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Mercury Chalcogenide Nanoplateleta??Quantum Dot Heterostructures as a New Class of Continuously Tunable Bright Shortwave Infrared Emitters
摘要： Despite broad applications in imaging, energy conversion and telecommunications, there are few nanoscale moieties that emit light efficiently in the shortwave infrared (SWIR, 1000-2000 nm or 1.24-0.62 eV). We report quantum confined mercury chalcogenide (HgX, X=Se, Te) nanoplatelets (NPLs) can be induced to emit bright (QY >30%) and tunable (900-1500+ nm) infrared emission from attached quantum dot (QD) “defect” states. We demonstrate near unity energy transfer from NPL to these QDs, which completely quench NPL emission and emit with high QY through the SWIR. This QD defect emission is kinetically tunable, enabling controlled mid-gap emission from NPLs. Spectrally resolved photoluminescence demonstrates energy dependent lifetimes, with radiative rates 10-20 times faster than their PbX analogs in the same spectral window. Coupled with their high quantum yield, mid-gap emission HgX dots on HgX NPLs provides a potential platform for novel optoelectronics in the SWIR.
关键词： nanoplatelets,shortwave infrared,mercury chalcogenide,optoelectronics,quantum dots
更新于2025-09-23 15:19:57
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Long Range Energy Transfer in Self-Assembled Stacks of Semiconducting Nanoplatelets
摘要： Fluorescent emitters like ions, dye molecules or semiconductor nanoparticles are widely used in opto-electronic devices, usually within densely-packed layers. Their luminescence properties can then be very different from when they are isolated, because of short-range interparticle interactions such as F?rster resonant energy transfer (FRET). Understanding these interactions is crucial to mitigate FRET-related losses and could also lead to new energy transfer strategies. Exciton migration by FRET hopping between consecutive neighbor fluorophores has been evidenced in various systems but was generally limited to distances of tens of nanometers and involved only a few emitters. Here we image self-assembled linear chains of CdSe nanoplatelets (colloidal quantum wells) and demonstrate exciton migration over 500-nm distances, corresponding to FRET hopping over 90 platelets. By comparing a diffusion-equation model to our experimental data, we measure a (1.5 ps)-1 FRET rate, much faster than all decay mechanisms, so that strong FRET-mediated collective photophysical effects can be expected.
关键词： nanoplatelets,exciton transfer,self-assembly,fluorescence microscopy,FRET
更新于2025-09-23 15:19:57
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Nanoplatelet-Based Light-Emitting Diode and Its Use in All-Nanocrystal LiFi-like Communication
摘要： Since colloidal nanocrystals (NCs) were integrated as green and red sources for LCD displays, the next challenge for quantum dots has been their use in electrically driven light emitting diodes (LEDs). Among various colloidal nanocrystals, nanoplatelets (NPLs) appeared as promising candidates for light emitting devices because their two-dimensional shape allows a narrow luminescence spectrum, directional emission and high light extraction. To reach high quantum efficiency it is critical to grow core/shell structures. High temperature growth of the shells seems to be a better strategy than previously reported low temperature approaches to obtain bright NPLs. Here, we synthesize CdSe/CdZnS core/shell NPLs whose shell alloy content is tuned to optimize the hole injection in the LED structure. The obtained LED has exceptionally low turn-on voltage, long-term stability (>3100 h at 100 Cd.m-2), external quantum efficiency above 5% and luminance up to 35000 cd.m-2. We study the low-temperature performance of the LED and find that there is a delay of droop in terms of current density as temperature decreases. In the last part of the paper, we design a large LED (56 mm2 emitting area) and test its potential for LiFi-like communication. In such approach, the LED is not only a lightning source but also used to transmit a communication signal to a PbS quantum dot solar cell used as a broad band photodetector. Operating conditions compatible with both lighting and information transfer have been identified. This work paves the way toward an all nanocrystal-based communication setup.
