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Improved Quantum Efficiency of Organic Light Emitting Diodes with Gradiently Doped Double Emitting Zone |
GAO Wen-Bao1;JIANG Wen-Long2;SUN Jia-Xin1;FENG Jing1;HOU Jing-Ying1;LIU Shi-Yong1 |
1National Laboratory of Integrated Optoelectronics, Jilin University, Changchun 130023
2Electronic Information and Engineering Department, Jilin Normal University, Siping 136000
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Cite this article: |
GAO Wen-Bao, JIANG Wen-Long, SUN Jia-Xin et al 2003 Chin. Phys. Lett. 20 938-941 |
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Abstract We investigate electroluminescent characteristics of gradiently doped organic light-emitting diodes, which were gradiently doped in both the hole and the electron-transporting layer to form a double emitting zone. The device structure was ITO/(15 nm) CuPc/(60 nm)NPB:rubrene/(30 nm)Alq3:rubrene (20 nm)Alq3/(0.5 nm)LiF/Al. We observed that charge carriers were well trapped by the dopant molecules and the main emitting zone was localized at the NPB:rubrene side close to the interface of NPB:rubrene/Alq3:rubrene. The quantum efficiency (cd/A) was enhanced to 5.89 cd/A at 6 V. We attributed this improvement to the charge carriers trapping and the emitting of the double emitting zone.
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Keywords:
78.60.Fi
78.20.e
78.55.Et
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Published: 01 June 2003
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