Ultralong and High‐Efficiency Room Temperature Phosphorescence of Organic‐Phosphors‐Doped Polymer Films Enhanced by 3D Network

Abstract Ultralong room temperature phosphorescence (URTP) is an attractive phenomenon in organic photonics. Polymer‐based URTP materials are superior alternatives to traditional inorganic or organometallic phosphors because of their unique transparency and flexibility. However, few URTP polymer films achieve room temperature phosphorescence lifetimes longer than 2 s and the polymer films with longer lifetimes show extremely low phosphorescence quantum yields (<2%). Herein, a reasonable strategy is proposed to simultaneously achieve ultralong room temperature phosphorescence lifetimes and high phosphorescence quantum yields in polymer films, based on the effective suppression of nonradiative decay of organic phosphors by dense 3D network. A record‐breaking 2.28 s ultralong phosphorescence lifetime and up to 8.35% phosphorescence quantum yield are realized simultaneously in the tetramethylbenzidine (TMB)‐doped URTP polymer film fabricated by a simple doping method. The URTP can be excited by ultralow power UV light (5 µW cm −2 ) or only sunlight, which demonstrates the superb practicality of the polymer network films. In addition, it is noted that the film can still emit phosphorescence lasting 3 s at a temperature as high as 60 °C. A double encryption system is successfully developed based on the unique features of the URTP films.