Transparent Programmable\nLuminescent Tags Enabled\nby Spiro[fluorene-9,9′-xanthene]-Based Hole-Transporting Molecules

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