Optimization Requirements of Efficient Polythiophene:Nonfullerene Organic Solar Cells

Polythiophene (PT) and its derivatives have attracted long-standing attention in the organic photovoltaic community for their low cost and high scalability of synthesis. However, due to the lack of rational guidelines in controlling morphology and matching materials, the power conversion efficiencie...

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Bibliographic Details
Published in:Joule 2020-06, Vol.4 (6), p.1278-1295
Main Authors: Liang, Ziqi, Li, Miaomiao, Wang, Qi, Qin, Yunpeng, Stuard, Sam J., Peng, Zhongxiang, Deng, Yunfeng, Ade, Harald, Ye, Long, Geng, Yanhou
Format: Article
Language:English
Subjects:
crystallinity
film morphology
interaction parameter
miscibility
molecular order
nonfullerene acceptors
nonfullerene organic solar cells
polythiophenes
stability
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Summary:Polythiophene (PT) and its derivatives have attracted long-standing attention in the organic photovoltaic community for their low cost and high scalability of synthesis. However, due to the lack of rational guidelines in controlling morphology and matching materials, the power conversion efficiencies (PCEs) based on PTs reported so far are generally below 10%. Here, we establish the first-ever relationship between miscibility, morphology, and device performance of binary blends, based on various nonfullerene acceptors (ITIC-Th1, ITIC, IT4F, IDIC, and Y6) and a PT derivative named PDCBT-Cl by scattering and calorimetric characterizations. Benefiting from a properly quenched mixed phase, PDCBT-Cl:ITIC-Th1 system shows the best efficiency of over 12%. Conversely, the blend of PDCBT-Cl and the star acceptor Y6 remained in a homogeneous state due to their high miscibility, resulting in abysmal performance with PCE of 0.5%. Specific guidelines are also proposed to remediate the performance of PDCBT-Cl:Y6, which are crucial for advancing their practical applications. [Display omitted] •Full structural characterizations of the vitally important PT:nonfullerene systems•New design rules to rationally screen high-efficiency PT:nonfullerene systems•The first-ever report of the spectacular failure of the star nonfullerene acceptor Y6 Recently, the efficiencies of organic photovoltaics (OPVs) have surpassed 18%. The realization of these high-efficiency OPVs is based on the use of push-pull type polymer donors, which are costly and can seldom be produced in high quantity. In contrast, polythiophenes (PTs) hold great promises in cost and scalability, rendering them alternatives to the push-pull type donors for commercial applications. Here, we reveal the crucial role of miscibility and molecular ordering in determining the performance of PT:nonfullerene systems. Our study underscores the need for nonfullerene acceptors to match PTs thermodynamically and provides design rules for higher efficiency PT:nonfullerene solar cells. We also emphasize the effectiveness of using the physical parameters to exclude low-performance pairs and screen promising PT:nonfullerene pairs. This approach will accelerate the development of low-cost yet high-efficiency PT:nonfullerene solar cells and be applicable to more OPV systems. This research underscores the importance of considering both miscibility and molecular ordering in the design of higher efficiency polythiophene (PT):nonfullerene s
ISSN:2542-4351
2542-4351
DOI:10.1016/j.joule.2020.04.014