Influence of Sn source on the performance of dye-sensitized solar cells based on Sn-doped TiO2 photoanodes: A strategy for choosing an appropriate doping source

Abstract

Six different Sn sources were applied to prepare Sn-doped TiO2 at low concentration (0.5mol%) via hydrothermal method and its performance as the photoanode of dye-sensitized solar cells (DSSCs) was investigated. The Sn-doped TiO2 was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Compared with the pure TiO2 based DSSCs (7.61%), higher conversion efficiencies of 8.55% and 8.66% were achieved by the DSSCs based on the tetramethyltin doped and the tetra-n-butyltin doped TiO2, respectively. And they were found to improve the open-circuit voltage due to the negative shift of Vfb of TiO2 and enhance the short circuit current density due to the faster electron transport in the Sn-doped TiO2 films. Chloride ion, containing in Sn source, has a negative effect on DSSCs based on Sn-doped TiO2. IMVS and EIS measurements indicate that the charge recombination increases with increasing of Cl− doping content, and this is the main reason for the decline in efficiency. Based on these results, we further studied the performance of DSSCs based on Ta-, Nb-, and Sb-doped TiO2, and the results indicate that the metallo-organic compound is an appropriate doping source for the high performance of DSSCs.