Control over emissivity of zero-static-power thermal emitters based on phase-changing material GST

Controlling the emissivity of a thermal emitter has attracted growing interest, with a view toward a new generation of thermal emission devices. To date, all demonstrations have involved using sustained external electric or thermal consumption to maintain a desired emissivity. In the present study, we demonstrated control over the emissivity of a thermal emitter consisting of a film of phase-changing material Ge₂Sb₂Te₅ (GST) on top of a metal film. This thermal emitter achieves broad wavelength-selective spectral emissivity in the mid-infrared. The peak emissivity approaches the ideal blackbody maximum, and a maximum extinction ratio of >10 dB is attainable by switching the GST between the crystalline and amorphous phases. By controlling the intermediate phases, the emissivity can be continuously tuned. This switchable, tunable, wavelength-selective and thermally stable thermal emitter will pave the way toward the ultimate control of thermal emissivity in the field of fundamental science as well as for energy harvesting and thermal control applications, including thermophotovoltaics, light sources, infrared imaging and radiative coolers.