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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. [ABSTRACT FROM AUTHOR]

Single‐component metal halides with white light emission are highly attractive for solid‐state lighting applications, but it is still challenging to develop all‐inorganic lead‐free metal halides with high white‐light emission efficiency. Herein, by rationally introducing silver (Ag) into zero‐dimensional (0D) Cs3Cu2Br5 as new structural building unit, a one‐dimensional (1D) bimetallic halide Cs6Cu3AgBr10 is designed that emits strong warm‐white light with an impressive photoluminescence quantum yield (PLQY) of 94.5% and excellent stability. This structural transformation lowers the conduction band minimum while maintaining the localized nature of the valence band maximum, which is crucial in expanding the excitation spectrum and obtaining efficient self‐trapped excitons (STEs) emission simultaneously. Detailed spectroscopy studies reveal that the white‐light originates from triplet STEs emission, which can be remarkably improved by weakening the strong electron‐phonon coupling and thus suppressing phonon‐induced non‐radiative processes. Moreover, the interesting temperature‐dependent emission behavior, together with self‐absorption‐free property, make Cs6Cu3AgBr10 as sensitive luminescent thermometer and high‐performance X‐ray scintillator, respectively. These findings demonstrate a general approach to achieving effective single‐component white‐light emitters based on lead‐free, all‐inorganic metal halides, thereby opening up a new avenue to explore their versatile applications such as lighting, temperature detection and X‐ray imaging. [ABSTRACT FROM AUTHOR]

Strong carrier‐phonon coupling‐induced self‐trapped excitons (STEs) limit the application of 2D double‐perovskites in optoelectronic devices because the separation and collection of the highly localized STEs are challenging. In this study, antimony (Sb) is incorporated into (BA)4AgBiBr8 (BA = CH3(CH2)3NH3+) to form (BA)4AgSbxBi1‐xBr8 (0 ≤ x ≤ 1) trivalent‐metal alloyed 2D double‐perovskites. It is found that introducing Sb into the (BA)4AgBiBr8 2D double‐perovskite will decrease the carrier‐phonon coupling strength and change STEs from "dark" states to "bright" states at room temperature. Combining detailed spectroscopic analysis with density functional theory calculation, it is concluded that STEs localized at [SbBr6] octahedron in (BA)4AgSbxBi1‐xBr8 give the broadband bright emission. The "bright" STEs with moderate carrier‐phonon coupling opens the possibility to efficiently separate and collect charge‐carriers in (BA)4AgSbBr8 2D double‐perovskites. Photodetectors based on (BA)4AgSbBr8 crystals are further fabricated. The photodetectors exhibit high responsivity up to 1368 A W−1 and an external quantum efficiency of 4.7 × 105. These figures are over three times higher than that in (BA)4AgBiBr8‐based photodetectors. This study provides a unique strategy for developing high‐performance optoelectronic devices based on STEs. [ABSTRACT FROM AUTHOR]

Low‐dimensional lead‐free metal halides have recently attracted a great deal of attention for their unique photoluminescence properties. In this work, a new all‐inorganic zero‐dimensional (0D) rare‐earth perovskite, namely Cs2ScCl5·H2O is reported. The 0D crystal exhibits a rare phenomenon of excitation‐wavelength dependent emission from blue‐green to white to yellow at room temperature. Spectroscopic characterizations indicate the tunable emission is originated from two distinct self‐trapped exciton states. In addition, the yellow emission quantum yield can be enhanced from 1.2% to ≈100% by doping Sb3+ ions into the crystal. The work not only presents a new all‐inorganic semiconductor with tunable emission colors, but also provides a design strategy for developing nontoxic and high‐performance light‐emitting materials. [ABSTRACT FROM AUTHOR]

Scintillators have been widely used for high‐energy radiation imaging. It is in great demand and challenge to develop scintillator materials with fast decay time, high scintillation light yield, and low detection limit for high‐resolution imaging applications such as time‐of‐flight positron emission tomography. However, it is still a challenge to develop the ultrafast carrier dynamics to achieve 100% ultrafast decay time with high scintillation light yield. To meet the demand, a series of component‐tunable Cs2ZnCl4: x%Zr single crystals as promising ultrafast scintillators is successfully developed. With 8% of Zr‐dopant (Cs2ZnCl4: 8%Zr), the single crystal exhibits high light yield (28000 photons MeV−1) and low detection limit (51 nGy s−1) under X‐ray excitation. Photo‐induced transient absorption signals on sub‐nanosecond and nanosecond scales ensure almost 100% fast decay time (≈3 ns) in nanoseconds under γ‐ray excitation. In particular, the different radiative transition processes are achieved under ultraviolet and high‐energy radiation due to the tunable carrier dynamics from the shallow trapped state to the self‐trapped exciton (STE) state. [ABSTRACT FROM AUTHOR]

