions were further investigated experimentally using Fourier-transform infrared (FTIR) spectroscopy, as shown in Fig. 3 c-d and Supplementary Fig. 5. The SnI 2 -mixtures with the three types of non-fullerene ETLs exhibit significant shifts, indicating strong interactions due to their high electrostatic potentials, while the fullerene-based ICBA ETL and the ICBA-SnI 2 mixture display no discernible shifts, suggesting limited interaction due to the lack of functional groups. Such large shifts can be attributed to the presence of functional groups in these non-fullerene ETLs, such as C-S bonds, C-N bonds, and C-F bonds, as shown in Fig. 1 c. Among them, the P3 -SnI 2 mixture shows more pronounced shifts, indicating P3 possesses the strongest interaction with the Sn-based perovskite among the three types of non-fullerene ETLs. It is well established that strong interactions facilitate smooth electron transport dynamics from Sn-based perovskites to non-fullerene ETLs. To demonstrate this, kelvin probe force microscopy (KPFM) measurements were conducted, as shown in Supplementary Fig. 6 . Sn-based perovskites with the three types non-fullerene ETLs exhibit a smaller surface potential compared to that with the fullerene-based ICBA ETL, suggesting the stronger interaction and faster electron transfer. Moreover, the P3 ETL shows the smallest surface potential among them, indicative of the strongest interaction and the fastest electron transfer. This observation was further corroborated by calculating the total charge transfer between the non-fullerene ETLs and Sn perovskites and compared it to that of ICBA, as shown in Supplementary Note 2 . All three types of non-fullerene ETLs exhibit higher charge transfer values than the ICBA ETL, with the P3 ETL displaying the greatest value, highlighting the fastest electron transfer from the Sn-based perovskite to the P3 ETL. To gain more insights into the effective electron transfer dynamics between the non-fullerene ETLs and Sn-based perovskites in TPSCs, photoluminescence (PL) and time-resolved PL (TRPL) measurements were also conducted. The PL peak intensities of the Sn-based perovskites with the three types of non-fullerene ETLs are weaker than that of the bare Sn-based perovskite, and the Sn-based perovskite with the P3 ETL shows the lowest peak intensities (Fig. 3 e). This result demonstrated that the P3 ETL possesses the most efficient electron transfer with the Sn-based perovskite, which is agreement with the KPFM result. Figure 3 f displays the TRPL decays of the Sn-based perovskite film without and with the three types of non-fullerene ETLs. The corresponding PL lifetime was calculated using a biexponential fitting to the TRPL decays, as shown in Supplementary Table 1 [ 42 ] . Clearly, all the Sn-based perovskites with the three types of non-fullerene ETLs show shorter PL decay lifetime than the bare Sn-based perovskite, with the Sn-based perovskite with the P3 ETL showing the shortest lifetime of 2.88 ns, further verifying the most efficient electron transfer between the P3 ETL and the Sn-based perovskite film. To highlight the structural advantages of fullerene-free TPSCs, we have proposed and plotted schematic diagrams based on above discussions, as shown in Figs. 3 g-h. At the interface between the Sn-based perovskite layer and the non-fullerene ETL, the functional groups in the non-fullerene ETL effectively interact with Sn 2+ and I − in the Sn-based perovskite layer, reducing Sn 2+ oxidation and inhibiting I − migration. This promotes process a and suppresses process b (Fig. 3 g). In contrast, in the case of the fullerene-based ETL, process a proceeds slowly, while process b is more severe due to the weaker interaction between the Sn-based perovskite and the fullerene-based ETL (Fig. 3 h). Furthermore, process c in non-fullerene ETLs occurs significantly faster than in fullerene-based ETLs, owing to the three orders magnitude higher electron mobility of the former. Additionally, the intrinsic hydrophobicity of the long alkyl side chains in non-fullerene ETLs contributes to enhanced stability in fullerene-free TPSCs. Have demonstrated the strong interaction and fast electron transfer, the effects of the three types of non-fullerene ETLs on the morphologies and crystallinities of Sn-based perovskite films were investigated as well. Supplementary Figs. 7a-d exhibit the typical scanning electron microscopy (SEM) images of Sn-based perovskite films without and with the three types of non-fullerene ETLs. Compared to the morphology of the bare Sn-based perovskite film, the surfaces of the Sn-based perovskite films with the three types non-fullerene ETLs appear slightly blurred but uniform, suggesting that the three types non-fullerene ETLs were deposited on the Sn-based perovskite surfaces successfully but had negligible impacts on the film morphologies. The atomic force microscopy (AFM) images corroborate the SEM results, as shown in Supplementary Figs. 7e-h . Moreover, after depositing the three types non-fullerene ETLs on the Sn-based perovskite films, root-mean-square roughness was reduced. Supplementary Fig. 8 exhibits the X-ray diffraction (XRD) patterns of the Sn-based perovskite films with and without the three types non-fullerene ETLs. Similar to the morphologies, the influences of the three types non-fullerene ETLs on the crystallinity of the Sn-based perovskite films can also be omitted. 2.4 Device performance Next, TPSCs were fabricated with the structure of ITO/PEDOT:PSS/Sn-based perovskites/ETLs/BCP/Ag, as illustrated in Supplementary Fig. 9 . Figure 4 a shows the current density-voltage ( J–V ) curves of fullerene-based TPSCs (0.04 cm 2 ) with ICBA ETL and fullerene-free TPSCs (0.04 cm 2 ) with P1 , P2 , and P3 ETLs. The corresponding photovoltaic parameters were listed in Supplementary Table 2 . The fullerene-based TPSC with the ICBA ETL exhibits a PCE of 11.74%, with an open-circuit voltage ( V OC ) of 0.81 V, a short circuit current density ( J SC ) of 18.57 mA/cm 2 , and a fill factor (FF) of 78.04%, comparable to previous reports. [ 1 ] As anticipated, compared with fullerene-based TPSCs, all photovoltaic parameters were significant increased for fullerene-free TPSCs (Fig. 4 a and Supplementary Fig. 10 ). Specifically, the TPSC with the non-fullerene P3 ETL shows a PCE of 16.06%, with V OC = 0.99 V, J SC = 19.79 mA/cm 2 , and FF = 81.98%, which is one of the highest PCE among all reported TPSCs. Notably, one such device was measured by an independently accredited testing centre (Chinese National PV Industry Measurement and Testing Center, NPVM) and obtained a certified PCE of 15.90% ( Supplementary Fig. 11 ). For practical applications, TPSCs in this study were also fabricated with a large-area of 1-cm 2 . Figure 4 b shows the current density-voltage ( J-V ) curves of fullerene-based TPSCs with ICBA ETLs and fullerene-free TPSCs with P1 , P2 , and P3 ETLs. Their photovoltaic parameters were listed in Supplementary Table 3 . The 1-cm 2 fullerene-based TPSC with the ICBA ETL displays a PCE of 10.60% with a J SC of 17.65 mA cm − 2 , a V OC of 0.78 V, and a FF of 76.97%, comparable to previous literature results. [ 11 – 15 ] In contrast, the fullerene-free TPSCs exhibit significantly enhanced performance. Specifically, the 1-cm 2 TPSC with the P1 ETL achieve a PCE of 12.88%, with V OC = 0.92 V, J SC = 17.91 mA/cm 2 , and FF = 78.19%; P2 ETL yields a PCE of 13.39%, with V OC = 0.93 V, J SC = 18.38 mA/cm 2 , and FF = 78.32%; and P3 ETL achieves a PCE of 14.39%, with V OC = 0.94 V, J SC = 19.45 mA/cm 2 , and FF = 78.34%. These results represent an enhancement of more than 30% in PCE for fullerene-free TPSCs compared to fullerene-based TPSCs. To the best of our knowledge, this marks the highest efficiency for TPSCs with large area so far (Fig. 4 c and Supplementary Table 4 ). [ 5 , 10 , 14 , 43 – 48 ] In addition to the basic advantages of well-matched band alignment and high electron mobility, this impressive performance can be largely attributed to the uniform and strong interaction of the P3 ETL with the Sn-based perovskite layer. This is evidenced by PL mapping of 0.5 cm x 0.5 cm Sn-based perovskite films with ICBA, P1 , P2 , and P3 ETLs, as shown in Figs. 4 d-e and Supplementary Fig. 12 . The PL mapping for the P3 ETL exhibits the highest uniformity, indicating a consistent interaction between the Sn-based perovskite layer and the P3 ETL. Furthermore, the lowest intensity of the PL mapping for the P3 ETL reflects the strongest interaction with the Sn-based perovskite layer, which is in accordance with the trends observed in Fig. 3 e. To get more insight into the uniform and strong interaction between the layers, cross-sectional SEM and transmission electron microscopy (TEM) images were tested for the fullerene-free TPSC structure, as