Abstract: The bulk-heterojunction (BHJ) polymer solar cell (PSC) has been considered as one of the most promising next-generation photovoltaic technologies. Electron-accepting material, which is the key component as important as polymer donor in the BHJ blend of a PSC, can almost only choose from fullerene derivatives before 2015. Currently, nonfullerene acceptor (NFA) materials are attracting drastically increasing interest in organic photovoltaics as alternatives for fullerene derivatives, due to their advantages of structural diversity, low-cost, as well as extraordinary chemical, thermal, and photostability. Benefiting from the facile functionalization of NFA molecules, their photoelectric properties and stacking characteristics can be adequately adjusted to promote photoinduced charge separation and extraction. In recent five years, a lot of NFA molecules have been successfully designed and synthesized, and the power conversion efficiencies of NFA-based PSCs have reached ~13%, revealing the great potential of NFA-material for improving PSCs performances. In this review, the summary and discussion are focused on the molecular architecture and device performance of three types of NFAs materials including PDI-based acceptors, A-D-A and A-π-D-π-A conjugated acceptors, aiming to understand the structure-property relationship.

Key words: polymer solar cells, bulk-heterojunction, electron acceptor, nonfullerene, structure-property relationship