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

Abstract

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.