Tang Ziye, Xu Xiaopeng, Li Ruipeng, Yu Liyang, Meng Lei, Wang Yuliang, Li Ying, Peng Qiang
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610064, P. R. China.
National Synchrotron Light Source II, Brookhaven National Laboratory, Suffolk, Upton, New York 11973, United States.
ACS Appl Mater Interfaces. 2020 Apr 15;12(15):17760-17768. doi: 10.1021/acsami.9b20204. Epub 2020 Mar 16.
In this work, three benzodithiophene-benzotriazole alternated wide band gap copolymers attaching symmetric or asymmetric conjugated side chains, namely, PDBTFBTA-2T, PBDTFTBA-TSi, and PBDTFBTA-2Si, were developed for efficient nonfullerene polymer solar cells. The symmetry effect of the side chains was investigated in detail on the overall properties of these donor polymers. The results demonstrated that the introduced siloxane functional groups showed less effect on the absorption and frontier orbital levels of the prepared polymers but had a significant effect on the miscibility between these polymer donors and the nonfullerene acceptor. When increasing the content of siloxane functional groups, the miscibility of the polymer donors and Y6 would be improved, leading to the decreased domain size and more mixed domains. Interestingly, the active blend based on PBDTFTBA-TSi with asymmetric side chains exhibited more balanced miscibility, carrier mobility, and phase separation, benefiting exciton diffusion and dissociation. Therefore, a champion power conversion efficiency (PCE) of 14.18% was achieved finally in PBDTFTBA-TSi devices, which was 20.6 and 19.0% higher than the symmetric counterparts of PBTFBTA-2T devices (PCE = 11.76%) and PBDTFBTA-2Si devices (PCE = 11.92%), respectively. This work highlights that the asymmetric side-chain engineering based on siloxane functional groups is a promising design strategy for high-performance polymer donor semiconductors.
在本工作中，我们开发了三种连接对称或不对称共轭侧链的苯并二噻吩-苯并三唑交替宽带隙共聚物，即PDBTFBTA-2T、PBDTFTBA-TSi和PBDTFBTA-2Si，用于高效非富勒烯聚合物太阳能电池。详细研究了侧链的对称性对这些供体聚合物整体性能的影响。结果表明，引入的硅氧烷基官能团对所制备聚合物的吸收和前沿轨道能级影响较小，但对这些聚合物供体与非富勒烯受体之间的混溶性有显著影响。当增加硅氧烷基官能团的含量时，聚合物供体与Y6的混溶性会得到改善，导致域尺寸减小和更多混合域。有趣的是，基于具有不对称侧链的PBDTFTBA-TSi的活性共混物表现出更平衡的混溶性、载流子迁移率和相分离，有利于激子扩散和解离。因此，PBDTFTBA-TSi器件最终实现了14.18%的最佳功率转换效率（PCE），分别比PBTFBTA-2T器件（PCE = 11.76%）和PBDTFBTA-2Si器件（PCE = 11.92%）的对称对应物高20.6%和= 19.0%。这项工作突出表明，基于硅氧烷基官能团的不对称侧链工程是一种用于高性能聚合物供体半导体的有前途的设计策略。
