Ink-Free Screen Printing in Water Environment-Based Slightly Cross-Linked Polymer Phosphorescence Systems

Organic room-temperature phosphorescence (RTP) materials have garnered extensive interest in recent years. Among them, polymeric RTP systems with excellent luminescence properties and processing performances have potential applications in organic light-emitting diodes, anticounterfeiting, bioimaging, and sensing. However, simultaneously achieving prolonged phosphorescence, high quantum yield, and high brightness in polymeric systems remains a considerable challenge. Herein, a facile strategy to achieve enhanced phosphorescence properties by copolymerizing novel phosphors onto poly(methyl methacrylate) (PMMA) chains was proposed. Slight cross-linking between phosphors and PMMA chains is devised as an effective strategy to minimize the molecular motions of systems, resulting in the polymer obtaining high phosphorescence brightness (2 cd/m2), long phosphorescence lifetime (1803 ms), and maximum phosphorescence quantum yield up to 24.1% under ambient conditions. Further studies have indicated that the enhancement of the intersystem crossing, effective stabilization of the triplet excitons, as well as the oxygen consumption properties of the polymer under UV irradiation contribute significantly to efficient phosphorescence emission. In addition, the desired polymer films exhibited high transparency and good processing properties. Interestingly, as polymer films can isolate water and oxygen to a certain extent, a new ink-free green screen printing technology in the water environment was developed. Visualization of latent information on the polymer films by UV irradiation was demonstrated toward covert anticounterfeiting and display device applications in various environments.