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Chiral 3D perovskites pose challenges compared to lower-dimensional variants due to limited chiral organic cation options. Here, we present a universal and controlled method for synthesizing chiral 3D lead halide perovskites using organic amines or alcohols as chiral templates. Introducing these templates to PbCl2in N,N-dimethylformamide (DMF) under acidic conditions induces the crystallization of R/S [DMA]PbCl3(DMA = dimethylamine). The resulting structure aligns with the templates used, stemming from the helical Pb2Cl95–chain as verified by single-crystal X-ray diffraction. Furthermore, the chiral perovskite exhibits absorption and circular dichroism (CD) signals in the high-energy band, enabling the circularly polarized light (CPL) detection in the UV spectrum. A CPL detector constructed by this chiral perovskite demonstrates excellent performance, boasting an anisotropy factor for photocurrent (gIph) of 0.296. Our work not only introduces a novel and controllable method for crafting chiral perovskites but also opens new avenues for circularly polarized light detection.

Developing highly sensitive optical thermometers is of great significance due to their capability to enable remote and non-contact temperature measurements, rendering them highly applicable in diverse and harsh environments. Herein we report a temperature-dependent phosphor of 0D metal halide hybrid by incorporating Bi3+into the (MePPh3)2ZnCl4matrix. Through Bi3+doping, the initially non-luminescent (MePPh3)2ZnCl4matrix exhibits a deep-blue emission centered at 453 nm, with a photoluminescence quantum yield (PLQY) of 5.71% and a Stokes shift of 75 nm at room temperature. Experimental characterization demonstrates that exciton-like luminescence of Bi3+is mainly responsible for the blue emission. Single crystals of Bi3+-doped (MePPh3)2ZnCl4show an unusual correlation between photoluminescence (PL) lifetime and temperature. Particularly, the dependence of luminescence lifetime on temperature is most remarkable in the temperature range of 80 to 100 K with an exceptional sensitivity up to 0.09 K−1, representing one of the best levels for thermometry based on PL decay lifetime. Our work not only provides a viable strategy for designing a novel, environmentally friendly, and stable blue emitter, but also paves the way for precise thermometric application at low temperature.

Perovskites are promising environmentally sustainable materials for circularly polarized electroluminescence (CPEL). While another chiral nonemissive layer is required for the developed perovskite-based CPEL, we report herein a highly efficient circularly polarized electroluminescence based on a single layer of quasi-2D perovskite with achiral phenethylammonium iodide (PEAI) and chiral S/R-1-(1-naphthyl)ethylammonium iodide (S/R-NEAI) as dual spacer cations. The quasi-2D perovskite was further passivated by carbazole-functionalized phosphonium. The as-fabricated film exhibits not only a circular dichroism (CD) signal but also prominent circularly polarized luminescence (CPL) activity with a maximum photoluminescence dissymmetry factor (glum) of ∼2.1 × 10–3. More importantly, a highly efficient, spin-polarized light-emitting diode (LED) was fabricated based on the in situpassivated quasi-2D perovskite with a peak external quantum efficiency of 3.7% and a maximum electroluminescence dissymmetry factor (gEL) of ∼4.0 × 10–3.

Ion doping has been demonstrated as a practical approach to achieving highly efficient luminescence in both inorganic phosphors and organic-inorganic hybrids. The as-formed doping species show great potential in optoelectronic applications due to their high photoluminescence quantum yield (PLQY) and excellent stability. Herein, we report highly emissive Sb3+-doped indium halides (C6H18N2)InCl5·H2O:Sb (C6H18N22+= N,N,N′,N′-tetramethylethane-1,2-diammonium) prepared by solution evaporation methods with an emission that peaked at 565 nm and a PLQY of 74.6%. Photophysical characterizations and density functional theory computational studies verify the broadband emission originating from a self-trapped exciton. Interestingly, a drastic red shift of the emission peak from 565 to 663 nm with yellow luminescence turning to red is observed once the (C6H18N2)InCl5·H2O:Sb hybrid is exposed to methanol vapor. Moreover, when the methanol-exposed hybrid is put in air, the emission reverts to 565 nm in several minutes. Single-crystal X-ray diffraction studies show a subsequent structure distortion upon the coordination of methanol to the Sb(III) center, which is responsible for the drastic red shift of the emission. Encouragingly, we found that (C6H18N2)InCl5·H2O:Sb exhibits a specific response to methanol vapor after screening a series of volatile organic compounds with different polarities. Besides, a negligible change of the emission intensity is observed after several cycles of uptaking and releasing methanol. The high fatigue resistance and specific solvent response of the Sb3+-doped indium halide make it a very promising methanol detector.

