Spectral and total temperature-dependent emissivities of few-layer structures on a metallic substrate

Abstract

We investigate the thermal radiative emission of few-layer structures deposited on a metallic substrate and its dependence on temperature with the Fluctuational Electrodynamics approach. We highlight the impact of the variations of the optical properties of metallic layers on their temperature-dependent emissivity. Fabry-Pérot spectral selection involving at most two transparent layers and one thin reflective layer leads to well-defined peaks and to the amplification of the substrate emission. For a single Fabry-Pérot layer on a reflective substrate, an optimal thickness that maximizes the emissivity of the structure can be determined at each temperature. A thin lossy layer deposited on the previous structure can enhance interference phenomena, and the analysis of the participation of each layer to the emission shows that the thin layer is the main source of emission. Eventually, we investigate a system with two Fabry-Pérot layers and a metallic thin layer, and we show that an optimal architecture can be found. The total hemispherical emissivity can be increased by one order of magnitude compared to the substrate emissivity.

New insights into the thermal behavior and management of thermophotovoltaic systems

“…Several experimental studies assessed the validity of the concept of thermophotovoltaic energy converters, with increasing efficiencies [2][3][4][5][6], recently reaching promising efficiency around 29% [7]. During the past years, many studies focused mainly on tailoring the spectral emission of the radiator [8][9][10][11][12][13][14][15][16][17][18] or the PV cell [19] such that the energy of the emitted photons are selected with respect to the bandgap of the PV cell, using various geometries and materials. Later, an emphasis was put on using materials withstanding high temperatures, like tungsten or molybdenum, such that the radiator is thermally stable and keeps its spectral selectivity at high-temperature.…”

General formulation of coupled radiative and conductive heat transfer between compact bodies

“…In the following, we take AZO as an illustrative example and assume a temperature-independent dielectric constant to illustrate the main effects stemming from CR coupling, leaving a full description, which is more relevant in the presence of large temperature gradients, to future work. Note that we recently considered the full temperature-dependent dielectric response in the context of far-field emission [46,47], which can also be handled by the FVC framework. To begin with, we show that even in the absence of CR interplay, the RHT spectrum and spatial distribution inside the nanorods differs significantly from those of AZO slabs of the same thickness.…”

“…In this work, we focused primarily on describing the extension and application of the FVC technique to such situations, providing only a proof-of-concept example where CR interplay is relevant while ignoring other practically important effects associated with the possibility of significant temperature gradients in multiple bodies or additional nonlinearites stemming from the temperature-dependent dielectric response of materials [47].…”