illustrated in Figs. 4 f-g. The cross-sectional SEM image reveals that the P3 ETL establishes a continuous and conformal interface with the Sn-based perovskite layer and the TEM image confirms an intimate and defect-free interface between the P3 ETL and the Sn-based perovskite layer. Supplementary Fig. 13 presents the incident photo-to-electric current conversion efficiency (IPCE) spectra and integrated J SC values for fullerene-based TPSCs with ICBA ETLs and fullerene-free TPSCs with P1 , P2 , and P3 ETLs. Their integrated J SC values were calculated to be 18.76, 19.86, 19.88 and 20.87 mA cm − 2 respectively, indicating that the fullerene-free TPSC with the P3 ETL shows the highest photon absorption ability across the wavelength range. This enhanced absorption is attributed to the rapid electron transfer from the Sn-based perovskite layer to the P3 ETL. Supplementary Fig. 14 exhibits the J-V plots of the fullerene-free TPSC with the P3 ETL measured in forward and reverse scanning modes. These results reveal an ignorable hysteresis, whereas the fullerene-based TPSC with the ICBA ETL exhibits a significant hysteresis. To assess device reproducibility, 13 individual fullerene-based TPSCs with ICBA ETLs and fullerene-free TPSCs with P1 , P2 , and P3 ETLs were fabricated, respectively, as shown in Supplementary Fig. 15 . The statistical histograms show that the PCE of the fullerene-free TPSC with the P3 ETL distribute over a narrower range. To further elucidate the underlying mechanism, electrochemical impedance spectroscopy (EIS) was performed to analyze the interface resistance, as shown in Supplementary Fig. 16 . The corresponding parameters, including inner series resistances ( R s s), charge transfer resistances ( R ct s), and carrier recombination resistances ( R rec s), are summarized in Supplementary Table 5 . The fullerene-based TPSCs with ICBA ETLs show higher R s and R ct values but a lower R rec compared to fullerene-free TPSCs with P1 , P2 , and P3 ETLs. This result further underscores the weak interaction between the ICBA ETL and the Sn-based perovskite layer, attributed to the lack of functional groups in the ICBA ETL. Among the three types of non-fullerene ETLs, the fullerene-free TPSC with the P3 ETL displays the lowest R s and R ct and the highest R rec compared to those with P1 and P2 ETLs, indicating the strongest interaction between the P3 ETL and the Sn-based perovskite layer due to significant functional groups. This results in the most efficient charge transfer from the Sn-based perovskite layer to the P3 ETL and reducing carrier recombination at the interface. The lower recombination rate is attributed to the reduced defect density at the interface between the Sn-based perovskite layer and the P3 ETL. To further investigate these defects, dark J-V curves of fullerene-free TPSCs with P1 , P2 , and P3 ETLs were tested, as shown in Supplementary Fig. 17 . The dark J SC of the fullerene-free TPSC with the P3 ETL is an order of magnitude lower than those with P1 and P2 ETLs, indicative of the smallest defect density at the interface between the Sn-based perovskite layer and the P3 ETL, consequently, the lowest carrier recombination rate. Additionally, V OC versus incident light intensity plots further supported these findings ( Supplementary Fig. 18 ). The ideality factor (n = 1.19 kT/q) for the fullerene-free TPSC with the P3 ETL is closer to the ideal value of 1 kT/q and significantly smaller compared to fullerene-free TPSC with the P2 ETL (n = 1.41 kT/q) and the P1 ETL (n = 1.52 kT/q), signifying improved device characteristics. To quantitatively assess defect densities, SCLC curves were obtained from electron-only devices structured as FTO/SnO 2 /Sn-based perovskites/ETLs/Ag ( Supplementary Fig. 19 ). The tested ETLs included P1 , P2 , and P3 . In the space-charge-limited current region, the sharp rise in the curve indicates a trap-filled limit, where all defects are occupied by charge carriers. The defect density can be estimated using the equation: $$\:{V}_{TFL}=\:\frac{{N}_{defects}\:\times\:e{L}^{2}}{2\epsilon\:{\epsilon\:}_{0}}$$ Here, V TFL represents the trap-filled limit voltage, L and ε denote the thickness and relative dielectric constant of the Sn-based perovskite film, respectively, ε 0 is the vacuum permittivity, and e is the elementary charge. The calculated defect densities ( N defects ) are 3.42 × 10 16 , 1.33 × 10 16 and 5.23 × 10 15 cm − 3 for electron-only devices with P1 , P2 , and P3 ETLs, respectively, as shown in Supplementary Table 6 . These results clearly demonstrate a significant reduction in defect density when employing the non-fullerene P3 as the ETL. Finally, the long-term operational stabilities of fullerene-free TPSCs were studied, as shown in Figs. 4 h-i. Figure 4 h presents the normalized PCEs of encapsulated TPSCs as a function of aging time under ambient atmosphere. The fullerene-based TPSC with the ICBA ETL exhibits noticeable degradation throughout the testing period, maintaining 65% PCE after 900 h. Conversely, fullerene-free TPSCs with the P3 ETL displays much better performance. Specifically, the fullerene-free TPSC with the P3 ETL exhibits negligible degradation for a period of 1200 h. Figure 4 i displays the normalized PCEs during maximum power point tracking (MPPT) under continuous 1-sun white-light LED illumination. The fullerene-free TPSCs with the P3 ETL retains approximately 86% of its initial PCE after 550 h, whereas the fullerene-based TPSCs with the ICBA ETL maintains only 49% under the same condition. The enhanced stability is attributed to the hydrophobic nature conferred by long-chain alkyl groups in these non-fullerene ETLs. To demonstrate the hydrophobicity of these non-fullerene ETLs, water contact angle measurements were conducted on the fullerene-based TPSCs and fullerene-free TPSCs without the BCP layer and the Ag electrode. Supplementary Fig. 20 exhibit that water contact angles of these non-fullerene P1 , P2 , and P3 ETLs process from approximately 102° at 0 min to around 90°-100° at 12 min and the non-fullerene P3 ETL possess the best performance. In contrast, the water contact angle of the fullerene-based ICBA ETL diminishes to 35.8° at 12 min. This improvement in hydrophobicity suggests that fullerene-free TPSCs and non-fullerene ETLs are preferable structure for improving the stability of TPSCs. Conclusion In summary, we have proposed a novel fullerene-free TPSC structure aimed at enhancing both the PCE and stability compared to conventional fullerene-based TPSCs. A series of innovative non-fullerene ETLs were developed to replace traditional fullerene-based ETLs. These non-fullerene ETLs, namely P1 , P2 , and P3 , were synthesized through a combination of fluorination, triple-acceptor modulation and Stille-coupling polymerization. These new non-fullerene ETLs address key challenges encountered with fullerene-based ETLs, offering three orders of magnitude higher mobilities, stronger interactions with Sn-based perovskite layers, and greater tunability in chemical and electrical structures, rendering them highly suitable for TPSC applications. The small-area and large-area fullerene-free TPSCs with the three types of non-fullerene ETLs, particularly the P3 ETL, achieved record PCEs of 16.06% and 14.39%, respectively, surpassing the performance of fullerene-based TPSCs with the ICBA ETL. In addition, the inclusion of robust hydrophobic long alkyl side chains in these non-fullerene ETLs contributed to exceptional stability, with the fullerene-free TPSC with the P3 ETL showing no significant degradation over 1200 hours, and maintaining 86% of its initial PCE after 550 h of MPPT under continuous 1-sun illumination. This comprehensive study not only provides valuable insights into the design and development of fullerene-free TPSCs and cutting-edge non-fullerene ETL materials, but also opens the door for the production of non-toxic large-area PSCs with high PEC and long-term stability, making the practical application of PSCs a real possibility. Declarations Acknowledgements J.L. acknowledges the funding support from the National Natural Science Foundation of China (52102219 and 52471197). Y.W. acknowledges the funding support from the National Natural Science Foundation of China (52203216 and 22375051). References Chen, J. et al. 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Benzodithiophene hole-transporting materials for efficient tin-based perovskite solar cells. Adv. Funct. Mater. 