Triphenylamine–thiazolothiazole–benzodithiophene based conjugated copolymers for polymer solar cells

Two novel conjugated copolymers (P1 and P2) with donor–acceptor architecture, based on triphenylamine, benzodithiophene and thiazolothiazole (TTz), have been prepared by the Stille coupling reaction. Compared with alternative copolymer P1 with the single electron-withdrawing unit TTz, random copolymer P2 introduced another stronger electron-withdrawing unit benzothiadiazole intramolecularly. Incorporation of two different electron-withdrawing units on the backbone was proved to have a significant influence on the optical and electrical properties. Compared with P1, copolymer P2 has the wider absorption spectrum, lower bandgap, and therefore the better device performances.