Aggregation‐induced emission (AIE) is an attractive phenomenon in which materials display strong luminescence in the aggregated solid states rather than in the conventional dissolved molecular ...states. However, highly luminescent inks based on AIE are hard to be obtained because of the difficulty in finely controlling the crystallinity of AIE materials at nanoscale. Herein, we report the preparation of highly luminescent inks via oil‐in‐water microemulsion induced aggregation of Cu–I hybrid clusters based on the highly soluble copper iodide‐tris(3‐methylphenyl)phosphine (Cu4I4(P‐(m‐Tol)3)4) hybrid. Furthermore, we can synthesize a series of AIE inks with different light‐emission colors to cover the whole visible spectrum range via a facile ligand exchange processes. The assemblies of Cu–I hybrid clusters with AIE characteristics will pave the way to fabricate low‐cost highly luminescent inks.
Ink‐lined to glow: Highly luminescent inks based on AIE Cu–I hybrids clusters are prepared by the self‐assembly of Cu–I hybrid cluster aggregates in microemulsion droplets. A subsequent ligand exchange step expands the color pallet of the as‐fabricated inks.
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Inorganic perovskite CsPbBr3 nanocrystals (NCs) are emerging, highly attractive light emitters with high color purity and good thermal stability for light-emitting diodes (LEDs). Their high ...photo/electroluminescence efficiencies are very important for fabricating efficient LEDs. Here, we propose a novel strategy to enhance the photo/electroluminescence efficiency of CsPbBr3 NCs through doping of heterovalent Ce3+ ions via a facile hot-injection method. The Ce3+ cation was chosen as the dopant for CsPbBr3 NCs by virtue of its similar ion radius and formation of higher energy level of conduction band with bromine in comparison with the Pb2+ cation to maintain the integrity of perovskite structure without introducing additional trap states. It was found that by increasing the doping amount of Ce3+ in CsPbBr3 NCs to 2.88% (atomic percentage of Ce compared to Pb) the photoluminescence quantum yield (PLQY) of CsPbBr3 NCs reached up to 89%, a factor of 2 increase in comparison with the native, undoped ones. The ultrafast transient absorption and time-resolved photoluminescence (PL) spectroscopy revealed that Ce3+-doping can significantly modulate the PL kinetics to enhance the PL efficiency of doped CsPbBr3 NCs. As a result, the LED device fabricated by adopting Ce3+-doped CsPbBr3 NCs as the emitting layers exhibited a pronounced improvement of electroluminescence with external quantum efficiency (EQE) from 1.6 to 4.4% via Ce3+-doping.
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The exploration of lead‐free halide perovskite nanocrystals (NCs) with intriguing optical properties is highly desirable owing to the toxicity and instability of lead halide perovskite NCs. Here, a ...new kind of uniform lead‐free double perovskite Cs2NaBiCl6 NCs are reported as versatile hosts to accommodate ionic dopants for improving optical properties especially the photoluminescence (PL). In contrast to the low deep‐blue PL with a quantum yield of only 1.7% of the as‐synthesized pristine Cs2NaBiCl6 NCs, the PL of the Cs2NaBiCl6 NCs can be impressively regulated and enhanced via doping Ag+, Mn2+, or Eu3+ ions in the double perovskite lattices. The femtosecond time‐resolved transient absorption spectroscopy is adopted to unravel the PL enhancement mechanism of the ion doping in the Cs2NaBiCl6 NCs. For the Ag+‐doping, the excitonic absorption energy of the Cs2NaBiCl6 NCs can be tuned from 3.82 to 3.48 eV with the significant improvement of the PL quantum yield (PLQY) from 1.7% to 20%. The Mn2+‐doped Cs2NaBiCl6 NCs show broad orange–red emission peak centered at 585 nm with a PLQY of 3%, owing to the 4T1→6A1 transition of octahedrally coordinated Mn2+. Eu3+‐doped Cs2NaBiCl6 NCs are endowed with strong Eu3+5D0→7FJ (J = 1, 2) orange–red emission at 591 and 615 nm.
