Synthesis and photovoltaic behaviors of narrow-band-gap π-conjugated polymers composed of dialkoxybenzodithiophene- and thiophene-based fused aromatic rings



π-Conjugated polymers, PBDT-CNETT and PBDT-CNECPDT, were prepared by the Stille cross-coupling polymerization. Optical and thermal properties of the obtained polymers were investigated by UV–vis spectroscopy and thermogravimetric analysis. PBDT-CNETT and PBDT-CNECPDT exhibited very narrow band gaps of 1.39 and 1.13 eV, respectively. Highest occupied molecular orbital energy levels estimated by surface analyzer were −5.17 and −5.11 eV for PBDT-CNETT and PBDT-CNECPDT, respectively. The solar cells based on these polymers were evaluated with the cell configuration of ITO/PEDOT-PSS/polymer:PC61BH/LiF/Al. The power conversion efficiencies of the solar cells were estimated to be 1.57 and 0.16% for PBDT-CNETT and PBDT-CNECPDT, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011