Contents lists available at ScienceDirect Solar Energy Materials and Solar Cells journal homepage: www.elsevier.com/locate/solmat High-temperature air-stable solar absorbing coatings based on the cermet of MoSi 2 embedded in SiO 2 Yijie Liu a , Zuoxu Wu a , Li Yin b , Zongwei Zhang b , Xingxing Wu b , Dong Wei a , Qian Zhang b,* , Feng Cao a,** a School of Science, Harbin Institute of Technology, Shenzhen, 518055, Guangdong, China b Department of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, Guangdong, China ARTICLE INFO Keywords: Solar absorber Molybdenum disilicide Spin coating SiO 2 barrier ABSTRACT Solar absorbing coating is a critical component in concentrated solar power (CSP) system. How to further de- crease costs and enhance thermal stability of coatings is crucial for large-scaled CSP systems. Herein, we present a cost-effective and facile strategy to prepare the MoSi 2 –SiO 2 based coatings, which can survive at 850 °C in air for 100 h due to the formation of a SiO 2 barrier in cermet that prevents the coatings from further oxidation. The absorbers demonstrate a high absorptance of ∼95%, and the total efficiency using this absorber could reach 63.5% with the conditions of a solar concentration ratio of C = 1000 at 850 °C, which exceeds most of spectrally selective coatings. These results suggest that the MoSi 2 –SiO 2 based absorbing coating would be a potential candidate for a large-scale deployment in high-temperature solar thermal conversion systems. 1. Introduction Solar absorbing coating plays an important role in CSP systems. For decades, solar spectrally selective coatings (SSSCs) with high solar ab- sorptance (α) and low thermal emittance (ε) have been developed to achieve the high solar–thermal conversion efficiency [1,2]. Spectrally selective absorption of these coatings relies on the difference of spec- trum response between solar spectrum regime and blackbody radiation regime. Peak of the blackbody radiation moves toward the shorter wavelength when the operating temperature increases, which will re- sult in the large overlap between blackbody radiation wavelength coverage and solar spectrum wavelength coverage, so it could be a huge challenge to obtain the spectrally selective absorbers utilized in higher temperature applications. Currently the operating temperature of CSP systems is lower than 750 °C, due to the limited stability of absorbers, HTF (heat-transfer fluid), and heat engines [3], but it will be sig- nificantly improved for higher thermal efficiency with the development of technology in the future. In solar-thermal applications, high tem- perature must be achieved through solar concentration because solar energy is a kind of low-grade energy source. Compared with solar ab- sorptance, thermal emittance has a negligible impact on the efficiency at high concentrations. Therefore, the high-temperature stability of solar absorber with high solar absorptance is more meaningful for high temperature applications. Conventionally, spectrally selective absorbing coatings have com- plex structures including multiple absorbing layers with different vo- lume fractions, infrared (IR) reflector layers, diffusion barrier layers and anti-reflective coatings (ARCs) [4–9]. All these designs require accurate thickness control, therefore most of the fabrication techniques for existing coatings are limited to vacuum deposition, such as mag- netron sputtering [10,11] and evaporation [12–14], resulting in high production costs. In addition, the coatings with complex structures cannot survive at high temperature due to interfacial diffusion and decomposition of the coatings. Thus, the highest working temperature of most reported spectrally selective coatings is still lower than 750 °C [6,15–17]. Since cost-effectiveness is an essential requirement of a solar absorbing coating for a large-scale deployment, and improving the se- lectivity of absorber at a high concentration has relatively less con- tribution to solar thermal conversion, we should focus on the stability rather than selective absorption in high temperature systems. Spectrally selective coatings prepared by more economical technologies, such as sol-gel method, have been extensively investigated [18–21]. Recent reports of black cobalt oxide coating [22] and Ni–SiO 1.5 pigmented coating [23] show no degradation at 750 °C in air because of a self- terminated oxidation process, suggesting a promising method to achieve high-temperature stable solar absorbing coatings. https://doi.org/10.1016/j.solmat.2019.109946 Received 18 November 2018; Received in revised form 2 April 2019; Accepted 10 May 2019 * Corresponding author. ** Corresponding author. E-mail addresses: zhangqf@hit.edu.cn (Q. Zhang), caofeng@hit.edu.cn (F. Cao). Solar Energy Materials and Solar Cells 200 (2019) 109946 0927-0248/ © 2019 Elsevier B.V. All rights reserved. T