Luo Dou, Jiang Zhengyan, Shan Chengwei, Li Lanqing, Duan Chenghao, Liu Qian, Wang Zhaojin, Wang Kai, Xu Baomin, Kyaw Aung Ko Ko
Guangdong University Key Laboratory for Advanced Quantum Dot Displays and Lighting, Department of Electrical & Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Department of Materials Science and Engineering and Shenzhen Engineering Research and Development Center for Flexible Solar Cells, Southern University of Science and Technology, Shenzhen 518055, China.
ACS Appl Mater Interfaces. 2022 Jun 1;14(21):24374-24385. doi: 10.1021/acsami.2c03723. Epub 2022 May 17.
Fine-tuning the alkyl chains and end groups of non-fused ring electron acceptors (NFREAs) plays vital roles in the promotion of charge transfer (CT) and power conversion efficiency (PCE). In this work, we developed a series of A-D-A'-D-A-type NFREAs, which possess the same terminals (A), the cyclopentadithiophene unit (D), and the thieno[3,4-]pyrrole-4,6-dione (A'). Despite the subtle difference in side chains and halogenated end groups, the six acceptors exhibit a considerable difference in the efficiency and device stability of the organic solar cells (OSCs). Among the molecules, chlorinated NFREAs show a broader light absorption than the fluorinated ones do. Compared with C8C8-4F (1-octylnonyl and fluorination) and C6C4-4Cl (2-butyloctyl and chlorination), C8C8-4Cl (1-octylnonyl and chlorination) exhibits a lower highest occupied molecular orbital level, higher electron mobility, and denser molecular packing. The OSCs based on PM6:C8C8-4Cl yield the best PCE of 14.11%, which is attributed to the faster charge transport, high miscibility, and preferable morphology. Moreover, the PM6:C8C8-4Cl devices retain 91.1% of the initial PCE after being placed in air with 67% relative humidity for 50 days. This work shows that the simultaneous optimization of side chains and end groups facilitates the CT and improves the stability in the OSCs, offering a novel view into the molecular design of A-D-A'-D-A-type NFREAs.
微调非稠环电子受体（NFREAs）的烷基链和端基在促进电荷转移（CT）和功率转换效率（PCE）方面起着至关重要的作用。在这项工作中，我们开发了一系列A-D-A'-D-A型NFREAs，它们具有相同的端基（A）、环戊二噻吩单元（D）和噻吩并[3,4-b]吡咯-4,6-二酮（A'）。尽管侧链和卤化端基存在细微差异，但这六种受体在有机太阳能电池（OSCs）的效率和器件稳定性方面表现出相当大的差异。在这些分子中，氯化NFREAs比氟化NFREAs表现出更宽的光吸收。与C8C8-4F（1-辛基壬基和氟化）和C6C4-4Cl（2-丁基辛基和氯化）相比，C8C8-4Cl（1-辛基壬基和氯化）表现出更低的最高占据分子轨道能级、更高的电子迁移率和更密集的分子堆积。基于PM6:C8C8-4Cl的OSCs产生了14.11%的最佳PCE，这归因于更快的电荷传输、高混溶性和良好的形态。此外，PM6:C8C8-4Cl器件在相对湿度为67%的空气中放置50天后，仍保留初始PCE的91.1%。这项工作表明，侧链和端基的同时优化有助于电荷转移，并提高OSCs中的稳定性，为A-D-A'-D-A型NFREAs的分子设计提供了新的视角。
