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A computational investigation is presented, in conjunction with synthesis and experimental characterization, into the structural, electronic, and optical properties of layered two‐dimensional organic lead bromide perovskites. Materials based on the chiral (R/S)‐4‐fluoro‐α‐methylbenzylammonium (R/S‐FMBA), which have been shown to lead to bright room‐temperature circularly polarized luminescence, are contrasted with the similar achiral 4‐fluorobenzylammonium (FBA). Using density functional theory (DFT) with van der Waals (vdW) corrections, relaxed structures (compared with X‐ray diffraction, XRD) and optical absorption spectra (compared with experiments) are studied, as well as band structure and orbital character of transitions. A Python code is developed and provided to calculate octahedral distortions and compare DFT and XRD results, finding that vdW corrections are important for accuracy and that DFT overestimates octahedral tilt angles. (FMBA)₂PbBr₄shows among the largest tilt angle differences (often termed ) reported, 14°–15°, indicating strong inversion symmetry‐breaking, which enables its chiral emission. A large resulting Dresselhaus spin‐splitting effect is found. The lowest‐energy optical transitions involve the perovskite only and are polarized within the layer. This work furthers understanding of structure‐property relations with applications to optoelectronics and spintronics. 

Organic metal halide hybrids with low-dimensional structures at the molecular level have received great attention recently for their exceptional structural tunability and unique photophysical properties. Here we report for the first time the synthesis and characterization of a one-dimensional (1D) organic metal halide hybrid, which contains metal halide nanoribbons with a width of three octahedral units. It is found that this material with a chemical formula C 8 H 28 N 5 Pb 3 Cl 11 shows a dual emission with a photoluminescence quantum efficiency (PLQE) of around 25%. Photophysical studies and density functional theory (DFT) calculations suggest the coexisting of delocalized free excitons and localized self-trapped excitons in metal halide nanoribbons leading to the dual emission. 

Abstract Low dimensional (LD) organic metal halide hybrids (OMHHs) have recently emerged as new generation functional materials with exceptional structural and property tunability. Despite the remarkable advances in the development of LD OMHHs, optical properties have been the major functionality extensively investigated for most of LD OMHHs developed to date, while other properties, such as magnetic and electronic properties, remain significantly under‐explored. Here, we report for the first time the characterization of the magnetic and electronic properties of a 1D OMHH, organic‐copper (II) chloride hybrid (C₈H₂₂N₂)Cu₂Cl₆. Owing to the antiferromagnetic coupling between Cu atoms through chloride bridges in 1D [Cu₂Cl₆²⁻]_∞chains, (C₈H₂₂N₂)Cu₂Cl₆is found to exhibit antiferromagnetic ordering with a Néel temperature of 24 K. The two‐terminal (2T) electrical measurement on a (C₈H₂₂N₂)Cu₂Cl₆single crystal reveals its insulating nature. This work shows the potential of LD OMHHs as a highly tunable quantum material platform for spintronics. 

Optically pumped white light-emitting diodes (WLEDs), consisting of blue/ultraviolet LED chips and down conversion phosphors, have a wide range of applications in our daily life, such as full color display and solid-state lighting. While remarkable progress in light quality, device efficiency, and lifetime has been achieved during the last two decades, many challenges remain in optically pumped WLEDs, and searching for low cost high performance down conversion phosphors is still of great interest. Recently, metal halide perovskites have emerged as a highly promising new generation of light emitters for their exceptional optical properties with high quantum efficiencies and color tunability, which have also inspired researchers to investigate their derivatives. In this perspective, we briefly review the progress during the last few years in the development of metal halide perovskites and perovskite-related materials as down conversion phosphors for optically pumped WLEDs. We also highlight some major issues and challenges that need to be addressed to enable perovskite-based light emitters to possibly replace currently used rare-earth doped inorganic phosphors and quantum dots. 

Metal halide perovskites (MHPs) have emerged as new‐generation highly efficient narrow‐band luminescent materials with applications in various optoelectronic devices, including photovoltaics (PVs), light‐emitting diodes (LEDs), lasers, and scintillators. Since the demonstration of efficient room‐temperature electroluminescence from MHPs in 2014, remarkable progress has been achieved in the development and study of light‐emitting MHP materials and devices. While the device efficiencies of MHP LEDs (PeLEDs) have significantly improved over a short period of time, their overall performance has not reached the levels of mature technologies yet, such as organic LEDs (OLEDs) and quantum dot LEDs (QDLEDs), to enable practical applications. Many issues and challenges, including low operational stability, lack of efficient blue PeLEDs, and toxicity of MHPs, remain to be addressed. Herein, some of the most exciting progress achieved in the development of efficient and stable PeLEDs during the last few years are introduced, the main issues and challenges in the field are discussed, and the prospects on addressing these issues and challenges are provided. With continuous effort, the potential of PeLEDs to become a commercially available LED technology for display and lighting applications in the future looks optimistic. 

