The synthesis of copolymers based on thiophene, benzothiadiazole and benzo-bis-thiadiazole are described. The
polymers were obtained by employing Stille cross coupling polymerization. The polymers were characterized by NMR,
size exclusion chromatography, UV-vis and ultraviolet photoelectron spectroscopy. The results obtained from UV-vis
and ultraviolet photoelectron spectroscopy showed band gaps of 2.1-1.7 eV for polymers based on benzothiadiazole and
0.7 eV for polymers based on benzo-bis-thiadiazole. Furthermore the results showed that the band gap decreases with an
increase in the number, n, of thiophenes in the polymer repeating unit (n= 1-4). Large area photovoltaic devices were
prepared and the results of these devices are described.