2019, 29, 1905393 (2019). Ke, W. et al Dopant-free tetrakis-triphenylamine hole transporting material for efficient tin-based perovskite solar cells. J. Am. Chem. Soc. 2018, 140, 388–393 (2018). Ke, W. et al. Efficient lead-free solar cells based on hollow {en}MASnI 3 perovskites. J. Am. Chem. Soc. 139, 14800–14806 (2017). Additional Declarations There is NO Competing Interest. Supplementary Files NPSICentimeterscalefullerenefreeTPSC.docx Supplementary Information Cite Share Download PDF Status: Posted 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-6079304","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":424458908,"identity":"d004b046-38ff-4297-93be-d30f12a17ba6","order_by":0,"name":"Jia 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University","correspondingAuthor":false,"prefix":"","firstName":"Yunqi","middleName":"","lastName":"Liu","suffix":""},{"id":424458924,"identity":"1b97e7fc-8027-4055-9657-36975be8b4ac","order_by":16,"name":"Yang Wang","email":"","orcid":"","institution":"Fudan University","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2025-02-21 12:05:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6079304/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6079304/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":77841533,"identity":"f2a09c4e-1781-4294-8061-44f5f691415a","added_by":"auto","created_at":"2025-03-06 04:58:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":4106332,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign of a fullerene-free TPSC and synthesis of non-fullerene ETLs. \u003c/strong\u003eTypical structures of \u003cstrong\u003ea\u003c/strong\u003e, fullerene-based TPSCs and \u003cstrong\u003eb\u003c/strong\u003e, fullerene-free TPSCs. Compared with the fullerene-based TPSCs, fullerene-free TPSCs exhibit low cost and facile synthetic process, high mobility, high structural flexibility, strong interaction with perovskite layer, and hydrophobicity. \u003cstrong\u003ec\u003c/strong\u003e, Schematic illustration of synthesis routes of three types of non-fullerene ETLs, including \u003cstrong\u003eP1\u003c/strong\u003e, \u003cstrong\u003eP2\u003c/strong\u003e, and \u003cstrong\u003eP3\u003c/strong\u003e. Substantial functional groups exist in them, indicating strong interactions with Sn-based perovskites.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6079304/v1/dc70b8f7a458d6cc5f352520.png"},{"id":77841538,"identity":"f7bdc666-3190-41ca-ad5a-2a205e1cb240","added_by":"auto","created_at":"2025-03-06 04:58:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1197466,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacterizations of non-fullerene ETLs\u003c/strong\u003e. \u003cstrong\u003ea-b,\u003c/strong\u003e UPS spectra of VBM onsets and photoemission cutoff energy boundaries of non-fullerene \u003cstrong\u003eP1\u003c/strong\u003e, \u003cstrong\u003eP2\u003c/strong\u003e, and \u003cstrong\u003eP3\u003c/strong\u003e ETLs. \u003cstrong\u003ec\u003c/strong\u003e, UV-vis spectra of non-fullerene \u003cstrong\u003eP1\u003c/strong\u003e, \u003cstrong\u003eP2\u003c/strong\u003e, and \u003cstrong\u003eP3\u003c/strong\u003eETLs. \u003cstrong\u003ed\u003c/strong\u003e, Energy level diagram of a typical fullerene-free TPSC with the structure of ITO/PEDOT:PSS/Sn-based perovskites/non-fullerene ETLs/BCP/Ag. The ETLs include \u003cstrong\u003eP1\u003c/strong\u003e, \u003cstrong\u003eP2\u003c/strong\u003e, and \u003cstrong\u003eP3 \u003c/strong\u003eETLs. Both \u003cstrong\u003eP1\u003c/strong\u003e and \u003cstrong\u003eP2\u003c/strong\u003e ETLs exhibit slightly deeper CBMs than Sn-based perovskite, while the \u003cstrong\u003eP3\u003c/strong\u003e ETL shares the same CBM with Sn-based perovskite. \u003cstrong\u003ee\u003c/strong\u003e, SCLC curves of devices with ITO/Ag/non-fullerene ETLs/Ag structures, from which their mobilities were calculated. They exhibit three orders of magnitude higher electron mobilities than the ICBA ETL. \u003cstrong\u003ef\u003c/strong\u003e, Water contact angles of ICBA, \u003cstrong\u003eP1\u003c/strong\u003e, \u003cstrong\u003eP2\u003c/strong\u003e, and \u003cstrong\u003eP3\u003c/strong\u003e ETLs deposited on Sn-based perovskite films, respectively, indicating super hydrophobic behavior due to their hydrophobic nature of long-chain alkyl groups.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6079304/v1/b261c9d75cfa64302c436a74.png"},{"id":77841890,"identity":"35ea2cc2-0fc8-4c3f-b529-e30645b53449","added_by":"auto","created_at":"2025-03-06 05:06:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":4598674,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStrong interaction and fast electron transfer between Sn-based perovskites and non-fullerene ETLs\u003c/strong\u003e. Calculated electrostatic potentials (ESPs) of \u003cstrong\u003ea\u003c/strong\u003e, \u003cstrong\u003eP3\u003c/strong\u003e and \u003cstrong\u003eb\u003c/strong\u003e, ICBA, respectively. FTIR spectra of \u003cstrong\u003ec\u003c/strong\u003e, \u003cstrong\u003eP3\u003c/strong\u003e and the \u003cstrong\u003eP3\u003c/strong\u003e-SnI\u003csub\u003e2\u003c/sub\u003e mixture and \u003cstrong\u003ed\u003c/strong\u003e, ICBA and ICBA-SnI\u003csub\u003e2\u003c/sub\u003e mixture. These results indicate \u003cstrong\u003eP3\u003c/strong\u003e possesses the strongest interaction with the Sn-based perovskite. \u003cstrong\u003ee\u003c/strong\u003e, PL and \u003cstrong\u003ef\u003c/strong\u003e, TRPL spectra of the Sn-based perovskite films with and without the three types of non-fullerene ETLs. These results suggest the electron transfer between the \u003cstrong\u003eP3\u003c/strong\u003e and the Sn-based perovskite film is most efficient. \u003cstrong\u003eg\u003c/strong\u003e, Schematic illustration of interaction between the fullerene-based ICBA and the Sn-based perovskite. \u003cstrong\u003eh\u003c/strong\u003e, Schematic illustration of interaction between the non-fullerene \u003cstrong\u003eP3\u003c/strong\u003e and the Sn-based perovskite. The latter shows faster electron transfer due to the stronger interaction and higher mobility; superior hydrophobicity attributed to long-chain alkyl groups.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6079304/v1/a05934a79168ad37fe3495e4.png"},{"id":77841537,"identity":"93ed3b5f-3243-4f3e-9907-4367596cbf2a","added_by":"auto","created_at":"2025-03-06 04:58:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2903097,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePhotovoltaic performance of TPSCs with non-fullerene ETLs\u003c/strong\u003e. \u003cstrong\u003ea\u003c/strong\u003e,\u003cem\u003e J-V\u003c/em\u003e curves of the 0.04-cm\u003csup\u003e2\u003c/sup\u003e TPSC with the fullerene-based ICBA ETL and non-fullerene \u003cstrong\u003eP1\u003c/strong\u003e, \u003cstrong\u003eP2\u003c/strong\u003e, and \u003cstrong\u003eP3\u003c/strong\u003e ETLs. \u003cstrong\u003eb\u003c/strong\u003e, \u003cem\u003eJ-V\u003c/em\u003e curves of the 1-cm\u003csup\u003e2\u003c/sup\u003e TPSC with the fullerene-based ICBA ETL and non-fullerene \u003cstrong\u003eP1\u003c/strong\u003e, \u003cstrong\u003eP2\u003c/strong\u003e, and \u003cstrong\u003eP3\u003c/strong\u003e ETLs (the inset is a photo of a typical 1 cm\u003csup\u003e2\u003c/sup\u003e cell). \u003cstrong\u003ec\u003c/strong\u003e,\u003cem\u003e \u003c/em\u003eA comparison of PCE between this work and other reported PCEs of 1-cm\u003csup\u003e2\u003c/sup\u003e TPSCs. The impressive PCE of the TPSC with the \u003cstrong\u003eP3\u003c/strong\u003e ETL surpasses those of previously reported TPSCs. PL mappings of 0.5 cm x 0.5 cm perovskite films with \u003cstrong\u003ed\u003c/strong\u003e, fullerene-based ICBA ETL and \u003cstrong\u003ee,\u003c/strong\u003e \u003cstrong\u003eP3\u003c/strong\u003e ETL. \u003cstrong\u003ef\u003c/strong\u003e, Cross-sectional TEM image of the fullerene-free TPSC with the \u003cstrong\u003eP3\u003c/strong\u003e ETL, exhibiting the conformal structure between the \u003cstrong\u003eP3\u003c/strong\u003e ETL and the Sn-based perovskite layer.\u003cstrong\u003e g, \u003c/strong\u003eCross-sectional TEM image of the fullerene-free TPSC with the \u003cstrong\u003eP3\u003c/strong\u003e ETL, indicating the interface between the \u003cstrong\u003eP3\u003c/strong\u003e ETL and the Sn-based perovskite layer touches perfectly. \u003cstrong\u003eh,\u003c/strong\u003e Long-term stability measurements of the encapsulated TPSCs with the ICBA and three types of non-fullerene ETLs. \u003cstrong\u003ei,\u003c/strong\u003e Operational stability of encapsulated devices under continuous 1-sun-equivalent white LED illumination with MPPT. Both \u003cstrong\u003eh\u003c/strong\u003e and \u003cstrong\u003ei\u003c/strong\u003e indicate that fullerene-free TPSCs possess significantly better stability than fullerene-based TPSCs.