Nonfullerene All-Small-Molecule Organic Solar Cells

All-small-molecule organic solar cells (ASM-OSCs) combine advantages of both small-molecule donors and nonfullerene acceptors and have aroused considerable academic interest. The development of ASM-OSCs lags behind that of polymer-based OSCs and is largely limited by the lack of the well-matched donor and acceptor materials and the challenge of morphology control and device engineering. Very recently, ASM-OSCs have achieved remarkable progress thanks to optimization of active layer materials and blend film morphology. In this Perspective, we summarize recent advances in the innovation of photovoltaic materials (small-molecule donors and nonfullerene acceptors) and morphology optimization for ASM-OSCs. We focus on the compatibility between donor and acceptor materials as well as the structure–property relationships, provide guidelines for future materials design, morphology control, and device engineering, and propose the challenges and future directions for the development of ASM-OSCs.