Blue Perovskite LEDs In article number 2201605, Biwu Ma and co-workers develop highly efficient and stable blue emitting CsPbBr3 nanoplatelets with surface passivation via a multifunctional organic sulfate, 2,2-(ethylenedioxy) bis(ethylammonium) sulfate. Blue light emitting diodes with emission peaks at 462 nm are fabricated and exhibit remarkable spectral stability.

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 CsPbBr 3 nanoplatelets (NPLs) with treatment by an organic sulfate is reported, 2,2‐(ethylenedioxy) bis(ethylammonium) sulfate (EDBESO 4 ), which exhibit remarkably enhanced photoluminescence quantum efficiency (PLQE) and stability as compared to pristine CsPbBr 3 NPLs coated with oleylamines. The PLQE is improved from ≈28% for pristine CsPbBr 3 NPLs to 85% for EDBESO 4 treated CsPbBr 3 NPLs. Detailed structural characterizations reveal that EDBESO 4 treatment leads to surface passivation of CsPbBr 3 NPLs by both EDBE 2+ and SO 4 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 −2 and a half‐lifetime of 20 min, which represents one of the brightest pure blue PeLEDs based on NPLs reported to date.

Accident tolerant fuel (ATF) are currently being developed as part of an international effort to modify or replace zirconium-based cladding materials in light water reactors. The main objective of ATF cladding materials is to improve fuel reliability and safety during accident scenarios. Thus, these materials should perform comparable to or better than the current zirconium alloy. One of the ATF concepts explores modifying standard Zircaloy cladding by coating their outer surface. In this study, surface-modified Zr-4 is produced by depositing a protective coating of chromium through two different coating techniques, Physical Vapor Deposition (PVD) and Cold Spray (CS). The coated specimens were tested at ∼300 °C in out-of-pile autoclaves simulating Boiling Water Reactor (BWR) conditions. Results show that after one month of immersion, Cr-coated Zr-4 evidenced a small mass gain in hydrogenated environments. However, both types of coated specimens showed significant coating degradation and mass loss in oxygenated environments.

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.

Mechanochemical synthesis has emerged as a facile method for the preparation of a wide range of organic, inorganic, and polymeric materials. Here, we report the use of mechanochemical synthesis for the preparation of ionically bonded organic metal halide hybrids with a zero-dimensional (0D) structure at the molecular level. (Ph4P)(2)SbCl5 and (Ph4P)(2)MnCl4 were synthesized by grinding appropriate ratios of organic halide salt Ph4PCl with inorganic metal halide salts SbCl3 and MnCl2, respectively. The structural and photophysical properties of mechanochemically synthesized (Ph4P)(2)SbCl(5)and (Ph4P)(2)MnCl(4)were characterized, which are almost identical to those of single crystals prepared by slow solution growth. By reacting Ph4PCl with both SbCl(3)and MnCl2, we have been able to produce a mixture of two 0D organic metal halide hybrids that exhibit a dual emission covering a wide range of the spectrum with Commission Internationale de l'Eclairage (CIE) coordinates of (0.4898, 0.4800). Our work has clearly established mechanochemical synthesis as an effective method to produce ionically bonded organic-inorganic hybrids.

Perovskite light-emitting diodes (PeLEDs) have received great attention for their potential as next-generation display technology. While remarkable progress has been achieved in green, red, and near-infrared PeLEDs with external quantum efficiencies (EQEs) exceeding 20%, obtaining high performance blue PeLEDs remains a challenge. Poor charge balance due to large charge injection barriers in blue PeLEDs has been identified as one of the major roadblocks to achieve high efficiency. Here band edge control of perovskite emitting layers for blue PeLEDs with enhanced charge balance and device performance is reported. By using organic spacer cations with different dipole moments, that is, phenethyl ammonium (PEA), methoxy phenethyl ammonium (MePEA), and 4-fluoro phenethyl ammonium (4FPEA), the band edges of quasi-2D perovskites are tuned without affecting their band gaps. Detailed characterization and computational studies have confirmed the effect of dipole moment modification to be mostly electrostatic, resulting in changes in the ionization energies of approximate to 0.45 eV for MePEA and approximate to -0.65 eV for 4FPEA based thin films relative to PEA-based thin films. With improved charge balance, blue PeLEDs based on MePEA quasi-2D perovskites show twofold increase of the EQE as compared to the control PEA based devices.

Ionically bonded organic metal halide hybrids have emerged as versatile multicomponent material systems exhibiting unique and useful properties. The unlimited combinations of organic cations and metal halides lead to the tremendous structural diversity of this class of materials, which could unlock many undiscovered properties of both organic cations and metal halides. Here we report the synthesis and characterization of a series benzoquinolinium (BZQ) metal halides with a general formula (BZQ)Pb2X5 (X = Cl, Br), in which metal halides form a unique two-dimensional (2D) structure. These BZQ metal halides are found to exhibit enhanced photoluminescence and stability as compared to the pristine BZQ halides, due to the scaffolding effects of 2D metal halides. Optical characterizations and theoretical calculations reveal that BZQ+ cations are responsible for the emissions in these hybrid materials. Changing the halide from Cl to Br introduces heavy atom effects, resulting in yellow room temperature phosphorescence (RTP) from BZQ+ cations.

