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Cesium Lead Halide Perovskite Nanocrystals Prepared by Anion-exchange for Light-Emitting Diodes
摘要： Cesium lead halide perovskite nanocrystals (NCs) have emerged as a promising emitter for lighting and display technologies. However, the iodide containing CsPb(Br/I)3 and CsPbI3 NCs suffer from chemical and phase degradation to non-functional orthorhombic (δ) phase. To address this challenge, we developed a facile synthetic protocol for halide exchange in pristine CsPbBr3 NCs. The protocol involves change in the nucleophilicity (or basicity) of the halide ions in aqueous-organic media which acts as the driving force to facilitate the halide exchange. Our method avoids the use of additives for anion solubilization, which otherwise induces chemical instability and quench the emission. The halide exchanged CsPb(Br/I)3 and CsPbI3 NCs showed enhanced structural and optical properties, such as high phase stability and emission quantum yields up to 94.2% as compared to the NCs (of same composition) obtained from direct synthesis. In addition, we demonstrated fabrication of light emitting devices (LED) based on halide exchanged CsPb(Br/I)3 and CsPbI3 NCs. The devices showed peak external quantum efficiency (EQE) of 1.9% with a peak wavelength of 670 nm and low luminance turn-on voltage of 2.5 V.
关键词： Lead halide Perovskite,Halide exchange,Quantum dots,Nanocrystals,LED
更新于2025-09-19 17:13:59
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Ultrasonication-Assisted Ambient-Air Synthesis of Monodispersed Blue-Emitting CsPbBr3 Quantum Dots for White Light Emission
摘要： Colloidal all-inorganic perovskite CsPbBr3 nanocrystals present versatile outstanding optoelectronic properties, as well as greatly improved stability when compared with their hybrid analogues. However, the performance of blue-emitting CsPbBr3 nanocrystals is still inferior to their green counterpart. Moreover, their synthesis generally demands high temperature and inert gas environment. Synthesis of perovskite nanocrystals with high efficiency blue emission in air ambience is highly desired. In this work we demonstrate a top-down strategy for the facile synthesis of blue-emitting CsPbBr3 quantum dots (QDs) in air ambience, through cutting CsPbBr3 nanoplatelets (NPLs) into spherical QDs with the assistance of ultrasonication and hydrobromic acid (HBr) treatment. The CsPbBr3 QDs show excellent monodispersion with an average size of about 5 nm and a blue emission at 460 nm with high photoluminescence quantum yield (PL QY) of 53.2%. The key role of HBr is suggested to solubilize the inorganic cores of the NPLs and repair the surface. The CsPbBr3 QDs are used to prepare mixed phosphors emitting high quality white light.
关键词： Blue-emitting,Luminescence,Lead halide perovskite,Reprecipitation,Quantum dots,Ambient-Air synthesis
更新于2025-09-19 17:13:59
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Surface Ligands Stabilized Lead Halide Perovskite Quantum Dot Photocatalyst for Visible Light‐Driven Hydrogen Generation
摘要： Solar hydrogen conversion represents a clean and economic approach to addressing global energy and environmental issues, for which efficient photocatalysts are heavily pursued. Lead halide perovskites are promising candidates for efficient photocatalysts in solar hydrogen generation due to their attractive properties in light absorption, photogenerated charge transportation, and utilization. However, photocatalytic applications of lead halide perovskites are limited owing to their poor stability in the presence of water or other polar solvent environment. This work presents the rational control of surface ligands in achieving a good balance between stability and photocatalytic activity of CsPbBr3 quantum dots (QDs). Detailed studies reveal that the deliberate surface ligands engineering is crucial for maximizing the photocatalytic activity of CsPbBr3 QDs while maintaining good QD stability. A certain amount of surface ligands protect the CsPbBr3 QDs from decomposition in moisture during the photocatalytic reaction while still enabling efficient charge transfer for photocatalytic reactions on the surface of QDs. The well-controlled CsPbBr3 photocatalyst shows efficient visible light-driven H2 generation with outstanding stability (≥160 h).
