Improved efficiency of CdS/CdSe quantum dot sensitized solar cells by tetrabutyl titanate surface modification

The surface of TiO₂ photoanode films for CdS/CdSe quantum dot-sensitized solar cells (QDSSCs) was modified through in situ hydrolysis and condensation of tetrabutyl titanate (TBT). Results showed that the surface area of the film increased after TBT modification, which was due mainly to the generation of small TBT generated TiO₂ nanocrystallites (TBT-TiO₂) adjoined the gaps in TiO₂ photoanode films, resulting in the increase of quantum dots (QDs) loading and light absorption. The TBT-TiO₂ also facilitated the electron transfer through the TiO₂ photoanode films. Owing to these synergistic effects, the short-circuit current density, open-circuit voltage, and resultant power conversion efficiency were significantly increased for the designed QDSSCs. And a power conversion efficiency of 4.76% was achieved under the TBT modification with an optimal concentration that was 28% greater than the bare device. Meanwhile, a comparison of the photovoltaic performance for TBT modified photoanode was made with traditional TiCl₄ modified one. It was found that the TBT modification on photoanode film contributed to higher light absorption capability and less charge recombination compared to TiCl₄ modification. The findings suggest TBT modification to be an effective approach to improve the performance of QDSSCs. (paper)