A series of ions (Ag+, Mn2+, and Eu3+) doped lead‐free double perovskite Cs2NaBiCl6 nanocrystals (NCs) with uniform morphologies and good air stability are synthesized, exhibiting impressively enhanced photoluminescence in comparison to pristine Cs2NaBiCl6 NCs. The ion doping mechanisms for improving the PL are unraveled by the femtosecond time‐resolved transient absorption spectroscopy characterizations as well.
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Fabricating a robust interfacial layer on the lithium metal anode to isolate it from liquid electrolyte is vital to restrain the rapid degradation of a lithium metal battery. Here, we report that the ...solution-processed metal chloride perovskite thin film can be coated onto the lithium metal surface as a robust interfacial layer to shield the lithium metal from liquid electrolyte. Via phase analysis and density functional theory calculations, we demonstrate that the perovskite layer can allow fast lithium ion shuttle under a low energy barrier of 0.45 eV without the collapse of framework. Such perovskite modification can realize stable cycling of LiCoO
|Li cells with an areal capacity of 2.8 mAh cm
using thin lithium metal foil (50 μm) and limited electrolyte (20 μl mAh
) for over 100 cycles at 0.5 C. The metal chloride perovskite protection strategy could open a promising avenue for advanced lithium metal batteries.
Chiral chromophores and their ordered assemblies are intriguing for yielding circularly polarized luminescence (CPL) and exploring intrinsic structure–light emission relationships. With the ...extensively studied chiral organic molecules and inorganic nanoparticle assemblies for the amplified CPL, the assemblies of copper halide hybrid clusters have attracted intensive attention due to their potential efficient CPL. Here, we report robust chiral phosphine–copper iodide hybrid clusters and their layered assemblies in crystalline states for amplified CPL. We reveal that the intermolecular interactions endow the clusters with the capability of assembling into chiral crystalline CPL materials, including hexagonal platelet-shaped microcrystals (g lum ≈ 9.5 × 10–3) and highly oriented crystalline films (g lum ≈ 5 × 10–3). Owing to the high crystalline feature of the thin film, we demonstrate an electroluminescent device with bright electroluminescence (1200 cd m–2).
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Conspectus With the development of solid-state lighting technology, efficient light sources that combine high brightness, wide range, and good stability are in high demand for next-generation ...lighting and displays. Metal halides are emerging as promising luminescent materials due to their versatility for desirable light emission manipulations. This is because the optical activity of the metal halide material depends on the metal halide structural unit and the organic ions or coordinated organic ligands. The different assembly of metal halide units and organic parts can enable versatile light emissions, such as lead halide perovskites (LHPs) and copper halide–organic hybrids. Impressively, the external quantum efficiency of the LHP based light-emitting diodes (LEDs) has improved significantly from 0.1% to over 20% in just five years. With this great progress, the structural lability and toxicity of the LHPs are now the critical issues that need to be addressed for practical applications. These issues are mainly rooted in the intrinsic lead composition and low formation energy crystal structure of the widely adopted LHPs. Thus, the modulation of the structure and composition of the basic metal halide structural units is considered a rational strategy to address these issues. In this Account, we will present a general material design using metal halide structural units as basic building blocks to build up metal halide luminescent materials for solid-state lighting devices. Following this route, we will emphasize the modulation of metal halide structural units to tackle the existing challenges in lead halides, including the instability of crystalline structure, ion migration, and the presence of toxic lead. Considering basic components in structural units, we will highlight ionic engineering in LHPs via ion doping, substitution, and modification to enhance the crystal structural stability and suppress ion migration. To replace toxic lead, we will introduce recent advances in the modulation of lead-free halide structural units by active ion doping and organic ligand coordination to fabricate highly luminescent materials. Finally, we will present future strategies of metal halide structural unit modulation for solid-state light emissions. We hope this Account will provide new insights for designing metal halide materials from the viewpoint of the modulation of the basic building blocks and inspire future studies of advanced metal halide materials for solid-state light emitting applications.
