Tailored SrTiO3/TiO2 heterostructures for dye-sensitized solar cells with enhanced photoelectric conversion performance

Abstract

We present a novel type of SrTiO₃/TiO₂ nanosheet heterostructure via a facile hydrothermal process, with a tunable microstructure, phase component and surface area by adjusting the molar ratio of Sr and Ti precursors. The synthesized SrTiO₃/TiO₂ heterostructure nanostructures can provide a high surface area and porous structure for improving the dye loading capacity and hence the amount of photogenerated charges contributing to the photocurrent. The formation of heterostructures between SrTiO₃ and TiO₂ with a uniquely matched band gap energy structure can efficiently separate photogenerated charge carriers. Photoluminescence emission and electrochemical impedance spectroscopy (EIS) and incident photon-to-electron conversion efficiency (IPCE) measurements reveal a lower recombination rate of photogenerated electrons and holes, and a longer electron lifetime for DSSCs based on the SrTiO₃/TiO₂ heterostructures. The photoelectric conversion efficiency and short-circuit current density of DSSCs based on SrTiO₃/TiO₂ heterostructures are greatly enhanced over those of pure TiO₂ nanosheets. DSSCs based on the SrTiO₃/TiO₂ heterostructures show a highest short-circuit current density of 12.55 mA cm⁻² and a maximal photoelectric conversion efficiency of 7.42% under one sun illumination.