Effect of ZrO2 barrier layers on the photovoltaic parameters of rose bengal dye-sensitized TiO2 solar cell

Abstract

Dye-sensitized solar cells (DSSCs) based on thin porous TiO2 and ZrO2 coated TiO2 thin films with rose bengal as the sensitizer were investigated. The TiO2 as well as ZrO2 coated TiO2 photo-electrodes were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and UV–vis spectroscopy. The electrochemical behavior of TiO2, TiZr5, TiZr10 and TiZr15 photo-electrodes were studied using electrochemical impedance spectroscopy. A facile successive ionic layer adsorption reaction (SILAR) method was used to deposit a thin overlayer of ZrO2 on TiO2 photo-electrode film to minimize interfacial recombination losses as the ZrO2 layer acts as a barrier for electron transfer at the interfaces. Thin ZrO2 layers were deposited by alternate dipping TiO2 film in 0.1 M Zr(SO4)2 and 0.1 M NaOH solutions, maintained at room temperature, followed by annealing at 450 °C. The cells fabricated using these films showed good correlation between current/voltage analyses. The introduction of ZrO2 overlayers with five SILAR cycles increases the overall cell efficiency to 0.052% from 0.030% of the pure TiO2 photo-electrode film. The improved solar conversion efficiency exhibited by TiZr5 makes the technique as a novel promising method to enhance efficiency of DSSC.