Density functional theory analysis of a mixed‐ligand iridium compound for multi‐color organic light‐emitting diodes |
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| Authors: | Silviu Polosan Tahsin J. Chow Taiju Tsuboi |
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| Affiliation: | 1. Faculty of Engineering, Kyoto Sangyo University, Kamigamo, Kita‐ku, Kyoto 603‐8555, Japan;2. National Institute for Materials Physics, Bucharest‐Magurele 077125, Romania;3. Institute of Chemistry, Academia Sinica, 115 Taipei, Taiwan, Republic of China |
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| Abstract: | Electronic states and their energies are calculated for a mixed‐ligand Ir(III) compound, (5‐chloro‐8‐hydroxyquinoline) bis(2‐phenylpyridyl) iridium (called IrQ(ppy)2‐5Cl) using time‐dependent density functional theory (TDDFT) calculations and are compared with the experimental result. A good agreement is obtained between the calculated and measured absorption spectra. The d‐πQ* molecular orbital transition gives the lowest‐energy triplet state absorption band. Its energy is estimated as 1.84 eV (671 nm), which is close to the absorption band position of 1.86 eV (666 nm) observed for IrQ(ppy)2‐5Cl doped in 4,4′‐N,N′‐dicarbazole‐biphenyl (CBP) host and of 1.88 eV (660 nm) observed for IrQ(ppy)2‐5Cl doped in polystyrene (PS). The second triplet state absorption band is caused by d‐πppy transition. Its position is calculated as 2.51 eV (494 nm). The dipole moment is estimated as 3.45 D, which is lower than the dipole moment of fac‐Ir(ppy)3. This is understood by a reduced charge transfer between Ir(III) and quinoline ligand. Copyright © 2008 John Wiley & Sons, Ltd. |
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| Keywords: | OLED TDDFT |
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