Strontium titanate nanoparticles as the photoanode for CdS quantum dot sensitized solar cells

SrTiO3 has the potential to be used as the photoanode for quantum dot sensitized solar cells (QDSSCs) since it has very similar band structures to TiO2 that exhibits the best performance in QDSSCs. In this work, SrTiO3 nanoparticles (NPs) with a cubic crystal structure were prepared by a hydrothermal method. 120, 70 and 30 nm SrTiO3 NPs were obtained by using different starting materials. CdS quantum dots (QDs) were coated on three different sized SrTiO3 NPs using the successive ion layer adsorption and reaction (SILAR) method. QDSSCs based on three different sized SrTiO3 NPs were fabricated and investigated. Due to the higher surface area compared to larger NPs, the device based on 30 nm SrTiO3 NPs shows the best open-circuit voltage (V-oc) of 0.76 V and fill factor (FF) of 67% which are relatively high for V-oc and FF reported for CdS-QDSSCs. Comparison studies of light-harvesting efficiency, electron transfer processes and band diagrams were performed to analyze the device performance in the SrTiO3-QDSSCs and TiO2-QDSSCs. The 30 nm SrTiO3 NPs can be combined with TiO2 NPs (P25) to improve the performance of the CdS-QDSSCs with an increasing percentage of 12.5%, which represents an alternative way to realize high efficiencies in QDSSCs.