Fermi surface anisotropy in plasmonic metals increases the potential for efficient hot carrier extraction

TL;DR

This study demonstrates that Fermi surface anisotropy in plasmonic metals enhances hot carrier extraction efficiency, with directional conductors showing significant advantages over traditional noble metals for energy conversion applications.

Contribution

The paper introduces the concept that Fermi surface anisotropy in plasmonic metals can be exploited to improve hot carrier harvesting, supported by first-principles calculations of optical and transport properties.

Findings

Directional conductors have optical responses similar to 2D or 1D metals.

Carrier injection efficiency can exceed 10%, much higher than noble metals.

Materials like PtCoO2 and CoSn show competitive carrier lifetimes and transport distances.

Abstract

Realizing the potential of plasmonic hot carrier harvesting for energy conversion and photodetection requires new materials that resolve the bottleneck of extracting carriers prior to energy relaxation within the metal. Using first-principles calculations of optical response and carrier transport properties, we show that directional conductors with Fermi velocities restricted predominantly to one or two directions present significant advantages for efficient hot carrier harvesting. We show that the optical response of film-like conductors, PtCoO$_2$ and Cr$_2$AlC, resemble that of 2D metals, while that of wire-like conductors, CoSn and YCo$_3$B$_2$, resemble that of 1D metals, which can lead to high mode confinement and efficient light collection in small dimensions, while still working with 3D materials with high carrier densities. Carrier lifetimes and transport distances in these materials, especially in PtCoO$_2$ and CoSn, are competitive with noble metals. Most importantly, we predict that carrier injection efficiency from all of these materials into semiconductors can exceed 10% due to the small component of carrier velocity parallel to the metal surface, substantially improving upon the typical less than 0.1% injection efficiency from noble metals into semiconductors.