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- Ràfols-Ribé, Joan, et al.
(author)
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Controlling the Emission Zone by Additives for Improved Light-Emitting Electrochemical Cells
- 2022
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In: Advanced Materials. - : John Wiley and Sons Inc. - 0935-9648 .- 1521-4095. ; 34:8
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Journal article (peer-reviewed)abstract
- The position of the emission zone (EZ) in the active material of a light-emitting electrochemical cell (LEC) has a profound influence on its performance because of microcavity effects and doping- and electrode-induced quenching. Previous attempts of EZ control have focused on the two principal constituents in the active material—the organic semiconductor (OSC) and the mobile ions—but this study demonstrates that it is possible to effectively control the EZ position through the inclusion of an appropriate additive into the active material. More specifically, it is shown that a mere modification of the end group on an added neutral compound, which also functions as an ion transporter, results in a shifted EZ from close to the anode to the center of the active material, which translates into a 60% improvement of the power efficiency. This particular finding is rationalized by a lowering of the effective electron mobility of the OSC through specific additive: OSC interactions, but the more important generic conclusion is that it is possible to control the EZ position, and thereby the LEC performance, by the straightforward inclusion of an easily tuned additive in the active material. © 2022 The Authors.
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| 5. |
- Zhang, Xiaoli, et al.
(author)
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Hybrid Perovskite Light-Emitting Diodes Based on Perovskite Nanocrystals with Organic-Inorganic Mixed Cations
- 2017
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In: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 29:18
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Journal article (peer-reviewed)abstract
- Organic-inorganic hybrid perovskite materials with mixed cations have demonstrated tremendous advances in photovoltaics recently, by showing a significant enhancement of power conversion efficiency and improved perovskite stability. Inspired by this development, this study presents the facile synthesis of mixed-cation perovskite nanocrystals based on FA((1-x))Cs(x)PbBr(3) (FA = CH(NH2)(2)). By detailed characterization of their morphological, optical, and physicochemical properties, it is found that the emission property of the perovskite, FA((1-x))Cs(x)PbBr(3), is significantly dependent on the substitution content of the Cs cations in the perovskite composition. These mixed-cation perovskites are employed as light emitters in light-emitting diodes (LEDs). With an optimized composition of FA(0.8)Cs(0.2)PbBr(3), the LEDs exhibit encouraging performance with a highest reported luminance of 55 005 cd m(-2) and a current efficiency of 10.09 cd A(-1). This work provides important instructions on the future compositional optimization of mixed-cation perovskite for obtaining high-performance LEDs. The authors believe this work is a new milestone in the development of bright and efficient perovskite LEDs.
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| 6. |
- Bing, Zhao, 1990, et al.
(author)
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Unconventional Charge–Spin Conversion in Weyl-Semimetal WTe2
- 2020
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In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 32:38
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Journal article (peer-reviewed)abstract
- An outstanding feature of topological quantum materials is their novel spin topology in the electronic band structures with an expected large charge-to-spin conversion efficiency. Here, a charge-current-induced spin polarization in the type-II Weyl semimetal candidate WTe2 and efficient spin injection and detection in a graphene channel up to room temperature are reported. Contrary to the conventional spin Hall and Rashba–Edelstein effects, the measurements indicate an unconventional charge-to-spin conversion in WTe2, which is primarily forbidden by the crystal symmetry of the system. Such a large spin polarization can be possible in WTe2 due to a reduced crystal symmetry combined with its large spin Berry curvature, spin–orbit interaction with a novel spin-texture of the Fermi states. A robust and practical method is demonstrated for electrical creation and detection of such a spin polarization using both charge-to-spin conversion and its inverse phenomenon and utilized it for efficient spin injection and detection in the graphene channel up to room temperature. These findings open opportunities for utilizing topological Weyl materials as nonmagnetic spin sources in all-electrical van der Waals spintronic circuits and for low-power and high-performance nonvolatile spintronic technologies.
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| 7. |
- Fu, Pan, et al.
(author)
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Metasurface Enabled On-Chip Generation and Manipulation of Vector Beams from Vertical Cavity Surface-Emitting Lasers
- 2023
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In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; In Press
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Journal article (peer-reviewed)abstract
- Metasurface polarization optics that consist of 2D array of birefringent nano-antennas have proven remarkable capabilities to generate and manipulate vectorial fields with subwavelength resolution and high efficiency. Integrating this new type of metasurface with the standard vertical cavity surface-emitting laser (VCSEL) platform enables an ultracompact and powerful solution to control both phase and polarization properties of the laser on a chip, which allows to structure a VCSEL into vector beams with on-demand wavefronts. Here, this concept is demonstrated by directly generating versatile vector beams from commercially available VCSELs through on-chip integration of high-index dielectric metasurfaces. Experimentally, the versatility of the approach for the development of vectorial VCSELs are validated by implementing a variety of functionalities, including directional emission of multibeam with specified polarizations, vectorial holographic display, and vector vortex beams generations. Notably, the proposed vectorial VCSELs integrated with a single layer of beam shaping metasurface bypass the requirements of multiple cascaded optical components, and thus have the potential to promote the advancements of ultracompact, lightweight, and scalable vector beams sources, enriching and expanding the applications of VCSELs in optical communications, laser manipulation and processing, information encryption, and quantum optics.
