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