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An efficient thermal emitter for selective radiative cooling is realized with vanadium dioxide metamaterials. The novel structure consists of patterned V O 2 metamaterials on the multilayer substrate and a composite layer on it. To obtain the enhanced emissivity, the influence of the top composite layer and external thermal stimuli are comprehensively optimized. The emissivity can reach up to 0.952 in the metallic phase of V O 2 with a composite layer in the atmospheric window, which is due to strong localization of the electric field in the cavity. The influence on the emissivity with different incident angles and geometric parameters is investigated elaborately. Finally, the cooling power is calculated and achieves a high value of 710 W / m 2 at 383 K, which is significantly higher than that of previous works. Thus, our proposed tunable emitter with high performance will be beneficial to the dynamic radiative cooling system and may open a potential application in building cooling and intelligent windows.

In this work, we have proposed a thermal emitter composing of triangular prism metamaterials deposited on a multilayer film. Ultra-high average emissivity and broadband spectra have been realized in the first and second atmospheric windows, where the patterned metamaterial is responsible for the high transmission and the multilayer serves as a reflector in the solar band. The corresponding electric field distribution at resonant positions are explored elaborately to figure out the origin of such high emissivity. Moreover, controllable emissivity is achieved with different incident angles for both the transverse electric and transverse magnetic polarization. In particular, the net cooling power approaches a high value with considering the radiative cooling performance in the daytime and night-time separately. Finally, the influence of the geometry parameters is also demonstrated to obtain optimal high emissivity. Our proposed inorganic metamaterials design paves a new avenue in the application of thermal emitter and thermal management.

A tunable selective emitter with hollow zigzag SiO2 metamaterials, which are deposited on Si3N4 and Ag film, is proposed and numerically investigated for achieving excellent radiative cooling effects. The average emissivity reaches a high value of 98.7% in the atmospheric window and possesses a high reflectivity of 92.0% in the solar spectrum. To reveal the enhanced absorptivity, the confined electric field distribution is investigated, and it can be well explained by moth eye effects. Moreover, tunable emissivity can also be initiated with different incident angles and it stays above 83% when the incident angle is less than 80°, embodying the excellent cooling performance in the atmospheric transparency window. Its net cooling power achieves 100.6 W⋅m−2, with a temperature drop of 13°, and the cooling behavior can persist in the presence of non-radiative heat exchange conditions. Therefore, high and tunable selective emitters based on our designed structure could provide a new route to realizing high-performance radiative cooling. This work is also of great significance for saving energy and environmental protection.

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