Improved plasmon-assisted photoelectric conversion efficiency across entire ultraviolet–visible region based on antenna-on zinc oxide/silver three-dimensional nanostructured films

Abstract

ZnO has received tremendous attention for applications in photoelectrochemical water splitting, photocatalysis, and photovoltaic devices. However, the photoelectric conversion efficiency of ZnO is limited by the rapid recombination of photoexcited electron–hole pairs and the wide band gap, which allows only a small fraction of the solar spectrum to be absorbed. Recently, substantial research efforts have aimed to increase the photoelectric conversion efficiency across the entire ultraviolet–visible (UV–vis) spectrum by coupling semiconductors such as ZnO with noble metal nanoparticles (NPs). In this study, we compare the performance of a pure ZnO film and ZnO/Ag nanostructured films as photoelectrodes.We show that under broad-spectrum UV–vis illumination, the photocurrent generated in the ZnO/Ag three-dimensional (3D) nanostructured films increases 3.75 times relative to the photocurrent generated in the pure ZnO films. We attribute the high photocurrent to the electric-field enhancement associated with the localized surface plasmon resonance of the Ag NPs, which are present at a high density in the 3D nanostructured films, and to the creation of photoexcited hot electrons in Ag that are transferred to ZnO, promoting electron–hole pair separation. We propose a mechanism to explain the observed enhancement of the photoelectric conversion efficiency.