Mn2+-doped lead halide perovskites either in 3D or 2D have been extensively explored due to their rich energy-transfer behaviors. While their application on LED is still lagging behind in comparison to non-doped 3D perovskite due to inferior film-formation and low luminescent efficiency. Here we report an in-situ-formed Mn2+doped 2D perovskite nanocrystal (NCs) film by introducing quaternary phosphonium salt during the crystallizing process. The as-formed film shows improved luminescent efficiency with emission peaked at 600 nm and photoluminescence quantum yield (PLQY) of as high as 73.37%, which is about 1.3 times higher than that of pristine film. Further characterizations confirm the enhanced confinement effect from smaller size particle is responsible for the improved luminescent efficiency. The perovskite LEDs based on pristine and phosphonium passivated thin films were fabricated, and a great improvement in the external quantum efficiency of these LEDs (from 0.0017% to 0.12%) is observed due to the improved morphology and enhanced luminescent efficiency.

Yellow emission is a complementary color of blue for achieving white emission. Here, we report two yellow-emitting PtAg2heterotrinuclear complexes (1and 2) of 4-ethynyl-N,N-diphenylaniline, supported by bis(diphenylphosphinomethyl)phenylphosphine (dpmp) and bis(di-o-tolylphosphinomethyl)phenylphosphine (dTolmp), respectively. The solution-processed organic light-emitting diode based on complex 1exhibits yellow emission peaked at 567 nm with the highest current efficiency (CE) of 49.7 cd A–1and an external quantum efficiency (EQE) of 14.3%. Remarkably, the device performance of complex 2containing dTolmp with a larger steric hindrance as the supporting ligand is dramatically enhanced with the CE boosting to 69.1 cd A–1and EQE of 21.7% and, more importantly, a better color saturation of yellow emission peaked at 579 nm with the CIE of (0.49, 0.50).

The reaction of 3,6-ditert-butyl-1,8-bis(diphenylphosphino)-9-methyl-9H-carbazole (L) with CuBr resulted in the isolation of tetranuclear copper(I) complex Cu4Br4L2as two colorless crystal morphs, i.e., green-emitting 1Gand yellow-emitting 1Y. As demonstrated by X-ray crystallography, the Cu4Br4moiety in both 1Gand 1Yadopts the same chair conformations. When L is bonded perpendicularly to the Cu4plane, 1Gwith green emission is obtained, while it gives a yellow emission of 1Yonce the L is parallelly bonded to Cu4plane. Theoretical computational studies suggest that the variation in ligand orientation results in a different degree of structural distortion in triplet state and thus different luminescent energy. Particularly, 1Yundergoes dramatic structural distortion from the ground (S0) to triplet excied state (T1). Interestingly, 1Gcan be converted into 1Yupon exposed to saturated hexane vapor, which would return to 1Gupon exposure to acetonitrile vapor. As demonstrated experimentally and theoretically, the reversible luminescence transformation between 1Gand 1Yis ascribed to the variation of ligand L orientations.

The fabrication of efficient and spectrally stable pure-blue perovskite light-emitting diodes (LEDs) has been elusive and remains of great interest. Herein, we incorporate diammonium salts into quasi-2D perovskite 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 diammonium 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, 75% 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 nm and a full width at half-maximum of 26 nm could be fabricated to exhibit a brightness of 290 cd m–2at 8 V and an external quantum efficiency of 2.17%.

