Enhancing Thermal Robustness of a High-entropy Nitride Based Solar Selective Absorber by the Incorporation of Al Element

• Published in: Materials today physics 2022-10, Vol.27, p.100836, Article 100836
• Main Authors: He, Cheng-Yu, Zhao, Peng, Gao, Xiang-Hu, Liu, Gang, La, Pei-Qing
• Format: Article
• Language: English
• Subjects: High-entropy nitride; Solar-thermal efficiency; Spectral selectivity; Spectrally selective absorber; Thermal stability
• ISSN: 2542-5293; 2542-5293
• DOI: 10.1016/j.mtphys.2022.100836

Engineering a high-performance spectrally selective absorber (SSA) has been a long-standing effort to address the challenges of inferior spectral selectivity and thermal instability at high temperatures. High-entropy nitrides have shown distinct merits in solar absorption and thermal robustness simultaneously. It is highly desirable to elaborately choose element compositions and optimize absorber structure to enable outstanding solar harvesting ability even at extremely high temperatures above 700 °C. Herein, by modulating the Al element content through a co-sputtering system, a high-entropy nitride MoTaTiCr-Al-N based SSA with a simple double-layer structure is successfully fabricated. As-deposited SSA shows a superior solar absorptance of 92.3% and a suppressed thermal emittance of 7%, together with satisfactory absorption over incident angles up to 60°, ideal for solar-thermal applications. Furthermore, the absorber also exhibits attractive thermal robustness, retaining decent optical performance even after annealing at 700 °C for 168 h. More significantly, the solar-thermal efficiency could reach up to 80.5% at a working temperature of 700 °C under 100 suns, which equals or even outperforms those of state-of-the-art solar absorbers. The competitive performance of the MoTaTiCr-Al-N based SSA is accompanied by a favorable cost reduction compared with those of multilayer thin film structures. All these merits enable it with enormous potentiality for practical solar-thermal applications. [Display omitted] •By an aluminum-doped strategy, the well-designed high-entropy nitride MoTaTiCr-Al-N based SSA that embraces a high solar absorptance of 92.3% and low thermal emittance of 7% as well as a direction-independent absorption.•The incorporation of Al element greatly enhanced thermal stability of the SSA, no significant changes of reflectance spectra are observed even after annealing at 700°C for 168 h.•Solar-thermal efficiency reaches as high as 80.4% under the irradiation of 100 suns at 700 °C, which equals or surpasses state-of-the-art SSA, capable of those high-temperature solar-thermal applications.•Upon 1 sun (1 kW m-2) irradiation, the high surface temperature of more than 85 °C is captured, suggesting great potential in solar interface evaporation-related applications.