Enhanced performance of CdS quantum dot sensitized solar cells by low temperature vacuum annealing

A sensitized-type solar cell based on TiO₂ photoanode and CdS quantum dots as sensitizers had been studied. CdS QDs were grown in situ on TiO₂ film, utilizing successive ionic layer adsorption and reaction method. Vacuum annealing process was carried out on the CdS incorporated TiO2 (CdS-TiO₂) films at different temperatures. It is found that the short circuit current density and conversion efficiency of QDSSCs are significantly improved by vacuum annealing. A power conversion efficiency of about 1.84% has been obtained for the cell with CdS-TiO₂ film annealed at 373 K, which is about 28% higher than that for as-prepared cell (1.43%) under one sun illumination. The proper crystallinity of CdS and good interfacial contact between CdS and TiO₂ are obtained by annealing at 373 K, which can benefit the electron transfer from CdS to TiO₂, resulting in a highest conversion efficiency.