A heptacyclic carbon–oxygen-bridged ladder-type building block for A–D–A acceptors

Abstract

A heptacyclic carbon–oxygen-bridged ladder-type unit, CO_i7, was designed. Two corresponding nonfullerene acceptors, CO_i7IC and CO_i7DFIC, were developed. The single crystal structure of CO_i7IC indicates an S-shaped backbone and a packing via π–π interaction of the end groups. PTB7-Th:CO_i7DFIC solar cells gave a power conversion efficiency of 8.32%, with a decent fill factor of 71.9%.