Immediate Organic Room‐Temperature Phosphorescence in Programmable Luminescent Tags Enabled by Oxygen‐Free Fabrication

ABSTRACT Programmable luminescent tags (PLTs) exploit the oxygen sensitivity of room‐temperature phosphorescence (RTP) from organic emitters to enable reversible information storage. In conventional PLTs, phosphorescence is initially quenched by oxygen incorporated during ambient processing. Upon UV irradiation, oxygen is photochemically consumed, activating RTP emission. While a single‐use application is already commercially exploited in UV sensors, reusability is prevented by decreasing activation dose and RTP intensity over multiple activation cycles, which had previously been attributed to oxygen trapped during the fabrication process. Here, we introduce an oxygen‐free fabrication workflow that enables direct control of the oxygen content in PLTs and thereby allows systematic investigation of its role in the activation process. It is demonstrated that oxygen can diffuse out of the active layer under oxygen‐free conditions, resulting in oxygen‐free devices with immediate RTP emission. A comparison of the reusability of oxygen‐free and conventional PLTs reveals similar behavior, indicating that photodegradation rather than trapped oxygen dominates long‐term performance. In addition, thermal preconditioning of oxygen‐free PLTs enables regulated oxygen re‐entry, allowing the activation dose to be tuned without modifying the material composition or device architecture. These findings clarify degradation processes in PLTs and establish a general framework for activation‐tuned RTP in photonic devices.