Improved conversion efficiency of CdS quantum dots-sensitized TiO ₂ nanotube array using ZnO energy barrier layer

We report that the use of a chemically deposited ZnO energy barrier between a CdS quantum dot sensitizer and TiO₂ nanotubes (TNTs) can improve the efficiency of quantum dots-sensitized solar cells (QDSCs). The experimental results show that the formation of the ZnO layers over TNTs significantly improved the performances of the CdS QDSCs based on the TNTs electrodes. In particular, a maximum photoconversion efficiency of 4.6% was achieved for the CdS/ZnO/TNTs electrode under UV-visible light illumination, corresponding to an increase of 43.7% as compared to the CdS/TNTs electrode without the ZnO layers. The improved CdS QDSCs efficiency is attributed to the suppressed recombination of photoinjected electrons with redox ions from the electrolyte resulting from the ZnO energy barrier layers.