CdS/TiO2–SrTiO3 heterostructure nanotube arrays for improved solar energy conversion efficiency

TiO2–SrTiO3 heterostructure nanotube arrays have been utilized as a novel oxide substrate for CdS quantum dot sensitized solar cells (QDSCs). SrTiO3 on TiO2 surface passivates surface states of TiO2 and builds cascade-structured band alignment, which significantly reduces charge recombination at electrode surface. CdS/TiO2–SrTiO3 electrode exhibits a superior photoelectrochemical performance than CdS/TiO2 electrode with ∼ 70% increase in external quantum efficiency. This study suggests that the suppression of charge recombination at electrode surface is critical to efficient solar energy conversion.