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

Abstract

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.