关键词： surface ligand,lead halide perovskite,stability,photocatalysis,quantum dot
更新于2025-09-19 17:13:59
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Phonon-Mediated and Weakly Size-Dependent Electron and Hole Cooling in CsPbBr <sub/>3</sub> Nanocrystals Revealed by Atomistic Simulations and Ultrafast Spectroscopy
摘要： We combine state-of-the-art ultrafast photoluminescence and absorption spectroscopy and nonadiabatic molecular dynamics simulations to investigate charge-carrier cooling in CsPbBr3 nanocrystals over a very broad size regime, from 0.8 nm to 12 nm. Contrary to the prevailing notion that polaron formation slows down charge-carrier cooling in lead-halide perovskites, no suppression of carrier cooling is observed in CsPbBr3 nanocrystals except for a slow cooling (over ~ 10 ps) of ‘warm’ electrons in the vicinity (within ~ 0.1 eV) of the conduction band edge. At higher excess energies, electrons and holes cool with similar rates, on the order of 1 eV ps-1 carrier-1 and increasing weakly with size. Our ab initio simulations suggest that cooling proceeds via fast phonon-mediated intra-band transitions driven by strong and size-dependent electron-phonon coupling. The presented experimental and computational methods yield the spectrum of involved phonons and may guide the development of devices utilizing hot charge carriers.
关键词： electron-phonon coupling,hot carriers,nonadiabatic molecular dynamics,Charge-carrier cooling,lead-halide perovskite nanocrystal,excited-states dynamics
更新于2025-09-19 17:13:59
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Anti‐Oxidizing Radical Polymer‐Incorporated Perovskite Layers and their Photovoltaic Characteristics
摘要： A small amount of a radical-bearing redox-active polymer, poly(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl methacrylate) (PTMA), incorporated into the photovoltaic organo-lead halide perovskite layer significantly enhanced durability of both the perovskite layer and its solar cell even exposure to ambient air or oxygen. The radical PTMA polymer acted as an eliminating agent of the superoxide anion radical formed upon light-irradiation on the layer, which can react with the perovskite compound and decompose it to lead halide. A cell fabricated with the PTMA-incorporated perovskite layer and a hole-transporting polytriarylamine layer gave a photovoltaic conversion efficiency of 18.8 % (18.2 % for the control without PTMA). The photovoltaic current was not reduced in the presence of PTMA in the perovskite layer probably owing to a carrier conductivity of PTMA. The incorporated PTMA also worked as a water-repelling coating for the organo-lead halide perovskite layer, providing humidity-resistance to their.
关键词： perovskite solar cell,nitroxide radical,organo-lead halide perovskite,redox polymer,anti-oxidizing agent
更新于2025-09-11 14:15:04
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Rationalizing and Controlling the Surface Structure and Electronic Passivation of Cesium Lead Halide Nanocrystals
摘要： Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as versatile photonic sources. Their processing and luminescent properties are challenged by the lability of their surfaces, i.e. the interface of the NC core and the ligand shell. On the example of CsPbBr3 NCs, we model the nanocrystal surface structure and its effect on the emergence of trap states using density functional theory. We rationalize the typical observation of a degraded luminescence upon aging or the luminescence recovery upon post-synthesis surface treatments. The conclusions are corroborated by the elemental analysis. We then propose a strategy for healing the surface trap states and for improving the colloidal stability by the combined treatment with didodecyldimethyl ammonium bromide and lead bromide and validate this approach experimentally. This simple procedure results in robust colloids, which are both highly pure and exhibit high photoluminescence quantum yields of up to 95-98%, retained even after 3-4 rounds of washing.
关键词： trap states,didodecyldimethyl ammonium bromide,luminescence recovery,photoluminescence quantum yields,lead bromide,CsPbBr3 NCs,density functional theory,Colloidal lead halide perovskite nanocrystals,surface structure
更新于2025-09-09 09:28:46
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Binary metal zinc-lead perovskite built-in air ambient: Towards lead-less and stable perovskite materials
摘要： Organo-metal halide perovskites are promising new-generation photovoltaic materials owing to their efficient electrical/optical characteristics. Despite having high efficiency, perovskites are toxic due to the presence of lead and instable in air ambient. Therefore, the toxicity and instability call for more efforts in this area. Here, methylammonium-zinc-lead iodide (MAZn0.2Pb0.8I3) is synthesized in air ambient as lead-less and more stable perovskite material for applying as the active layer of solar cells. 1.65 eV optical band gap and 51 nm minority carrier diffusion length (Ldiff) have been obtained with the help of UV–Visible spectroscopy (UV–Vis) and steady-state photocarrier grating (SSPG) technique respectively. Structural, chemical bonding and surface studies are done by X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM) respectively. The sample has been stored in dark air ambient with average relative humidity of 45% at room temperature (27 °C) for 60 days and the properties of 60 days aged sample is investigated and compared with characteristics of 60 days aged MAPbI3. The results confirm MAZn0.2Pb0.8I3 is more stable than MAPbI3.
