Organic, Transparent, and Flexible Films Exhibiting White-Light Emission via Polymer-Network Engineering: A Non-Dye-Centric Strategy

White light-emitting (WLE) materials are often engineered by tailoring fluorescent dyes to generate balanced emission spectra. In such dye-focused methodologies, the matrix plays a minimal role beyond hosting the emitters. However, this strategy can be unpredictable due to the complexity of modifying dye photophysics with precision. In the work here presented, a matrix-driven approach to WLE is introduced, where the properties of the polymeric host are leveraged to regulate light emission. By adjusting the composition of the polymer network with variation in monomers and cross-linkers, it is possible to control the spatial arrangement and interaction of two dyes, enabling effective color mixing. The system employs readily available monomers, 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) dimethacrylate (PEGDMA), along with two simple, synthetically accessible dyes: a pyridinium salt and a pyrylium derivative. The resulting hydrogel-based films emit white light with Commission Internationale de l'Éclairage (CIE) chromaticity coordinates at (0.30, 0.33) and a high photoluminescence quantum yield of 0.51. The films are highly transparent, flexible, and suitable for back-illumination, making them excellent candidates for integration into next-generation optoelectronic platforms, such as bendable lighting elements, transparent displays, and wearable light sources. This strategy highlights the untapped potential of polymer matrices in fine-tuning emissive behavior.