The role of ZnO-coating-layer thickness on the recombination in CdS quantum-dot-sensitized solar cells

摘要

To prevent recombination at the interface of TiO_2/polysulfide-electrolyte, a ZnO layer was deposited on a TiO_2 electrode. The optimized ZnO-coated solar cell exhibited a ~32% increase in the power-conversion efficiency compared to the bare cell. The coating layer acts as an energy barrier, which plays an important role in reducing the charge recombination from the TiO_2 electrode to the electrolyte. Moreover, CdS quantum-dot adsorption was enhanced by employing the ZnO-coated layer. The thicker ZnO layer (more than 8-cycle deposition), however, led to a less porous electrode, as confirmed by electrolyte diffusivity, and also deteriorated the cell efficiency by introducing defect states verified by electron lifetime and chronoamperometric reduction current.