Room-Temperature Phosphorescence of Organic Indium Halides with Applications of Information Security.

Zero-dimensional (0D) organic-inorganic metal halides (OIMHs) have recently emerged as a highly promising platform for advanced photonic applications owing to their structural tunability and exceptional luminescence properties, particularly in the field of room-temperature phosphorescence (RTP). In this study, we report successful syntheses of three new 0D indium-based OIMHs, namely, [2-AMP]2InCl6·Cl, [3-APD]3InCl6·Cl3, and [4-APD]2InCl6·Cl via a facile low-temperature solvothermal method. By rationally incorporating inorganic metal halide units into organic matrices, a moderate spin-orbit coupling (SOC) effect is achieved to evidently promote intersystem crossing and suppress nonradiative recombination. Under UV excitation, the resulting single crystals exhibit intense blue fluorescence with a maximum photoluminescence quantum yield (PLQY) of 43.6% and short nanosecond-scale lifetimes. Remarkably, these materials also display bright and durable green RTP with finely tunable lifetimes across a wide range from 80.7 to 168.66 ms and the highest phosphorescence quantum yield of 5.48%. Comprehensive photophysical investigations reveal that the introduction of inorganic skeletons promotes the generation of triplet state electrons, which is crucial for stabilizing the RTP phenomenon. Leveraging the distinct dual-emission colors and varied phosphorescence lifetimes, we designed advanced anticounterfeiting tags and multilevel information encryption technologies. This work not only establishes new efficient In-based RTP materials but also advances the RTP materials toward next-generation optical security applications.