State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China.
Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195-2120, USA.
Adv Mater. 2018 Dec;30(52):e1803769. doi: 10.1002/adma.201803769. Epub 2018 Nov 6.
Solar photon-to-electron conversion with polymer solar cells (PSCs) has experienced rapid development in the recent few years. Even so, the exploration of molecules and devices in efficiently converting near-infrared (NIR) photons into electrons remains critical, yet challenging. Herein presented is a family of near-infrared nonfullerene acceptors (NIR NFAs, T1-T4) with fluorinated regioisomeric A-Aπ-D-Aπ-A backbones for constructing efficient single-junction and tandem PSCs with photon response up to 1000 nm. It is found that the tuning of the regioisomeric bridge (Aπ) and fluoro (F)-substituents on a molecular skeleton strongly influences the backbone conformation and conjugation, leading to the optimized optoelectronic and stable stacking of resultant NFAs, which eventually impacts the performance of derived PSCs. In PSCs, the proximal NFAs with varied F-atoms (T1-T3) mostly outperform than that of distal NFA (T4). Notably, single-junction PSC with PTB7-Th:T2 blend can reach 10.87% power conversion efficiency (PCE), after implementing a solvent additive to improve blend morphology. Moreover, efficient tandem PSCs are fabricated through integrating such NIR cells with mediate bandgap nonfullerene-based subcells, to achieve a PCE of 14.64%. The results reveal the structural design of organic semiconductor and device with improved photovoltaic performance.
近年来，聚合物太阳能电池（PSCs）的太阳能光子-电子转换取得了快速发展。即便如此，探索高效将近红外（NIR）光子转化为电子的分子和器件仍然至关重要，但也极具挑战性。本文介绍了一类具有氟化区域异构体 A-Aπ-D-Aπ-A 骨架的近红外非富勒烯受体（NIR NFAs，T1-T4），用于构建高效的单结和串联 PSCs，其光子响应可达 1000nm。研究发现，区域异构体桥（Aπ）和分子骨架上氟（F）取代基的调谐强烈影响骨架构象和共轭，导致所得 NFAs 的光电和稳定堆积得到优化，最终影响衍生 PSCs 的性能。在 PSCs 中，具有不同 F 原子（T1-T3）的近 NFA 大多优于远端 NFA（T4）。值得注意的是，通过添加溶剂添加剂改善共混形貌，以 PTB7-Th:T2 共混为给体的单结 PSC 可达到 10.87%的功率转换效率（PCE）。此外，通过将此类近红外电池与具有中等能带隙的非富勒烯基子电池集成，可制造高效的串联 PSCs，实现 14.64%的 PCE。结果表明，通过改善光伏性能，对有机半导体和器件进行了结构设计。
