1995 Fiscal Year Final Research Report Summary
Elucidation of the mechanism of organic EL devices
| Project/Area Number |
06453116
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
工業物理化学
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| Research Institution | OSAKA UNIVERSITY |
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Principal Investigator |
MATSUMURA Michio Osaka University, Research Center for Photoenergetics of Organic Materials, Professor, 有機光工学研究センター, 教授 (20107080)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Hikaru Osaka University, Faculty of Engineering Science, Associate Professor, 基礎工学部, 助教授 (90195800)
NAKATO Yoshihiro Osaka University, Faculty of Engineering Science, Professor, 基礎工学部, 教授 (70029502)
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| Project Period (FY) |
1994 – 1995
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| Keywords | EL device / Electroluminescence / Organic thin layr / Carrier injection / Interface / Energy barrier / Schottky emission / Luminescent material |
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| Research Abstract |
Organic EL devices have the structure of stacked thin layrs. The interfaces between the layrs affect the properties of the EL devices. We therefore surveyed the mechanisms of the organic EL devices, laying stress on the effects of the interfaces.
(1) Electron injection from the cathode :
Electrons are injected from the cathode into the layr of aluminum-hydroxyquinoline, which is the light emitting material. In order to study the electron injection mechanism, samples having the structure of metal/ALQ/metal were prepared. From the analysis of the I-V characteristics at different temperatures, the electron injection is assigned to the Schottky emission.
From the detailed analysis of the temperature dependence of the current, the energy barrier height between ALQ and magnesium (cathode) was determined to be 0.58 eV.
(2) Hole injection from ITO :
The hole injection from ITO into the layr of a diamine compound, which is the hole transporting material, was also studied. From the results it was found that the holes are also injected by the Schottky emission mechanism. The barrier height between ITO and the diamine layr was determined to be 0.41 eV.
(3) Effect of the interface between ALQ and hole transporting layrs on the EL efficiency :
It is difficult to determine the quantum efficiency of the EL emission because of the thin layr structure. We therefore studied the efficiency of the EL emission by comparing the intensities of photoluminescence (PL) and EL emissions. From the results, we found that the EL efficiency was 13 % of the PL efficiency. The low EL efficiency was attributed to the direct recombination of electrons and holes at the ALQ/hole transporting layr interface.
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Research Products
(4 results)
