Molecular Oligothiophene–Fullerene Dyad Reaching Over 5% Efficiency in Single‐Material Organic Solar Cells

Abstract A novel donor–acceptor dyad, 4, in which the conjugated oligothiophene donor is covalently connected to fullerene PC₇₁BM by a flexible alkyl ester linker, is synthesized and applied as photoactive layer in solution‐processed single‐material organic solar cells (SMOSCs). Excellent photovoltaic performance, including a high short‐circuit current density (J_SC) of 13.56 mA cm⁻², is achieved, leading to a power conversion efficiency of 5.34% in an inverted cell architecture, which is substantially increased compared to other molecular single materials. Furthermore, dyad 4‐based SMOSCs display excellent stability maintaining 96% of the initial performance after 750 h (one month) of continuous illumination and operation under simulated AM 1.5G irradiation. These results will strengthen the rational molecular design to further develop SMOSCs for potential industrial application.