We demonstrate highly efficient white and nonwhite hybrid organic light-emitting diodes (OLEDs) in which singlet and triplet excited states, generated in the recombination zone, are utilized by fluorescence and phosphorescence, respectively. The excited states are formed at a blue fluorescent light-emitting layer (LEL), and the triplets diffuse through a spacer layer to one or more phosphorescent LEL(s). A key feature enabling the triplet diffusion in such OLEDs is the use of a blue fluorescent emitter with triplet energy above, or not much below, that of the fluorescent host. Additional material properties required for triplet harvesting are outlined. At 1000 cd/m2 a blue and yellow harvesting OLED shows 13.6% external quantum efficiency, 3.8 V, 30.1 lm/W, and color characteristics suitable for display application. High-efficiency harvesting R+G+B white, and B+G and B+R nonwhite OLEDs are also demonstrated. The triplet-harvesting mechanism was verified in all devices by physical methods including spectral analysis, time-resolved electroluminescence, magnetic field effect, and electron paramagnetic resonance.
The organogallium compound, Me2Ga(CsHs) has been observed to react at room temperature or below with primary and secondary amines and phosphines to form[Me2GaPPh2]2 and cyclopentadiene. All new compounds have been fully characterized by their melting points, partial elemental analyses (C and H), 1HNMR, 3IPNMR (as appropriate), and IR spectroscopic data, and cryoscopic molecular weight studies. The compound [Me2-GaP(Me)(Ph)J3 crystallizes in the trigonal space group R3 with a = 16.526(5) A, c = 10.242(2) A,V = 2421(1) A3, and Z = 3 (trimeric molecules). The molecule contains a GasP3ringin the chair conformation with phenyl groups in axial positions. The Ga-P distances range from 2.407-(4) to 2.413(6) A.Compounds of the type R2MEIV2 ( = group 13 element, E = group 15 element) are being investigated as single-source precursors for the preparation of group 13-15 materials.2 The best precursors should be volatile liquids which can be prepared in very high purity. The typical synthetic routes to these types of compounds are either hydrocarbon elimination reactions or metathesis reactions. The major source of impurities in precursors prepared by elimination reactions originates with the high temperatures needed to initiate the elimination reaction between the pure starting materials, the organo group 13 compound, and the group 15 compound. elimination mr3 + HER'2 -R2MER'2 + RH reaction Typically, elimination reactions in gallium-nitrogen systems3-5 require 100-130 °C whereas gallium-phosphorus compounds4,5 need 110-150 °C. For example, the compounds [Me2GaNH2l3,3 [Me2GaN(H)(Me)]3,3 ß2-GaNMe2,3 [Me2GaN(H)(t-Bu)]2,4 and (Me2GaNPh2)25 were prepared from the neat reagents, GaMes, and the corresponding amine, at 90, 125, 125, 110, and 120 °C, respectively, whereas (Me2GaNHPh)2,6 [Me2GaN (H) Ad] 26 (Ad = 1-adamantyl), [Me2GaN(H)Dipp]26 (Dipp = 2,6--Pr2C6H3) were formed from GaMea and the corresponding amine in refluxing toluene (bp 110 °C). The gallium-(1) (a) State University of New York at Buffalo, (b) University of Delaware.
Self-aggregation of organic pigment nanoparticles in organic solvent produces poor quality thin-film coatings. The nonuniformity of surface layers produced by dense aggregates within films of nanopigments can be detrimental for light transmission. Formulating dispersions composed of an organic pigment and an organic solvent with minimized aggregation must be achieved for use as precursors for high-performance optical thin-films. The goal of our investigation was to determine the influence of deaggregating dispersants with and without a surface-modifying synergist, as well as the influence of solvent polarity on the dispersion properties. The work was focused on establishing nanoparticles smaller than 50 nm in size, which is an area not broadly published for solventbased systems. A working hypothesis of using an acid-functionalized synergist capable of establishing stable acid/base ionic-pair interactions was investigated. Our work demonstrated that a synergist that incorporates acid functional groups can be combined with an amine-functionalized polymeric dispersant to form a stable organic solvent-based dispersion composed of dispersed pigment nanoparticles that also incorporate amine functional groups. Stabilizing ionic-pair interactions are proposed. The dispersion and coatings of the dispersion were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Optical properties of thin-films were evaluated from transmission spectroscopy measurements. Within this study, a correlation was established between spectral properties of coated dispersions and detected nanoparticle aggregation.
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