Improved Photovoltaic Response of Nanocrystalline CdS-Sensitized Solar Cells through Interface Control

Nanocrystalline CdS-sensitized solar cells (CdS-SSCs) based on mesoporous TiO2 were fabricated by the spray pyrolysis deposition method. The energy conversion efficiency of these cells was drastically increased (156%) by modifying the junction structure through post-treatment that included soaking in a dilute TiCl4 aqueous solution and subsequent thermal annealing. We propose that the post-treatment is responsible for an increased number of interconnections between TiO2 and CdS, as well as surface passivation of the CdS sensitizer. The increase in the cell efficiency is attributed to the improved charge carrier transport, suppression of photoelectron recombination with holes both in the same sensitizer particle and in nearby ones, and suppression of photoelectron capture by the electrolyte.