Active Layer Morphology Engineering of All-polymer Solar Cells by Systematically Tuning Molecular Weights of Polymer Donors/Acceptors

• Published in: Chinese journal of polymer science 2021-11, Vol.39 (11), p.1449-1458
• Main Authors: Wang, Ning, Yu, Ying-Jian, Zhao, Ru-Yan, Zhang, Ji-Dong, Liu, Jun, Wang, Li-Xiang
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Energy conversion efficiency; Industrial Chemistry/Chemical Engineering; Molecular weight; Morphology; Photovoltaic cells; Polymer blends; Polymer Sciences; Polymers; Solar cells; Thiadiazoles
• ISSN: 0256-7679; 1439-6203
• DOI: 10.1007/s10118-021-2609-9

In all-polymer solar cells (APSCs), number-average molecular weights ( M n s) of polymer donors and polymer acceptors play an important role in active layer morphology and photovoltaic performance. In this work, based on a series of APSCs with power conversion efficiency of approaching 10%, we study the effect of M n s of both polymer donor and polymer acceptor on active layer morphology and photovoltaic performance of APSCs. We select poly[4-(5-(4,8-bis(5-((2-butyloctyl)thio)thiophen-2-yl)-6-methylbenzo[1,2- b :4,5- b′ ]dithiophen-2-yl)thiophen-2-yl)-5,6-difluoro-2-(2-hexyldecyl)-7-(5-methylthiophen-2-yl)-2 H -benzo[ d ][1,2,3]triazole] (CD1) as the polymer donor and poly[4-(5-(5,10-bis(2-dodecylhexadecyl)-4,4,9,9-tetrafluuoro-7-methyl-4,5,9,10-tetrahydro3a,5,8,10-tetraaza-4,9-diborapyren-2-yl)thiophen-2-yl)-7-(5-methylthiophen-2-yl)benzo[ c ][1,2,5]thiadiazole] (PBN-14) as the polymer acceptor. The M n s of polymer donor CD1 are 14.0, 35.5 and 56.1 kg/mol, respectively, and the M n s of polymer acceptor PBN-14 are 32.7, 72.4 and 103.4 kg/mol, respectively. To get the desired biscontinueous fibrous network morphololgy of the polymer donor/polymer acceptor blends, at least one polymer should have high or medium M n . Moreover, when the M n of polymer acceptor is high, the active layer morphology and APSC device performance are insensitive to the M n of polymer donor. The optimal APSC device performance is obtained when the M n of both the polymer donor and the polymer acceptor are medium. These results provide a comprehensive and deep understanding on the interplay and the effect of M n of polymer donors and polymer acceptors in highperformance APSCs.