High‐Performance All‐Polymer Solar Cells: Synthesis of Polymer Acceptor by a Random Ternary Copolymerization Strategy.

Demonstrated in this work is a simple random ternary copolymerization strategy to synthesize a series of polymer acceptors, PTPBT‐ETx, by polymerizing a small‐molecule acceptor unit modified from Y6 with a thiophene connecting unit and a controlled amount of an 3‐ethylesterthiophene (ET) unit. Compared to PTPBT of only Y6‐like units and thiophene units, PTPBT‐ETx (where x represents the molar ratio of the ET unit) with an incorporated ET unit in the ternary copolymers show up‐shifted LUMO energy levels, increased electron mobilities, and improved blend morphologies in the blend film with the polymer donor PBDB‐T. And the all‐polymer solar cell (all‐PSC) based on PBDB‐T:PTPBT‐ET0.3 achieved a high power conversion efficiency over 12.5 %. In addition, the PTPBT‐ET0.3‐based all‐PSC also exhibits long‐term photostability over 300 hours. [ABSTRACT FROM AUTHOR]