Effect of an electrodeposited TiO2 blocking layer on efficiency improvement of dye-sensitized solar cell

A TiO2 blocking layer in DSSC provides good adhesion between the fluorinated tin oxide (FTO) and an active TiO2 layer, and represses the electron back transport between electrolyte and FTO by blocking direct contact. In addition, it offers a more uniform layer than bare FTO glass. In this study, a dense TiO2 layer is prepared by electrodeposition technique onto an FTO substrate, and it is further used for efficiency measurement of dye-sensitized solar cell (DSSC). The thickness of TiO2 blocking layers is controlled by applied voltage and deposition time. The morphology and crystalline structure of TiO2 blocking layers are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The effect of thickness of TiO2 blocking layers on transmittance is also examined by UV-vis spectrophotometer. For the best performance of the cell efficiency, the optimum blocking layer thickness is about 450 nm fabricated at 0.7 V for 20 min. The conversion efficiency from the DSSC including the optimum blocking layer is 59.34% improved compared to the reference cell from 2.41% to 3.84%. It demonstrates that the electrodeposition is a useful method to produce TiO2 blocking layer for DSSC applications.