Photoelectrochemical solar cells made from SnO₂/ZnO films sensitized with an indoline dye

A dye-sensitized photoelectrochemical (DS-PEC) cell consisting of SnO₂ and ZnO nanoparticles was found to yield higher solar energy conversion efficiency than similar cells made of the individual oxide semiconductors when they were sensitized with an indoline dye. The SnO₂/ZnO composite solar cell gave an overall energy conversion efficiency of 3.8% while the SnO₂ and ZnO individual cells yielded efficiencies of 2.8% and 1.2%, respectively, under standard AM 1.5 irradiation (100 mW cm⁻²). The broadening of the absorption spectra and a large red shift of the absorption peak were observed by the adsorbing dyes on the composite film suggesting the formation of various kinds of J-aggregates. It is suggested that the formation of the J-aggregates and the presence of the ZnO barrier were responsible for the higher efficiency of the composite cell.