Spatial profiles of photon chemical potential in near-field thermophotovoltaic cells

TL;DR

This paper develops a new iterative method combining fluctuational electrodynamics and drift-diffusion models to analyze the spatial variation of photon chemical potential in near-field thermophotovoltaic cells, revealing limitations of traditional assumptions.

Contribution

It introduces a novel computational approach to determine the spatial profile of photon chemical potential, surpassing the conventional constant assumptions in near-field TPV modeling.

Findings

Photon chemical potential varies spatially in near-field TPV cells.

Traditional assumptions of zero or constant chemical potential are inadequate.

The new model improves performance evaluation accuracy of TPV systems.

Abstract

Emitted photons stemming from the radiative recombination of electron-hole pairs carry chemical potential in radiative energy converters. This luminescent effect can substantially alter the local net photogeneration in near-field thermophotovoltaic cells. Several assumptions involving the luminescent effect are commonly made in modeling photovoltaic devices; in particular, the photon chemical potential is assumed to be zero or a constant prescribed by the bias voltage. The significance of photon chemical potential depends upon the emitter temperature, the semiconductor properties, and the injection level. Hence, these assumptions are questionable in thermophotovoltaic devices operating in the near-field regime. In the present work, an iterative solver that combines fluctuational electrodynamics with the drift-diffusion model is developed to tackle the coupled photon and charge transport problem, enabling the determination of the spatial profile of photon chemical potential beyond the detailed balance approach. The difference between the results obtained by allowing the photon chemical potential to vary spatially and by assuming a constant value demonstrates the limitations of the conventional approaches. This study is critically important for performance evaluation of near-field thermophotovoltaic systems.