Dynamic Multicolor Room‐Temperature Phosphorescence of Carbon Dots via Exciton Delocalization Engineering for Programmable Photonic Encryption

Dynamic multicolor room‐temperature phosphorescent carbon dots (RTP CDs) hold great promise for applications in programmable photonic encryption. However, their intrinsic confinement effects inevitably lead to exciton localization, making it difficult to regulate emissive behavior within extended conjugated systems. Herein, an exciton delocalization‐mediated strategy was employed to realize tunable RTP emission ranging from blue to red in CDs@boron oxide (PACDs@B 2 O 3 , 23NA‐CDs@B 2 O 3 , 18NA‐CDs@B 2 O 3 , and ND‐CDs@B 2 O 3 ), and time‐dependent dynamic RTP emission was further demonstrated in both 18NA‐CDs@B 2 O 3 and ND‐CDs@B 2 O 3 . Combined characterizations show that regulating the benzene‐ring structures of the precursors effectively extends the π‐conjugated system of the carbon core in the CDs, thereby markedly promoting exciton delocalization and reducing the energy gap between singlet and triplet states, leading to a redshifted RTP emission. Furthermore, exciton delocalization between graphitic domains with different conjugation sizes enables cascade energy transfer from larger domains to smaller ones, resulting in dynamic RTP emission. The successful application of dynamic multicolor RTP CDs@B 2 O 3 in programmable photonic encryption clearly demonstrates their broad application potential. This work opens up a new avenue for the on‐demand design of dynamic multicolor RTP materials.