Influences of Sr-Incorporated TiO2 Layer on the Photovoltaic Properties of Dye-Sensitized Solar Cells

Effects of a mixed overlayer composed of TiO2 and TiSrO3 on the performance of dye-sensitized solar cells (DSSCs) were investigated. The surface of TiO2 photoelectrode formed on F-doped SnO2 (FTO) was modified by soaking it in a TiCl4: SrCl2 mixed aqueous solution with various molar ratios and then calcining to produce the TiCl4: SrCl2-treated TiO2 photoelectrode (Ti: Sr-TiO2/FTO). The highest power conversion efficiency (PCE) was obtained from DSSC with Ti: Sr(7: 3)-TiO2/FTO, which was prepared from the mixed solution with the molar ratio of 7: 3 (TiCl4: SrCl2). An enhancement in short-circuit photocurrent (J(sc)) and open-circuit voltage (V-oc) of DSSC with Ti: Sr(7: 3)-TiO2/FTO was achieved, compared to those of the reference device with Ti: Sr(10: 0)-TiO2/FTO (i. e., TiO2-coated TiO2/FTO). The incorporation of the mixed overlayer on the nanoporous TiO2 photoelectorde led to an improvement in the electron collection efficiency by a prolonged electron lifetime, thereby increasing the Jsc value. The increase in Voc value of the device with Ti: Sr(7: 3)-TiO2/FTO was due to the suppression of the charge recombination between injected electrons and I-3 ions.