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

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 filmlike conductors PtCoO2 and Cr2AlC resembles that of two-dimensional (2D) metals, while that of wirelike conductors CoSn and YCo3B2 resembles 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 PtCoO2 and CoSn, are competitive with noble metals. Most importantly, we predict that the carrier injection efficiency from all of these materials into semiconductors can exceed 10% due to the small component of carrier momentum parallel to the metal surface, substantially improving upon the typical injection efficiency of less than 0.1% from noble metals into semiconductors.

Automated summary

Directional conductors show significant advantages for efficient hot carrier harvesting. Filmlike conductors PtCoO2 and Cr2AlC have optical response resembling 2D metals, while wirelike conductors CoSn and YCo3B2 resemble 1D metals, enabling efficient light collection in small dimensions.