The role of a TiCl4 treatment on the performance of CdS quantum-dot-sensitized solar cells

To investigate the interface of TiO2/CdS/polysulfide-electrolyte in CdS quantum-dot-sensitized solar cells (QDSCs), a thin TiO2-coating layer is deposited onto a nanocrystalline TiO2 electrode by TiCl4. This nanoscale coating enhances the power-conversion efficiency by ∼40% compared with a bare CdS-sensitized solar cell. The main contribution to the efficiency enhancement lies in the reduced recombination rate at the TiO2/polysulfide-electrolyte interface by passivating the surface defects, as confirmed by the open-circuit decay, electrochemical impedance, and chronoamperometry. While the amount of CdS sensitizer remains the same with the coating layer, the optimum coating thickness demonstrates that electrolyte diffusion is another factor affecting the performance of QDSCs. [Display omitted] ▸ Nanoscale coating enhances the efficiency by ∼40% compared with a bare QDSC. ▸ The main contribution lies in the reduced recombination rate at the interface. ▸ The amount of CdS sensitizer remains the same with the coating layer. ▸ Electrolyte diffusion is another factor affecting the performance of QDSCs.