Diffusion-emission theory of photon enhanced thermionic emission solar energy harvesters

TL;DR

This paper develops detailed models for PETE solar energy harvesters, accounting for electron diffusion, recombination, and inhomogeneous photogeneration, predicting device efficiencies and the impact of surface recombination.

Contribution

It introduces a comprehensive diffusion-emission model for PETE devices that improves upon previous rate-equation models by including detailed physical processes.

Findings

Surface recombination can significantly reduce efficiency at high temperatures and illumination.

High injection levels can boost PETE device efficiency to around 15%.

The model predicts different electron affinity and temperature dependence than earlier models.

Abstract

Numerical and semi-analytical models are presented for photon-enhanced-thermionic-emission (PETE) devices. The models take diffusion of electrons, inhomogeneous photogeneration, and bulk and surface recombination into account. The efficiencies of PETE devices with silicon cathodes are calculated. Our model predicts significantly different electron affinity and temperature dependence for the device than the earlier model based on a rate-equation description of the cathode. We show that surface recombination can reduce the efficiency below 10% at the cathode temperature of 800 K and the concentration of 1000 suns, but operating the device at high injection levels can increase the efficiency to 15%.