Red polymer light-emitting devices based on an oxadiazole-functionalized europium(III) complex

A novel tris(dibenzoylmethanato)[5-(2-(4-tert-butylbenzenyl)-5-benzenyl-1,3,4-oxadiazole-4′)-1,10-phenanthroline]europium(III) [Eu(DBM)₃(BuOXD-Phen)] containing an electron-transporting oxadiazole-functionalized phenanthroline ligand was synthesized and characterized. Its UV–vis absorption and photoluminescence (PL), as well as the electroluminescence (EL) in polymer light-emitting devices (PLEDs) were investigated. The double-layer PLEDs with a configuration of ITO/PEDOT:PSS (50 nm)/PVK (40 nm)/PFO:PBD (30%):Eu(DBM)₃(BuOXD-Phen) (1–8 wt %) (80 nm)/Ba (4 nm)/Al (150 nm) were fabricated. Saturated red Eu³⁺ ion emission, based on the ⁵D₀ → ⁷F₂ transition, is centered at a wavelength of 614 nm with a full width at half maximum (FWHM) of 10 nm. The highest external quantum efficiency (QE_ext) of 1.26% at current density of 1.65 mA cm⁻², with a maximum brightness of 568 cd m⁻² at 137.8 mA cm⁻² was achieved from the device at 1 wt % dopant concentration.     

Effects of the concentrations of precursor and catalyst on the formation of monodisperse silica particles in sol–gel reaction

The monodispersed hybrid silica particles could be synthesized through the one-step sol–gel reaction with organosilane (3-mercaptopropyl trimethoxysilane, MPTMS) in aqueous solution. In this study, the effects of the concentrations of organosilane and the catalyst ((NH₄OH) on the formation of silica particles were investigated. For the first time we reported the successful one-step synthesis of monodisperse hybrid silica particles using organosilane chemicals in the previous study. In order to obtain better insight about the reaction processes, the silica particles were prepared in the presence of various concentrations of MPTMS and NH₄OH. On the basis of the experimental results, it was found that particle size increases as the concentration of organosilane increases. Also, as the concentration of catalyst increases, the diameter of these monodisperse particles decreases significantly. This research can contribute to a new broad avenue for the surface functionalization and hybrid material formation with various sizes.     

Lead zirconate titanate thin films on ruthenium dioxide; in situ synthesis using organometallic chemical vapor deposition

Abstract

In this paper the organometallic chemical vapor deposition (OMCVD) of RuO₂ using the precursor ruthenocene, Ru(C₅H₅)₂, will be discussed. Stoichiometric RuO₂ thin films with a specific resistivity of about 50 μΩcm were obtained both on strontium titanate and platinized silicon wafers at temperatures between 300–700°C. PbZr_0.8Ti_0.2O₃ thin films were in situ deposited onto these RuO₂ electrodes. The ferroelectric behavior of the films obtained on the RuO₂ electrodes is compared with those obtained on platinum electrodes. Attempts to deposit in-situ a RuO₂ top electrode on the PbZr_0.8Ti_0.2O₃ were unsuccessful.     

Enhanced performance of urea electro-oxidation in alkaline media on PtPdNi/C,PtNi/C,and Ni/C catalysts synthesized by one-pot reaction from organometallic precursors

In this work, one-pot synthesis of metal nanoparticles from organometallic precursors namely Pt₂(dba)₃, Pd(dba)₂ and Ni(cod)₂ employing octylamine as stabilizer and carbon Vulcan XC-72R as support was carried out to obtain Ni/C, PtNi/C, and PtPdNi/C catalysts. Transmission Electron Microscopy (TEM) analysis of the as-synthesized materials shows semi-spherical particles with good dispersion on the carbon Vulcan having sizes of 3.2, 2.5 and 2.2 nm for Ni, PtNi, and PtPdNi, respectively. X-ray diffraction (XRD) confirms the presence of Pt, Pd, and Ni FCC crystal structure and reveals the formation PtNi and PtPdNi solid solutions. Additionally, XPS Pt4f core-level spectra shown a shift to lower binding energy at the alloy formation due to the addition of nickel and palladium evidencing a solid solution. The tri-metallic PtPdNi/C catalyst exhibits better performance than PtNi/C and Ni/C catalysts toward urea oxidation reaction in alkaline conditions suggesting an activity enhancement due to the oxidized Ni species from NiOOH. Using differential electrochemical mass spectroscopy (DEMS), it has been demonstrated that species such as NH₃ (m/z = 17), CO₂ -or N₂O- (m/z = 44) and NO (m/z = 30) are generated during polarization at 4 mV s^?1. Concomitant pollution control, this study demonstrated that urea could be used as a source of protons for energy generation in fuel cells systems.     

