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

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.