Sn-Doped TiO2 Photoanode for Dye-Sensitized Solar Cells

A series of Sn-doped TiO2 with Sn content ranging from 0.25 to 1 mol % were successfully synthesized by the hydrothermal method, and its performance as the photoanode of dye-sensitized solar cells (DSSCs) was investigated. TEM and XRD results indicate that the doping has no effect on the morphology and the crystal form of TiO2. The shift of XRD peaks observed at higher angle and the XPS results indicate Sn4+ ions incorporation into the TiO2 lattice. The flatband potential of Sn-TiO2 films shifts from -0.505 V (vs SCE) to -0.55 V with increasing Sn content from 0 to 1 mol at. %, which is beneficial to the increase of V-oc. The higher transfer rate of electrons in the Sn-doped TiO2 films than in the undoped TiO2 films is confirmed by IMPS measurements, which is favorable to the higher J(sc). IMVS and EIS measurements indicate that the charge recombination increases with increasing Sn doping content. Taking these factors, the optimum efficiency of 8.31% was found at 0.5 mol % Sn-doped TiO2 based DSSCs, which gave an efficiency improved by 12.1% compared with that of the cells based on pure TiO2 (7.45%). This work shows that Sn-doped TiO2 is a most interesting material and has good potential for application in photoenergy conversion devices.