Omnidirectional Flexible Transmissive Structural Colors with High‐Color‐Purity and High‐Efficiency Exploiting Multicavity Resonances

This study demonstrates flexible structural color filters that create angle‐insensitive transmissive colors with capabilities of retaining high‐color‐purity and simultaneously high‐efficiency, based on multicavity resonances. Optimized antireflection coatings in a symmetric configuration yield greatly boosted transmission efficiency without sacrificing the color purity. Exploiting a material with a high index of refraction in the visible range allows the angle dependent property to be remarkably mitigated, thus presenting wide acceptance angles over 70°. A simple fabrication process that only involves a thin‐film deposition method shows a great potential for large scale applications. Furthermore, optical properties of the structural colors, fabricated on a flexible substrate, remain almost unchanged to the 5 mm bending radius condition and after over 3000 times bending tests. The strategy presented in this work could be adopted for diverse research fields such as displays, anticounterfeiting tags, light modulators, colored solar cells, and chemical sensors.