Evidence of a strong electron–hole separation effect in ZnO@TiO2 core/shell nanowires

In this work, a strong electron-hole separation effect in ZnO@TiO2 core/shell nanowire arrays was investigated. On the surface of well-aligned ZnO nanowires, a high-quality TiO2 shell was grown in a range of thicknesses through the deposition of TiO2 nanoparticles on ZnO nanowire arrays by pulsed laser deposition (PLD). In the photoluminescence (PL) spectra of the ZnO@TiO2 core/shell nanowires, a strong and broad visible emission band from 450 to 650 nm appears, which is related to surface defects; meanwhile, the ultraviolet (UV) emission due to exciton recombination simultaneously disappears. These changes in the PL spectra originate from a highly efficient electron-hole separation effect. This work presents evidence of this strong electron-hole separation effect in these ZnO@TiO2 core/shell nanowire arrays, which makes them promising candidates for use in optoelectronic devices for dye-sensitized solar cells and ultraviolet photodetectors.