Trans‐reflective color filters with brilliant colors by integrating organic dyes with photonic crystals

Abstract Color filters are essential components for optical modulation. However, conventional filters are restricted to operating exclusively in either reflective or transmissive mode. Furthermore, they suffer from limited UV and thermal stability, low color purity, and exhibit identical coloration on both surfaces. Herein, we propose a novel design strategy for trans‐reflective color filters by integrating the absorptive properties of dye‐doped polysulfone (PSU) with the diffractive capabilities of photonic crystals. This composite filter achieved broad‐spectrum transmission with deep color outputs—yellow (0.410, 0.510), magenta (0.446, 0.231), and cyan (0.201, 0.425)—closely aligned with standard color space coordinates. By tuning the refractive index of CeO 2 @SiO 2 nanoparticles to match dye‐based PSU matrix, the transmittance of filters exceeded 70%. Moreover, dye‐mediated absorption reduces the scattering light, thereby enhancing reflection color purity (full width at half maxima (FWHM) = 25 nm) and producing vibrant blue, green, and red hues. The incorporation of UV‐absorbing CeO 2 @SiO 2 nanoparticles effectively mitigated dye photodegradation, yielding exceptional UV stability (Δ T < 2% under prolonged UV exposure). The filters also exhibited outstanding thermal stability (Δ T < 1% after 30 min heat treatment at 230°C). This work establishes a robust materials design framework for multifunctional optical filters, advancing the development of high‐fidelity dual‐mode color systems for next‐generation display technologies.