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Metal-halide perovskite light-emitting diodes (PeLEDs) have attracted great interest because of their tunable emission wavelength, narrow emission bandwidth and high external quantum efficiency. However, PeLEDs face two critical i...
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Metal-halide perovskite light-emitting diodes (PeLEDs) have attracted great interest because of their tunable emission wavelength, narrow emission bandwidth and high external quantum efficiency. However, PeLEDs face two critical issues that limit their potential applications: short device lifetime due to ion migration and low brightness due to severe Auger recombination. Here we demonstrate that both issues can be mitigated by in situ solution-grown perovskite single crystals (SCs). By minimizing the trap density using mixed cations and adding excess ammonium halides and polyvidone to the precursor, the external photoluminescence quantum yield (PLQY) of the SCs is enhanced to 28.3%, corresponding to an internal PLQY of 89.4%. Benefitting from the suppressed Auger recombination in SCs, SC-PeLEDs with a thickness of 1.5 mu m exhibit a high luminance of 86,000 cd m(-2) and a peak external quantum efficiency of 11.2%. Thanks to suppressed ion migration, the extrapolated T-50 lifetime for SC-PeLEDs reaches a value of 12,500 h at an initial luminance of 100 cd m(-2). Our results show that SC growth represents a viable route to increase the lifetime of PeLEDs for practical applications. Single-crystal perovskite LEDs exhibit reduced ion migration and Auger recombination and increased device lifetime. Perovskite single-crystals-based LEDs exhibit a maximum brightness of 86,000 cd m(-2), a peak EQE of 11.2% and T-50 lifetime of 12,500 h at an initial luminance of 100 cd m(-2).
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The Pb-free hybrid-layered-double perovskites (HLDPs) have been proposed as green and stable semiconducting materials for optoelectronic devices, but the synthesized members are still limited. Here, we report the synthesis of thre...
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The Pb-free hybrid-layered-double perovskites (HLDPs) have been proposed as green and stable semiconducting materials for optoelectronic devices, but the synthesized members are still limited. Here, we report the synthesis of three new HLDPs, (C8H20N2)(2)AgMBr8 (M = In, Sb, and Bi), by a solution method using 1,4-bis(ammoniomethyl)cyclohexane (C8H20N22+) as the organic spacing cation. All three of these HLDPs show < 100 >-oriented layered structures with Ag and In/Sb/Bi order arranged in corner-sharing octahedral layers. The first-principle calculations indicate the indirect-gap nature of (C8H20N2)(2)AgInBr8 and (C8H20N2)(2)AgSbBr8, while their Bi counterpart shows a direct band gap after considering spin-orbit coupling. The band gaps obtained by diffuse-reflectance spectroscopy are 3.11, 2.60, and 2.70 eV for M = In, Sb, and Bi, respectively. (C8H20N2)(2)AgInBr8 shows a broadband red emission centered at 690 nm, and it is mainly attributed to the self-trapped-excitons mechanism. Our results not only provide a series of new "Pb-free" HLDPs with chemical diversity but also help us to further understand the structure-property relationships of HLDP materials.
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Herein, a new organic-inorganic hybrid cuprous iodide of [(Me)(2)-DABCO]Cu6I8 was prepared and structurally characterized with a novel three-dimensional (3D) [Cu6I8](2-) framework. Significantly, this 3D cuprous iodide displays in...
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Herein, a new organic-inorganic hybrid cuprous iodide of [(Me)(2)-DABCO]Cu6I8 was prepared and structurally characterized with a novel three-dimensional (3D) [Cu6I8](2-) framework. Significantly, this 3D cuprous iodide displays infrequent broadband red-to-near-infrared light emission (600-1000 nm) stemming from the radiative recombination of self-trapped excitons.
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Chloride is extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI(3-x)Cl(x)), but its persistence and role in solution-processed materials has not yet been rationalized. Multiple...
