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.