Abstract
The functional application of high entropy alloys, which emerge as a novel multi-principal component alloy, has been constantly expanding in the field of solar photothermal harvesting from optical materials to high temperature materials due to their excellent properties. A solar spectrally selective absorbing coating requires such materials that show not only outstanding optical properties but also prominent thermal stability. It is desirable but challenging to fabricate high performance solar absorbing coatings. A prospective strategy for the preparation of solar absorbing coatings is the introduction of high entropy alloys. In this work, we have developed a simple, cost-conscious, scalable and highly efficient solar selective absorbing coating using a single layer high entropy nitride AlCrTaTiZrN by choosing appropriate elemental compositions. The as-deposited coatings show an outstanding spectral selectivity of alpha/epsilon = 92.8%/5.1% or 91.6%/5.1%. High temperature thermal stability tests are performed in depth, indicating that the coating could endure annealing treatment at 800 degrees C for 2 h with insignificant reflectance spectrum variation. A prolonged period of thermal stability characterization presents that this coating could maintain good optical performance after annealing at 650 degrees C for 300 h. Furthermore, high temperature thermal emittance can be suppressed to as low as 15.4% at 600 degrees C, which contributes to the state-of-the-art photothermal conversion efficiency under 100 suns (87.7% at 600 degrees C, and 84.6% at 650 degrees C). Overall, the high entropy nitride AlCrTaTiZrN based coating contributes to good thermal stability and optical properties, showing great potential for extensive applications in solar energy harvesting.

Published in JOURNAL OF MATERIALS CHEMISTRY A，Volume 9；10.1039/d0ta09988k，MAR 14 2021