Thermally Responsive Radiative Cooling and Heating Enabled by Ge2Sb2Te5 Phase-Change Metamaterials

Abstract

Solar energy harvesting and radiative cooling through the atmospheric transparency window are complementary approaches for sustainable thermal management. However, their conflicting spectral requirements make it difficult for conventional static structures to simultaneously realize efficient cooling and heating. Here, we propose a thermally responsive selective emitter based on a Ge2Sb2Te5 (GST) phase-change metamaterial that enables reversible switching between radiative cooling and solar heating through GST phase modulation. In the crystalline state, the emitter achieves an average emissivity of 92.5% within the atmospheric window (8–13 μm), facilitating strong thermally activated radiative heat dissipation that significantly outweighs daytime solar heat gain. In the amorphous state, the atmospheric-window emissivity drops to 9% while solar absorptance reaches 85%, enabling effective photothermal heating. Unlike conventional passive emitters, the proposed device offers thermally reconfigurable spectral characteristics through the non-volatile GST phase transition, making it particularly attractive for elevated-temperature thermal management and thermal-protection applications. These results demonstrate the potential of GST phase-change metamaterials for dynamic spectral engineering and thermally adaptive photonic thermal management, offering a promising strategy for switchable solar heating and radiative heat dissipation in energy-efficient thermal-management systems.