Enhanced Efficiency of Dye-Sensitized Solar Cells by Trace Amount Ca-Doping in TiO₂ Photo electrodes

Trace amount Ca-doped TiO₂ films were synthesized by the hydrothermal method and applied as photoanodes of dye-sensitized solar cells (DSSCs). To prepare Ca-doped TiO₂ film electrodes, several milliliters of Ca(NO₃)₂ solution was added in TiO₂ solution during the hydrolysis process. The improvements of DSSCs were confirmed by photocurrent density-voltage (J-V) characteristics, electrochemical impedance spectroscopy (EIS) measurements. Owing to the doping effect of Ca, the Ca-doped TiO₂ thin film shows power conversion efficiency of 7.45% for 50 ppm Ca-doped TiO₂ electrode, which is higher than that of the undoped TiO₂ film (6.78%) and the short-circuit photocurrent density (J-s_c) increases from 13.68 to 15.42 mA .cm^-2. The energy conversion efficiency and short-circuit current density (J-s_c) of DSSCs were increased due to the faster electron transport in the Ca-doped TiO₂ film. When Ca was incorporated into TiO₂ films, the electrons transport faster and the charge collection efficiency (η_Cc) is higher than that in the undoped TiO₂ films