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)2SnBr4(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)4SnBr6][(PEA)Br]2[CCl2H2]2was found to exhibit strong yellow emission peak at 566 nm with a photoluminescence quantum efficiency (PLQE) of ∼90%, while 2D (PEA)2SnBr4had weak emission peak at 470 nm with a PLQE of <0.1%. Interestingly, 0D [(PEA)4SnBr6][(PEA)Br]2[CCl2H2]2can be converted into 2D (PEA)2SnBr4upon drying, which would return to 0D [(PEA)4SnBr6][(PEA)Br]2[CCl2H2]2upon 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)4SnBr6][(PEA)Br]2[CCl2H2]2are highly localized, resulting in a strongly Stokes shifted broadband emission, while delocalized electronic states in 2D (PEA)2SnBr4result in weaker exciton binding, a higher exciton mobility, and a higher nonradiative decay.

Abstract

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.

The rapid development of halide perovskite synthesis offers the opportunity to fabricate high-quality perovskite nanocrystals (NCs), whose structural uniformity can lead to assembled supra-structures with improved device performance and novel collective properties. Light is known to significantly affect the structure and properties of halide perovskites and plays a crucial role in the growth and assembly of their crystals. Nevertheless, the light-induced growth mechanisms of perovskite NCs are not yet clearly understood. In this work, we performed a systematic study of the visible-light-induced template-free synthesis of CsPbBr3nanowires (NWs) generated through self-assembly of cubic (in phase and close to cubic morphology) NCs. Using atomic-resolution electron microscopy, we visualized the cubic-to-orthorhombic phase transition in NCs and the interface between coalesced NCs. Remarkably, the images of the interface revealed the coexistence of CsBr and PbBr2surface terminations in halide perovskites. Our results shed light on the mechanism underlying the observed anisotropic assembly of halide perovskites and elucidate the vital role of light illumination during this process. More importantly, as an elegant and promising green-chemistry approach, light-induced self-assembly represents a rational method for designing perovskites.

Scintillators, which are capable of converting ionizing radiation into visible photons, are an integral part of medical, security, and commercial diagnostic technologies such as X-ray imaging, nuclear cameras, and computed tomography. Conventional scintillator fabrication typically involves high-temperature sintering, generating agglomerated powders or large bulk crystals, which pose major challenges for device integration and processability. On the other hand, colloidal quantum dot scintillators cannot be cast into compact solid films with the necessary thickness required for most X-ray applications. Here, we report the room-temperature synthesis of a colloidal scintillator comprising CsPbBr3nanosheets of large concentration (up to 150 mg/mL). The CsPbBr3colloid exhibits a light yield (∼21000 photons/MeV) higher than that of the commercially available Ce:LuAG single-crystal scintillator (∼18000 photons/MeV). Scintillators based on these nanosheets display both strong radioluminescence (RL) and long-term stability under X-ray illumination. Importantly, the colloidal scintillator can be readily cast into a uniform crack-free large-area film (8.5 × 8.5 cm2in area) with the requisite thickness for high-resolution X-ray imaging applications. We showcase prototype applications of these high-quality scintillating films as X-ray imaging screens for a cellphone panel and a standard central processing unit chip. Our radiography prototype combines large-area processability with high resolution and a strong penetration ability to sheath materials, such as resin and silicon. We reveal an energy transfer process inside those stacked nanosheet solids that is responsible for their superb scintillation performance. Our findings demonstrate a large-area solution-processed scintillator of stable and efficient RL as a promising approach for low-cost radiography and X-ray imaging applications.

