Polarization Effect of Hot Electrons in Tandem-Structured Plasmonic Nanodiode

Abstract

Energy conversion from light to electricity mediated by hot electrons in a plasmonic metal nanostructure caused by the decay of surface plasmons has been proposed as a promising way to obtain novel photovoltaics and photocatalytic devices. In Schottky barriers composed of metal nanostructures supported on a semiconductor surface, hot electrons produced in the metal with sufficient photon energy can be extracted into the conduction band of the semiconductor by overcoming the Schottky barrier. An important parameter for the efficient extraction of hot electrons is the polarization of the incident light, which can be tuned by the angle between the electric field of the incident light and the plane of the Schottky barrier. Here, we investigate polarization-dependent hot electrons detected on planar (two-dimensional) and three-dimensional (3D) tandem plasmonic Au/TiO2 nanodiodes. We confirm that the maximum photocurrent was obtained with the planar structure in transverse mode and with the 3D tandem structure in longitudinal mode. These results indicate that hot electrons can be extracted most efficiently when the direction of the electric field of the incident light coincides with the plane of the Schottky interface. This study sheds light on the fundamental mechanism for the polarization effect on hot electrons, with applications in the advanced design of hot-electron-based photonic devices with high energy conversion efficiency. © 2018 American Chemical Society