Narrow-optical-gap π-conjugated small molecules based on terminal isoindigo and thienoisoindigo acceptor units for photovoltaic application

Abstract

Two acceptor–donor type conjugated small molecules based on isoindigo and thienoisoindigo acceptor units are synthesized. The small molecules showed broad and low-energy light absorption properties. On application of the small molecules in organic photovoltaic cells, thienoisoindigo-based small molecule in combination with PC₇₁BM showed moderate photovoltaic efficiency with a PCE of 1.51% with an open-circuit voltage of 0.72 V under AM 1.5 solar irradiation.