Theoretical study of thieno-thiophene based low band gap copolymers and substituent effect on the optoelectronic properties of them

The photo-physical properties of the three main structures of thieno[3,4-b]thiophene copolymers (X = S, O and NH atoms) and the substituent effects of Cl, Br, CCH, COH, NO2, OH, SH and NH2 are investigated.50