By introducing tridentate Schiff base ligands, a binuclear gallium complex with mixed ligands, bis(salicylidene-o-aminophenolato)-bis(8-quinolinolato)-bis-gallium(III) [Ga(2)(saph)(2)q(2)], has been synthesized and structurally characterized by single-crystal X-ray crystallography. Crystal data for C(44)H(30)Ga(2)N(4)O(6) are as follows: space group, triclinic, P; a = 11.357(3) A, b = 12.945(3) A, c = 12.947(3) A, alpha = 103.461(15) degrees, beta = 100.070(7) degrees, gamma = 96.107(18) degrees, Z = 2. This complex was identified as a dimeric complex of hexacoordinated gallium with strong intermolecular and intramolecular pi-pi stacking interactions between the pyridyl/pyridyl rings. The thermal analysis showed that Ga(2)(saph)(2)q(2) can readily form a stable amorphous glass with a high glass transition temperature (T(g) = 204 degrees C), which is 27 degrees C higher than that of tris(8-hydroxyquinolinolate)aluminum (Alq(3)). In addition, a high photoluminescence efficiency (phi(PL)) of 0.318 in DMF has been demonstrated, although the central gallium atom can result in heavy-atom quenching. Organic light-emitting diodes (OLEDs) based on this complex displayed a turn-on voltage as low as 2.5 V and a high efficiency. Even at a low doping concentration of 1%, the doped Ga(2)(saph)(2)q(2) devices with 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as the dopant exhibited excellent red emission centered at 628 nm with improved durability, compared with the case of Alq(3) as the host. These distinguishing properties of Ga(2)(saph)(2)q(2) make it a good candidate as a novel electron-transporting and emitting material for OLEDs.
A binuclear aluminium(III) chelate with rigid and flexible mixed ligands has been synthesized and structurally characterized, which exhibits polymer-like molecular packing and solution-processiblity, as well as high photoluminescence quantum yield for organic light-emitting diodes (OLEDs); with this new compound as the emissive and host layer, the multi-layer OLEDs prepared via low-cost spin-coating showed encouraging performance.
Organic electrophosphorescent materials and devices are the prime focus of organic light-emitting diodes research due to their high external quantum efficiency and power efficiency. The host materials with both high triplet energy level and high thermal stability are especially formidable for blue phosphorescent emitters. Herewith we report a novel triplet host material based on fluorene, 9,9-bis(4'-carbazol-phenyl)fluorene (CPF), in which two phenyl-carbazole moieties are connected to C9 carbon of the fluorene. This compound possesses not only desirably high triplet (2.9 eV) energies, but also extremely high glass transition temperature (Tg = 165 o C) and thermal stability. By using CPF as the host material, blue-emitting phosphorescent devices exhibited much higher efficiency and longer lifetime than those with CBP host.
The discovery of the icosahedral phase (i-phase) in rapidly quenched Ti(1.6)V(0.4)Ni(1-x)Co(x) (x=0.02-0.1) alloys is described herein. The i-phase occurs in a similar amount relative to the coexisting beta-Ti phase. The electron diffraction patterns show the distinct spot anisotropy, indicating that the i-phase is metastable. The electrochemical hydrogen storage performances of these five alloy electrodes are also reported herein. The hydrogen desorption of nonelectrochemical recombination in the cyclic voltammetric (CV) response exhibits the demand for electrocatalytic activity improvement. A discharge capacity of 261.5 mA h g(-1) was measured in a Ti(1.6)V(0.4)Ni(0.96)Co(0.04) alloy electrode at 30 mA g(-1) and 303 K and it is shown that an appropriate amount of Co element addition would enhance the cycling stability at the expense of high-rate discharging ability.
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