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

Abstract 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.