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Chloride is extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI(3-x)Cl(x)), but its persistence and role in solution-processed materials has not yet been rationalized. Multiple-source vacuum deposition of perovskites enables a fine control over thin-film stoichiometry and allows the incorporation of chemical species irrespective of their solubility. Herein, the first example of mixed MAPbI(3-x)Cl(x) thin films prepared by three-source vacuum deposition is presented using methylammonium iodide (MAI), PbI2, and PbCl2 as precursors. The optoelectronic properties of the material are evaluated through photovoltaic and electro-/photoluminescent characterizations. Besides the very similar structural and optical properties of MAPbI(3) and MAPbI(3-x)Cl(x), an increased electroluminescence efficiency, longer photoluminescence lifetimes, as well as larger photovoltage, are observed in the presence of chloride, suggesting a reduction of nonradiative charge recombination.
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Fully-inorganic halide perovskites (HPs) have realized respectable progress in multiple optoelectronic applications. However, Cl-based fully-inorganic HPs that are ideal for ultraviolet (UV) photodetection applications in high dem...
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Fully-inorganic halide perovskites (HPs) have realized respectable progress in multiple optoelectronic applications. However, Cl-based fully-inorganic HPs that are ideal for ultraviolet (UV) photodetection applications in high demand still remain rarely explored mainly due to the poor solution processability compared with other counterparts. Here we propose a facile solution method to fabricate CsPbCl3 with not only high crystallinity but also a two dimensional (2D) morphology for efficient UV photodetection. 2D Ruddlesden-Popper perovskites (RPPs) are firstly prepared as the intermediate phase, which habitually grow into microplates owing to an intrinsic 2D structure. Then Cs+ was introduced in the form of highly soluble cesium acetate to exchange with the organic cations in the RPPs to produce 2D CsPbCl3 with preserved morphology and micron scale size. By this chemical route, the poor solubility issue can be addressed. All the procedures are conducted at room temperature in open air. The perfect band gap, high crystallinity and 2D morphology promise superior UV light sensing capability, one of the best overall performances featuring high responsivity, fast response speed, low driving voltages and good stability is obtained. This work is believed to fill in the "Cl-gap" for this promising class of material. (C) 2019 Elsevier Inc. All rights reserved.
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Replacing lead in halide perovskites is of great interest due to concerns about stability and toxicity. Recently, lead free double perovskites in which the unit cell is doubled and two divalent lead cations are substituted by a co...
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Replacing lead in halide perovskites is of great interest due to concerns about stability and toxicity. Recently, lead free double perovskites in which the unit cell is doubled and two divalent lead cations are substituted by a combination of monoand trivalent cations have been synthesized as bulk single crystals and as thin films. Here, we study stability and optical properties of all-inorganic cesium silver(I) bismuth(III) chloride and bromide nanocrystals with the double perovskite crystal structure. The cube-shaped nanocrystals are monodisperse in size with typical side lengths of 8 to 15 nm. The absorption spectrum of the nanocrystals presents a sharp peak, which we assign to a direct bismuth s-p transition and not to a quantum confined excitonic transition. Using this spectroscopic handle combined with high-resolution transmission electron microscopy (TEM) based elemental analysis, we conduct stoichiometric studies at the single nanocrystal level as well as decomposition assays in solution and observe that Ag+ diffusion and coalescence is one of the pathways by which this material degrades. Drying the nanocrystals leads to self-assembly into ordered nanocrystal solids, and these exhibit less degradation than nanocrystals in solution. Our results demonstrate that Cs2AgBiX6 (X = Cl, Br) nanocrystals are a useful model system to study structure-function relationships in the search for stable nontoxic halide perovskites.
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Halide perovskites have emerged as high-performance semiconductors for efficient optoelectronic devices, not least because of their bandgap tunability using mixtures of different halide ions. Here, temperature-dependent photolumin...
