Clusteroluminescence-enabled active optical waveguiding in polyesters

Organic active waveguides are emerging as multifunctional photonic materials capable of simultaneously transmitting light and regulating optical signals through wavelength conversion and emission modulation. However, most reported systems rely on high-quality single crystals, doped matrices, or complex fabrication procedures, limiting their scalability and practical implementation. Here, we report a simple copolymerization strategy that introduces efficient clusteroluminescence into poly(ethylene terephthalate) (PET)-derived copolyesters, thereby enabling active optical waveguiding in an intrinsically emissive, single-component polymer system. The excitation-dependent emission of the resulting copolyester gives rise to pronounced propagation-distance-dependent spectral evolution. During propagation, wavelength-selective attenuation and reabsorption progressively enrich the long-wavelength fluorescence component, producing emission-peak shift of up to 125 nm over 65 mm. The copolyesters are amenable to scalable synthesis and melt processing, which retain active optical waveguiding in flexible, thick, and geometrically irregular filaments. This work establishes clusteroluminescent PET-derived copolyesters as a scalable platform for active polymer photonics, with potential applications in optical encoding, visual information transmission, and flexible photonic devices.