Hot Electron Dynamics in Plasmonic Thermionic Emitters

TL;DR

This paper demonstrates that plasmonic nanostructures can sustain high electronic temperatures for thermionic emission at lower lattice temperatures, enabling more efficient and thermally stable thermionic energy conversion.

Contribution

It introduces a novel approach using resonant plasmonic absorption to achieve high electronic temperatures without high lattice temperatures, improving thermionic device performance.

Findings

Plasmonic nanostructures enable steady-state high electronic temperatures at below 600 K.

Optical thermometry confirms unique electron dynamics in these structures.

Thermionic devices outperform other solar power conversion methods in efficiency and stability.

Abstract

Thermionic converters generate electricity from thermal energy in a power cycle based on vacuum emission of electrons. While thermodynamically efficient, practical implementations are limited by the extreme temperatures required for electron emission (> 1500 K). Here, we show how metal nanostructures that support resonant plasmonic absorption enable an alternative strategy. High electronic temperatures required for efficient vacuum emission can be maintained during steady-state optical absorption while the lattice temperature remains within the range of thermal stability, below 600 K. We have also developed an optical thermometry technique based on anti-Stokes Raman spectroscopy that confirms these unique electron dynamics. Thermionic devices constructed from plasmonic absorbers show performance that can out-compete other strategies of concentrated solar power conversion in terms of efficiency and thermal stability.