Transforming polymorphs of Co-doped TiO2 nanoparticles: an efficient photo-electrode for dye-sensitized solar cells

摘要： Simple sol–gel assisted spin coating technique was used to prepare cobalt-doped TiO2 films for the application of dye-sensitized solar cells (DSSC). TiO2 photo-electrodes with few Co concentrations (0, 0.025, 0.05, 0.075 and 0.1 M) were prepared on conducting glass substrates. The morphology, structure and composition of the Co:TiO2 films were observed using SEM, XRD and EDAX analysis. The average crystallite size of Co:TiO2 nanoparticles obtained from diffractograms are in the range of 3–12 nm. The transformation of polymorphs from anatase to rutile and vice versa for the increasing concentrations of Co in TiO2 films is observed. The values of optical bandgap energy for Co-doped films are observed to be higher than the pure TiO2 film and the highest is for the dopant level of 0.025 M. Doping of 0.1 M Co in TiO2 enhances the power conversion efficiency of DSSC by 65% compared to pure TiO2 film, demonstrating the influence of Co doping on the functioning of DSSC.