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  • 1.
    Mindemark, Jonas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Tang, Shi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Jia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kaihovirta, Nikolai
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brandell, Daniel
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    High-Performance Light-Emitting Electrochemical Cells by Electrolyte Design2016Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, nr 8, s. 2618-2623Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polymer light-emitting electrochemical cells (LECs) are inherently dependent on a suitable electrolyte for proper function. Here, we design and synthesize a series of alkyl carbonate-capped star-branched oligoether-based electrolytes with large electrochemical stability windows, facile ion release, and high compatibility with common light-emitting materials. LECs based on such designed electrolytes feature fast turn-on, a long operational lifetime of 1400 h at >100 cd m(-2) and a record-high power conversion efficiency of 18.1 lm W-1, when equipped with an external outcoupling film.

  • 2. Mone, Mariza
    et al.
    Tang, Shi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Murto, Petri
    Abdulahi, Birhan A.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Jia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mammo, Wendimagegn
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Ergang
    Star-Shaped Diketopyrrolopyrrole-Zinc Porphyrin that Delivers 900 nm Emission in Light-Emitting Electrochemical Cells2019Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, nr 23, s. 9721-9728Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development and application of a deep near-infrared (NIR) emitting star-shaped diketopyrrolopyrrole–Zn-porphyrin compound, ZnP(TDPP)4, is reported. The structure, conjugation, and planarity of the porphyrin compound were carefully tuned by molecular design, which resulted in a low-energy photoluminescence peak at 872 nm. The ZnP(TDPP)4 compound was employed as the emissive guest in light-emitting electrochemical cells (LECs), which also comprised the conjugated polymer poly[1,3-bis(2-ethylhexyl)-5-(5-(6-methyl-4,8-bis(5-(tributylsilyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophen-2-yl)thiophen-2-yl)-7-(5-methylthiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione] (PBDTSi-BDD) as the majority host, an ionic liquid as the electrolyte, and two air-stabile electrodes. These systematically optimized host–guest LECs featured a peak electroluminescence at 900 nm, which was delivered at a significant radiance of 36 μW/cm2 and at a low drive voltage of 3.8 V. It is notable that this is the most redshifted NIR emission attained from an LEC device to date, and as such, this work introduces Zn porphyrins as a sustainable and tunable option for emerging emissive NIR applications.

  • 3.
    Nguyen, Anh Mai
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nguyen, Thanh Duc
    Irgum, Knut
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sizeable Macroporous Monolithic Polyamide Entities Prepared in Closed Molds by Thermally Mediated Dissolution and Phase Segregation2008Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, nr 19, s. 6244-6247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simple method is presented for the preparation of macroporous monoliths from an aliphatic polyamide in closed molds, based on swelling/dissolution in benzyl alcohol at elevated temperature, followed by precipitation into a continuous monolithic structure by cooling the solution below the upper critical solution temperature. Subsequent removal of the solvent led to the formation of rigid macroporous nylon monoliths with a continuous and evenly spaced macropore system. The intended use is as supports for flow-through systems, where efficient mass transport at low flow resistance is the key optimization criterion.

  • 4.
    Sharifi, Tiva
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Materials Science and Nanoengineering, Rice University, Houston, Texas 77005, United States.
    Yazdi, Sadegh
    Costin, Gelu
    Apte, Amey
    Coulter, Gabriel
    Tiwary, Chandrashekar
    Ajayan, Pulickel M.
    Impurity-Controlled Crystal Growth in Low-Dimensional Bismuth Telluride2018Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, nr 17, s. 6108-6115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Topological insulators, such as layered Bi2Te3, exhibit extraordinary properties, manifesting profoundly only at nanoscale thicknesses. However, it has been challenging to synthesize these structures with controlled thicknesses. Here, control over the thickness of solvothermally grown Bi2Te3 nanosheets is demonstrated by manipulating the crystal growth through select and controlled impurity atom addition. By a comprehensive analysis of the growth mechanism and intentional addition of Fe impurity, we demonstrate that the nucleation and growth of few-layer nanosheets of Bi2Te3 can be stabilized in solution. Via optimization of the Fe concentration, nanosheets thinner than 6 nm, and as thin as 2 nm, can be synthesized. Such thicknesses are smaller than the anticipated critical thickness for the transition of topological insulators to the quantum spin Hall regime.

  • 5.
    Siebeneichler, Stefanie
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, Stockholm, Sweden.
    Ovchinnikov, Alexander
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, Stockholm, Sweden.
    Sheptyakov, Denis
    Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen, Switzerland.
    Mudring, Anja-Verena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, Stockholm, Sweden; Intelligent Advanced Materials, Department of Biological & Chemical Engineering and iNANO, Aarhus University, Aarhus C, Denmark.
    Making a hedgehog spin-vortex state possible: geometric frustration on a square lattice2024Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 36, nr 8, s. 3546-3554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetic materials with noncollinear spin arrangements are of considerable interest owing to their potential use in emerging computational technologies and memory devices. Competing magnetic interactions, i.e., magnetic frustration, are one of the main origins of noncollinear magnetic structures. While frustrated systems have been mainly studied among magnetic insulators, combining magnetic frustration with electrical conductivity can allow simultaneous charge and spin manipulation, which is crucial for the design of electronic devices. Here, we present a new intermetallic solid solution LaMn2-xAu4+x, whose crystal structure accommodates magnetically frustrated Mn square nets. Powder neutron diffraction and first-principles analysis provide evidence that the metallic LaMn2-xAu4+x phase can host the frustration-driven hedgehog spin-vortex crystal─a rare noncollinear magnetic state, which was previously exclusively observed for iron pnictides.

