A review of nonfullerene solar cells: Insight into the correlation among molecular structure, morphology, and device performance

Nonfullerene acceptors (NFAs) lead the continuous development of organic solar cells (OSCs) with competitive efficiency over 19%. Design and synthesis of novel photovoltaic materials are effective methods to improve the OSCs performance, which can regulate the optoelectric properties, such as energy level, absorption spectra, charge transport, and so on. So far, hundreds of NFAs have been reported. Meanwhile, it has been demonstrated that intrinsic morphology of active layer is partially determined by the chemical structures of NFAs. Hence, only in-depth understanding of the relationship between different structures of NFAs and morphology can guide the molecular design of NFAs for highly efficient OSCs. Herein, we review some state-of-the-art NFAs according to their functional moieties, that is, arene core, end group and side chain, and discuss the relationship between molecular structure, morphology and device parameter. Additionally, the challenges and prospects for further development of OSCs based on NFAs are briefly considered. This review brings a unique insight into structure-function correlation in this field, which may help to rapidly develop efficient OSCs.