Impedance analysis for dye-sensitized solar cells based on TiO2 electrode coated with Cr2O3

•A TiO2 electrode with Cr2O3 coating layer was prepared.•The Is and η of TiO2/Cr2O3 cells enhanced by 19.3% and 21% than TiO2 cell.•The EIS at different applied potential is discussed in details.•Rw, Rct and Cfilm switch to exponential behavior at high bias.•Rk of TiO2/Cr2O3 cell is lower than TiO2 cell at high bias. TiO2 nanomaterial with typical anatase was prepared by hydrothermal method. A surface modification method was carried out by dip TiO2 electrode into Cr(NO3)3 solution. The TiO2/Cr2O3 thin film was characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The current–voltage (I–V) curve revealed that short circuit current and photoelectric transfer efficiency of the modified electrode enhanced by 19.3% and 21%, respectively. The main features of electrochemical impedance spectroscopy (EIS) were discussed in a wide range of potential applied. The parameters of electron transport resistance in TiO2 film (Rw), the overall charge transfer resistance (Rct) and capacitance (Cfilm) of film were analyzed using an equivalent circuit. It was found that Rw, Rct and Cfilm switch to exponential behavior at high bias.