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  • 6.
    Tang, Shi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mindemark, Jonas
    Department of Chemistry − Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Araujo, Carlos Moyses Graca
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Brandell, Daniel
    Department of Chemistry − Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. ludvig.edman@physics.umu.se.
    Identifying Key Properties of Electrolytes for Light-Emitting Electrochemical Cells2014Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, nr 17, s. 5083-5088Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrolyte is a key component in light-emitting electrochemical cells (LECs), as it facilitates in situ electrochemical doping and associated attractive device features. LiCF3SO3 dissolved in hydroxyl-capped trimethylolpropane ethoxylate (TMPE-OH) constitutes an electrolyte with which we have attained high stability and efficiency for polymer LECs, but the turn-on time of such devices is unfortunately slow. By replacing hydroxyl with methoxy as the TMPE end-group, we produced LECs with a desired combination of high efficiency, good stability, and fast turn-on time. Specifically, we showed that the turn-on time to high luminance (300 cd/m(2)) at a current density of 7.7 mA/cm(2) is lowered from 1740 to 16 s, that the efficiency is improved by similar to 20%, and that the other device properties are either maintained or improved. In a parallel modeling and experimental effort, we demonstrated that the faster kinetics following the shift in the TMPE end-group is attributed to a marked decrease in the level of both inter- and intramolecular interactions of the electrolyte, as manifested in a lowered electrolyte viscosity, faster ion transport, and more facile ion release during doping.

  • 7.
    Tang, Shi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Murto, Petri
    Xu, Xiaofeng
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Wang, Ergang
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Intense and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells Comprising a Metal-Free Indacenodithieno[3,2-b]thiophene-Based Copolymer as the Single Emitter2017Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, nr 18, s. 7750-7759Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the synthesis, characterization, and application of a series of metal-free near-infrared (NIR) emitting alternating donor/acceptor copolymers based on indacenodithieno[3,2-b]thiophene (IDTT) as the donor unit. A light-emitting electrochemical cell (LEC), comprising a blend of the copolymer poly[indacenodithieno[3,2-b]thiophene-2,8-diyl-alt-2,3-diphenyl-5,8-di(thiophen-2-y1)- quinoxaline-5,5'-diy1] and an ionic liquid as the single-layer active material sandwiched between two air-stable electrodes, delivered NIR emission (lambda(peak) = 705 nm) with a high radiance of 129 mu W/cm(2) when driven by a low voltage of 3.4 V. The NIR-LEC also featured good stress stability, as manifested in that the peak NIR output from a nonencapsulated device after 24 h of continuous operation only had dropped by 3% under N-2 atmosphere and by 27% under ambient air. This work accordingly introduces IDTT-based donor/acceptor copolymers as functional metal-free electroluminescent materials in NIR-emitting devices and also provides guidelines for how future NIR emitters should be designed for further improved performance.

  • 8. Tumanov, Nikolay A.
    et al.
    Roedern, Elsa
    Lodziana, Zbigniew
    Nielsen, Dorrit B.
    Jensen, Torben R.
    Talyzin, Alexandr V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Cerny, Radovan
    Chernyshov, Dmitry
    Dmitriev, Vladimir
    Palasyuk, Taras
    Filinchuk, Yaroslav
    High-Pressure Study of Mn(BH4)(2) Reveals a Stable Polymorph with High Hydrogen Density2016Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, nr 1, s. 274-283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-pressure behavior of alpha-Mn(BH4)(2) was studied up to 29.4 GPa in diamond anvil cells using powder Xray diffraction combined with DFT calculations and Raman spectroscopy, and two new polymorphs were discovered. The first polymorph, delta-Mn(BH4)(2), forms near 1 GPa and is isostructural to the magnesium analogue delta-Mg(BH4)(2). This polymorph is stable upon decompression to ambient conditions and can also be obtained by compression of alpha-Mn(BH4)(2) in a large-volume steel press as well as by high-energy ball milling. It shows a high volumetric density of hydrogen of 125 g H-2/L at ambient conditions. delta-Mn(BH4)(2) was refined in the space group I4(1)/acd with the cell parameters a = 7.85245(6), c = 12.1456(2) angstrom, and V = 748.91(1) angstrom(3) at ambient conditions; it can also be described in a stable P-4n2 superstructure. Its thermal stability was studied by in situ X-ray powder diffraction and thermal analysis coupled with mass-spectroscopy. delta-Mn(BH4)(2) transforms back to alpha-Mn(BH4)(2) upon heating in the temperature range of 67-109 degrees C in Ar (1 bar) or H-2 (100 bar) atmosphere, and a decomposition is initiated at 130 degrees C with the release of hydrogen and some diborane. Mn(BH4)(2) undergoes a second phase transition to delta'-Mn(BH4)(2) in the pressure range of 8.6-11.8 GPa. delta'-phase is not isostructural to the second high-pressure phase of Mg(BH4)(2), and its structure was determined in the root 2a X c supercell compared to the delta-phase and refined in the space group Fddd with a = 9.205(17), b = 9.321(10), c = 12.638(15) angstrom, and V = 1084(3) angstrom(3) at 11.8 GPa. Equations of state were determined for alpha- and delta-Mn(BH4)(2).

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