Enhanced conversion efficiency of dye-sensitized titanium dioxide solar cells by Ca-doping

Ca salts [CaSO4]-doped TiO2 electrodes prepared with well-optimized condition by the hydrothermal method show an increase in short-circuit (JSC), resulting in a power conversion efficiency (PCE) of 8.35%, which is higher than that of the undoped TiO2 thin film (7.33%). The doping of Ca shifts the flat band potential of TiO2 photoanode positively and increases the electron density indicated by the Mott–Schottky plot. The driving force of injecting electrons from the LUMO of the dye to the conduct band of TiO2 improves apparently because of the positive shift of the flat band potential. The intensity-modulated photocurrent spectroscopy measurement confirms that increased electron density accelerates the electrons transfer rate in the Ca-doped TiO2 thin films by comparison to undoped films.

► Ca-doped TiO2 electrode showed a power conversion efficiency of 8.35%.
► The doping of Ca shifts the flat band potential of TiO2 photoanode positively.
► The driving force of injecting electrons is improved.
► We confirmed that increased electron density by measurement.