Photoactivatable Time‐Evolving Afterglow of Carbon Dots via Coupled Triplet and Exciplex Persistent Emission for Programmable Photonic Encoding

Photoactivatable time-evolving afterglow color (TEAC) materials offer programmable delayed emission for dynamic photonic applications. However, achieving light-triggered and multistate afterglow control in metal-free systems remains a formidable challenge. Here we report a carbon dot-polymer composite (CDs@ABS) that exhibits dual photoactivatable delayed emissions with distinct lifetimes, generating reversible TEAC with optical memory. Upon brief UV exposure, the film shows no visible afterglow; prolonged irradiation activates a dynamic emission that evolves from red to orange, yellow, and finally green, with a memory duration of up to 40 min and excellent long-term stability. In this architecture, electron-rich CDs act as triplet emitters and donors, while the electron-deficient, oxygen-permeable ABS matrix serves as both acceptor and regulator of exciton dynamics. The coupled emissive channels originate from oxygen-regulated red phosphorescence of CDs triplet excitons and green long-persistent luminescence from donor-acceptor exciplexes, which is progressively enhanced by photoinduced charge accumulation and strengthened hydrogen bonding. Their cooperative interplay produces light-triggered, reversible TEAC behavior. Leveraging this functionality, the CDs@ABS film enables programmable and multilevel photonic encryption and dynamic anti-counterfeiting. This work presents a generalizable strategy for cost-effective, metal-free, photoactivatable afterglow systems, opening avenues toward next-generation dynamic information security and spatiotemporal photonics.