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

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 (JSC) 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. The novel structurally defined and covalently linked donor–acceptor dyad 4 is implemented into single‐material organic solar cells as the essential ambipolar and photoactive layer. The combination of an oligothiophene donor and PC71BM fullerene as acceptor not only leads to enhanced 5.34% power conversion efficiency, but also to impressive long‐term stability after 750 hours (one month) of continuous illumination.