Browsing by Subject "Iridium compounds"

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    Electronic structure of conventional slater type antiferromagnetic insulators: AIrO3 (A=Sr, Ba) perovskites
    (Institute of Physics, 2022) Koc, Husnu; Mamedov, Amirullah M.; Özbay, Ekmel
    The structural, mechanical, and electronic properties of Perovskite BaIrO3 and SrIrO3 compounds based on the density functional theory (DFT) have been examined in four different structures (C2/c, R-3m, P6_3/mmc and Pm-3m) and Pnma structure, respectively. The spin polarized generalized gradient approximation has been used for modeling exchange-correlation effects. As a result of spin polarized calculations, it has been observed that BaIrO3 compound showed magnetic properties in C2/c and R-3m structures, but not in Pm-3m and P6_3/mmc structures. SrIrO3 compound also shows magnetic properties in Pnma structure. The elastic constants have been calculated using the strain-stress method and the other related quantities (the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, sound velocities, and Debye temperature) have also been estimated. In electronic band structure calculations, while Pm-3m and P6_3/mmc structures of NaIrO3 compound are metallic and semiconductor (Eg = 1.190 eV indirect), respectively, while C2/c and R-3m structures showing magnetic properties are metallic in spin down state and semiconductor (Eg=0.992 eV indirect and Eg=0.665 eV direct, respectively) in the spin up state. The Pmna structure in the SrIrO3 compound is a semiconductor in both spin states (Eg=0.701 eV “0.632 eV” indirect in the spin up “spin down”). © 2022 Institute of Physics Publishing. All rights reserved.
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    Graded-host phosphorescent light-emitting diodes with high efficiency and reduced roll-off
    (A I P Publishing LLC, 2012) Liu, S. W.; Sun, X. W.; Demir, Hilmi Volkan
    We demonstrated graded-host phosphorescent organic light-emitting diodes with high efficiency and reduced efficiency roll-off. The emissive layer of the graded host device consists of both electron and hole transport type hosts, 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBI) and 4,4-,4- tris(Ncarbazolyl) triphenylamine, respectively, with graded composition, and the phosphorescent red emitter bis(2-phenylquinoline) (acetylacetonate) iridium(III), which wasuniformly doped into the graded hostmatrix. The graded host device shows improved quantum efficiency and power efficiency with significantly reduced efficiency rolloff as compared to the unipolar-host and double layer heterojunction host devices.