Symmetric Thin Films Based on Silicon Materials for Angle‐Insensitive Full‐Color Structural Colors

Here, reflective full-color structural colors with symmetrical thin film structures made from all silicon-based materials are demonstrated. Considering practical application scenarios, the five-layer reflection enhancement unit located in the core of the device is composed of amorphous silicon (a-Si) and SiO2. Because of the large refractive index difference, the high reflection efficiency can be achieved, and the highest peak reflectivity of the sample can reach 89%. On both sides of the device, the same anti-reflection (AR) unit composed of SiOx and SiO2 is deposited, which can significantly reduce the reflection of non-target wavelength and enhance the color purity of the device. Meanwhile, the thin thickness of the absorbing materials provides the better angular insensitivity and the device shows a stable color appearance in the range of 0-60 degrees. Based on the idea of symmetrical structure, a variety of angular insensitive structural colors can be realized. The scheme is simple in structure and material, which provides the feasibility for mass production. Particularly, the symmetry of the structure makes structural colors have unique advantages and the potential to be widely applied in the color paint fields of printing, decoration, and counterfeit detection.