Single‐Layer Cholesteric Liquid Crystal Polymer Films With Visible Broadband Reflection

Achieving visible broadband reflection in cholesteric liquid crystal (CLC) polymer films through a single‐layer architecture remains a challenge. In this study, we present the fabrication of a broadband reflective CLC polymer film that covers the entire visible spectrum (400–750 nm) with a peak reflectance of 35%. This broadband response arises from the in situ formation of a smooth pitch‐gradient helical structure, realized by combining a chiral monomer, a UV absorber, and a nonpolymerizable nematic liquid crystal (LC) into a photopolymerizable LC host. The optimized films demonstrate sharp circular polarization selectivity, mirror‐like reflection, and minimal optical scattering. Beyond broadband reflection, the films support direct photolithographic patterning, allowing the creation of periodic or customized structures for diffractive optics. Moreover, integration into polarization volume gratings demonstrates high‐efficiency broadband diffraction across the visible range. This work presents a simple yet powerful approach for producing multifunctional broadband reflective films, opening the door to advanced, cost‐effective devices.