The effects of Li2O doping on TiO2 nanocrystalline film are investigated to improve the conversion efficiency of dye-sensitized solar cells (DSC), while considering the mechanism of electric conduction in the TiO2 nanocrystalline film. The temperature dependence of carrier concentration and electric conductivity of Li2O-doped TiO2 nanocrystalline film are determined by Hall effect and high-impedance conductivity measurements. At the doping condition of $4.5 \times 10^{-5}$ molar ratio of Li2O to TiO2, the electric conductivity at room temperature is maximum, which is almost two orders of magnitude higher than that of the undoped sample. The conduction type and carrier concentration at 500 K are n-type and $1.75 \times 10^{13}$ cm-3, respectively. From the temperature dependence of the electron concentration, the donor depth is estimated as 1.0 eV. By applying Li2O doping to DSC, the conversion efficiency and open-circuit voltage are maximum at the highest conductivity of the Li2O-doped TiO2 layer.