Halogen Content Tunes the Color Temperature of White Light and Afterglow in Zero-Dimensional Hybrid Indium Halides

Zero-dimensional (0D) organic-inorganic hybrid metal halides (OIMHs) have been a category of non-negligible candidates with potential application in light-emitting diodes (LEDs), optical information storage, and anticounterfeiting. Herein, we first obtained two 0D isomorphic indium-based OIHMs, namely, IBPAInCl(6)<middle dot>H2O and IBPAInBr(6)<middle dot>H2O (IBPA(3+) = bis(3-aminopropyl)amine cation), and further prepared a family of crystal samples of mixed-halogen IBPAIn(Cl1-xBrx)(6)<middle dot>H2O (x = 0.25, 0.5, and 0.75) with the strategy of halogen substitution, which integrated the bluish-white photoluminescence (PL) emission of IBPAInCl(6)<middle dot>H2O and the orange PL emission of IBPAInBr(6)<middle dot>H2O as a perfect pair of complementary colors affording white-light emission. Interestingly, the cold-warm-tunable white-light emission in single-metal-templated In-based OIMHs was realized for the first time via continuous halogen content control. Mechanistic studies disclose that the ratios of the emission intensities at higher energies and lower energies present a gradual variation tendency, resulting in cold-warm-tunable white-light emissions. Moreover, the ultralong afterglow of IBPAInCl(6)<middle dot>H2O (1.1 s) that can be identified by the naked eyes was found to be facilely tuned by regulating the content of Br- anions. Hence, the crystal samples of halogen substitution in In-based halides were applied as anticounterfeiting/information storage materials to fabricate a time-resolved encryption system with high performance.