A series of benzodithiophene–benzotriazole push–pull copolymers were synthesised and characterised and their performance in bulk heterojunction solar cells devices was assessed. By incorporating strong electron acceptor units, such as benzothiadiazole and pyridylthiadiazole, into the polymer backbone, significant absorption across the entire visible range (300 nm to 750 nm) was observed for the random copolymers. The importance of investigating photophysical as well as bulk material properties of the polymers was demonstrated with a correlation of properties with device performance.
