Tunable‐Threshold UV Dosimetry With Programmable Luminescent Tags via Oxygen‐Mediated Room‐Temperature Phosphorescence

ABSTRACT Accurate monitoring of UV radiation is critical across numerous disciplines, yet bridging the gap between complex electronic devices and ambiguous, gradual colorimetric indicators remains challenging. Addressing this challenge, a novel approach for a customizable, purely organic UV threshold dosimeter based on oxygen‐mediated room‐temperature phosphorescence (RTP) is presented. The active layer comprises a purely organic emitter (BP‐2TA) dispersed in a poly(methyl methacrylate) (PMMA) host, protected by a polyvinyl alcohol layer. Upon UV irradiation, photochemical oxygen consumption yields a high‐contrast, sharp turn‐on of the emitter's phosphorescent emission once a specific cumulative UV dose is reached. This activation depends strictly on the cumulative dose rather than irradiation intensity and is systematically tunable by adjusting the emitter concentration. A comprehensive physical model is introduced that describes the wavelength and thickness dependencies, revealing a thin‐film regime where the activation dose becomes independent of the active layer thickness. Supported by shelf‐life stability tests, these findings, alongside the proposed operational modes, establish the RTP‐based sensors as robust UV dosimeters that could be easily integrated into production processes.