Coupled Charge and Radiation Transport Processes in Thermophotovoltaic and Thermoradiative Cells

Abstract

Accurate modeling of charge transport and both thermal and luminescent radiation is crucial to the understanding and design of radiative thermal energy converters. Charge carrier dynamics in semiconductors are well-described by the Poisson-driftdiffusion equations, and thermal radiation in emitter/absorber structures can be computed using multilayer fluctuational electrodynamics. These two types of energy flows interact through radiation absorption/luminescence and charge carrier generation/recombination. However, past research has typically only assumed limited interaction, with thermal radiation absorption as an input for charge carrier models to predict device performance. To examine this assumption, we develop a fully-coupled iterative model of charge and radiation transport in semiconductor devices, and we use our model to analyze near-field and far-field GaSb thermophotovoltaic and thermoradiative systems. By comparing our results to past methods that do not consider cross-influences between charge and radiation transport, we find that a fully-coupled approach is necessary to accurately model photon recycling and near-field enhancement of external luminescence. Because these effects can substantially alter device performance, our modeling approach can aid in the design of efficient thermophotovoltaic and thermoradiative systems.

Overcoming non-radiative losses with AlGaAs PIN junctions for near-field thermophotonic energy harvesting

“…It is set to 0 for ω < ω g (no electroluminescence below the bandgap), and can be approximated by µ ≈ eU above the bandgap. The validity of such approximation for NF-TPV applications was discussed by Callahan et al 23 . Here, both components are assumed to be thermal reservoirs, i.e.…”

The effects of electronic and photonic coupling on the performance of a photothermionic-photovoltaic hybrid solar device

“…The PV sub-device temperature was kept at 300 K. Note that there could be a coupling between the radiation transfer and charge transport within the PV sub-device; however, this effect is negligible for gap sizes over 100 nm [49].…”

GaAs-Based Near-Field Thermophotonic Devices: Approaching The Idealized Case With One-Dimensional PN Junctions

“…E is the gap energy, ℏ is the reduced Planck constant, the radiation frequency, the Boltzmann constant and T the temperature. In this work, we consider that the electrochemical potential is constant and equal to , a quite common approximation whose precision has been studied in [43]. By doing this approximation, we assume that the Bose-Einstein distribution is similar in all points of the LED (resp.…”

“…Note that in the existing literature for TPV (including in the near-field), radiative recombinations are modeled either by using a radiative recombination coefficient B [40] [15] or by using an iterative process that allows for a precise modelling of photon recycling and transfer between the PV cell and the LED [43]. Of course, our modelling should tend towards precision (thus the second solution).…”

“…6,7,8) instead of the Simplified Drift-Diffusion. These developments have already been developed for near-field thermophotovoltaic applications respectively in [43] and [40], and could be applied to near-field thermophotonics, allowing for an accurate description of the photon recycling and of the charge carrier behaviour in general. Apart from the algorithm itself, the device considered could also be modified to approach more realistic geometries, by considering the use of pin junctions [48] and back reflectors [20].…”