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)(2)SbCl5 (PPN = bis(triphenylphosphoranylidene)ammonium cation), as an X-ray scintillation material with high light yield and exceptional environmental stability. Our study shows that (PPN)(2)SbCl5 single crystals prepared by solution growth exhibit visible photoluminescence with a quantum efficiency of 98.1%. When excited by Xrays, (PPN)(2)SbCl5 single crystals exhibit radioluminescence with a near-perfect linearity over a large range of X-ray dose rates and a light yield of similar to 49000 ph MeV-1, which is comparable to that of a commercial CsI(Tl) scintillator (similar to 54000 ph MeV-1). Moreover, the detection limit of (PPN)(2)SbCl5 (191.4 nGy(air) s(-1)) is much lower than the required value for regular medical diagnostics (5.5 mu Gy(air) s(-1)). (PPN)(2)SbCl5 single crystals also display remarkable stability, with little-to-no change in properties after storage under ambient conditions for 2 years.

Metal halide perovskite nanocrystals (NCs) have emerged as a new generation light emitting materials with narrow emissions and high photoluminescence quantum efficiencies (PLQEs). Various types of perovskite NCs, e.g. platelets, wires, and cubes, have been discovered to exhibit tunable emissions across the whole visible spectral region. Despite remarkable advances in the field of metal halide perovskite NCs over the last few years, many nanostructures in inorganic NCs have yet been realized in metal halide perovskites and producing highly efficient blue emitting perovskite NCs remains challenging and of great interest. Here we report for the first time the discovery of highly efficient blue emitting cesium lead bromide perovskite (CsPbBr3) NCs with hollow structures. By facile solution processing of cesium lead bromide perovskite precursor solution containing additional ethylenediammonium bromide and sodium bromide, in-situ formation of hollow CsPbBr3 NCs with controlled particle and pore sizes is realized. Synthetic control of hollow nanostructures with quantum confinement effects results in color tuning of CsPbBr3 NCs from green to blue with high PLQEs of up to 81 %.

AbstractThe photophysical tuning is reported for a series of tetraphenylphosphonium (TPP) metal halide hybrids containing distinct metal halides, TPP2MXn (MXn=SbCl5, MnCl4, ZnCl4, ZnCl2Br2, ZnBr4), from efficient phosphorescence to ultralong afterglow. The afterglow properties of TPP+ cations could be suspended for the hybrids containing low band gap emissive metal halide species, such as SbCl52− and MnCl42−, but significantly enhanced for the hybrids containing wide band gap non‐emissive ZnCl42−. Structural and photophysical studies reveal that the enhanced afterglow is attributed to stronger π–π stacking and intermolecular electronic coupling between TPP+ cations in TPP2ZnCl4 than in the pristine organic ionic compound TPPCl. Moreover, the afterglow in TPP2ZnX4 can be tuned by controlling the halide composition, with the change from Cl to Br resulting in a shorter afterglow due to the heavy atom effect.

Metal-halide perovskites, in particular their nanocrystal forms, have emerged as a new generation of light-emitting materials with exceptional optical properties, including narrow emissions covering the whole visible region with high photoluminescence quantum efficiencies of up to near-unity. Remarkable progress has been achieved over the last few years in the areas of materials development and device integration. A variety of synthetic approaches have been established to precisely control the compositions and microstructures of metal-halide perovskite nanocrystals (NCs) with tunable bandgaps and emission colors. The use of metal-halide perovskite NCs as active materials for optoelectronic devices has been extensively explored. Here, we provide a brief overview of recent advances in the development and application of metal-halide perovskite NCs. From color tuning via ion exchange and manipulation of quantum size effects, to stability enhancement via surface passivation, new chemistry for materials development is discussed. In addition, processes in optoelectronic devices based on metal-halide perovskite NCs, in particular, light-emitting diodes and radiation detectors, will be introduced. Opportunities for future research in metal-halide perovskite NCs are provided as well.

