Spraying distance and titanium chloride surface treatment effects on DSSC performance of electrosprayed SnO2 photoanodes†
A facile electrospray synthesis method and potential dye sensitized solar cell (DSSC) application of SnO2 photoanodes (of ∼10 μm thickness) have been investigated. Nanocrystallites with irregular dimensions have similar crystallite sizes and appearance when the distance between fluorine–tin-oxide (FTO) substrate and metal capillary was increased from 4 to 8 cm (maximum limit). However, increase in metal capillary distance caused reduction in charge transfer resistance and a negative shift in the flat band potential. As a result, electron lifetime was increased with the open circuit voltage (410 to 510 mV). Under 1 sun light intensity, the SnO2 photoanode (obtained at 8 cm) by a thin layer of TiO2 exhibited as high as 5.56% power conversion efficiency which was ∼350% higher than only SnO2 (1.66%) photoanode. This enhanced DSSCs performance could be attributed to better dye adsorption and increased active surface area, or boosted light-harvesting efficiency. The presence of TiO2 layer on SnO2 photoanode was confirmed with X-ray diffraction and Raman shift analysis measurements. The electrochemical impedance spectroscopy revealed increased electron lifetime and suppressed charge recombination for SnO2 photoanode that was modified with TiO2 compact surface layer.