关键词： Lead-less organo-zinc-lead halide perovskite,Synthesis in air ambient,Stability
更新于2025-09-09 09:28:46
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Room-temperature synthesis of Mn2+-doped cesium lead halide perovskite nanocrystals via a transformation doping method
摘要： Currently, Mn2+-doped cesium lead halide perovskite nanocrystals have attracted research interests. Here, we report a novel room-temperature transformation doping method for the synthesis of Mn2+-doped CsPbCl3 and CsPb(Br/Cl)3 nanocrystals. Innovatively, the transformation of Cs4PbX6 (X=Cl, Br) phase which has no excitation emission to CsPbX3 phase which has strong luminescence was used in this mechanism. Simply injecting MnCl2 precursor into Cs4PbX6 solution could result in the full transformation of Cs4PbX6 phase to CsPbX3 phase and Mn2+-doped CsPbCl3 or CsPb(Br/Cl)3 were obtained. The basic idea for the transformation doping method is that MnCl2 can not only drive the transformation of the two structures but also Mn2+ can substitute Pb2+. In this reaction, the concentration of Mn precursor is a key influence factor. Moreover, instead of the ligand of OA, the acetic acid was used in our method. Through the adjustment of the ligand in precursor, not just the photoluminescence quantum yields of as-prepared Mn2+-doped CsPbCl3 nanocrystals were improved from 7.8 to 32.6% (Mn2+-doped CsPb(Br/Cl)3 nanocrystals even could reach to 42.7%), the nanocrystals also retained outstanding stability. We propose a combination of structure transformation and ion doping as a perovskite doping mechanism. Our doping method is a novel strategy for lead halide perovskite nanocrystals doping project and it could provide more possibilities in the future.
关键词： photoluminescence quantum yields,Cs4PbX6,Mn2+-doped cesium lead halide perovskite nanocrystals,CsPbX3,room-temperature transformation doping method
更新于2025-09-09 09:28:46
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Ellipsometry - Principles and Techniques for Materials Characterization || Spectroscopic Ellipsometry Study of Organic-Inorganic Halide: FAPbIxBr3?x Perovskite Thin Films by Two-Step Method
摘要： Spectroscopic ellipsometry (SE) was used to investigate the role of isopropyl alcohol (IPA) solvent in the synthesis of organic-lead-halide perovskite CH(NH2)2PbIxBr3?x [FAPbIxBr3?x] thin films including the effect of I/Br composition ratio by the two-step reaction of an amorphous (a-)PbIxBr2?x layer and FAIxBr1?x solution diluted in IPA. An optical dispersion model was developed to extract the complex refractive index N (=n + ik), optical transition, and film thickness of FAPbIxBr3?x perovskites by SE analysis at different I/Br composition ratio as a function of immersion time in a solution of FAIxBr1?x diluted in IPA. SE combined with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) revealed that Br incorporation into films promoted the densification of FAPbIxBr3?x perovskite network along with increased film thickness and volume fraction of void. IPA promoted film crystallization of a-PbIxBr2?x accompanied by the formation of surface roughness, grain boundaries, and voids, followed by enhanced diffusion of FAIxBr1?x into the grain boundaries/voids in the mesoporous crystallized PbIxBr2?x network. These processes contribute synergistically to the growth of the perovskite structure.
关键词： growth mechanism,two-step reaction,ellipsometry,role of isopropyl alcohol (IPA) solvent,organic-lead-halide perovskite
更新于2025-09-09 09:28:46
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Room-Temperature Synthesis of Cesium Lead Halide Perovskite Nanorods
摘要： Low-dimensional materials attract much attention because of their unique and outstanding properties in optical and electronic products, giving a promising class of materials for optoelectronic applications. A facile synthesis method of CsPbBr3 nanorods (NRs) was presented in this paper. The nanorods have a one-dimensional (1D) scale, a high photoluminescence quantum yield (PLQY, 60%) and a narrow FWHM. By tuning the ratio of organic ligands, the CsPbBr3 NRs with the diameter of less than 20 nm and length up to several hundred nanometers were obtained. Moreover, because of the quantum confinement effects, a large blue-shift have happened in PL spectra. A light-emitting diode (LED) device was fabricated with our synthesized CsPbBr3 NRs. The LED device showed a strong green emission. All of these shows the ability of halide perovskite nanocrystals for applications on photoelectron, such as optical communication, display, lightning and so on.
关键词： formation mechanism,cesium lead halide perovskite nanorods,light-emitting diode
更新于2025-09-09 09:28:46