Synthesis and Properties of Stannole-Containing Polymers by Reaction of Bis(cyclopentadienyl)titanacyclopentadiene-Containing Polymers and Tin(IV) Chloride

Polymers having bis(cyclopentadienyl)titanacyclopentadiene units in the main chain were prepared by the polymerization of a low-valent bis(cyclopentadienyl)-titanium(II) complex, generated in situ from bis(cyclopentadienyl)titanium dichloride (Cp₂TiCl₂) and n-butyllithium (2 equiv), with internal diynes such as 1,4-bis(1-hexynyl)-benzene and 4,4′-bis(1-hexynyl)biphenyl. The bis(cyclopentadienyl)titanacyclopentadiene-containing polymers were subjected to the reaction with tin(IV) chloride, followed by the treatment with methyllithium to give 1,1-dimethylstannole-containing organometallic polymers in moderate yields. The stannole containing polymers are soluble in organic solvents, whose number-average molecular weight was estimated to be 2,700–2,800 by GPC. Optical and electrochemical properties of the resulting stannole-containing polymers were studied by their UV-vis spectra and cyclic voltammetric analyses, from which they were supposed to have low LUMO energy levels.     

Growth of GaBN ternary solutions by organometallic vapor phase epitaxy

Layers of Ga_1-xB_xN with compositions from x = 0 to x = 0.07 were grown by organometallic vapor phase epitaxy on sapphire substrates using trimethylgallium, triethylboron (TEB) and NH₃ as precursors. Growth was done in the temperature range from 450 to 1000°C. The presence of boron was detected by the shift in the (0002) peak position in x-ray diffraction, by x-ray photoelectron spectroscopy, secondary ion mass spectrometry measurements, and by the changes in the band gap as measured by optical transmission. It was found that for the studied range of compositions the band gap varied from 3.4 eV for x = 0 to 3.63 eVfor x = 0.05. At certain TEB concentrations in the gas phase, the growth rate decreased abruptly, most likely because of a growth poisoning by the onset of growth of a very slow growing B-rich phase. The threshold TEB concentration for this growth poisoning decreased with increasing growth temperature; and at 1000°C, less than 1% of B could be incorporated as a result. GaBN alloys with about 7% substitutional boron were also produced by implantation of 5 × 10¹⁶ cm⁻² B ions at 60 keV into GaN, as evidenced by the shift of the band edge emission in cathodoluminescence spectra from 3.4 eV for GaN to 3.85 eV for GaBN.     

The growth and characterization of uniform Ga1-xInxAs (X ≤.25) by Organometallic VPE

Compositionally uniform Ga_1-xIn_xAs epitaxial layers with 0 ≤ x ≤ 0.2 5 have been grown by organometallic VPE on ◃100▹ GaAs substrates. Compositional uniformities of ±0.25 InAs percentage and ±5% thickness over a 3-cm long wafer have been achieved and are essentially independent of small changes in reactor geometry such as the angle of the susceptor tilt or wafer position on the susceptor. Growth has also been demonstrated at x = 0.52. The Ga_1-xIn_xAs is grown using trimethylgallium (TMGa), triethylindium (TEIn) or trimethylindium (TMIn), and trimethylarsenic (TMAs). The use of TMAs eliminates the roomtemperature gas-phase reaction between AsH₃ and either TEIn or TMIn, and allows one atmospnere pressure growth conditions to be used without any special mixing arrangements in the reactor. The comparative effects of using TEIn or TMIn as the In source are discussed in terms of crystal quality. Data on crystal composition as a function of gas phase composition and growth rate as a function of composition are presented, and n doping and carrier mobilities and p doping of Ga_.80In_.20As ars characterized. The vapor pressure of TMIn at 0°C is determined to be 0.21 mmHg.     

3D π‐Conjugated Oligothiophenes Based on Sterically Twisted Bithiophene Nodes

3D conjugated architectures consisting of short oligothiophene chains attached to a connecting node formed by a sterically twisted bithiophenic system have been synthesized by various combinations of bromination and organometallic couplings. The analysis of the electronic properties of these systems by UV‐vis absorption spectroscopy and cyclic voltammetry shows that the effective conjugation length depends on the twist angle in the central bithiophene node and on the number, length, and composition of the conjugated branches. A first evaluation of the potential of this new class of compounds for the realization of organic solar cells has been carried out. To this end two prototype bulk heterojunctions based on two representative compounds as donors and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) as acceptor have been realized. A short‐circuit current density of 1.33 mA cm^–2 and a power conversion efficiency of 0.20 % have been measured under AM 1.5 (air‐mass 1.5) simulated solar irradiation.