Decoding nanosphere-driven structural color in photonic crystals

Structural colors of photonic crystals demonstrate significant application value in optical sensing and anti-counterfeiting due to their high stability and environmental friendliness. However, current research still lacks systematic investigation into the structure-property relationship between face-centered cubic (FCC) photonic crystal nanosphere parameters (e.g., particle size, refractive index) and structural color characteristics (e.g., peak wavelength, reflectance). This unresolved scientific issue hinders the further development and applications of photonic crystal structural colors. This study establishes a three-dimensional FCC photonic crystal model using COMSOL Multiphysics simulations. Through systematic adjustment of key parameters including nanosphere radius (r = 75–150 nm), refractive index (n = 1.5–3.0), and crystal thickness, we investigate the color variation patterns. Based on the obtained reflection spectra, mathematical models are developed to describe the relationships between reflectance peak (R_M), full width at half maximum (FWHM), peak wavelength (λ_M), and nanosphere parameters. Furthermore, combining CIE 1931 xyY colorimetric analysis with HSV color space, we propose optimization criteria for achieving high-saturation structural colors. The findings provide theoretical guidance for parametric design and performance optimization of photonic crystal structural colors.