关键词： efficiency droop,nanoplatelets,electronic transport,light emitting diode,nanocrystal-based communication
更新于2025-09-23 15:19:57
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Prolonged Lifetime in Nanocrystal Light-Emitting Diodes Incorporating MoS <sub/>2</sub> -Based Conjugated Polyelectrolyte Interfacial Layer as an Alternative to PEDOT:PSS
摘要： Colloidal semiconductor nanocrystals (NCs), and recently nanoplatelets (NPLs), owing to their efficient and narrowband luminescence, are considered as frontier materials for the light-emitting diode (LED) technology. NC-LEDs typically incorporate interfacial layers as charge regulators to ensure charge balancing and high performance. In this communication, we show the prolongation of the lifetime of multilayer solution-processed NC-LEDs by combining a self-doped conductive conjugated polyelectrolyte and exfoliated molybdenum disulfide (MoS2) flakes as an alternative to PEDOT:PSS. The ink features a neutral pH and a tunable hydrophobicity that mainly results in a remarkable stability of LEDs, using CdSe/CdZnS NPLs.
关键词： di-chalcogenides,colloidal nanoplatelets,interfacial layers,light-emitting devices,conjugated polyelectrolytes
更新于2025-09-23 15:19:57
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Influence of morphology on the blinking mechanisms and the excitonic fine structure of single colloidal nanoplatelets
摘要： Colloidal semiconductor nanoplatelets with a similar electronic structure as quantum wells have recently emerged as exciting materials for optoelectronic applications. Here we investigate how morphology affects important photoluminescence properties of single CdSe and core/shell CdSe/CdZnS nanoplatelets. By analyzing photoluminescence intensity-lifetime correlation and second-order photon correlation results, we demonstrate that, irrespective of the morphology, Auger recombination plays only a minor role in dictating the blinking behavior of the nanoplatelets. We find that a rough shell induces additional non-radiative channels presumably related to defects or traps of an imperfect shell. Furthermore, polarization-resolved spectroscopy analysis reveals exciton fine-structure splitting of the order of several tens of meV in rough-shell nanoplatelets at room temperature, which is attributed to exciton localization and is substantiated by theoretical calculations taking into account the nanoplatelet shape and electron–hole exchange interaction.
关键词： exciton fine structure,photoluminescence,nanoplatelets,blinking,Auger recombination
更新于2025-09-19 17:15:36
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P-9.11: Synthesis and optical properties of CdSe <sub/>x</sub> S <sub/>1-x</sub> nanomaterials with different morphologies
摘要： The optical properties of colloidal nanometer quantum dots, including fluorescence peak position, fluorescence peak width, fluorescence quantum yield, fluorescence attenuation channel, fluorescence scintillation and brightness of single quantum dots, are determined by the properties of Exciton states, and the properties of Exciton states are closely related to their structure. During the synthesis of CdSexS1-x Nanomaterials, a series of different morphologies are obtained by controlling the reaction solvent, reaction temperature, reaction time, type and concentration of the reaction ligand and the precursor type CdSeXS1-x nanomaterial.
关键词： CdSe,Nanoplatelets,Nanorods,Quantum Dots
更新于2025-09-19 17:15:36
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Robust Polymer Matrix Based on Isobutylene (Co)Polymers for Efficient Encapsulation of Colloidal Semiconductor Nanocrystals
摘要： We introduce new oxygen- and moisture-proof polymer matrices based on polyisobutylene (PIB) and its block copolymer with styrene (poly(styrene-block-isobutylene-block-styrene), PSt-b-PIB-b-PSt) for encapsulation of colloidal semiconductor nanocrystals. In order to prepare transparent and processable composites, we developed a special procedure of the nanocrystal surface engineering including ligand exchange of parental organic ligands to inorganic species followed by attachment of specially designed short-chain PIB functionalized with amino-group (PIB-NH2). The latter provides excellent compatibility of the particles with the polymer matrices. As colloidal nanocrystals, we chose CdSe nanoplatelets (NPLs), since they possess a large surface and thus are very sensitive to the environment, in particular in terms of their limited photostability. The encapsulation strategy is quite general and can be applied to a wide variety of semiconductor nanocrystals, as demonstrated on the example of PbS quantum dots. All obtained composites exhibited excellent photostability being tested in a focus of a powerful white-light source, as well as exceptional chemical stability in a strongly acidic media. We compared these properties of the new composites with those of widely used polyacrylate based materials, demonstrating the superiority of the former. The developed composites are of particular interest for application in optoelectronic devices, such as color-conversion light emitting diodes (LEDs), laser diodes, luminescent solar concentrators, etc.