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Although the efficiency of metal halide perovskite light emitting diodes (PeLEDs) has been improved to an attractive level, the poor stability of perovskite emitting layers is a major concern for the ...application of PeLEDs. Herein, we report a facile ligand-assisted precipitation synthesis of stable dual-phase CsPbBr3–CsPb2Br5 nanocrystals (NCs) for improving the stability of PeLEDs. In our synthetic process, the bromide-rich circumstance is beneficial to generate high quality dual-phase perovskite NCs with PLQY as high as 92% and a narrow emission linewidth (19 nm). More importantly, as-synthesized dual phase perovskite NCs exhibit extremely high thermal stability in heating tests in air with a considerable humidity of 30%–55% in comparison with previously reported single phase CsPbBr3 NCs. The aforementioned advantages of our synthesized dual-phase CsPbBr3–CsPb2Br5 NCs allow for the fabrication of light emitting layers of PeLEDs under ambient conditions. The fabricated green PeLED based on CsPbBr3–CsPb2Br5 NCs shows a low turn-on voltage of 2.5 V and a high brightness of 8383 cd m−2 at 8 V. Owing to the high stability of dual-phase CsPbBr3–CsPb2Br5 NCs, the fabricated PeLED also exhibits better operational stability in comparison with those PeLEDs based on single phase CsPbBr3 NCs. Our work presents a new route to fabricate stable perovskite light-emitting diodes using room temperature precipitated dual-phase CsPbBr3–CsPb2Br5 NCs as emitting layer materials.
Highly luminescent inks are desirable for various applications such as decorative coating, art painting, and anticounterfeiting, to name a few. However, present inks display low photoluminescent ...efficiency requiring a strong excitation light to make them glow. Here, we report a highly luminescent ink based on the copper-iodide/1-Propyl-1,4-diazabicyclo2.2.2octan-1-ium (Cu4I6(pr-ted)2) hybrid cluster with a quantum efficiency exceeding 98%. Under the interaction between the Cu4I6(pr-ted)2 hybrid cluster and polyvinylpyrrolidone (PVP), the highly luminescent Cu4I6(pr-ted)2/PVP ink can be facilely prepared via the one-pot solution synthesis. The obtained ink exhibits strong green light emission that originates from the efficient phosphorescence of Cu4I6(pr-ted)2 nanocrystals. Attractively, the ink displays high conversion efficiency for the ultraviolet light to bright green light emission due to its wide Stokes shift, implying great potential for anticounterfeiting and luminescent solar concentrator coating.
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All‐inorganic CsPbX3 (X = Cl, Br, or I) perovskite thin films are attractive emissive layers for high‐performance light‐emitting diodes (LEDs) due to their precisely tunable bandgaps, excellent color ...purities, good stabilities, and solution processabilities. However, the fabrication of high‐quality CsPbI3−xBrx thin films is very challenging because the crystal growth of mixed halide CsPbI3−xBrx is in low controllability. Herein, a synergetic regulation strategy using fluorine polymer (Poly(vinylidene fluoride‐co‐hexafluoropropylene)) and a small amino acid molecule (L‐Arginine) is developed to fabricate high‐quality CsPbI3−xBrx thin films for efficient pure red perovskite LEDs. In the fabricated CsPbI3−xBrx thin film, the fluorine polymer plays a crucial role in confining CsPbI3−xBrx crystal size at the nanoscale and the small amino acid molecule acts as a passivation agent to reduce the trap‐state density. Under this synergetic effect, a uniform CsPbI3−xBrx thin film with a high photoluminescence quantum yield up to 40% can be obtained to fabricate an efficient pure red perovskite LED with a maximum external quantum efficiency of 4.5% and a maximum brightness of 3100 cd m−2. The reported synergistic regulation strategy will open a new avenue to fabricate efficient pure color CsPbX3 perovskite LEDs.
A chemically regulated strategy using poly(vinylidene fluoride‐cohexafluoropropylene) (PVDF‐HFP) and L‐Arginine (L‐Arg) to prepare a high‐quality pure red emissive CsPbI3−xBrx thin film with photoluminescence quantum yield of 40% is reported. An efficient pure red perovskite LED based on the fabricated CsPbI3−xBrx thin film achieves a maximum external quantum efficiency of 4.5% and a maximum brightness of 3100 cd m−2.
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