We have reported the synthesis of antimony-based metal-halide crystals in five different solvents. They show different self-trapped exciton photoluminescence, especially their photoluminescence quantum yield (PLQY) ranges from below 1% to 90%. Their different luminescent properties are caused by their crystal structure formed in different solvents. The effect of solvent on self-trapped exciton emission has been thoroughly investigated. Furthermore, one of the developed materials, with 90% photoluminescence quantum yield, has been used for efficient LEDs, sensitive solvent detection, and optical anti-counterfeiting. [Display omitted] • Synthesis of Sb-based halide crystals in five different solvents. • In-depth study of solvent effects on crystal structure and luminescent properties. • Achieved single crystals with efficient STE emission with PLQY of 90% • STE dynamics probed by time-resolved optical spectroscopies. • Applications for LEDs, rapid solvent detection, and optical anti-counterfeiting. Low-dimensional organic–inorganic hybrid metal halides, with broadband luminescence, have attracted much attention for optoelectronic applications due to their rich in structural diversity and solution processibility. However, it is still unclear about how the solvent molecules influence the optoelectronic properties of the solution processed low-dimensional metal halides. Here, we prepared five different antimony-based crystal structures, [SbCl 6 ]3- as the metal halide octahedron and 4, 4-difluoropiperidine (DFPD+) as organic cation, by using different solvents: hydrochloric acid (HCl) aqueous solution and four organic solvents (dimethylformamide (DMF), methanol (MeOH), acetonitrile (ACN) and dimethylacetamide (DMAC)). We revealed the relation between their crystal structures and optical properties, and we found the participation of organic molecules in the crystal structure causes significant lattice distortions, which is beneficial for achieving self-trapped exciton (STE) emission. Among them, (DFPD) 6 SbCl 9 ·2DMAC exhibits a remarkable photoluminescence (PL) quantum yield of approximately 90 %. The STE dynamics in (DFPD) 6 SbCl 9 ·2DMAC were characterized by femtosecond transient absorption and time-resolved PL spectroscopies. Simultaneously, this study also provides new directions for expanding the application of low-dimensional luminescent metal halides: in addition to UV-LEDs, efficient and rapid detection of methanol or acetonitrile can be achieved using the raw materials, while also realizing the potential application of multi-level optical anti-counterfeiting. [ABSTRACT FROM AUTHOR]

• The influence of steric hindrance of organic cations in copper halides is studied. • TBMACuI 2 exhibits bright white-light dual emission with a quantum yield of 93%. • The white light emitting diodes based on TBMACuI 2 show an ultrahigh CRI of 95.7. • TBMACuI 2 exhibits interesting an-thermal quenching behaviors. Searching for single-component white-light emitting materials with excellent color rendering index (CRI) is significant to the development of white-light emitting diodes (WLEDs). Herein, we introduce three different cations with increasing steric hindrance to develop novel luminescent low-dimensional organic copper halides: one-dimensional (1D) ETMACu 2 I 3 (ETMA: ethyltrimethylammonium), 1D TEACu 2 I 3 (TEA: tetraethylammonium), and zero-dimensional (0D) TBMACuI 2 (TBMA: tributylmethylammonium). The dimensionality of the prepared copper halides decreases with the increase of the steric hindrance of the organic cations. Meanwhile, the photoluminescence spectra become broader. The two 1D compounds exhibit weak single broad emission originating from self-trapped excitons (STEs) and defects. Interestingly, 0D TBMACuI 2 emits bright warm white light with dual emission bands. The mechanism of the unique dual emission is unveiled by systematic spectroscopic study including temperature-dependent and femtosecond transient absorption spectroscopies. Two spin-triplet STE states contribute to the intriguing dual emission. A WLED based on TBMACuI 2 can exhibit an ultra-high CRI of 95.7, which is promising for single-component white-light emitting applications. [ABSTRACT FROM AUTHOR]