Recent Advances in All-Inorganic Zero-Dimensional Metal Halides

Emerging Hybrid Metal Halide Glasses for Sensing and Displays

Glassy hybrid metal halides have emerged as promising materials in recent years due to their high structural adjustability and low melting points, offering unique merits that overcome the limitations of their crystalline and polycrystalline counterparts as well as other conventional amorphous semiconductors. This review article comprehensively explores the structural characteristics, electronic properties, and chemical coordination of hybrid metal halides, emphasizing their role in the glass transition from the crystalline phase to the amorphous phase. We examine the intrinsic disorder within the amorphous phase that facilitates light transmission and discuss recent advances in device architecture and interface engineering by optimizing the charge transport of glassy hybrid metal halides for high-quality applications. With full theoretical understanding and rational structural design, potential applications in displays, information storage, X-ray imaging, and sensing are highlighted, underscoring the transformative impact of glassy hybrid metal halides in the fields of materials science and information science.

Tuneable Efficient White Emission of Sb3+/Mn2+ Co-Doped Lead-Free Perovskites for Single-Component White Light-Emitting Diodes

Inorganic lead-free perovskite nanocrystals (NCs) with broadband self-trapped exciton (STEs) emission and low toxicity have shown enormous application prospects in the field of display and lighting. However, white light-emitting diodes (WLEDs) based on a single-component material with high photoluminescence quantum yield (PLQY) remain challenging. Here, we demonstrate a novel codoping strategy by introducing Sb3+/Mn2+ ions to achieve the tuneable dual emission in lead-free perovskite Cs3InCl6 NCs. The PLQY increases to 59.64% after doping with Sb3+. The codoped Cs3InCl6 NCs exhibit efficient white light emission due to the energy transfer channel from STEs to Mn2+ ions with PLQY of 51.38%. Density functional theory (DFT) calculations have been used to verify deeply the effects of Sb3+/Mn2+ doping. WLEDs based on Sb3+/Mn2+-codoped Cs3InCl6 NCs are explored with color rendering index of 85.5 and color coordinate of (0.398, 0.445), which have been successfully applied as photodetector lighting sources. This work provides a new perspective for designing novel lead-free perovskites to achieve single-component WLEDs.

Polymeric Metal Halides with Bright Luminescence and Versatile Processability

Most of current metal halide materials, including all inorganic and organic-inorganic hybrids, are crystalline materials with poor workability and plasticity that limit their application scope. Here, we develop a novel class of materials termed polymeric metal halides (PMHs) through introducing polycations into antimony-based metal halide materials as A-site cations. A series of PMHs with orange-yellow broadband emission and large Stokes shift originating from inorganic self-trapped excitons are successfully prepared, which meanwhile exhibit the excellent processability and formability of polymers. The versatility of these PMHs is manifested as the broad choices of polycations, the ready extension to manganese- and copper-based halides, and the tolerance to molar ratios between polycations and metal halides in the formation of PMHs. The merger of polymer chemistry and inorganic chemistry thus provides a novel generic platform for the development of metal halide functional materials.

Synthesis and hybridization of CuInS2 nanocrystals for emerging applications

Copper indium sulfide (CuInS2) is a ternary A(I)B(III)X(VI)2-type semiconductor featuring a direct bandgap with a high absorption coefficient. In attempts to explore their practical applications, nanoscale CuInS2 has been synthesized with crystal sizes down to the quantum confinement regime. The merits of CuInS2 nanocrystals (NCs) include wide emission tunability, a large Stokes shift, long decay time, and eco-friendliness, making them promising candidates in photoelectronics and photovoltaics. Over the past two decades, advances in wet-chemistry synthesis have achieved rational control over cation-anion reactivity during the preparation of colloidal CuInS2 NCs and post-synthesis cation exchange. The precise nano-synthesis coupled with a series of hybridization strategies has given birth to a library of CuInS2 NCs with highly customizable photophysical properties. This review article focuses on the recent development of CuInS2 NCs enabled by advanced synthetic and hybridization techniques. We show that the state-of-the-art CuInS2 NCs play significant roles in optoelectronic and biomedical applications.

