MECHANISM BEHIND PLASMONIC ENHANCEMENT OF PHOTOCURRENT OF METAL OXIDE NANOSTRUCTURES

摘要

Recently, metal nanomaterials with novel plasmonic properties have been considered as potential sensitizers for metal oxides in solar energy conversion applications. 1-3 While the observed photocurrent seems to be convincing, as observed by several research groups in the last few years, the mechanism behind is not well established. Several explanations have been proposed. The first is hot electron injection, in which electrons generated in metal nanostructures due to light absorption are injected into MO for current generation or subsequent photoelectrochemical (PEC) reactions. The second is local field enhancement that increases the light absorption and charge transport in MO. The third is enhanced light absorption of bandgap states in the MO due to enhanced light scattering by the metal nanostructures. In the meantime, metal nanomaterials have been used in conjunction with dyes or quantum dots (QDs) to improve the performance of solar conversion as well. , in which one or more than one of the different mechanisms mentioned above could be in operation. In this work, we employ ultrafast laser techniques to directly study the hot electron dynamics in Au/ZnO nanocomposite structure to look for possible evidence of direct charge injection from Au nanoparticles to ZnO. We also conducted PEC studies of related metal-metal oxide systems to understand the mechanism behind enhanced photocurrent in the visible and UV regions.