Effect of Extended Conjugation on the Optoelectronic Properties of Benzo[1,2-d:4,5-d′]bisoxazole Polymers

Abstract

Four copolymers comprising benzo[1,2-d:4,5-d']bisoxazole (BBO) and benzo[1,2-b:4,5-b′]dithiophene (BDT) bearing phenylethynyl substituents on either the BBO, BDT moieties or both units were synthesised and the influence of two-dimensional conjugation on their optoelectronic properties investigated. Extending conjugation along the BBO resulted in a 0.5 eV decrease in the LUMO level, whereas the HOMO level was raised by 0.2 eV. Extending conjugation across the BDT moiety in also resulted in a 0.5 eV decrease in the LUMO level, however, the effect was negligible on the HOMO level. Thus, cross-conjugation can be used to independently tune the LUMO level within these systems.