Tellurium-Doped 0D Organic-Inorganic Hybrid Lead-Free Perovskite for X-ray Imaging

The application of X-ray imaging in military, industrial flaw detection, and medical examination is inseparable from the wide application of scintillator materials. In order to substitute for lead, lower costs, and reduce self-absorption, organic-inorganic hybrid lead-free perovskite scintillators are emerging as a new option. In this work, novel (TEA)2Zr1-xTexCl6 perovskite microcrystals (MCs) were successfully synthesized by a hydrothermal method, with Te4+ doping, which leads to yellow triplet-state self-trapped excitons emission. The emission peak of (TEA)2Zr1-xTexCl6 located at 605 nm under X-ray excitation, which was applied to X-ray imaging, shows a clear wiring structure inside the USB connector. The detection limit (DL) of 820 nGyair/s for (TEA)2Zr0.9Te0.1Cl6 is well below the dose rate corresponding to a standard medical X-ray diagnosis is 5.5 μGyair/s. This work opens up a new path for organic-inorganic hybrid lead-free scintillators.

Emerging Halide Perovskite Ferroelectrics

Halide perovskites have gained tremendous attention in the past decade owing to their excellent properties in optoelectronics. Recently, a fascinating property, ferroelectricity, has been discovered in halide perovskites and quickly attracted widespread interest. Compared with traditional perovskite oxide ferroelectrics, halide perovskites display natural advantages such as structural softness, low weight, and easy processing, which are highly desirable in applications pursuing miniaturization and flexibility. This review focuses on the current research progress in halide perovskite ferroelectrics, encompassing the emerging materials systems and their potential applications in ferroelectric photovoltaics, self-powered photodetection, and X-ray detection. The main challenges and possible solutions in the future development of halide perovskite ferroelectric materials are also attempted to be pointed out.

Regulating the coordination geometry of polyhedra in zero-dimensional metal halides for tunable emission

Although self-trapped exciton (STE) emissions in zero-dimensional metal halides have been intensively investigated, the understanding of the relationship between the coordination geometries of the metal halides and their photophysical properties is still lacking. In this work, we successfully synthesized single crystals, with strong STE emissions, of the bimetallic materials (Bmpip)₉[Pb₃Br₁₁](ZnBr₄)₂ (PbZn-Br) and (Bmpip)₉[Pb₃Br₁₁](MnBr₄)₂ (PbMn-Br), where Bmpip⁺ is 1-butyl-1-methyl-piperidinium (C₁₀H₂₂N⁺), via a facile anti-solvent crystallization strategy. With respect to the monometallic material, (Bmpip)₂[PbBr₄] (Pb-Br), the introduction of Zn²⁺ and Mn²⁺ effectively alters the coordination geometry of the lead bromide polyhedral configuration from a PbBr₄^2- tetrahedron to a Pb₃Br₁₁^5- trimer. As a result, the maximum emission peak of PbZn-Br exhibits an obvious red shift and the full width at half maximum is almost two-fold wider than that of Pb-Br due to stronger electron-phonon coupling. Moreover, due to the intrinsic emission of the Mn²⁺ ions, an intriguing tunable emission was achieved in PbMn-Br with an impressively high photoluminescence quantum yield of up to 67%. The ultra-stable PbMn-Br single crystals show potential as an ideal down-conversion phosphor for use in UV-pumped white light-emitting diode devices.

Visualization of X-rays with an Ultralow Detection Limit via Zero-Dimensional Perovskite Scintillators

X-rays play an extremely significant role in medical diagnosis, safety testing, scientific research, and other practical applications. However, as the main sources of radioactive pollution, the hazard of X-rays to human health and the environment has been a major concern. Herein, the explored perovskite scintillator of Cs₂Zr_1-xPb_xCl₆ in this work exhibits an ultrahigh radioluminescence intensity owing to the enhanced X-ray absorption for the introduction of Pb²⁺ ions. The Cs₂Zr_1-xPb_xCl₆ crystals are demonstrated as efficient scintillators with a self-trapped exciton emission and extremely high steady-state light yield (∼101,944 photons meV^-1). This fascinating scintillator provides a convenient visual tool for X-ray detection even for an indoor lighting environment, reaching a low detection limit of ∼14.2 nGy·s^-1, which is about 1/387 of the typical medical imaging dose (5.5 μGy·s^-1). Moreover, X-ray imaging with a high resolution of 16.6 lp·mm^-1 is achieved with the as-explored Cs₂Zr_1-xPb_xCl₆ scintillator film. Herein, the Cs₂Zr_1-xPb_xCl₆ scintillator provides a feasible strategy for X-ray monitoring in the field of biomedicine, high-energy physics, national security, and other applications.