Improvement of nonlinear response for the power conversion efficiency with light intensities in cobalt complex electrolyte system

A vertically aligned TiO2 photoelectrode with sufficient space between TiO2 nanorods was synthesized by sacrificial templating of ZnO nanorods grown on a dense TiO2 layer/FTO film. The more expanded pore space in the TiO2 nanorod film than conventional mesoscopic TiO2 film greatly reduces the mass transport problem of cobalt electrolyte in the vicinity of the Sb2S3 sensitizer in Sb2S3-sensitized photoelectrochemical solar cells. Therefore, the nonlinearity of the power conversion efficiency (PCE) under illumination intensity was greatly relieved to 5.0% (0.1 sun), 4.7% (0.5 sun), and 3.7% (1 sun) in a TiO2-nanorod-based Sb2S3-sensitized solar cell, whereas the efficiency of a mesoscopic-TiO2-based solar cell was significantly degraded to 5.3% (0.1 sun), 3.8% (0.5 sun), and 2.3% (1 sun).