Switchable absorbers and multicolor pixels based on phase-change materials

We introduce multilayer structures with the phase-change material (PCM) germanium-antimony-tellurium (GST) for use as broadband switchable absorbers in the infrared wavelength range. We use a memetic optimization algorithm to optimize both the material composition and the layer thicknesses of the structures. We show that in the optimized structures near perfect absorption can be switched to very low absorption in a broad wavelength range by switching GST from its crystalline to its amorphous phase. In addition, we show that our design approach can be used for switchable radiative cooling based on PCMs. We also introduce multilayer structures based on PCMs for reconfigurable structural color generation. These structures generate multiple colors within a single pixel by switching between the two phases of the PCM. Our design approach leads to maximally distinct colors with large distances between them on the International Commission on Illumination (CIE) chromaticity diagram. Our optimized lithography-free structures have better performance than harder-to-fabricate three-dimensional structures. Our results could pave the way to novel switchable absorbers and multicolor pixels.