| Project/Area Number |
14350500
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
高分子構造・物性(含繊維)
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| Research Institution | Cihtose Institute of Science and Technology |
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Principal Investigator |
ADACHI Chihaya Chitose Institute of Science and Technology, Department of Photonics Materials Science, Professor, 光科学部, 教授 (30283245)
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| Co-Investigator(Kenkyū-buntansha) |
SASABE Hiroyuki Chitose Institute of Science and Technology, Department of Photonics Materials Science, Professor, 光科学部, 教授 (20015126)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥14,700,000 (Direct Cost: ¥14,700,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥13,700,000 (Direct Cost: ¥13,700,000)
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| Keywords | OLED / Organic light-emitting diode / electroluminescence / exciton / annihilation / high current / singlet / triplet / 有機EL / 有機LED / 励起子失活 / 高電流密度 / S-S annihilation / T-T annihilation / S-P annihilation / 有機発光ダイオード |
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| Research Abstract |
It has been recognized that organic light emitting diodes using phosphors (ex. Ir complexes) demonstrated significant decrease of electroluminescence (EL) efficiency (next) due to the triplet-triplet exciton annihilation at rather high current density over 100mA/cm^2. In addition to the phosphorescence materials, fluorescence materials also show significant decrease of EL efficiency at high current density. However, there are little studies on this subject.
In this study, we clarify the exciton annihilation processes in electro-fluorescence devices using a typical OLED structure of α-NPD/Alq_3. At the current density of J<100mA/cm^2 we observed that change of η_<ext> is dependent on the cathode configuration. With efficient electron injection CsAl electrode, flext was independent of current density, whereas flext showed gradual increase with a current increase, suggesting that charge injection balance of hole and 2 electron influences the fluctuation of η_<ext-> Further, at high current density J>100mA/cm^2, flex steeply decreased with a current increase. We classified the annihilation processes at the high current density into three categories, singlet-singlet annihilation (SSA), singlet-polaron annihilation (SPA) and singlet-heat annihilation (SHA) models.
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