Distannylated Bithiophene Imide: Enabling High‐Performance n‐Type Polymer Semiconductors with an Acceptor–Acceptor Backbone

Abstract

A distannylated electron‐deficient bithiophene imide (BTI‐Tin) monomer was readily synthesized and polymerized with imide‐functionalized co‐units via Stille coupling to afford homopolymer PBTI and copolymer P(BTI‐BTI2), both featuring acceptor‐acceptor backbone with high molecular weight. Benefitting from their improved electronic property and increased molecular weight, both polymers exhibited excellent unipolar n‐type character in transistors with electron mobility up to 2.60 cm2 V‐1 s‐1. When applied as acceptor materials in all‐polymer solar cells, PBTI and P(BTI‐BTI2) achieved high power conversion efficiency (PCE) of 6.67% and 8.61%, respectively. The PCE (6.67%) of polymer PBTI, synthesized from the novel distannylated monomer, is substantially higher than that (0.14%) of the same polymer PBTI*, synthesized from typical dibrominated monomer. The 8.61% PCE of copolymer P(BTI‐BTI2) is also substantially higher than those (< 1%) of homopolymers synthesized from dibrominated monomers. The results demonstrate the great success of BTI‐Tin for facilely accessing structurally novel n‐type polymers with greatly improved device performance.