Critical Role of Polymer Aggregation and Miscibility in Nonfullerene‐Based Organic Photovoltaics. Issue 8 (29th January 2020)

• Record Type: Journal Article
• Authors: Yi, Xueping; Peng, Zhengxing; Xu, Bing; Seyitliyev, Dovletgeldi; Ho, Carr Hoi Yi; Danilov, Evgeny O.; Kim, Taesoo; Reynolds, John R.; Amassian, Aram; Gundogdu, Kenan; Ade, Harald; So, Franky
• Is Part Of: Advanced energy materials. Volume 10:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-01-29
• Subjects: charge generation -- charge transport -- morphology -- nonfullerene acceptors -- polymer aggregation; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201902430
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: Understanding the correlation between polymer aggregation, miscibility, and device performance is important to establish a set of chemistry design rules for donor polymers with nonfullerene acceptors (NFAs). Employing a donor polymer with strong temperature‐dependent aggregation, namely PffBT4T‐2OD [poly[(5, 6‐difluoro‐2, 1, 3‐benzothiadiazol‐4, 7‐diyl)‐ alt ‐(3, 3″′‐di(2‐octyldodecyl)‐2, 2′;5′, 2″;5″, 2″′‐quaterthiophen‐5, 5‐diyl)], also known as PCE‐11 as a base polymer, five copolymer derivatives having a different thiophene linker composition are blended with the common NFA O‐IDTBR to investigate their photovoltaic performance. While the donor polymers have similar optoelectronic properties, it is found that the device power conversion efficiency changes drastically from 1.8% to 8.7% as a function of thiophene content in the donor polymer. Results of structural characterization show that polymer aggregation and miscibility with O‐IDTBR are a strong function of the chemical composition, leading to different donor–acceptor blend morphology. Polymers having a strong tendency to aggregate are found to undergo fast aggregation prior to liquid–liquid phase separation and have a higher miscibility with NFA. These properties result in smaller mixed donor–acceptor domains, stronger PL quenching, and more efficient exciton dissociation in the resulting cells. This work indicates the importance of both polymer aggregation and donor–acceptor interaction on the formation of bulk heterojunctions in polymer:NFA blends. Abstract : Polymer aggregation and miscibility have been demonstrated to influence photovoltaic performance in nonfullerene‐based organic solar cells. Polymers having a strong tendency to aggregate are herein found to undergo aggregation prior to liquid–liquid phase separation and have a higher miscibility with nonfullerene acceptors, resulting in mixed donor–acceptor domains, stronger PL quenching, and a higher exciton dissociation efficiency.