The Eis Method Of Tio <sub> 2 </ Sub> Thin Film Photoanode Interfacial Charge Transfer

In this paper, the electron transfer process across the interfaces between TiO₂ and ITO and electrolyte were investigated under the variation of the external bias by EIS method. Mott-Schottky plots of the different TiO₂ electrodes were measured to determine both the flat-band potential and the concentration of carriers in the space charge layer. Moreover, the effects of the light intensity, the thickness of TiO₂ film, the amount of Pt on counter electrode and the content of electrolyte on charge transfer process in DSSC were investigated with impedance spectroscopy.The experimental results showed that: The energy band bend of TiO₂/electrolyte interface and TiO₂/ITO interface were increased at the positive bias. The former is favor to the separation of photogenerated electrons and holes, and the latter is able to inhibit the injection of electrons from the TiO₂ to the ITO substrate. So the arc size of the EIS was increasing. While at the negative bias, the situation was just opposite. The EIS of DSSC demonstrated that impedance spectra of the DSSC consisted of three components: the low-frequency corresponds to the diffusion within the electrolyte, the middle-frequency peak reflects the properties of the photoinjected electrons within the TiO₂, and high-frequency peak corresponds to the charge-transfer at the platinum counter electrode. In conclusion, the EIS method can help to obtain more information which can provides the theory basis for improving the performance of the DSSC system.