Polythiophene Derivatives for Efficient All‐Polymer Solar Cells

Abstract Polymerized small molecule acceptors have recently greatly facilitated the development of all‐polymer solar cells (All‐PSCs) with respect to the power conversion efficiencies (PCEs). However, high‐performance and low‐cost polymer donors for All‐PSCs are still lacking, limiting further large‐scale manufacturing of All‐PSCs. Herein, this work designs and synthesizes a new thiophene derivative, FETVT, featuring vinyl‐bridged fluorine and ester‐substituted monothiophene. Incorporation of FETVT into a polymer yields a high‐performance polythiophene derivative PFETVT‐T, which exhibits deep‐lying HOMO level, suitable solution pre‐aggregation ability, finely‐tuned polymer crystallinity, and appropriate thermodynamic miscibility with the polymer acceptor L15. As a result, binary based on PFETVT‐T achieves a record PCE of 11.81% with agood stability, representing a breakthrough for polythiophenes and their derivatives‐based All‐PSCs, which is also significantly higher than that (1.92%) of All‐PSCs based on its isomerized analog. Remarkably, PFETVT‐T achieves an impressive PCE exceeding 16% via the implementation of a ternary blend design. These findings offer a hopeful pathway toward attaining high‐performance, stable, and cost‐effective PSCs.