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6079304/v1/09c4fc57d7be3d7487494af8.png"},{"id":80781274,"identity":"998817fc-9280-4466-9c3b-7b1bb3d8cb53","added_by":"auto","created_at":"2025-04-17 04:38:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":13478791,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6079304/v1/61804883-6d1f-454b-95ac-537ae1d10cac.pdf"},{"id":77841539,"identity":"7306b17b-e052-4c5d-a484-8ba37d065b5b","added_by":"auto","created_at":"2025-03-06 04:58:46","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":7540761,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"NPSICentimeterscalefullerenefreeTPSC.docx","url":"https://assets-eu.researchsquare.com/files/rs-6079304/v1/c37c96003714b2ddd74257f5.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Centimeter-scale fullerene-free tin-based perovskite solar cells achieving over 14% efficiency","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eTin-based perovskite solar cells (TPSCs) are attracting increasing attention from the research community as a promising next-generation perovskite-based photovoltaic technology because of their competitive advantages such as environmental friendliness, ideal bandgaps, low cost, ease of growth, and high power conversion efficiencies (PCEs).\u003csup\u003e[\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e Currently, fullerene-based materials, such as fullerene (C\u003csub\u003e60\u003c/sub\u003e),\u003csup\u003e[\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e phenyl-C\u003csub\u003e60\u003c/sub\u003e-butyric acid methyl ester (PC\u003csub\u003e60\u003c/sub\u003eBM),\u003csup\u003e[\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e and indene-C\u003csub\u003e60\u003c/sub\u003e bisadduct (ICBA),\u003csup\u003e[\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e have been the dominant electron transport layers (ETLs) used in TPSCs. Despite several advancements, persistent issues and limitations with TPSCs necessitate the replacement of these outdated ETLs. Scientifically, fullerene-based materials exhibit low electron mobilities, limited interactions with Sn-based perovskites, poor resistance to moisture penetration, thermal instability, and photochemical instability, all of which are detrimental to TPSC performance.\u003csup\u003e[\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e Moreover, chemical modifications of fullerenes are challenging, leading to low structural flexibility and difficulty in tuning electronic properties. From an engineering perspective, fullerene-based materials are hindered by high-cost precursors, complex synthetic processes, and the need for time-consuming purification. Therefore, exploring new ETLs to enhance TPSCs is imperative.\u003csup\u003e[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eNon-fullerene materials present a promising solution to these challenges and may emerge as optimal ETLs for TPSCs due to several distinct advantages. On one hand, non-fullerene materials benefit from a vast molecular design space, enabling excellent synthetic flexibility with utilizing more readily available source materials\u003csup\u003e[\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. This flexibility allows for easily tunable electronic properties and improved solubility, facilitating their integration into TPSC architectures. On the other hand, non-fullerene materials can be specifically tailored to work with Sn-based perovskites in terms of both high electron mobilities, strong interaction with Sn-based perovskites, and protection from moisture in the air\u003csup\u003e[\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. Additionally, the use of low-cost cores, coupled with facile synthesis and simplified purification contributes to significant reductions in the production cost of non-fullerene materials\u003csup\u003e[\u003cspan additionalcitationids=\"CR23 CR24 CR25 CR26 CR27 CR28 CR29 CR30\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFurthermore, achieving high PCEs in small-area devices is critical, but scaling up to centimeter-scale devices is essential for the practical deployment of TPSCs. The transition to larger-scale devices often presents challenges, such as maintaining uniformity and stability across the functional layer, which can significantly impact overall efficiency. Demonstrating high PCEs in centimeter-scale TPSCs thus serves as a crucial benchmark, indicating that the material and device architecture are robust enough for potential commercialization and large-scale manufacturing.\u003c/p\u003e \u003cp\u003eFollowing this line of thoughts, we put forward a fullerene-free TPSC architecture and developed a series of low-cost, n-type semiconducting non-fullerene ETLs (named as \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e), through molecular design strategies involving fluorination and triple-acceptor modulation. Using Stille-coupling polymerization, these non-fullerene materials can be synthesized in high yield, offering potential for large-scale production. While maintain band structures similar to those of fullerene-based counterpart, these non-fullerene materials demonstrated electron mobilities that were three orders of magnitude higher, making them ideal candidates for ETLs in TPSCs. Moreover, the functional groups present in these non-fullerene materials facilitated the formation of continuous and conformal interfaces with Sn-based perovskite layers, resulting in more uniform and stronger interactions, and enabling efficient electron transfer across the interface. As a result of these advancements, the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL exhibited record PCEs of 16.06% for small-area devices and 14.39% for large-area devices. Additionally, the enhanced stability of these fullerene-free TPSCs, attributed to their robust hydrophobicity conferred by long alkyl side chains, further underscores their potential. Specifically, the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL shows no significant change after 1200 h of shelf storage and retains 86% of its initial PCE after 550 h of maximum power point tracking under continuous 1-sun illumination. These results highlight the potential of fullerene-free TPSCs with non-fullerene ETLs to enhance the photovoltaic performance and long-term stability.\u003c/p\u003e"},{"header":"2. Results and discussions","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Fullerene-free TPSC design\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe design of fullerene-free TPSC structure draws inspiration from, yet is distinct from, conventional organic solar cells. Typically, organic solar cells employ a blend of a conjugated polymer and a fullerene derivative as the active layer. However, the PCEs of organic solar cells has historically been capped around 10%, primarily due to several inherent drawbacks of fullerene derivatives.\u003csup\u003e[\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e–\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e These drawbacks include low structural flexibility, weak interaction with conjugated polymer, low charge mobility, high costs, and complex synthetic process. By introducing non-fullerene materials to replace these fullerene derivatives, these issues have been mitigated, resulting in a near doubling of PCEs in organic solar cells over the past decade.\u003csup\u003e[\u003cspan additionalcitationids=\"CR36 CR37\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e–\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eIn inverted TPSCs, similar challenges persist. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea shows the widely used structure of inverted TPSCs, typically comprising an ITO/HTL/Sn-based perovskite/ETL/BCP/Ag configuration, where the ETL is often composed of fullerene derivatives, such as C\u003csub\u003e60\u003c/sub\u003e, PC\u003csub\u003e60\u003c/sub\u003eBM, and ICBA. Beyond their intrinsic shortcomings, these fullerene derivative ETLs exhibit weak interactions with the perovskite layer, leading to sluggish electron transfer and severe non-radiative recombination. To overcome these challenges, we aimed to develop a fullerene-free TPSC that integrates several desirable features: (i) low cost and facile synthetic process; (ii) high charge mobility; (iii) high structure flexibility; (iv) hydrophobicity, attributed to long alkyl side chains; and (v) strong interactions with perovskite layers due to the presence of multiple functional groups. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb, the strong interaction between the perovskite layer and the non-fullerene ETL, coupled with the high mobility of the non-fullerene ETL, is anticipated to accelerate electron transfer from the Sn-based perovskite layer to the non-fullerene ETL and suppress non-radiative recombination at the interface.\u003c/p\u003e \u003cp\u003eWe selected Diketopyrrolopyrrole (DPP)-based materials as the non-fullerene ETLs for their planar structure, high crystallinity, acceptable electron-withdrawing properties and superior solubilizing capability \u003cem\u003evia N\u003c/em\u003e-alkylation.