Low band gap polymers for organic solar cells

摘要

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.