Reconfigurable, vivid reflective colors based on solution-processed Fabry–Perot absorber using thermochromic vanadium dioxide

Artificial structural color generation has attracted much attention in developing ink-free color technology for applications such as security devices, reflective displays, and functionalized color decoration. An asymmetric Fabry–Pérot (F–P) cavity-based absorber can play this role because of its advantages of an ultra-thin structure, lithographic-free manufacturing, and applicability to a large area. However, the optical response of F–P absorbers, which is determined by the structural parameters and compositions of the individual layers, is fixed at a single frequency, and only a static color can be passively implemented. In this study, we propose a new active metamaterial-based F–P absorber that exhibits dynamically tunable optical responses with temperature change. An active F–P absorber is fabricated by incorporating lossy nanoporous Ag nanoparticles (NPs) and a phase change material—vanadium dioxide (VO₂)— interlayer via a solution process. Coupled with finite-difference time-domain simulations and systematic experiments, we demonstrate that F–P absorbers generate enhanced reflective color purity due to their closely-coupled Ag NPs. The reflective colors were dynamically modulated by temperature changes owing to the variation of optical constants between the phase transition of the monoclinic VO₂. Furthermore, the demostrated tunable color image with micro-patterned absorbers opens the way for designing thermo-optical devices operating in the visible wavelength.