Thieno[3,4-b]pyrazine and 9,9-di-n-octylfluorene based copolymer for efficient inorganic-organic hybrid solar cells

Poly(9,9-di-n-octylfluorene-alt-thieno[3,4-b]pyrazine) (PF8TPZ) has been designed and synthesized by Pd-catalyzed Stille coupling reactions. The resulting copolymer was characterized by NMR, gel permeation chromatography, and thermogravimetric analysis. The polymer exhibited broad absorption spectra, covering the spectral range from 300 to 700 nm. The optical bandgap and HOMO level of the polymer was calculated from ultraviolet-visible spectroscopy and cyclic voltammetry measurements, respectively. The HOMO level of the polymer was −5.44 eV and the optical bandgap was 1.88 eV. The inorganic-organic hybrid solar cells based on the copolymer were fabricated and tested with a structure of Pt/PEDOT:PSS/copolymer:TiO2/FTO under the illumination of AM 1.5G, 100 mW cm−2. The corresponding Voc, Jsc, FF, and PCE parameters of these devices are measured to be 0.68 V, 1.98 mA cm−2, 0.54, and 0.74%, respectively.