Bright Luminescence from Nontoxic CsCu₂X₃ (X = Cl, Br, I)

Inexpensive and highly efficient luminescent materials based on multinary halides have received increased attention in recent years. Among those considered most promising are the perovskites such as CsPbX3 because of their highly efficient and tunable emission through precise control of chemical composition and nanostructuring. However, the presence of the toxic heavy metal Pb and relatively poor stability are among the major challenges for the introduction of lead-halide-based materials into the marketplace. Here, we report the optical properties of nontoxic and highly emissive one-dimensional (1D) all-inorganic halides CsCu2X3 (X = Cl, Br, I) and their mixed halide derivatives, which also show improved thermal and air stability. Photoluminescence (PL) measurements show tunable bright room temperature emission from green to yellow with photoluminescence quantum yields ranging from 0.37 (CsCu2Cl1.5Br1.5) to 48.0% (CsCu2Cl3). Temperature- and power-dependent PL measurements suggest that the emission results from self-trapped excitons induced by strong charge localization and structural distortions within the lD ribbon structure

Investigation of the Solution Chemistry of Hybrid Organic–Inorganic Indium Halides for New Material Discovery

Recently, metal halide perovskites (MHPs) have emerged as a new class of materials for optical and electronic applications such as solar cells and ionizing radiation detectors. Although the solution-processability of MHPs is among their greatest advantages, the solution chemistries of most metal halide systems and their relationship with the observed structural and chemical diversity are poorly understood. In this work, we study the solution chemistry of a model indium halide system, methylammonium (MA)–In–Br, using a combination of the UV–vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS) measurements, small-angle X-ray scattering (SAXS), and density functional theory (DFT) calculations. Our results show that indium could form either octahedral [InBr63–] or tetrahedral [InBr4–] anions in solution or a combination of both, depending on the loading ratios of MABr and InBr3 reactants. Understanding the solution chemistry of this system and recognizing the optical fingerprints of these polyanions allow for targeted crystallization of two novel compounds: MAInBr4 featuring tetrahedral [InBr4–] anions and MA2InBr5 containing both octahedral [InBr63–] and tetrahedral [InBr4–] anions. Further increase of the MABr content leads to the formation of previously reported MA4InBr7, containing only octahedral [InBr63–] anions separated by Br– anions. Our results suggest that understanding the solution chemistry of multinary metal halide systems could be a valuable tool for discovering functional materials for practical applications

Zero-Dimensional Broadband Yellow Light Emitter (TMS)₃Cu₂I₅ for Latent Fingerprint Detection and Solid-State Lighting

We report a new hybrid organic-inorganic Cu(I) halide, (TMS)3Cu2I5 (TMS = trimethylsulfonium), which demonstrates high efficiency and stable yellow light emission with a photoluminescence quantum yield (PLQY) over 25%. The zero-dimensional crystal structure of the compound is comprised of isolated face-sharing photoactive [Cu2I5]3– tetrahedral dimers surrounded by TMS+ cations. This promotes strong quantum confinement and electron-phonon coupling, leading to a highly efficient emission from self-trapped excitons. The hybrid structure ensures prolonged stability and nonblue emission compared to unstable blue emission from all-inorganic copper(I) halides. Substitution of Cu with Ag leads to (TMS)AgI2, which has a one-dimensional chain structure made of edge-sharing tetrahedra, with weak light emission properties. Improved stability and highly efficient yellow emission of (TMS)3Cu2I5 make it a candidate for practical applications. This has been demonstrated through utilization of (TMS)3Cu2I5 in white light-emitting diode with a high Color Rendering Index value of 82 and its use as a new luminescent agent for visualization of in-depth latent fingerprint features. This work illuminates a new direction in designing multifunctional nontoxic hybrid metal halides