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Enhancing the Photovoltaic Performance of Ladder‐Type Heteroheptacene‐based Nonfullerene Acceptors by Incorporating Halogen Atoms on Their Ending Groups
Author(s) -
Wan Shuo,
Ma Yunlong,
Cai Dongdong,
Lin Wenyuan,
Wang Pengsong,
Wang Jinyun,
Zheng Qingdong
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.202010436
Subject(s) - acceptor , halogen , organic solar cell , materials science , intermolecular force , halogenation , photovoltaic system , photochemistry , polymer , chemistry , molecule , alkyl , organic chemistry , physics , electrical engineering , engineering , composite material , condensed matter physics
Abstract Ending group halogenation is an effective strategy for modulating the energy levels, bandgaps, and intermolecular interactions of nonfullerene acceptors. Understanding the influence of different halogen atoms on the acceptor properties is of great importance for designing high‐performance nonfullerene acceptors. Here, three acceptor–donor–acceptor (A‐D‐A) type nonfullerene acceptors (M5, M6, and M7), which are constructed by using a ladder‐type heteroheptacene core without the traditional sp 3 carbon‐bonded side chains as the electron‐rich core, and 2‐(3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)malononitrile without or with halogen atoms as the ending groups. The nonfullerene acceptors with chlorinated (M6) and brominated (M7) ending groups exhibit broadened absorption spectra, down‐shifted energy levels, and enhanced molecular ordering compared to the counterpart without any halogenated ending groups (M5). Among the nonfullerene acceptors, M6 has the strongest intermolecular ππ interaction with its shortest ππ interaction distance and the longest coherent length which are beneficial for enhancing the charge transport and therefore boosting the photovoltaic performance. An excellent power conversion efficiency of 15.45% is achieved for the best‐performing polymer solar cell based on M6. These results suggest that the halogenated ending groups are essential for high‐performance heteroheptacene‐based nonfullerene acceptors considering their simultaneous enhancements in both the light‐harvesting and the charge transport.