Replacing alkyl side chain of non-fullerene acceptor with siloxane-terminated side chain enables lower surface energy towards optimizing bulk-heterojunction morphology and high photovoltaic performance

• 作者: Rihang Qiu Zhuhao Wu Suhan Li Haiying Jiang Qian Wang Yinchu Chen Xuanchen Liu Lianjie Zhang Junwu Chen
• 来源期刊: 中国科学：化学（英文版）
• 年，卷（期）: 2021,（7）
• 所属期刊栏目: ARTICLES
• 页码范围: 1208-1218
• 页数: 11页
• 语种: 英文

摘要

Towards a good control of the morphology of bulk-heterojunction(BHJ)active layers for polymer solar cells(PSCs),selecting an appropriate side chain for a polymer donor and a nonfullerene acceptor(NFA)is very crucial.In this work,two novel NFAs i-IE-4F and i-IESi-4F comprising alkyl and siloxane-terminated side chains on the central indacenodithiophene(IDT)core,respectively,were synthesized.Attaching the siloxane-terminated side chain to i-IESi-4F affords surface energy(y)of 33.32 mN/m,much lower than that of 39.83 mN/m for i-IE-4F,supplying a big chance to tune miscibility with a polymer donor.Two fluorobenzotriazole-based polymer donors J52 and PBZ-2Si bearing alkyl and siloxane-terminated side chains,respec-tively,show y values of 36.08 and 33.10 mN/m,respectively.The estimated Flory-Huggins interaction parameters(xD,A)indicate that the i-IESi-4F is more miscible than i-IE-4F in pairing with J52 or PBZ-2Si.The resulting i-IESi-4F-based blend film exhibits low film roughness and accompanies obviously improved BHJ uniformity.In PSCs,the J52:i-IESi-4F and PBZ-2Si:i-IESi-4F active layers display power conversion efficiencies(PCEs)of 12.67％and 14.54％,respectively,all remarkably higher than PCEs≤7.34％of the i-IE-4F-based active layers.Interestingly,the PBZ-2Si:i-IESi-4F active layer,a donor:acceptor blend system comprising siloxane-terminated side chains(Dsi:Asi matching)with the highest BHJ miscibility due to the combinatory effect of the side chains,shows the highest efficiency,as supported by efficient exciton dissociation,the lowest bimolecular re-combination,and the optimal charge transport.Our results demonstrate that attaching siloxane-terminated side chains to NFAs,as a side chain engineering,has big potential in lowering their surface energy towards fine control of BHJ morphology and leading to a better donor:acceptor blend system.