Visible Light‐Activated Ultralong‐Lived Triplet Excitons of Carbon Dots for White‐Light Manipulated Anti‐Counterfeiting

Room temperature phosphorescence (RTP) has emerged as an interesting but rare phenomenon with multiple potential applications in anti-counterfeiting, optoelectronic devices, and biosensing. Nevertheless, the pursuit of ultralong lifetimes of RTP under visible light excitation presents a significant challenge. Here, new phosphorescent materials that can be excited by visible light with record-long lifetimes are demonstrated, realized through embedding nitrogen doped carbon dots (N-CDs) into a poly(vinyl alcohol) (PVA) film. The RTP lifetime of the N-CDs@PVA film is remarkably extended to 2.1 s excited by 420 nm, representing the highest recorded value for visible light-excited phosphorescent materials. Theoretical and experimental studies reveal that the robust hydrogen bonding interactions can effectively reduce the non-radiative decay rate and radiative transition rate of triplet excitons, thus dramatically prolong the phosphorescence lifetime. Notably, the RTP emission of N-CDs@PVA film can also be activated by easily accessible low-power white-light-emitting diode. More significantly, the practical applications of the N-CDs@PVA film in state-of-the-art anti-counterfeiting security and optical information storage domains are further demonstrated. This research offers exciting opportunities for utilizing visible light-activated ultralong-lived RTP systems in a wide range of promising applications.