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A Nonfullerene Acceptor with Alkylthio‐ and Dimethoxy‐Thiophene‐Groups Yielding High‐Performance Ternary Organic Solar Cells
摘要： Herein, an A–D–A-type nonfullerene acceptor (named IDTS-4F) with an alkyl thiophenyl side chain and dimethoxy thiophene bridging unit is reported. The use of an alkyl thiophenyl group is important, as the insertion of sulfur atoms can slightly downshift the highest occupied molecular orbital (HOMO) level of the molecule and allows IDTS-4F to match with state-of-the-art donor polymer PM6 (or PM7). Compared with conventional nonfullerene acceptors, IT-4F, the IDTS-4F molecule, has a smaller optical bandgap and higher lowest unoccupied molecular orbital (LUMO) level, which are beneficial to increase the Voc and Jsc of the devices. Nonfullerene organic solar cell devices are fabricated using IDTS-4F. Although the binary device based on IDTS-4F exhibits a lower fill factor (FF, 70%), the ternary device by incorporating 0.2 of IDTS-4F and 0.8 of IT-4F (with PM6 as the donor polymer) can simultaneously achieve a higher Voc and Jsc, while maintaining the high FF (77%) of IT-4F based system. Morphology characterizations indicate the formation of homogeneous film morphology, the large increase in phase purity and crystallinity, and the reduction in domain size upon addition of crystalline IDTS-4F, while the electron/hole mobilities and recombination losses of the IT-4F system are both maintained.
关键词： polymer solar cells,nonfullerene acceptors,fullerene-free,organic solar cells,ternary solar cells
更新于2025-09-19 17:13:59
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Non-fullerene acceptor fibrils enable efficient ternary organic solar cells with 16.6% efficiency
摘要： Optimizing the components and morphology within the photoactive layer of organic solar cells (OSCs) can significantly enhance their power conversion efficiency (PCE). A new A-D-A type non-fullerene acceptor IDMIC-4F is designed and synthesized in this work, and is employed as the third component to prepare high performance ternary solar cells. IDMIC-4F can form fibrils after solution casting, and the presence of this fibrillar structure in the PBDB-T-2F:BTP-4F host confines the growth of donors and acceptors into fine domains, as well as acting as transport channels to enhance electron mobility. Single junction ternary devices incorporating 10 wt% IDMIC-4F exhibit enhanced light absorption and balanced carrier mobility, and achieve a maximum PCE of 16.6% compared to 15.7% for the binary device, which is a remarkable efficiency for OSCs reported in literature. This non-fullerene acceptor fibril network strategy is a promising method to improve the photovoltaic performance of ternary OSCs.
关键词： ternary solar cells,non-fullerene acceptor fibrils,power conversion efficiency
更新于2025-09-19 17:13:59
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A Trialkylsilylthienyl-Chain-Substituted Small-Molecule Acceptor with Higher-LUMO-Level and Reduced Bandgap for over 16%-Efficiency Fullerene-Free Ternary Solar Cells
摘要： The ternary approach using a smaller bandgap acceptor as the near infrared (NIR) absorber to increase the short-circuit current-density (Jsc) usually decreases the open-circuit voltage (Voc). In this contribution, we report a small-molecular acceptor, IN-4F, which has a reduced bandgap and a higher LUMO level than IT-4F, hence, enabling the concurrent increase in the Jsc and Voc when using as the acceptor guest of the host binary of PM6:IT-4F. IN-4F was judiciously designed by fusing benzodithiophene (BDT) and thieno[2′,3′:4,5]thieno to make a larger π?system so as to upshift the LUMO level and reduce the optical bandgap, and meanwhile, by substituting the BDT-4,8 positions with trialkylsilylthiophene chains to downshift the HOMO level to match the deep HOMO of PM6. Again, the structural similarity between IN-4F and IT-4F makes the nanoscaled homogeneous fine film-morphology and the ππ?stacking patterns both well-kept, hence, the fill-factor (FF) well-maintained. The IN-4F based binary solar cell shows 13.1% efficiency and its ternary solar cell blended with IT-4F supplies 14.9% efficiency. Again, the use of IN-4F as the guest acceptor of the PM6:Y6 system enables the increase of Voc due to its higher LUMO level, the increase of Jsc because of the increase of charge mobilities, and the maintenance of FF, affording 16.3% efficiency. This work demonstrates that the π?system extending plus the trialkylsilylthiophene chains substitution can be an effective strategy to synthesize a nonfullerene acceptor guest to realize a ternary material system which enables to increase Voc from its entanglement with Jsc (an issue of the current material approach).
关键词： small-molecule acceptor,higher LUMO level,nonfullerene acceptor,reduced bandgap,ternary solar cells
更新于2025-09-16 10:30:52
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Mediated Non-geminate Recombination in Ternary Organic Solar Cells Through a Liquid Crystal Guest Donor
摘要： The approach via ternary blends prompts the increase of absorbed photon density and resultant photocurrent enhancement in organic solar cells (OSCs). In contrast to actively reported high efficiency ternary OSCs, little is known about charge recombination properties and carrier loss mechanisms in these emerging devices. Here, through introducing a small molecule donor BTR as a guest component to the PCE-10:PC71BM binary system, we show that photocarrier losses via recombination are mitigated with respect the binary OSCs, owing to a reduced bimolecular recombination. The gain of the fill factor in ternary devices are reconciled by the change in equilibrium between charge exaction and recombination in the presence of BTR toward the former process. With these modifications, the power conversion efficiency in ternary solar cells receives a boost from 8.8 (PCE-10:PC71BM) to 10.88%. We further found that the voltage losses in the ternary cell are slightly suppressed, related to the rising charge transfer-state energy. These benefits brought by the third guest donor are important for attaining improvements on key photophysical processes governing the photovoltaic efficiencies in organic ternary solar cells.
关键词： charge transfer states,small molecule donor,voltage loss,ternary solar cells,charge recombination
更新于2025-09-16 10:30:52