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, IBPAInCl6·H2O and IBPAInBr6·H2O (IBPA3+ = bis(3-aminopropyl)amine cation), and further prepared a family
of crystal samples of mixed-halogen IBPAIn(Cl1–xBrx)6·H2O (x = 0.25, 0.5, and 0.75) with the strategy
of halogen substitution, which integrated the bluish-white photoluminescence
(PL) emission of IBPAInCl6·H2O and the
orange PL emission of IBPAInBr6·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 IBPAInCl6·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.