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

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.