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.

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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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The chemical properties of as well as routes to the formation of methylgallium(III) compounds in aqueous acidic solutions and in other protic solvents have been investigated. Aqueous perchloric acid solutions of Me2GaC104 at room temperature are surprisingly resistant to hydrolytic cleavage of the gallium-carbon bond. Only 14% of the available methyl groups of Me2GaC104 when dissolved in 0.0171 M HC104 are converted to CH4 after a 3-month time period. In contrast, Me2GaC104 undergoes a significantly faster methyl-transfer reaction with Ga(C104)3 in aqueous HC104 solution to form MeGa2+(aq) which in turn hydrolyzes to form Ga3+(aq) and methane. Approximately 36% of the initially available methyl groups form CH4 in 3 months. The dimethylgallium cation also methylates Hg2+(aq) to form MeGa2+(aq) and MeHg+(aq) in aqueous solution, but Me2Ga+(aq) does not react with Al3+(aq), Zn2+(aq), or Na+(aq). In a second series of experiments the methylation of gallium(III) by Me2Co(BDMl,3pn) (BDMl,3pn = \NyN -propane-1,3-diyl[bis(biacetyl monooxime imino)]}) was investigated in ethanol and acetone solutions by using UV titration and NMR data. The observed stoichiometry of the reaction requires 1 mol of Ga(C104)3 for every 2 mol of Me2Co(BDMl,3pn). The identified products are Me2Ga+ and MeCo-(BDMl,3pn)+. In contrast, gallium(III) is not methylated by methylcobalamin in aqueous solution.

We demonstrate efficient white and non‐white hybrid OLED devices operating by a triplet harvesting mechanism to create light. Triplet excited states are generated in a blue fluorescent light‐emitting layer (LEL) and utilized upon their diffusion to the phosphorescent LEL(s). At 1000 cd/m2 a blue/yellow hybrid OLED device shows external quantum efficiency (EQE) of 13.6%, 3.8 V, 30.1 lm/W, and excellent color characteristics suitable for display application. Performance of non‐white‐emitting hybrids, RGB white, and a tandem hybrid device is discussed. The triplet harvesting mechanism in all hybrid devices was verified by several experimental methods (spectral analysis, time‐resolved electroluminescence (EL), magnetic field effect on EL).

In this paper, we describe a new class of highly efficient electron‐transporting materials evaluated using basic and advanced organic light‐emitting diode (OLED) device structures. Data collected showed that the new class of materials provides higher device efficiency with lower operating drive voltage resulting in lower power‐consuming devices. Competitive device lifetimes were also observed with some device structures showing significant improvements for the new materials. The data presented in this paper show that the advancements in efficiency and drive voltage can be realized in blue and red devices.