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

Abstract 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.