Ultrabroad wavelength absorption in high-temperature solar selective absorber coatings enabled by high-entropy nanoceramic AlTiZrHfNbN for high-performance solar-thermal conversion

Abstract

The solar selective absorber coating (SSAC), which can maximally harvest solar energy over a broad wavelength range with near-perfect spectral selectivity, is of essential importance for many applications especially the generation of solar-thermal electricity. Herein, inspired by the emerging field of high-entropy nanoceramics, we propose and numerically demonstrate a high-performance AlTiZrHfNbN-based SSAC. Enabled by the synergetic intrinsic absorption and destructive interference characteristics, the AlTiZrHfNbN-based coating demonstrates a high absorptance (α = 0.95) across an ultrabroad wavelength range of 300–3220 nm. Meanwhile, the coating possesses a low emittance (ε = 0.12, 82 °C) in the infrared region. Furthermore, the multilayer coating is stable at elevated temperatures, which shows promising solar-thermal conversion efficiency that enables it to reach 83.9% (C = 200, T = 600 °C). Upon further elevating the annealing temperature to 700 °C, obvious oxidation becomes the driving force for the attenuation of optical properties and changes in microscopic morphology. The finite-difference time-domain (FDTD) indicates that the physical mechanisms of ultrabroad wavelength absorption and degradation are related to a high density of hybrid cavity and surface plasmon polariton modes overlapped with the double-absorption layers, respectively. All these properties of the multilayer coating suggest its great promise for application in on-site solar-thermal utilization facilities.