\u003csup\u003e[\u003cspan additionalcitationids=\"CR40\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e–\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/sup\u003e Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec outlines the synthesis routes for the novel non-fullerene ETLs based on DPP. First, through a strategic combination of fluorination and triple-acceptor modulation involving DPP and difluorobenzothiadiazole, an electron-deficient building block based on DPP-difluorobenzothiadiazole triad, i.e., 6,6′-((5,6-difluorobenzo[\u003cem\u003ec\u003c/em\u003e][1,2,5]thiadiazole-4,7-diyl)bis(thiophene-5,2-diyl))bis(2,5-bis(2-octyldodecyl)-3-(thiophen-2-yl)-2,5-dihydropyrrolo[3,4-\u003cem\u003ec\u003c/em\u003e]pyrrole-1,4-dione) (DFB), was synthesized. Second, bromination of DFB using N-bromosuccinimide was conducted to obtain the monomer 6,6″-(5,5″-(5,6-difluorobenzo[\u003cem\u003ec\u003c/em\u003e][1,2,5]thiadiazole-4,7-diyl)bis(thiophene-5,2-diyl))bis(3-(5-bromothiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo[3,4-\u003cem\u003ec\u003c/em\u003e]pyrrole-1,4(2\u003cem\u003eH\u003c/em\u003e,5\u003cem\u003eH\u003c/em\u003e)-dione) (DFB-Br). Finally, these three non-fullerene materials, designated as \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e, were synthesized using palladium-catalyzed Stille-coupling polymerization with three distinct tin compounds of thiophene donor derivatives. Detailed synthesis details are provided in the supplementary information. The structural and optical characteristics of these non-fullerene ETLs were confirmed through nuclear magnetic resonance (NMR) and Tauc plots (\u003cb\u003eSupplementary Figs.\u0026nbsp;1–2\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Characterization of non-fullerene ETLs\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAn ideal ETL for TPSCs should feature a favorable band structure aligned well with Sn-based perovskites and exhibit high mobility\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. To demonstrate the suitability of the three types of non-fullerene materials as ETLs in this regard, their ultraviolet photoelectron spectroscopy (UPS) data of the valence band maximum (VBM) onsets and the secondary electron cutoff energy boundaries were characterized, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-b. Utilizing the formula of VBM = 21.22 – (\u003cem\u003eE\u003c/em\u003e\u003csub\u003ecutoff\u003c/sub\u003e – \u003cem\u003eE\u003c/em\u003e\u003csub\u003eonset\u003c/sub\u003e) and bandgaps obtained from UV-vis spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec \u003cb\u003eand Supplementary Fig.\u0026nbsp;2\u003c/b\u003e), their VBM and conduction band minimum (CBM) energies were calculated, respectively, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed. Both \u003cb\u003eP1\u003c/b\u003e and \u003cb\u003eP2\u003c/b\u003e ETLs exhibit slightly deeper CBMs compared to Sn-based perovskites, while the \u003cb\u003eP3\u003c/b\u003e ETL shares the same CBM with Sn-based perovskite. Theoretically, the \u003cb\u003eP3\u003c/b\u003e ETL emerges as the most promising ETL candidate for TPSCs as it possesses the shallowest CBM among the three types of non-fullerene ETLs, maximizing the attainable photovoltage determined by the quasi-Fermi level splitting, \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e = (\u003cem\u003eE\u003c/em\u003e\u003csub\u003eFn\u003c/sub\u003e – \u003cem\u003eE\u003c/em\u003e\u003csub\u003eFp\u003c/sub\u003e)/\u003cem\u003eq\u003c/em\u003e.\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eIn addition to band structures, the mobilities of the three types of non-fullerene ETLs, including \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e, were assessed. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee shows their space-charge-limited current (SCLC) curves of devices with ITO/Ag/non-fullerene ETLs/Ag structures. Their mobilities (\u003cem\u003eµ\u003c/em\u003es) were quantitatively evaluated in the trap-free regions using the formula:\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\mu\\:=\\frac{8{L}^{3}\\bullet\\:{J}_{D}}{9\\epsilon\\:{\\epsilon\\:}_{0}{V}_{h}^{2}}$$\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003eHere, \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eh\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eD\u003c/em\u003e\u003c/sub\u003e represent the voltage and current density at the trap-free region, \u003cem\u003eL\u003c/em\u003e is the thickness of the non-fullerene ETLs, \u003cem\u003eε\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e is the vacuum permittivity, \u003cem\u003eε\u003c/em\u003e denotes the relative dielectric constant of the non-fullerene ETLs. Consequently, the calculated \u003cem\u003eµ\u003c/em\u003es of \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e are 1.98, 3.17, and 1.29 cm\u003csup\u003e2\u003c/sup\u003e V\u003csup\u003e-1\u003c/sup\u003e s\u003csup\u003e-1\u003c/sup\u003e, respectively (\u003cb\u003eSupplementary Note 1\u003c/b\u003e). Notably, these values are three orders of magnitude higher than that of fullerene-based ICBA ETL (6.9 × 10\u003csup\u003e− 3\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e V\u003csup\u003e-1\u003c/sup\u003e s\u003csup\u003e-1\u003c/sup\u003e), which further suggest these non-fullerene ETLs are promising candidates for TPSCs.\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR14 CR15 CR16\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e–\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eMoreover, beyond confirming their suitability as novel ETLs in TPSCs, the three types of non-fullerene ETLs exhibited super hydrophobic behavior in water contact angle experiments due to their hydrophobic nature of long-chain alkyl groups. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef, the water contact angles of the non-fullerene \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs on Sn-based perovskites were measured at 101.8°, 101.9°, and 103.2°, respectively, all significantly surpassing that of the fullerene-based ICBA ETL of 59.9°. This observation underscores the potential advantages of these non-fullerene ETLs in protecting Sn-based perovskites from moisture permeation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Interactions between non-fullerene ETLs and Sn-based perovskite layers\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAfter identifying the three types of non-fullerene ETLs as ideal candidates for TPSCs, their interactions with Sn-based perovskites were first assessed through calculated electrostatic surface potentials (ESPs), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and \u003cb\u003eSupplementary Fig.\u0026nbsp;3\u003c/b\u003e. For comparison, the ESP of fullerene-based ICBA ETL was also calculated (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). All three types of non-fullerene ETLs possess electron-rich (red areas) and electron-poor (blue areas) domains, confirming their potentials for effective interaction with Sn-based perovskites. Notably, the \u003cb\u003eP3\u003c/b\u003e ETL shows a higher ESP than \u003cb\u003eP1\u003c/b\u003e and \u003cb\u003eP2\u003c/b\u003e ETLs, suggesting a stronger interaction with the Sn-based perovskite. This was further validated by calculating the calculated adsorption energy (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eads\u003c/em\u003e\u003c/sub\u003e). \u003cb\u003eSupplementary Fig.\u0026nbsp;4\u003c/b\u003e shows that the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eads\u003c/em\u003e\u003c/sub\u003e of ICBA on the Sn-based perovskite surface is -1.26 eV, while the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eads\u003c/em\u003e\u003c/sub\u003es values for \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e and \u003cb\u003eP3\u003c/b\u003e ETLs are − 2.95, -2.90 and − 3.22 eV, respectively, indicating the same results with ESPs. These predicted interactions were further investigated experimentally using Fourier-transform infrared (FTIR) spectroscopy, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec-d and \u003cb\u003eSupplementary Fig.\u0026nbsp;5.\u003c/b\u003e The SnI\u003csub\u003e2\u003c/sub\u003e-mixtures with the three types of non-fullerene ETLs exhibit significant shifts, indicating strong interactions due to their high electrostatic potentials, while the fullerene-based ICBA ETL and the ICBA-SnI\u003csub\u003e2\u003c/sub\u003e mixture display no discernible shifts, suggesting limited interaction due to the lack of functional groups. Such large shifts can be attributed to the presence of functional groups in these non-fullerene ETLs, such as C-S bonds, C-N bonds, and C-F bonds, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec. Among them, the \u003cb\u003eP3\u003c/b\u003e-SnI\u003csub\u003e2\u003c/sub\u003e mixture shows more pronounced shifts, indicating \u003cb\u003eP3\u003c/b\u003e possesses the strongest interaction with the Sn-based perovskite among the three types of non-fullerene ETLs.