Transparent Programmable Luminescent Tags Enabled by Spiro[fluorene-9,9′-xanthene]-Based Hole-Transporting Molecules

Pure organic ultralong room temperature phosphorescent (URTP) materials have garnered significant attention for applications in luminescent materials, biosensing, and information encryption. These materials offer advantages over heavy metal phosphorescent materials, such as lower cost, reduced biological toxicity, and minimal environmental impact. Herein, for the first time, we demonstrate a series of organic RTP materials based on spiro[fluorene-9,9′-xanthene] (SFX) hole-transporting molecules, specifically X59 and X55. Our research presents that incorporating more rigid SFX units significantly extends RTP lifetime and enhances photoluminescence quantum yield (PLQY). The large steric hindrance of the rigid SFX structures suppresses nonradiative molecular motions, thereby prolonging phosphorescence emission. Compared to the baseline molecule X1, experimental results show that molecule X59 extends the phosphorescence lifetime by 230 ms, while X55 achieves an extension of 260 ms. Furthermore, we highlight the potential of this series of RTP molecules for use in transparent, programmable luminescent tags. Our work not only expands the molecular types of organic RTP materials but also provides innovative strategies for designing long-lived, high-quantum-yield RTP molecules. We envision that this will advance the smart device field of organic phosphorescent materials and their practical applications, such as intelligent labels, tags, and optical sensors.