All-Inorganic Luminescent Ternary Cadmium Halide Cs7Cd3Br13 with Two Types of Cd-Centered Polyhedrons

Enhanced Photoluminescence Quantum Yield of Metal Halide Perovskite Microcrystals for Multiple Optoelectronic Applications

Recently, metal 1halide perovskites have shown compelling optoelectronic properties for both light-emitting devices and scintillation of ionizing radiation. However, conventional lead-based metal halide perovskites are still suffering from poor material stability and relatively low X-ray light yield. This work reports cadmium-based all-inorganic metal halides and systematically investigates the influence of the metal ion incorporation on the optoelectronic properties. This work introduces the bi-metal ion incorporation strategy and successfully enhances the photoluminescence quantum yield (98.9%), improves thermal stability, and extends the photoluminescence spectra, which show great potential for white light emission. In addition, the photoluminescent decay is also modulated with single metal ion incorporation, the charge carrier lifetime is successfully reduced to less than 1 µs, and the high luminescent efficiency and X-ray light yield (41 000 photons MeV-1 ) are maintained. Then, these fast scintillators are demonstrated for high-speed light communication and sensitive X-ray detection and imaging.

Excitation-Dependent Luminescence of 0D ((CH3)4N)2ZrCl6 across the Full Visible Region

Herein, we report a novel hybrid organic-inorganic Zr(IV) metal halide ((CH₃)₄N)₂ZrCl₆, which demonstrates fascinating excitation-dependent luminescence across the full visible region. The single crystal of ((CH₃)₄N)₂ZrCl₆ showed an unexpected high degree of symmetry and formed a unique 0D structure with isolated [ZrCl₆]^2- octahedrons. Amazingly, three different emission groups emerged under changeable excitation light. The first emission group peaked at 462 nm with a ns lifetime and a μs lifetime, which is assigned to free-exciton fluorescence and thermally activated delayed fluorescence (TADF). The second group of emissions featured elaborate multipeak light-emitting components, which is ascribed to the d-d transitions of Zr(IV). The third emission group centered at 660 nm was attributed to the typical self-trapped exciton (STE) emission. To our best knowledge, this work for the first time reports a 0D organic-inorganic metal halide with distinctive excitation-dependent full-visible-spectrum luminescence via four different emission mechanisms.

A Red-Emitting Hybrid Manganese Halide Perovskite C5H5NOMnCl2·H2O Featuring One-Dimensional Octahedron Chains

Herein, we successfully synthesized a new organic-inorganic hybrid manganese halide perovskite C₅H₅NOMnCl₂·H₂O, in which organic molecules, water molecules (through O atoms), and Cl atoms coordinate with Mn atoms to form deformed [MnO₃Cl₃] octahedrons. Then, octahedrons form a chain through edge sharing, resulting in a 1D-chain single crystal structure. The high-quality C₅H₅NOMnCl₂·H₂O single crystal prepared by a simple solvent evaporation method produced bright red emission at 656 nm attributed to the d-d transition of Mn²⁺. Also, it has a photoluminescence quantum yield (PLQY) of 24.2%. Photoluminescence excitation and absorption spectra were both featured with multiple bands and were in good agreement with the Mn²⁺ 3d energy levels. The photoluminescence decay spectrum showed an average lifetime of 0.466 ms, which further proves the d-d transition mechanism. The C₅H₅NOMnCl₂·H₂O single crystal had a direct band gap of 1.43 eV. Moreover, a red light LED with a CCT of 1857 K was obtained based on the C₅H₅NOMnCl₂·H₂O powder, indicating its promising application in red-emitting LED.

Cs4CuSb2Cl12-xIx(x = 0-10) nanocrystals for visible light photodetection

Lead-free layered double perovskite nanocrystals (NCs) with tunable visible range emission, high carrier mobility and low trap density are the need of the hour to make them applicable for optoelectronic and photovoltaic devices. Introduction of Cu²⁺in the high band gap Cs₃Sb₂Cl₉lattice transforms it to the monoclinic Cs₄CuSb₂Cl₁₂(CCSC) NCs having a direct band gap of 1.96 eV. The replacement of 50% Cl^-by I^-ions generates <5 nm Cs₄CuSb₂Cl₆I₆(C6I6) monodispersed NCs with an unchanged crystal system but with further lowering of the band gap to 1.92 eV. Thep-type C6I6 NCs exhibit emission spectra, lower trap density, appreciable hole mobility and most importantly a lower exciton binding energy of only 50.8 ± 1.3 meV. The temperature dependent photoluminescence (PL) spectra of the C6I6 NCs show a decrease in non-radiative recombination from 300 K down to 78 K. When applied as the photoactive layer in out-of-plane photodetector devices, C6I6 NC devices exhibit an appreciable responsivity of 0.67 A W^-1at 5 V, detectivity of 4.55 × 10⁸Jones (2.5 V), and fast photoresponse with rise and fall time of 126 and 94 ms, respectively. On the other hand, higher I^-substitution in Cs₄CuSb₂Cl₂I₁₀NCs (C2I10) degrades the lattice into a mixture of monoclinic and trigonal crystal phases, which also lowers the device performance.

Phase-Selective Solution Synthesis of Cd-Based Perovskite Derivatives and Their Structure/Emission Modulation

The rich phase structures of perovskite derivatives have attracted extensive attention and can be applied in the fields of optoelectronics due to their high emission efficiency and tunable emission. Herein, we explored a phase-selective solution synthetic route to obtain different Cd-based perovskite derivatives. First, the pristine tetragonal Cs₇Cd₃Br₁₃ was obtained by a solvothermal method, and its photoluminescence quantum yield (PLQY) was boosted from 8.28% to 57.62% after appropriate Sb³⁺ doping. Furthermore, halogen substitution was adopted to modify Sb:Cs₇Cd₃Br₁₃ and produced a series of Cd-based perovskite derivatives with different crystal structures and tunable emission from cyan to orange (517-625 nm). The mechanisms behind such experimental phenomena were further investigated and discussed on the basis of material characterization and theoretical computation. This study presented an effective strategy to synthesize bright Cd-based perovskite derivatives with different structures and modulated emission, and it also provided insights to understand the structure/emission modulation via halogen substitution.