Quantitative relations between interaction parameter, miscibility and function in organic solar cells

Long Ye, Huawei Hu, Masoud Ghasemi, Tonghui Wang, Brian A Collins, Joo-Hyun Kim, Kui Jiang, Joshua H. Carpenter, Hong Li, Zhengke Li, Terry McAfee, Jingbo Zhao, Xiankai Chen, Joshua Lin Yuk Lai, Tingxuan Ma, Jean-Luc Bredas, He Yan, Harald Ade

Research output: Contribution to journalArticlepeer-review

284 Scopus citations

Abstract

Although it is known that molecular interactions govern morphology formation and purity of mixed domains of conjugated polymer donors and small-molecule acceptors, and thus largely control the achievable performance of organic solar cells, quantifying interaction-function relations has remained elusive. Here, we first determine the temperature-dependent effective amorphous-amorphous interaction parameter, χaa(T), by mapping out the phase diagram of a model amorphous polymer:fullerene material system. We then establish a quantitative 'constant-kink-saturation' relation between χaa and the fill factor in organic solar cells that is verified in detail in a model system and delineated across numerous high- and low-performing materials systems, including fullerene and non-fullerene acceptors. Our experimental and computational data reveal that a high fill factor is obtained only when χaa is large enough to lead to strong phase separation. Our work outlines a basis for using various miscibility tests and future simulation methods that will significantly reduce or eliminate trial-and-error approaches to material synthesis and device fabrication of functional semiconducting blends and organic blends in general.
Original languageEnglish (US)
Pages (from-to)253-260
Number of pages8
JournalNature Materials
Volume17
Issue number3
DOIs
StatePublished - Feb 5 2018

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