Ultrathin ALD coating on TiO2 photoanodes with enhanced quantum dot loading and charge collection in quantum dots sensitized solar cells

TiO 2 nanocrystals are widely used in photoanodes for quantum dot solar cells (QDSCs) owing to their chemical stability and suitable energy band structure. However, surface defects and grain boundaries of TiO 2 nanocrystals photoanodes allow high surface charge recombination, which limits the performance of QDSCs. In this work, an ultrathin TiO 2 layer is introduced to the surface of TiO 2 photoanodes by atomic layer deposition (ALD). The ultrathin layer not only reduces the surface defects of TiO 2 nanoparticles and strengthens the connection between adjacent nanoparticles to suppress the charge recombination for improving the electron collection efficiency (η cc ), but also increases the surface energy of photoanodes to load more quantum dots (QDs) for enhancing the light harvesting efficiency (LHE). As a result, the solar cell based on CdS/CdSe QDs with ALD treatment exhibits an efficiency of 5.07% that is much higher than that of the cells without modification (4.03%).