Improved Crystallization of High-Solubility Non-Fullerene Electron Acceptors for Enhanced Photoelectric Conversion Efficiency: Effect of the Terminal Group

Organic small-molecule acceptors with acceptor-donor-acceptor- donor-acceptor (A-DA'D-A)-type configurations typically exhibit photoinduced intra-and intermolecular charge transfer (CT) dynamics. Herein, using steady-state and transient absorption spectroscopy, we studied the impact of the three-dimensional (3D) terminal group on the intra-and intermolecular CT in the A-DA'D-A-type small-molecular acceptor and the effect of the photoelectric conversion process in the corresponding blend film. The results show that 3D terminal groups have little impact on intramolecular charge transfer but significantly improve solubility and regulate intermolecular interactions. 3D terminal groups can improve exciton generation and enhance exciton diffusion distance by preventing the film from over-aggregating, thus benefiting the charge transfer and photoelectric conversion in the blend film. This work demonstrated the advantages of the 3D terminal group and revealed the fundamental importance of regulating the intra-and intermolecular CT in enhancing photoelectric conversion.