Sn-Doped TiO₂ Photoanode for Dye-Sensitized\nSolar Cells

Abstract

A series of Sn-doped TiO₂ with Sn content\nranging from\n0.25 to 1 mol % were successfully synthesized by the hydrothermal\nmethod, and its performance as the photoanode of dye-sensitized solar\ncells (DSSCs) was investigated. TEM and XRD results indicate that\nthe doping has no effect on the morphology and the crystal form of\nTiO₂. The shift of XRD peaks observed at higher angle and\nthe XPS results indicate Sn⁴⁺ ions incorporation into the\nTiO₂ lattice. The flatband potential of Sn-TiO₂ films shifts from −0.505 V (vs SCE) to −0.55 V with\nincreasing Sn content from 0 to 1 mol at. %, which is beneficial to\nthe increase of <i>V</i>_oc. The higher transfer\nrate of electrons in the Sn-doped TiO₂ films than in the\nundoped TiO₂ films is confirmed by IMPS measurements, which\nis favorable to the higher <i>J</i>_sc. IMVS and\nEIS measurements indicate that the charge recombination increases\nwith increasing Sn doping content. Taking these factors, the optimum\nefficiency of 8.31% was found at 0.5 mol % Sn-doped TiO₂ based DSSCs, which gave an efficiency improved by 12.1% compared\nwith that of the cells based on pure TiO₂ (7.45%). This\nwork shows that Sn-doped TiO₂ is a most interesting material\nand has good potential for application in photoenergy conversion devices.