Plasmonic Hot-Carrier Extraction: Mechanisms of Electron Emission

TL;DR

This paper investigates the mechanisms of hot-electron emission in plasmonic nanoparticle-semiconductor systems, revealing that surface charge emission, rather than homogeneous electron distribution, dominates hot-carrier injection efficiency.

Contribution

It demonstrates that increased metal-semiconductor contact area enhances hot-electron injection, supporting a surface charge emission mechanism over the traditional homogeneous distribution model.

Findings

Increased contact area boosts hot-electron quantum yield.

Surface charge emission mechanism is supported by experimental data.

Homogeneous energy-momentum distribution model is challenged.

Abstract

When plasmonic nanoparticles are coupled with semiconductors, highly energetic hot carriers can be extracted from the metal-semiconductor interface for various applications in light energy conversion. Hot charge-carrier extraction upon plasmon decay using such an interface has been argued to occur after the formation of an intermediate electron population with a uniform momentum distribution. The efficiency of the charge separation process is thus discussed to be limited by this spatial homogeneity in certain plasmon-induced applications. Here we demonstrate using visible pump, near-infrared probe transient absorption spectroscopy that increases in the contact area between metal and semiconductor leads to an increase in the quantum yield for hot electron injection that is inconsistent with the homogeneous energy-momentum distribution of hot-electrons. Instead, further analysis of the experimental data suggests that the highly energetic electrons are emitted across the interface via a surface charge emission mechanism that occurs via a plasmon excitation