Ultrahigh Thermal Robustness of High‐Entropy Spectrally Selective Absorbers for Next‐Generation Concentrated Solar Power System

Abstract Spectrally selective absorbers (SSAs) are a critical component in concentrated solar power (CSP) systems, as they maximize sunlight absorption while suppressing heat radiative loss. Despite various SSAs being demonstrated, the challenges remain on the limitations of thermal instability at elevated operating temperatures especially above 650 °C due to component oxidation and diffusion in the absorption layer. To address these challenges, herein a high‐entropy strategy is resorted. By utilizing high‐entropy nitride film as an absorption layer, a double‐layer SSA is prepared by a facile magnetron sputtering method. High‐entropy engineering intensifies and complicates the localized electronic bands, concurrently exhibiting relatively flat bands around the Fermi level, which can significantly enhance 3d interband transition. The resultant SSA delivers the desired spectral selectivity (α/ɛ_{82 °C} = 92.7%/8.4%). Benefitting from the high‐entropy effect, the SSA maintains outstanding optical properties (α/ɛ_{82 °C} = 93.3%/9.4%) even after a 750 °C vacuum thermal treatment for 120 h. Under 1 kW m⁻² simulated illumination, the surface temperature of the absorber can easily rise to 95.3 °C, suggesting its remarkable solar‐thermal performance. Furthermore, its effectiveness in parabolic trough collectors (PTCs) is validated. All these competitive performances make the high‐entropy SSA a potentially promising candidate for PTCs.