\u003c/p\u003e \u003cp\u003eIt is well established that strong interactions facilitate smooth electron transport dynamics from Sn-based perovskites to non-fullerene ETLs. To demonstrate this, kelvin probe force microscopy (KPFM) measurements were conducted, as shown in \u003cb\u003eSupplementary Fig.\u0026nbsp;6\u003c/b\u003e. Sn-based perovskites with the three types non-fullerene ETLs exhibit a smaller surface potential compared to that with the fullerene-based ICBA ETL, suggesting the stronger interaction and faster electron transfer. Moreover, the \u003cb\u003eP3\u003c/b\u003e ETL shows the smallest surface potential among them, indicative of the strongest interaction and the fastest electron transfer. This observation was further corroborated by calculating the total charge transfer between the non-fullerene ETLs and Sn perovskites and compared it to that of ICBA, as shown in \u003cb\u003eSupplementary Note 2\u003c/b\u003e. All three types of non-fullerene ETLs exhibit higher charge transfer values than the ICBA ETL, with the \u003cb\u003eP3\u003c/b\u003e ETL displaying the greatest value, highlighting the fastest electron transfer from the Sn-based perovskite to the \u003cb\u003eP3\u003c/b\u003e ETL. To gain more insights into the effective electron transfer dynamics between the non-fullerene ETLs and Sn-based perovskites in TPSCs, photoluminescence (PL) and time-resolved PL (TRPL) measurements were also conducted. The PL peak intensities of the Sn-based perovskites with the three types of non-fullerene ETLs are weaker than that of the bare Sn-based perovskite, and the Sn-based perovskite with the \u003cb\u003eP3\u003c/b\u003e ETL shows the lowest peak intensities (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). This result demonstrated that the \u003cb\u003eP3\u003c/b\u003e ETL possesses the most efficient electron transfer with the Sn-based perovskite, which is agreement with the KPFM result. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef displays the TRPL decays of the Sn-based perovskite film without and with the three types of non-fullerene ETLs. The corresponding PL lifetime was calculated using a biexponential fitting to the TRPL decays, as shown in \u003cb\u003eSupplementary Table\u0026nbsp;1\u003c/b\u003e\u003csup\u003e[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]\u003c/sup\u003e. Clearly, all the Sn-based perovskites with the three types of non-fullerene ETLs show shorter PL decay lifetime than the bare Sn-based perovskite, with the Sn-based perovskite with the \u003cb\u003eP3\u003c/b\u003e ETL showing the shortest lifetime of 2.88 ns, further verifying the most efficient electron transfer between the \u003cb\u003eP3\u003c/b\u003e ETL and the Sn-based perovskite film.\u003c/p\u003e \u003cp\u003eTo highlight the structural advantages of fullerene-free TPSCs, we have proposed and plotted schematic diagrams based on above discussions, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg-h. At the interface between the Sn-based perovskite layer and the non-fullerene ETL, the functional groups in the non-fullerene ETL effectively interact with Sn\u003csup\u003e2+\u003c/sup\u003e and I\u003csup\u003e−\u003c/sup\u003e in the Sn-based perovskite layer, reducing Sn\u003csup\u003e2+\u003c/sup\u003e oxidation and inhibiting I\u003csup\u003e−\u003c/sup\u003e migration. This promotes process \u003cem\u003ea\u003c/em\u003e and suppresses process \u003cem\u003eb\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg). In contrast, in the case of the fullerene-based ETL, process \u003cem\u003ea\u003c/em\u003e proceeds slowly, while process \u003cem\u003eb\u003c/em\u003e is more severe due to the weaker interaction between the Sn-based perovskite and the fullerene-based ETL (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eh). Furthermore, process \u003cem\u003ec\u003c/em\u003e in non-fullerene ETLs occurs significantly faster than in fullerene-based ETLs, owing to the three orders magnitude higher electron mobility of the former. Additionally, the intrinsic hydrophobicity of the long alkyl side chains in non-fullerene ETLs contributes to enhanced stability in fullerene-free TPSCs.\u003c/p\u003e \u003cp\u003eHave demonstrated the strong interaction and fast electron transfer, the effects of the three types of non-fullerene ETLs on the morphologies and crystallinities of Sn-based perovskite films were investigated as well. \u003cb\u003eSupplementary Figs.\u0026nbsp;7a-d\u003c/b\u003e exhibit the typical scanning electron microscopy (SEM) images of Sn-based perovskite films without and with the three types of non-fullerene ETLs. Compared to the morphology of the bare Sn-based perovskite film, the surfaces of the Sn-based perovskite films with the three types non-fullerene ETLs appear slightly blurred but uniform, suggesting that the three types non-fullerene ETLs were deposited on the Sn-based perovskite surfaces successfully but had negligible impacts on the film morphologies. The atomic force microscopy (AFM) images corroborate the SEM results, as shown in \u003cb\u003eSupplementary Figs.\u0026nbsp;7e-h\u003c/b\u003e. Moreover, after depositing the three types non-fullerene ETLs on the Sn-based perovskite films, root-mean-square roughness was reduced. \u003cb\u003eSupplementary Fig.\u0026nbsp;8\u003c/b\u003e exhibits the X-ray diffraction (XRD) patterns of the Sn-based perovskite films with and without the three types non-fullerene ETLs. Similar to the morphologies, the influences of the three types non-fullerene ETLs on the crystallinity of the Sn-based perovskite films can also be omitted.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Device performance\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eNext, TPSCs were fabricated with the structure of ITO/PEDOT:PSS/Sn-based perovskites/ETLs/BCP/Ag, as illustrated in \u003cb\u003eSupplementary Fig.\u0026nbsp;9\u003c/b\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea shows the current density-voltage (\u003cem\u003eJ–V\u003c/em\u003e) curves of fullerene-based TPSCs (0.04 cm\u003csup\u003e2\u003c/sup\u003e) with ICBA ETL and fullerene-free TPSCs (0.04 cm\u003csup\u003e2\u003c/sup\u003e) with \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs. The corresponding photovoltaic parameters were listed in \u003cb\u003eSupplementary Table\u0026nbsp;2\u003c/b\u003e. The fullerene-based TPSC with the ICBA ETL exhibits a PCE of 11.74%, with an open-circuit voltage (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e) of 0.81 V, a short circuit current density (\u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e) of 18.57 mA/cm\u003csup\u003e2\u003c/sup\u003e, and a fill factor (FF) of 78.04%, comparable to previous reports.\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e As anticipated, compared with fullerene-based TPSCs, all photovoltaic parameters were significant increased for fullerene-free TPSCs (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea and \u003cb\u003eSupplementary Fig.\u0026nbsp;10\u003c/b\u003e). Specifically, the TPSC with the non-fullerene \u003cb\u003eP3\u003c/b\u003e ETL shows a PCE of 16.06%, with \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e = 0.99 V, \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e = 19.79 mA/cm\u003csup\u003e2\u003c/sup\u003e, and FF = 81.98%, which is one of the highest PCE among all reported TPSCs. Notably, one such device was measured by an independently accredited testing centre (Chinese National PV Industry Measurement and Testing Center, NPVM) and obtained a certified PCE of 15.90% (\u003cb\u003eSupplementary Fig.\u0026nbsp;11\u003c/b\u003e). For practical applications, TPSCs in this study were also fabricated with a large-area of 1-cm\u003csup\u003e2\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb shows the current density-voltage (\u003cem\u003eJ-V\u003c/em\u003e) curves of fullerene-based TPSCs with ICBA ETLs and fullerene-free TPSCs with \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs. Their photovoltaic parameters were listed in \u003cb\u003eSupplementary Table\u0026nbsp;3\u003c/b\u003e. The 1-cm\u003csup\u003e2\u003c/sup\u003e fullerene-based TPSC with the ICBA ETL displays a PCE of 10.60% with a \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e of 17.65 mA cm\u003csup\u003e− 2\u003c/sup\u003e, a \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e of 0.78 V, and a FF of 76.97%, comparable to previous literature results.