Tin halide perovskites and perovskite-related materials have emerged as promising lead-free hybrid materials for various optoelectronic applications. While remarkable progress has been achieved in the development of organic tin halide hybrids with diverse structures and controlled dimensionalities at the molecular level, some controversial results that have been reported recently need to be addressed. For instance, different photophysical properties have been reported for two-dimensional (2D) (PEA)(2)SnBr4 (PEA = phenylethylammonium) by several groups with distinct emission peaks at around 468 and 550 nm. Here we report our efforts in the synthesis of phenylethylammonium tin bromide hybrids with zero-dimensional (0D) and 2D structures, and characterizations of their structural and photophysical properties. 0D [(PEA)(4)SnBr6][(PEA)Br](2)[CCl2H2](2) was found to exhibit strong yellow emission peak at 566 nm with a photoluminescence quantum efficiency (PLQE) of similar to 90%, while 2D (PEA)(2)SnBr4 had weak emission peak at 470 nm with a PLQE of <0.1%. Interestingly, 0D [(PEA)(4)SnBr6] [(PEA)Br](2)[CCl2H2](2) can be converted into 2D (PEA)(2)SnBr4 upon drying, which would return to 0D [(PEA)(4)SnBr6][(PEA)Br](2)[CCl2H2](2) upon addition of dichloromethane. Powder X-ray diffraction results confirmed the reversible transformation between 0D and 2D structures. Density functional theory calculations showed that excitons in 0D [(PEA)(4)SnBr6] [(PEA)Br](2)[CCl2H2](2) are highly localized, resulting in a strongly Stokes shifted broadband emission, while delocalized electronic states in 2D (PEA)(2)SnBr4 result in weaker exciton binding, a higher exciton mobility, and a higher nonradiative decay.

Surface passivation of perovskite solar cells (PSCs) using a low-cost industrial organic pigment quinacridone (QA) is presented. The procedure involves solution processing a soluble derivative of QA, N , N -bis(tert-butyloxycarbonyl)-quinacridone (TBOC-QA), followed by thermal annealing to convert TBOC-QA into insoluble QA. With halide perovskite thin films coated by QA, PSCs based on methylammonium lead iodide (MAPbI 3 ) showed significantly improved performance with remarkable stability. A PCE of 21.1 % was achieved, which is much higher than 18.9 % recorded for the unmodified devices. The QA coating with exceptional insolubility and hydrophobicity also led to greatly enhanced contact angle from 35.6° for the pristine MAPbI 3 thin films to 77.2° for QA coated MAPbI 3 thin films. The stability of QA passivated MAPbI 3 perovskite thin films and PSCs were significantly enhanced, retaining about 90 % of the initial efficiencies after more than 1000 hours storage under ambient conditions.

The photophysical tuning is reported for a series of tetraphenylphosphonium (TPP) metal halide hybrids containing distinct metal halides, TPP 2 MX n (MX n =SbCl 5 , MnCl 4 , ZnCl 4 , ZnCl 2 Br 2 , ZnBr 4 ), from efficient phosphorescence to ultralong afterglow. The afterglow properties of TPP + cations could be suspended for the hybrids containing low band gap emissive metal halide species, such as SbCl 5 2− and MnCl 4 2− , but significantly enhanced for the hybrids containing wide band gap non-emissive ZnCl 4 2− . Structural and photophysical studies reveal that the enhanced afterglow is attributed to stronger π–π stacking and intermolecular electronic coupling between TPP + cations in TPP 2 ZnCl 4 than in the pristine organic ionic compound TPPCl. Moreover, the afterglow in TPP 2 ZnX 4 can be tuned by controlling the halide composition, with the change from Cl to Br resulting in a shorter afterglow due to the heavy atom effect.

Bulk assemblies of zero-dimensional (0D) metal halides with exceptional structural versatility have enabled the development of a number of highly efficient emitters with tunable photophysical properties. Here, we report a novel single crystalline bulk assembly of multicomponent 0D metal halides, (bmpy)(9)[SbCl5](2)[Pb3Cl11] (bmpy = 1-butyl-1-methylpyrrolidinium), which exhibits dual emissions from distinct metal halide species. Excitation-dependent warm white light emissions with high photoluminescence quantum efficiencies of >70% can be obtained by combining green emission from Pb3Cl115- and orange emission from SbCl52-. Because of complete site isolation by wide bandgap organic moieties and little-to-no spectral overlaps, no energy transfer occurs between two distinct emitting species, allowing for precise color control by manipulating the excitation wavelengths. Our discovery of dual emitting organic metal halide hybrid opens up a new way to develop precisely ordered single-crystalline multicomponent materials with multi-functionalities.

The fabrication of efficient and spectrally stable pure-blue perovskite light-emitting diodes (LEDs) has been elusive and remains of great interest. Herein, five incorporate diammorfium salts into quasi-2D perovsl<ite precursors for phase control of multiple quantum well structures to yield tunable and efficient emission in the blue region. With detailed characterizations and computational studies, we show that in situ passivation by the dian-fmonitim salts effectively modifies the surface energies of quasi-2D phases and inhibits the growth of low-band gap quasi-2D and 3D phases. Such phase control and in situ passivation could afford blue light-emitting perovskite thin films with high photoluminescence quantum efficiencies of, for instance, 759/o for the emission peak at 471 nm.. Using this perovskite thin film as an emitting layer, spectrally stable pure-blue LEDs with an emission peak at 474 ran and a full width at half-maximum of 26 nm could be fabricated to exhibit a brightness of 290 cd m-2 at 8 V and an external quantum efficiency of 2.17c/o.

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 state-of-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.