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Proceedings Paper

Highly efficient red phosphorescent organic light-emitting devices with facially encumbered and bulky Pt(II) porphyrins
Author(s): Masamichi Ikai; Fumiaki Ishikawa; Naoki Aratani; Atsuhiro Osuka; Shigeki Kawabata; Takanori Kajioka; Hisato Takeuchi; Hisayoshi Fujikawa; Yasunori Taga
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Paper Abstract

We report effective enhancement of external quantum efficiency of phosphorescent organic light-emitting devices (OLEDs) with facially encumbered and bulky meso-aryl substituted Pt(II) porphyrins, probably suppressing non-radiative deactivation. The peak external quantum efficiencies (QEs) of the phosphorescent OLEDs with facially non-encumbered Pt(II) porphyrin 1, facially encumbered Pt(II) porphyrin 2, Pt(II) porphyrin 3 that bears bulkier 3,5-di-tert-butylphenyl substituents, and "doubly-decamethylene-strapped" Pt(II) porphyrin 4 were 1, 4.2, 7.3, and 8.2 %, respectively. The trend increasing performance in the order of 1 < 2 < 3 < 4 is related to facial encumbrance and steric bulkiness of Pt(II) porphyrins. Furthermore, in the case of Pt(II) porphyrin 4, it is considered that the "double straps" severely restrict rotational freedom of the meso-aryl substituents. The lifetimes for Pt(II) porphyrins 1-4 at a current density of 0.55 mA/cm2 were 80, 103, 140, and 152 μs, respectively. The trend that the triplet lifetime becomes longer in the order of 1 < 2 < 3, 4 suggests that facial encumbrance and steric bulkiness suppress non-radiative deactivation. The triplet lifetimes of Pt(II) porphyrins 1-4 were all gradually shortened with increasing current densities, suggesting possible triplet-triplet annihilation and/or triplet-charge carrier recombination.

Paper Details

Date Published: 10 October 2005
PDF: 7 pages
Proc. SPIE 5937, Organic Light-Emitting Materials and Devices IX, 59370D (10 October 2005); doi: 10.1117/12.614708
Show Author Affiliations
Masamichi Ikai, Toyota Central Research and Development Labs., Inc. (Japan)
Fumiaki Ishikawa, Kyoto Univ. (Japan)
Naoki Aratani, Kyoto Univ. (Japan)
Atsuhiro Osuka, Kyoto Univ. (Japan)
Shigeki Kawabata, Toyama Prefectural Univ. (Japan)
Takanori Kajioka, Toyota Central Research and Development Labs., Inc. (Japan)
Hisato Takeuchi, Toyota Central Research and Development Labs., Inc. (Japan)
Hisayoshi Fujikawa, Toyota Central Research and Development Labs., Inc. (Japan)
Yasunori Taga, Toyota Central Research and Development Labs., Inc. (Japan)


Published in SPIE Proceedings Vol. 5937:
Organic Light-Emitting Materials and Devices IX
Zakya H. Kafafi; Paul A. Lane, Editor(s)

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