\u003csup\u003e[\u003cspan additionalcitationids=\"CR12 CR13 CR14\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e–\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e In contrast, the fullerene-free TPSCs exhibit significantly enhanced performance. Specifically, the 1-cm\u003csup\u003e2\u003c/sup\u003e TPSC with the \u003cb\u003eP1\u003c/b\u003e ETL achieve a PCE of 12.88%, with \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e = 0.92 V, \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e = 17.91 mA/cm\u003csup\u003e2\u003c/sup\u003e, and FF = 78.19%; \u003cb\u003eP2\u003c/b\u003e ETL yields a PCE of 13.39%, with \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e = 0.93 V, \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e = 18.38 mA/cm\u003csup\u003e2\u003c/sup\u003e, and FF = 78.32%; and \u003cb\u003eP3\u003c/b\u003e ETL achieves a PCE of 14.39%, with \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e = 0.94 V, \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e = 19.45 mA/cm\u003csup\u003e2\u003c/sup\u003e, and FF = 78.34%. These results represent an enhancement of more than 30% in PCE for fullerene-free TPSCs compared to fullerene-based TPSCs. To the best of our knowledge, this marks the highest efficiency for TPSCs with large area so far (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec \u003cb\u003eand Supplementary Table\u0026nbsp;4\u003c/b\u003e).\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan additionalcitationids=\"CR44 CR45 CR46 CR47\" citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e–\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]\u003c/sup\u003e In addition to the basic advantages of well-matched band alignment and high electron mobility, this impressive performance can be largely attributed to the uniform and strong interaction of the \u003cb\u003eP3\u003c/b\u003e ETL with the Sn-based perovskite layer. This is evidenced by PL mapping of 0.5 cm x 0.5 cm Sn-based perovskite films with ICBA, \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed-e and \u003cb\u003eSupplementary Fig.\u0026nbsp;12\u003c/b\u003e. The PL mapping for the \u003cb\u003eP3\u003c/b\u003e ETL exhibits the highest uniformity, indicating a consistent interaction between the Sn-based perovskite layer and the \u003cb\u003eP3\u003c/b\u003e ETL. Furthermore, the lowest intensity of the PL mapping for the \u003cb\u003eP3\u003c/b\u003e ETL reflects the strongest interaction with the Sn-based perovskite layer, which is in accordance with the trends observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee. To get more insight into the uniform and strong interaction between the layers, cross-sectional SEM and transmission electron microscopy (TEM) images were tested for the fullerene-free TPSC structure, as illustrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef-g. The cross-sectional SEM image reveals that the \u003cb\u003eP3\u003c/b\u003e ETL establishes a continuous and conformal interface with the Sn-based perovskite layer and the TEM image confirms an intimate and defect-free interface between the \u003cb\u003eP3\u003c/b\u003e ETL and the Sn-based perovskite layer.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSupplementary Fig.\u0026nbsp;13\u003c/b\u003e presents the incident photo-to-electric current conversion efficiency (IPCE) spectra and integrated \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e values for fullerene-based TPSCs with ICBA ETLs and fullerene-free TPSCs with \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs. Their integrated \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e values were calculated to be 18.76, 19.86, 19.88 and 20.87 mA cm\u003csup\u003e− 2\u003c/sup\u003e respectively, indicating that the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL shows the highest photon absorption ability across the wavelength range. This enhanced absorption is attributed to the rapid electron transfer from the Sn-based perovskite layer to the \u003cb\u003eP3\u003c/b\u003e ETL. \u003cb\u003eSupplementary Fig.\u0026nbsp;14\u003c/b\u003e exhibits the \u003cem\u003eJ-V\u003c/em\u003e plots of the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL measured in forward and reverse scanning modes. These results reveal an ignorable hysteresis, whereas the fullerene-based TPSC with the ICBA ETL exhibits a significant hysteresis. To assess device reproducibility, 13 individual fullerene-based TPSCs with ICBA ETLs and fullerene-free TPSCs with \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs were fabricated, respectively, as shown in \u003cb\u003eSupplementary Fig.\u0026nbsp;15\u003c/b\u003e. The statistical histograms show that the PCE of the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL distribute over a narrower range.\u003c/p\u003e \u003cp\u003eTo further elucidate the underlying mechanism, electrochemical impedance spectroscopy (EIS) was performed to analyze the interface resistance, as shown in \u003cb\u003eSupplementary Fig.\u0026nbsp;16\u003c/b\u003e. The corresponding parameters, including inner series resistances (\u003cem\u003eR\u003c/em\u003e\u003csub\u003es\u003c/sub\u003es), charge transfer resistances (\u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003es), and carrier recombination resistances (\u003cem\u003eR\u003c/em\u003e\u003csub\u003erec\u003c/sub\u003es), are summarized in \u003cb\u003eSupplementary Table\u0026nbsp;5\u003c/b\u003e. The fullerene-based TPSCs with ICBA ETLs show higher \u003cem\u003eR\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e and \u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e values but a lower \u003cem\u003eR\u003c/em\u003e\u003csub\u003erec\u003c/sub\u003e compared to fullerene-free TPSCs with \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs. This result further underscores the weak interaction between the ICBA ETL and the Sn-based perovskite layer, attributed to the lack of functional groups in the ICBA ETL. Among the three types of non-fullerene ETLs, the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL displays the lowest \u003cem\u003eR\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e and \u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e and the highest \u003cem\u003eR\u003c/em\u003e\u003csub\u003erec\u003c/sub\u003e compared to those with \u003cb\u003eP1\u003c/b\u003e and \u003cb\u003eP2\u003c/b\u003e ETLs, indicating the strongest interaction between the \u003cb\u003eP3\u003c/b\u003e ETL and the Sn-based perovskite layer due to significant functional groups. This results in the most efficient charge transfer from the Sn-based perovskite layer to the \u003cb\u003eP3\u003c/b\u003e ETL and reducing carrier recombination at the interface. The lower recombination rate is attributed to the reduced defect density at the interface between the Sn-based perovskite layer and the \u003cb\u003eP3\u003c/b\u003e ETL. To further investigate these defects, dark \u003cem\u003eJ-V\u003c/em\u003e curves of fullerene-free TPSCs with \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs were tested, as shown in \u003cb\u003eSupplementary Fig.\u0026nbsp;17\u003c/b\u003e. The dark \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003eSC\u003c/em\u003e\u003c/sub\u003e of the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL is an order of magnitude lower than those with \u003cb\u003eP1\u003c/b\u003e and \u003cb\u003eP2\u003c/b\u003e ETLs, indicative of the smallest defect density at the interface between the Sn-based perovskite layer and the \u003cb\u003eP3\u003c/b\u003e ETL, consequently, the lowest carrier recombination rate. Additionally, \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eOC\u003c/em\u003e\u003c/sub\u003e versus incident light intensity plots further supported these findings (\u003cb\u003eSupplementary Fig.\u0026nbsp;18\u003c/b\u003e). The ideality factor (n = 1.19 kT/q) for the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL is closer to the ideal value of 1 kT/q and significantly smaller compared to fullerene-free TPSC with the \u003cb\u003eP2\u003c/b\u003e ETL (n = 1.41 kT/q) and the \u003cb\u003eP1\u003c/b\u003e ETL (n = 1.52 kT/q), signifying improved device characteristics.\u003c/p\u003e \u003cp\u003eTo quantitatively assess defect densities, SCLC curves were obtained from electron-only devices structured as FTO/SnO\u003csub\u003e2\u003c/sub\u003e/Sn-based perovskites/ETLs/Ag (\u003cb\u003eSupplementary Fig.