Broadband Light Harvesting for Highly Efficient Hot-Electron Application Based on Conformal Metallic Nanorod Arrays

Abstract

The utilization of nonradiative decay of surface plasmons (SPs) in the form of hot electrons in metallic nanostructures has a great potential for applications in photovoltaics, photocatalysis, photodetection, and surface imaging. Unfortunately, the metallic nanostructures usually support only narrowband plasmon resonances; moreover, the hot-electron thermalization loss during the transport to Schottky interface and the confined momentum space for hot-electron injection into semiconductor together result in an inefficient internal quantum process. In this study, we propose and experimentally demonstrate a broadband super absorber based on the metallic nanorod arrays (NRs). Optically, the average absorption across the entire visible band is up to 0.8, which is over 16-fold enhancement of the planar reference. Electrically, the hot electrons are controlled to be preferentially generated near Schottky interface within the mean free path, relieving the severe hot-electron thermalization loss. Moreover, the three-dimensional Schottky junction provides much increased hot-electron momentum space for injection at the vertical surface. These optical and electrical benefits lead to over 30-fold enhancement in the IPCE (incident photon-to-electron conversion efficiency) relative to the reference. The IPCE can be up to 10.9% at Eph = 3.1 eV, which is close to the limit of the thick-film single-barrier hot-electron devices. The conformal NRs system provides a promising strategy to simultaneously improve the hot-electron generation, transport, and collection efficiencies and could be an outstanding candidate for efficient hot-electron optoelectronic and photocatalysis systems.