Gold nanoparticles inlaid TiO2 photoanodes: a superior candidate for high-efficiency dye-sensitized solar cells

Abstract

By designing a fine-controlled nanocomposite with Au nanoparticles (∼2 nm in size) directly inlaid in TiO₂ as working electrode, efficiency (η) of 10.1% for a dye-sensitized solar cell with an open-circuit photovoltage of 863 mV and a short-circuit photocurrent of 15.71 mA cm⁻² have been achieved, giving an enhancement of 97 mV in photovoltage, 63% in photocurrent and 84% in efficiency compared to the cell with pure TiO₂ photoanode (η = 5.5%). As compared to pure TiO₂, besides the local-field optical enhancement near the TiO₂ surface caused by plasma resonance of Au nanoparticles which increases the dye absorption and hence the amount of photogenerated charge contributing to the photocurrent, it is evidenced that not only the quasi-Fermi level of Au–TiO₂ photoanode can be modulated to more negative potentials by controlling the mass ratio of Au–TiO₂, but their mosaic nanostructure reduces the charge recombination rate effectively, both leading to a marked enhancement of photovoltage. Our results prove that the unique nanostructural, physical and chemical properties of the direct mosaic nanoarchitecture of ∼2 nm Au and TiO₂ make them valuable materials as working electrodes for DSSCs to achieve high photovoltage and hence further improve the performance.