Efficient direct electron transfer via band alignment in hybrid metal-semiconductor nanostructures toward enhanced photocatalysts

Plasmonic metal nanostructures can improve the photon-charge conversion efficiency in metal/semiconductor hybrid systems through direct electron transfer (DET), resonance energy transfer (RET), and accelerated exciton separation. These enhancement mechanisms of photon-charge conversion have been independently investigated, and it remains unclear which is the most efficient process for the conversion. Herein, DET is proposed as the most efficient pathway due to its ability to facilitate charge separation along with the extended band bending at the interface between the metal and the semiconductor under light irradiation. This investigation on plasmon-induced charge separation was carried out with metal-nanoparticle-decorated p-type semiconductor nanowires by wavelength-tunable light-irradiated Kelvin probe force microscopy and photocurrent measurements. In addition, the band alignment between the metal and the semiconductor was characterized by density functional theory calculations. DET was shown to be superior to RET by an approximated ratio of 8:2 with the coexistence of both plasmonic and excitonic excitations. This observation suggests a straightforward way to develop efficient photocatalysts – engineering individual pathways of plasmon-induced charge separation and transfer.