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| 8. |
- Fusco, Zelio, et al.
(author)
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Nanostructured Dielectric Fractals on Resonant Plasmonic Metasurfaces for Selective and Sensitive Optical Sensing of Volatile Compounds
- 2018
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In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 30:30
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Journal article (peer-reviewed)abstract
- Advances in the understanding and fabrication of plasmonic nanostructures have led to a plethora of unprecedented optoelectronic and optochemical applications. Plasmon resonance has found widespread use in efficient optical transducers of refractive index changes in liquids. However, it has proven challenging to translate these achievements to the selective detection of gases, which typically adsorb non-specifically and induce refractive index changes below the detection limit. Here, it's shown that integration of tailored fractals of dielectric TiO2nanoparticles on a plasmonic metasurface strongly enhances the interaction between the plasmonic field and volatile organic molecules and provides a means for their selective detection. Notably, this superior optical response is due to the enhancement of the interaction between the dielectric fractals and the plasmonic metasurface for thickness of up to 1.8 μm, much higher than the evanescent plasmonic near-field (≈30 nm). Optimal dielectric–plasmonic structures allow measurements of changes in the refractive index of the gas mixture down to <8 × 10−6at room temperature and selective identification of three exemplary volatile organic compounds. These findings provide a basis for the development of a novel family of dielectric–plasmonic materials with application extending from light harvesting and photocatalysts to contactless sensors for noninvasive medical diagnostics.
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| 9. |
- Meshkian, Rahele, et al.
(author)
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W-Based Atomic Laminates and Their 2D Derivative W1.33C MXene with Vacancy Ordering
- 2018
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In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 30:21
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Journal article (peer-reviewed)abstract
- Structural design on the atomic level can provide novel chemistries of hybrid MAX phases and their MXenes. Herein, density functional theory is used to predict phase stability of quaternary i-MAX phases with in-plane chemical order and a general chemistry (W 2/3 M 2 1/3 ) 2 AC, where M 2 = Sc, Y (W), and A = Al, Si, Ga, Ge, In, and Sn. Of over 18 compositions probed, only two—with a monoclinic C2/c structure—are predicted to be stable: (W 2/3 Sc 1/3 ) 2 AlC and (W 2/3 Y 1/3 ) 2 AlC and indeed found to exist. Selectively etching the Al and Sc/Y atoms from these 3D laminates results in W 1.33 C-based MXene sheets with ordered metal divacancies. Using electrochemical experiments, this MXene is shown to be a new, promising catalyst for the hydrogen evolution reaction. The addition of yet one more element, W, to the stable of M elements known to form MAX phases, and the synthesis of a pure W-based MXene establishes that the etching of i-MAX phases is a fruitful path for creating new MXene chemistries that has hitherto been not possible, a fact that perforce increases the potential of tuning MXene properties for myriad applications.
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| 10. |
- Minotto, Alessandro, et al.
(author)
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Efficient Near-Infrared Electroluminescence at 840 nm with “Metal-Free” Small-Molecule:Polymer Blends
- 2018
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In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 30:34
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Journal article (peer-reviewed)abstract
- Due to the so-called energy-gap law and aggregation quenching, the efficiency of organic light-emitting diodes (OLEDs) emitting above 800 nm is significantly lower than that of visible ones. Successful exploitation of triplet emission in phosphorescent materials containing heavy metals has been reported, with OLEDs achieving remarkable external quantum efficiencies (EQEs) up to 3.8% (peak wavelength > 800 nm). For OLEDs incorporating fluorescent materials free from heavy or toxic metals, however, we are not aware of any report of EQEs over 1% (again for emission peaking at wavelengths > 800 nm), even for devices leveraging thermally activated delayed fluorescence (TADF). Here, the development of polymer light-emitting diodes (PLEDs) peaking at 840 nm and exhibiting unprecedented EQEs (in excess of 1.15%) and turn-on voltages as low as 1.7 V is reported. These incorporate a novel triazolobenzothiadiazole-based emitter and a novel indacenodithiophene-based transport polymer matrix, affording excellent spectral and transport properties. To the best of knowledge, such values are the best ever reported for electroluminescence at 840 nm with a purely organic and solution-processed active layer, not leveraging triplet-assisted emission.
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