Stacked Ge₂Sb₂Te₅/Indium Tin Oxide Nanoscale-Thick Interference Units for Increased Saturation Reflective Colors and Shortwave Infrared Shielding

Fabry–Pérot structures comprising metal/interference medium/metal have attracted considerable attention as lithography-free and scalable color reflectors, as such structures can selectively absorb electromagnetic waves in the visible range to produce vivid reflected colors. However, traditional methods for producing high-saturation reflected colors generally use a narrow full width at half-maximum (fwhm) or high reflectivity. This work proposes a nanoscale multi-unit-stacking structure based on a Ge2Sb2Te5 (GST)-ITO interference unit to obtain high-saturation colors combined with fwhm and reflectivity. Finite element simulations and experimental measurements reveal that the additional absorption bands introduced by the stacking interference units reduce the fwhm of the peak and increase reflectivity, thus improving the saturation. Furthermore, adjustments in the number of stacking cells lead to changes in the saturation but have a negligible effect on the hue. The use of germanium–antimony–tellurium (also denoted as GST) as a phase-change material can facilitate further adjustments in the optical tenability of the structure upon phase transition, indicating certain potential applications. Moreover, the structure exhibits shortwave infrared shielding owing to the destructive interference of the GST layer. Additionally, the application of this structure in color printing was demonstrated. This study simplifies the design process of highly saturated colors, circumvents expensive preparation processes, and offers the possibility of shortwave infrared shielding. The nanoscale structures described herein indicate new opportunities in the field of color coatings, intelligent windows, and decorations.