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Halide perovskites have emerged as high-performance semiconductors for efficient optoelectronic devices, not least because of their bandgap tunability using mixtures of different halide ions. Here, temperature-dependent photoluminescence microscopy with computational modelling is combined to quantify the impact of local bandgap variations from disordered halide distributions on the global photoluminescence yield in mixed-halide perovskite films. It is found that fabrication temperature, surface energy, and charge recombination constants are keys for describing local bandgap variations and charge carrier funneling processes that control the photoluminescence quantum efficiency. It is reported that further luminescence efficiency gains are possible through tailored bandgap modulation, even for materials that have already demonstrated high luminescence yields. The work provides a novel strategy and fabrication guidelines for further improvement of halide perovskite performance in light-emitting and photovoltaic applications.
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Metal halide perovskites, a class of crystalline semiconductors with unique optical and electronic properties, are emerging as potential solutions for low-cost photovoltaics and photonic sources in fields of solar cells, sensors, ...
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Metal halide perovskites, a class of crystalline semiconductors with unique optical and electronic properties, are emerging as potential solutions for low-cost photovoltaics and photonic sources in fields of solar cells, sensors, light-emitting diodes and lasers. Regardless of significant progress on device efficiency with the control over perovskite structures and film morphologies, unveiling the interface energetics and band alignment of these perovskite systems is indispensable for the performance optimization in the optoelectronic applications by grasping the photon harvest and charge transport processes. Herein we review the recent advances in the energetics of metal halide perovskite interfaces. The electronic properties of perovskite materials are addressed in terms of halide substitution, thermal annealing and substrate effects as well as trap states. The energy level alignments of interfaces between perovskite films and charge transport layers are then discussed, which is correlated to the photovoltaic properties in perovskite solar cells.
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Emerging lead halide perovskite quantum dots (QDs) have attracted great research interest relative to conventional metal chalcogenide-based QDs for applications like solar cells. Meanwhile, such a new type of solution-processable ...
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Emerging lead halide perovskite quantum dots (QDs) have attracted great research interest relative to conventional metal chalcogenide-based QDs for applications like solar cells. Meanwhile, such a new type of solution-processable inorganic QD also provides an additional platform to design high performance organic-inorganic hybrid films to maximize their device performance. Herein, we report a hybrid strategy utilizing conjugated polyelectrolyte PFN-Br and all-inorganic CsPbI3 perovskite QDs. There is an urgency to further improve the electronic coupling as well as the ambient stability of CsPbI3 QDs. Using the hybrid strategy, we demonstrated that the hydrophobic PFN-Br can well passivate the CsPbI3 QD surface to reduce defect states as well as suppress the migration of halide ions for better stability. Consequently, the hybrid PFN-Br/CsPbI3 QD solar cell delivers a champion efficiency of 15.07%, outperforming that of 13.31% in the pristine CsPbI3 QD based one. Moreover, the hybrid blend film exhibits significantly improved storage stability under ambient conditions. We believe that these results would provide a new design principle for hybrid organic-inorganic systems for high-performance optoelectronic devices.
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Perovskite quantum dots (PQDs) have gained significantattentiondue to their exceptional optical and electronic properties, renderingthem promising materials for various optoelectronic applications,such as single-junction solar cel...
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Perovskite quantum dots (PQDs) have gained significantattentiondue to their exceptional optical and electronic properties, renderingthem promising materials for various optoelectronic applications,such as single-junction solar cells because of the multiple excitongeneration effects. To improve the electrical properties of CsPbI3 PQDs, ligand engineering was explored by introducing short-chainligands to exchange the original long-chain ligands on the PQD surfaceduring the purification process. However, the short-chain ligandssuffer from low solubility in the anti-solvent, resulting in insufficientligand exchange. To address this issue, we developed an in-situ ligandexchange (ILE) strategy to promote the replacement of long-chain ligandswith short-chain ones, leading to improved surface chemistry. In thiswork, 4-methoxyphenethylammonium iodide (CH3O-PEAI) wasdemonstrated as the short-chain ligand in the ILE strategy, therebymodifying halide vacancy trap states, and promoting carrier transportationand extraction. As a result, the ILE-CsPbI3-based solarcells achieved a higher power conversion efficiency of 14.4% witha high open circuit voltage (V (OC)) of 1.23V and exceptional long-term durability due to higher hydrophobicity.
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