High‐Efficiency P3HT‐Based All‐Polymer Solar Cells with a Thermodynamically Miscible Polymer Acceptor

Poly(3‐hexylthiophene) (P3HT) is the most classical conjugated polymer for organic photovoltaics due to its low‐cost and synthetic scalability. However, P3HT‐based organic photovoltaics suffer from inferior device performance with respect to donor–acceptor copolymers. Particularly, the device performance of P3HT‐based all‐polymer solar cells (all‐PSCs) is rather poor due to the challenges in reaching ideal bulk‐heterojunction morphology. Herein, highly efficient P3HT‐based all‐PSCs by blending P3HT with a thermodynamic miscible polymer acceptor are reported. Among the three state‐of‐the‐art polymer acceptors (N2200, PYT, and DCNBT‐IDT), N2200 and PYT are thermodynamically immiscible with P3HT and thus led to excessive phase separation when blended with P3HT, whereas DCNBT‐IDT displayed proper thermodynamic miscibility with P3HT and generated the formation of well‐mixed fibrillary active layer morphology. As a result, a power conversion efficiency of 7.35% has been achieved by P3HT:DCNBT‐IDT blend, which is a new record for P3HT‐based all‐PSCs and largely higher than any previous results. Broad implication for further efficiency enhancement of P3HT‐based all‐PSCs is provided in the results and a promising pathway to realize highly efficient yet cost‐effective solar energy production is suggested.