Abstract Scintillators, one of the essential components in medical imaging and security checking devices, rely heavily on rare‐earth‐containing inorganic materials. Here, a new type of organic‐inorganic hybrid scintillators containing earth abundant elements that can be prepared via low‐temperature processes is reported. With room temperature co‐crystallization of an aggregation‐induced emission (AIE) organic halide, 4‐(4‐(diphenylamino) phenyl)‐1‐(propyl)‐pyrindin‐1ium bromide (TPA‐PBr), and a metal halide, zinc bromide (ZnBr₂), a zero‐dimensional (0D) organic metal halide hybrid (TPA‐P)₂ZnBr₄with a yellowish‐green emission peaked at 550 nm has been developed. In this hybrid material, dramatically enhanced X‐ray scintillation of TPA‐P⁺is achieved via the sensitization by ZnBr₄²⁻. The absolute light yield (14,700 ± 800 Photons/MeV) of (TPA‐P)₂ZnBr₄is found to be higher than that of anthracene (≈13,500 Photons/MeV), a well‐known organic scintillator, while its X‐ray absorption is comparable to those of inorganic scintillators. With TPA‐P⁺as an emitting center, short photoluminescence and radioluminescence decay lifetimes of 3.56 and 9.96 ns have been achieved. Taking the advantages of high X‐ray absorption of metal halides and efficient radioluminescence with short decay lifetimes of organic cations, the material design paves a new pathway to address the issues of low X‐ray absorption of organic scintillators and long decay lifetimes of inorganic scintillators simultaneously. 

1D organic metal halide hybrids (OMHHs) exhibit strongly anisotropic optical properties, highly efficient light emission, and large Stokes shift, holding promise for novel photodetection and lighting applications. However, the fundamental mechanisms governing their unique optical properties and in particular the impacts of surface effects are not understood. Herein, 1D C₄N₂H₁₄PbBr₄by polarization‐dependent time‐averaged and time‐resolved photoluminescence (TRPL) spectroscopy, as a function of photoexcitation energy, is investigated. Surprisingly, it is found that the emission under photoexcitation polarized parallel to the 1D metal halide chains can be either stronger or weaker than that under perpendicular polarization, depending on the excitation energy. The excitation‐energy‐dependent anisotropic emission is attributed to fast surface recombination, supported by first‐principles calculations of optical absorption in this material. The fast surface recombination is directly confirmed by TRPL measurements, when the excitation is polarized parallel to the chains. The comprehensive studies provide a more complete picture for a deeper understanding of the optical anisotropy in 1D OMHHs. 

Abstract Metal halide perovskite nanocrystals (NCs) have emerged as highly promising light emitting materials for various applications, ranging from perovskite light‐emitting diodes (PeLEDs) to lasers and radiation detectors. While remarkable progress has been achieved in highly efficient and stable green, red, and infrared perovskite NCs, obtaining efficient and stable blue‐emitting perovskite NCs remains a great challenge. Here, a facile synthetic approach for the preparation of blue emitting CsPbBr₃nanoplatelets (NPLs) with treatment by an organic sulfate is reported, 2,2‐(ethylenedioxy) bis(ethylammonium) sulfate (EDBESO₄), which exhibit remarkably enhanced photoluminescence quantum efficiency (PLQE) and stability as compared to pristine CsPbBr₃NPLs coated with oleylamines. The PLQE is improved from ≈28% for pristine CsPbBr₃NPLs to 85% for EDBESO₄treated CsPbBr₃NPLs. Detailed structural characterizations reveal that EDBESO₄treatment leads to surface passivation of CsPbBr₃NPLs by both EDBE²⁺and SO₄^2–ions, which helps to prevent the coalescence of NPLs and suppress the degradation of NPLs. A simple proof‐of‐concept device with emission peaked at 462 nm exhibits an external quantum efficiency of 1.77% with a luminance of 691 cd m⁻²and a half‐lifetime of 20 min, which represents one of the brightest pure blue PeLEDs based on NPLs reported to date.