Hierarchical multilayer-structured TiO2 electrode for dye-sensitized solar cells

• We constructed a multilayer-structured TiO2 photoelectrode for improved charge transportation.
• The amount of dye adsorption and light scattering increased to a greater fraction.
• The multilayer-structured electrode showed very quick charge transportation from the top layer to the bottom layer.
• The multilayer-structured photoelectrode showed a superior performance compared to the normal TiO2 electrode.

A hierarchal multilayer-structured photoelectrode was prepared and the performance of dye-sensitized solar cell was compared with the standard P25 electrodes in different thickness and bilayer-structured TiO2 electrode. Scanning electron microscope and X-ray diffraction patterns were used to analyze the morphology and crystal phases of these electrodes. The multilayer-structured photoelectrode showed a superior performance compared to those of the other three electrodes. The enhancement was attributed to higher amount of dye adsorption, large incident photon-to-current conversion yield due to greater fraction of light scattering and the good charge transportation because of the optimized structure of the TiO2 electrode. The UV–vis measurement confirmed the higher dye loading capacity of the multilayered-structure. Electrochemical spectra (EIS) were used to analyze the charge transport kinetic in these electrodes. The EIS analysis showed large electron injection rate, the suppression of recombination rate and longer electron lifetime in the multilayer-structured photoelectrode due to the optimized structure. The incident photon-to-current conversion efficiency measurement revealed the greater light harvesting efficiency of the multilayer-structured photo-electrode.