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Efficient Hole Transfer via Delocalized Excited State in Small Molecular Acceptor: A Comparative Study on Photodynamics of PM6:Y6 and PM6:ITIC Organic Photovoltaic Blends
Author(s) -
Liang Shuyan,
Li Siying,
Zhang Yannan,
Li Tao,
Zhou Haoxiang,
Jin Feng,
Sheng Chuanxiang,
Ni Gang,
Yuan Jianyu,
Ma Wanli,
Zhao Haibin
Publication year - 2021
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202102764
Subject(s) - materials science , delocalized electron , acceptor , organic solar cell , ultrafast laser spectroscopy , photovoltaic system , intermolecular force , active layer , chemical physics , polymer solar cell , optoelectronics , band gap , energy conversion efficiency , photochemistry , spectroscopy , nanotechnology , polymer , layer (electronics) , organic chemistry , molecule , composite material , condensed matter physics , ecology , chemistry , physics , thin film transistor , quantum mechanics , biology
Organic solar cells (OSCs) based on small molecular acceptors (SMAs) have made great development with a power conversion efficiency (PCE) over 16% due to the design of novel materials and advances in device preparation technology. This work fabricates two bulk‐heterojunction photovoltaic devices containing the same wide‐bandgap donor PM6, respectively, matched with popular Y6 and ITIC SMAs. The PM6:Y6‐based device achieves a much higher PCE of 15.21% than the PM6:ITIC‐based device of 9.02%. On the basis of comparisons of macroscopic performances in the quasistatic regime, transient absorption spectroscopy (TAS) is further performed to better understand the microscopic dynamics difference in charge separation processes between the two photovoltaic blends. According to the TAS results, the calculated hole transfer efficiency in PM6:Y6 is 71.4%, far greater than the efficiency of 13.1% in PM6:ITIC, demonstrating favorable charge separation at donor/acceptor interfaces via hole transfer channel in PM6:Y6. The favorable hole transfer in PM6:Y6 is accounted for by its better mutual miscibility between the donor and acceptor, and the formation of long‐lived delocalized intramoiety excimer state in the acceptor. These results highlight the important role of proper molecular design strategy with strong intermolecular coupling and beneficial film morphology on facilitating charge generation in OSCs adopting SMAs.