关键词： photoluminescence,nanocrystals-in-polymer composites,lead sulfide quantum dots,semiconductor nanocrystals,isobutylene (co)polymers,cadmium selenide nanoplatelets,photostability,chemical stability
更新于2025-09-19 17:15:36
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Ultrahigh-efficiency aqueous flat nanocrystals of CdSe/CdS@Cd <sub/>1?x</sub> Zn <sub/>x</sub> S colloidal core/crown@alloyed-shell quantum wells
摘要： Colloidal semiconductor nanoplatelets (NPLs) are highly promising luminescent materials owing to their exceptionally narrow emission spectra. While high-efficiency NPLs in non-polar organic media can be obtained readily, NPLs in aqueous media suffer from extremely low quantum yields (QYs), which completely undermines their potential, especially in biological applications. Here, we show high-efficiency water-soluble CdSe/CdS@Cd1?xZnxS core/crown@shell NPLs formed by layer-by-layer grown and composition-tuned gradient Cd1?xZnxS shells on CdSe/CdS core/crown seeds. Such control of shell composition with monolayer precision and effective peripheral crown passivation, together with the compact capping density of short 3-mercaptopropionic acid ligands, allow for QYs reaching 90% in water, accompanied by a significantly increased photoluminescence lifetime (～35 ns), indicating the suppression of nonradiative channels in these NPLs. We also demonstrate the controlled attachment of these NPLs without stacking at the nanoscale by taking advantage of their 2D geometry and hydrophilicity. This is a significant step in achieving controlled assemblies and overcoming the stacking process, which otherwise undermines their film formation and performance in optoelectronic applications. Moreover, we show that the parallel orientation of such NPLs achieved by the controlled attachment enables directed emission perpendicular to the surface of the NPL films, which is highly advantageous for light extraction in light-emitting platforms.
关键词： nanoplatelets,quantum yield,core/crown@shell,aqueous media,directed emission
更新于2025-09-19 17:15:36
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Nonradiative Energy Transfer between Thickness-Controlled Halide Perovskite Nanoplatelets
摘要： Despite showing great promise for optoelectronics, the commercialization of halide perovskite nanostructure-based devices is hampered by inefficient electrical excitation and strong exciton binding energies. While transport of excitons in an energy-tailored system via F?rster resonance energy transfer (FRET) could be an efficient alternative, halide ion migration makes the realization of cascaded structures difficult. Here, we show how these could be obtained by exploiting the pronounced quantum confinement effect in two-dimensional CsPbBr3-based nanoplatelets (NPls). In thin films of NPls of two predetermined thicknesses, we observe an enhanced acceptor photoluminescence (PL) emission and a decreased donor PL lifetime. This indicates a FRET-mediated process, benefitted by the structural parameters of the NPls. We determine corresponding transfer rates up to kFRET = 0.99 ns?1 and efficiencies of nearly ηFRET = 70%. We also show FRET to occur between perovskite NPls of other thicknesses. Consequently, this strategy could lead to tailored energy cascade nanostructures for improved optoelectronic devices.
关键词： nanoplatelets,quantum confinement,FRET,halide perovskite,optoelectronics
更新于2025-09-19 17:13:59
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Shape-Controlled Synthesis of Copper Indium Sulfide Nanostructures: Flowers, Platelets and Spheres
摘要： Colloidal semiconductor nanostructures have been widely investigated for several applications, which rely not only on their size but also on shape control. CuInS2 (often abbreviated as CIS) nanostructures have been considered as candidates for solar energy conversion. In this work, three-dimensional (3D) colloidal CIS nanoflowers and nanospheres and two-dimensional (2D) nanoplatelets were selectively synthesized by changing the amount of a sulfur precursor (tert-dodecanethiol) serving both as a sulfur source and as a co-ligand. Monodisperse CIS nanoflowers (~15 nm) were formed via the aggregation of smaller CIS nanoparticles when the amount of tert-dodecanethiol used in reaction was low enough, which changed towards the formation of larger (70 nm) CIS nanospheres when it significantly increased. Both of these structures crystallized in a chalcopyrite CIS phase. Using an intermediate amount of tert-dodecanethiol, 2D nanoplatelets were obtained, 90 nm in length, 25 nm in width and the thickness of a few nanometers along the a-axis of the wurtzite CIS phase. Based on a series of experiments which employed mixtures of tert-dodecanethiol and 1-dodecanethiol, a ligand-controlled mechanism is proposed to explain the manifold range of the resulting shapes and crystal phases of CIS nanostructures.
关键词： nanoflowers,nanospheres,tert-dodecanethiol,nanoplatelets,CuInS2
更新于2025-09-16 10:30:52