\u0026nbsp;19\u003c/b\u003e). The tested ETLs included \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e. In the space-charge-limited current region, the sharp rise in the curve indicates a trap-filled limit, where all defects are occupied by charge carriers. The defect density can be estimated using the equation:\u003c/p\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:{V}_{TFL}=\\:\\frac{{N}_{defects}\\:\\times\\:e{L}^{2}}{2\\epsilon\\:{\\epsilon\\:}_{0}}$$\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003eHere, \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eTFL\u003c/em\u003e\u003c/sub\u003e represents the trap-filled limit voltage, \u003cem\u003eL\u003c/em\u003e and \u003cem\u003eε\u003c/em\u003e denote the thickness and relative dielectric constant of the Sn-based perovskite film, respectively, \u003cem\u003eε\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e is the vacuum permittivity, and \u003cem\u003ee\u003c/em\u003e is the elementary charge. The calculated defect densities (\u003cem\u003eN\u003c/em\u003e\u003csub\u003edefects\u003c/sub\u003e) are 3.42 × 10\u003csup\u003e16\u003c/sup\u003e, 1.33 × 10\u003csup\u003e16\u003c/sup\u003e and 5.23 × 10\u003csup\u003e15\u003c/sup\u003e cm\u003csup\u003e− 3\u003c/sup\u003e for electron-only devices with \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs, respectively, as shown in \u003cb\u003eSupplementary Table\u0026nbsp;6\u003c/b\u003e. These results clearly demonstrate a significant reduction in defect density when employing the non-fullerene \u003cb\u003eP3\u003c/b\u003e as the ETL.\u003c/p\u003e \u003cp\u003eFinally, the long-term operational stabilities of fullerene-free TPSCs were studied, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh-i. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh presents the normalized PCEs of encapsulated TPSCs as a function of aging time under ambient atmosphere. The fullerene-based TPSC with the ICBA ETL exhibits noticeable degradation throughout the testing period, maintaining 65% PCE after 900 h. Conversely, fullerene-free TPSCs with the \u003cb\u003eP3\u003c/b\u003e ETL displays much better performance. Specifically, the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL exhibits negligible degradation for a period of 1200 h. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ei displays the normalized PCEs during maximum power point tracking (MPPT) under continuous 1-sun white-light LED illumination. The fullerene-free TPSCs with the \u003cb\u003eP3\u003c/b\u003e ETL retains approximately 86% of its initial PCE after 550 h, whereas the fullerene-based TPSCs with the ICBA ETL maintains only 49% under the same condition. The enhanced stability is attributed to the hydrophobic nature conferred by long-chain alkyl groups in these non-fullerene ETLs. To demonstrate the hydrophobicity of these non-fullerene ETLs, water contact angle measurements were conducted on the fullerene-based TPSCs and fullerene-free TPSCs without the BCP layer and the Ag electrode. \u003cb\u003eSupplementary Fig.\u0026nbsp;20\u003c/b\u003e exhibit that water contact angles of these non-fullerene \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e ETLs process from approximately 102° at 0 min to around 90°-100° at 12 min and the non-fullerene \u003cb\u003eP3\u003c/b\u003e ETL possess the best performance. In contrast, the water contact angle of the fullerene-based ICBA ETL diminishes to 35.8° at 12 min. This improvement in hydrophobicity suggests that fullerene-free TPSCs and non-fullerene ETLs are preferable structure for improving the stability of TPSCs.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, we have proposed a novel fullerene-free TPSC structure aimed at enhancing both the PCE and stability compared to conventional fullerene-based TPSCs. A series of innovative non-fullerene ETLs were developed to replace traditional fullerene-based ETLs. These non-fullerene ETLs, namely \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e, were synthesized through a combination of fluorination, triple-acceptor modulation and Stille-coupling polymerization. These new non-fullerene ETLs address key challenges encountered with fullerene-based ETLs, offering three orders of magnitude higher mobilities, stronger interactions with Sn-based perovskite layers, and greater tunability in chemical and electrical structures, rendering them highly suitable for TPSC applications. The small-area and large-area fullerene-free TPSCs with the three types of non-fullerene ETLs, particularly the \u003cb\u003eP3\u003c/b\u003e ETL, achieved record PCEs of 16.06% and 14.39%, respectively, surpassing the performance of fullerene-based TPSCs with the ICBA ETL. In addition, the inclusion of robust hydrophobic long alkyl side chains in these non-fullerene ETLs contributed to exceptional stability, with the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL showing no significant degradation over 1200 hours, and maintaining 86% of its initial PCE after 550 h of MPPT under continuous 1-sun illumination. This comprehensive study not only provides valuable insights into the design and development of fullerene-free TPSCs and cutting-edge non-fullerene ETL materials, but also opens the door for the production of non-toxic large-area PSCs with high PEC and long-term stability, making the practical application of PSCs a real possibility.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eJ.L. acknowledges the funding support from the National Natural Science Foundation of China (52102219 and 52471197). Y.W. acknowledges the funding support from the National Natural Science Foundation of China (52203216 and 22375051).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen, J. et al. Efficient tin-based perovskite solar cells with trans-isomeric fulleropyrrolidine additives. Nat. 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Soc. 139, 14800\u0026ndash;14806 (2017).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6079304/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6079304/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFullerene-based materials have traditionally served as the primary electron transport layers (ETLs) in environmentally friendly tin-based perovskite solar cells (TPSCs) due to their suitable band structures. However, they suffer from limitations such as high cost, complex synthetic process, low electron mobilities, limited interactions with Sn-based perovskites, and challenges in tuning their chemical and electrical structures, which have hindered further improvements in power conversion efficiency (PCE) of TPSCs. To tackle these issues, we propose a fullerene-free TPSC architecture and introduce a series of low-cost non-fullerene materials, i.e. fluorinated triple-acceptor polymers (named as \u003cb\u003eP1\u003c/b\u003e, \u003cb\u003eP2\u003c/b\u003e, and \u003cb\u003eP3\u003c/b\u003e), as alternative ETLs. Compared to fullerene-based ETL, such as indene-C\u003csub\u003e60\u003c/sub\u003e bisadduct (ICBA), these non-fullerene ETLs exhibit facile synthetic process, three orders of magnitude higher electron mobilities, and high structural flexibility. Additionally, these non-fullerene ETLs form continuous and conformal interfaces with Sn-based perovskite layers, enabling stronger and more uniform interactions over large-area Sn-based perovskite layers. In 1-cm\u003csup\u003e2\u003c/sup\u003e TPSCs, particularly those using the \u003cb\u003eP3\u003c/b\u003e ETL, we achieve a remarkable PCE of 14.39%, surpassing the PCE of 10.61% observed in 1-cm\u003csup\u003e2\u003c/sup\u003e TPSCs with the ICBA ETL. Notably, TPSCs with the \u003cb\u003eP3\u003c/b\u003e ETL achieved a record PCE of 16.06% for small area of 0.04-cm\u003csup\u003e2\u003c/sup\u003e (certified at 15.90%). Furthermore, the fullerene-free TPSC with the \u003cb\u003eP3\u003c/b\u003e ETL demonstrates exceptional stability, showing no significant degradation over 1200 hours of shelf storage and maintaining nearly 86% of its initial PCE after 550 h of maximum power point tracking under continuous 1-sun illumination. This enhanced stability is attributed to the robust hydrophobicity conferred by the long alkyl side chains. Overall, this study substantiates the substantial potential of fullerene-free TPSCs using non-fullerene ETLs in advancing both the photovoltaic performance and stability of large-area TPSCs.\u003c/p\u003e","manuscriptTitle":"Centimeter-scale fullerene-free tin-based perovskite solar cells achieving over 14% efficiency","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-06 04:58:41","doi":"10.21203/rs.3.rs-6079304/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9ac76599-1673-4c92-8b27-b7a92ca53fdf","owner":[],"postedDate":"March 6th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":45232032,"name":"Physical sciences/Materials science/Materials for energy and catalysis/Solar cells"},{"id":45232033,"name":"Physical sciences/Materials science/Nanoscale materials/Carbon nanotubes and fullerenes"}],"tags":[],"updatedAt":"2025-04-17T04:30:34+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-06 04:58:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6079304","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6079304","identity":"rs-6079304","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}