Scintillation based X-ray detection has received great attention for its application in a wide range of areas from security to healthcare. Here, we report highly efficient X-ray scintillators with stateof-the-art performance based on an organic metal halide, ethylenebis-triphenylphosphonium manganese (II) bromide ((C 38 H 34 P 2)MnBr 4), which can be prepared using a facile solution growth method at room temperature to form inch sized single crystals. This zero-dimensional organic metal halide hybrid exhibits green emission peaked at 517 nm with a photoluminescence quantum efficiency of~95%. Its X-ray scintillation properties are characterized with an excellent linear response to X-ray dose rate, a high light yield of~80,000 photon MeV −1 , and a low detection limit of 72.8 nGy s −1. X-ray imaging tests show that scintillators based on (C 38 H 34 P 2)MnBr 4 powders provide an excellent visualization tool for X-ray radiography, and high resolution flexible scintillators can be fabricated by blending (C 38 H 34 P 2)MnBr 4 powders with polydimethylsiloxane.

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We report the synthesis and characterization of (Ph 4 P) 2 SbCl 5 , a novel ionically bonded organic metal halide hybrid with a zero-dimensional (0D) structure at the molecular level. By cocrystallization of tetraphenylphosphonium (Ph 4 P + ) and antimony (Sb 3+ ) chloride salts, (Ph 4 P) 2 SbCl 5 bulk single crystals can be prepared in high yield, which exhibit a highly efficient broadband red emission peaked at 648 nm with a photoluminescence quantum efficiency (PLQE) of around 87%. Density functional theory (DFT) calculations reveal the origin of emission as phosphorescence from the excitons localized at SbCl 5 2− with strong excited-state structural distortion. Interestingly, (Ph 4 P) 2 SbCl 5 bulk crystals with a PLQE of around 100% can be prepared via a rapid crystal growth process within minutes, followed by a spontaneous structural transformation. It was found that the rapid growth process yielded a yellow emitting kinetically favored metastable product containing solvent molecules, which turned into the red emitting thermodynamically stable product slowly at room temperature or quickly upon thermal treatment.

Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs.

The rich chemistry of organic-inorganic metal halide hybrids has enabled the development of a variety of crystalline structures with controlled morphological and molecular dimensionalities. Here we report for the first time a single crystalline assembly of metal halide clusters, (CNH)(PbCl)PbCl, in which lead chloride tetrahedrons (PbCl) and face-sharing lead chloride trimer clusters (PbCl) cocrystallize with organic cations (CNH) to form a periodical zero-dimensional (0D) structure at the molecular level. Blue light emission peaked at 470 nm with a photoluminescence quantum efficiency (PLQE) of around 83% was realized for this single crystalline hybrid material, which is attributed to the individual lead chloride clusters. Our discovery of single crystalline assembly of metal halide clusters paves a new path to functional cluster assemblies with highly tunable structures and remarkable properties.

Scintillators are utilized for X-ray detection in many important fields ranging from homeland security to health care. Developing low-cost, high-performance scintillation materials to address the issues of existing commercially available ones is of great interest. Recently, organic metal halide hybrids have emerged as highly promising luminescent materials with excellent optical properties and low-temperature solution processability. Herein, we report a zero-dimensional organic metal halide hybrid, (PPN)2SbCl5 (PPN = bis­(triphenylphosphoranylidene)­ammonium cation), as an X-ray scintillation material with high light yield and exceptional environmental stability. Our study shows that (PPN)2SbCl5 single crystals prepared by solution growth exhibit visible photoluminescence with a quantum efficiency of 98.1%. When excited by X-rays, (PPN)2SbCl5 single crystals exhibit radioluminescence with a near-perfect linearity over a large range of X-ray dose rates and a light yield of ∼49000 ph MeV–1, which is comparable to that of a commercial CsI­(Tl) scintillator (∼54000 ph MeV–1). Moreover, the detection limit of (PPN)2SbCl5 (191.4 nGyair s–1) is much lower than the required value for regular medical diagnostics (5.5 μGyair s–1). (PPN)2SbCl5 single crystals also display remarkable stability, with little-to-no change in properties after storage under ambient conditions for 2 years.

Organic metal halide hybrids with zero-dimensional (0D) structure at the molecular level, or single-crystalline bulk assemblies of metal halides, are an emerging class of light-emitting materials with high photoluminescence quantum efficiencies (PLQEs) and color tunability. Here we report the synthesis and characterization of a new single-crystalline bulk assembly of metal halide clusters, (bmpy) 9 [ZnCl 4 ] 2 [Pb 3 Cl 11 ] (bmpy: 1-butyl-1-methylpyrrolidinium), which exhibits green emission peaked at 512 nm with a remarkable near-unity PLQE at room temperature. Detailed structural and photophysical studies suggest that there are two emitting states in [Pb 3 Cl 11 ] 5− clusters, whose populations are strongly dependent on the surrounding molecular environment that controls the excitedstate structural distortion of [Pb 3 Cl 11 ] 5− clusters. High chemical-and photostability have also been demonstrated in this new material.

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