The reactions of MnBr2and ethane-1,2-diylbis(diphenylphosphine oxide) (dppeO2) in dichloromethane–methanol solutions gave colorless crystals with the general chemical formulas [MnBr2(dppeO2)]n(1), [MnBr2(dppeO2)(DMF)]n(1a), [Mn(dppeO2)3][MnBr4] (2), and Mn2Br4(dppeO2)2(3) depending on the crystallization conditions. Compounds 1and 1adisplay one-dimensional chain structures composed of Mn(II) ions linked by bridging dppeO2to exhibit tetrahedral (1) or trigonal-bipyramidal (1a) coordination geometry, whereas 3exhibits a cyclic dinuclear structure with two Mn(II) centers bridged by double dppeO2to adopt tetrahedral geometry. Compound 2consists of octahedrally coordinated cation [Mn(dppeO2)3]2+and tetrahedrally arranged anion [MnBr4]2–. While 1and 3in crystalline and powder states are highly luminescent with green emission bands centered at ca. 510 nm, 2shows intense orange luminescence peaking at 594 nm. Upon exposure of 1to N,N-dimethylformamide vapor, the green emission centered at 510 nm is converted to red luminescence peaking at 630 nm, ascribed to the formation of DMF-coordinated compound 1awith a trigonal-bipyramidal ligand field, as demonstrated by X-ray crystallography. Red-emitting 1acould be reverted to the original green-emitting 1with a tetrahedral ligand field upon heat at 160 °C, and such a reversible conversion could be perfectly repeated for several cycles. A new mechanism of luminescent vapochromism is thus proposed because of the reversible conversion of ligand fields in manganese(II) complexes.

A trace (BINAP)2Cu2Br2-doped TPP3CuBr complex TPP3CuBr:x(BINAP)2Cu2Br2(complex 1) was synthesized, which exhibits strong phosphorescence with a yellow-green emission peak at 525 nm and a shoulder peak at 560 nm. Nevertheless, no emissions were observed for either pure (BINAP)2Cu2Br2or pure TPP3CuBr. The plausible mechanism is that the incorporation of (BINAP)2Cu2Br2into the rigid environment provided by the TPP3CuBr matrix effectively restricts the variation of (BINAP)2Cu2Br2molecules, thus reducing nonradiative transitions. On the other hand, π–π stacking and hydrogen bond interactions may influence the conformation of (BINAP)2Cu2Br2, potentially leading to more efficient phosphorescence. Interestingly, complex 1was found to have a sensitive response to dichloromethane (DCM) solvent. An obvious blue shift in emission was observed when complex 1was exposed to a DCM atmosphere. Moreover, after removal from the DCM atmosphere, complex 1can be restored to its initial state. Additionally, complex 1demonstrated remarkable attributes, including high sensitivity, selectivity, and stability.

The utilization of phosphorescent metal cluster complexes as new types of emitting materials in organic light-emitting diodes (OLEDs) is becoming an alternative and viable approach for achieving high-efficiency electroluminescence. We report herein the design of cationic PtAu2cluster complexes with differently positioned 9-phenylcarbazole–acetylides to serve as phosphorescent emitters in OLEDs. The rigid structures of PtAu2complexes cause intense phosphorescence with quantum yields of over 85%, which originates from 3[π(phenylcarbazole–acetylide) → π*(dpmp)] ligand-to-ligand and 3[π(phenylcarbazole–acetylide) → p/s(PtAu2)] ligand-to-metal charge-transfer triplet excited states. When 8 wt % PtAu2is doped to blended host materials of TCTA and OXD-7 (2:1 weight ratio) as light-emitting layers, solution-processed OLEDs give a current efficiency of 78.2 cd A–1and an external quantum efficiency (EQE) of 21.5% at a practical luminance of 1029 cd m–2with a slow efficiency roll-off upon increasing luminance. This represents the best device performance and the highest efficiency recorded at practical luminance for solution-processed OLEDs.

Highly soluble d8–d10heteronuclear phosphors afford an alternative approach to achieve high-efficiency organic light-emitting diodes (OLEDs) through a solution process. In this work, four highly phosphorescent d8–d10heteronuclear complexes with significant Pt–Au interactions were prepared. By judicious selection of sterically hindered and π-conjugated substituents in triphosphine ligands, the phosphorescence is dramatically promoted through effectively prohibiting nonradiative thermal relaxation with an efficiency of 0.94–0.99 in doping films. Exploiting highly emissive Pt–Au complexes as phosphorescent dopants, ultrahigh-efficiency solution-processed OLEDs were attained. The peak current efficiency, power efficiency, and external quantum efficiency are 96.2 cd A–1, 65.0 lm W–1, and 26.4% for the green-emitting PtAu2phosphor and 68.6 cd A–1, 42.5 lm W–1, and 25.1% for the orange-emitting Pt2Au phosphor, which represent the state-of-art for solution-processed OLEDs based on non-iridium phosphors.