Influence of surface passivation by MgO on photovoltaic performance of SnO2 based dye-sensitized solar cells

The study highlights effect of surface modification of SnO₂ photoelectrode by MgO coating on photovoltaic properties of dye-sensitized solar cells (DSSCs). A thin coating of MgO on SnO₂ photoelectrode was prepared using sol-gel-derived dip coating technique. The bare SnO₂ and MgO coated SnO₂ composite photoanodes was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and UV–vis spectrophotometer. The optical absorption study revealed that the modification in SnO₂ by MgO coating caused an increase in absorption by photoanode in visible region. The solar cell was demonstrated by preparing FTO|SnO₂|Dye|MgO|Electrolyte|Pt coated FTO device structure and tested with current density-voltage (J-V) measurement. The effect of precursor concentration of MgO coating on the performance of DSSCs were investigated. It was found that, optimized coating of MgO for 90 seconds on SnO₂ improved all photovoltaic parameters, resulting in enhancement in efficiency by 42% compared to that of DSSC with bare SnO₂ photoanode. The coating of MgO would have reduced the trap states and suppressed interfacial recombination losses by preventing back electron transfer from the conduction band of the semiconductor to HOMO of dye molecule or redox species.