[KSCI] Korea Science Citation Index Service

A Study on Electron Injection Characteristics of Organic Light Emitting Diodes with Doped Cathodes of Organic Light Emitting Diodes

Kwak, Yun-Hee (Dept. of Electronics and Electrical Eng.)
Lee, Yong-Soo (Dept. of Electronics and Electrical Eng.)
Park, Jae-Hoon (Dept. of Electronics and Electrical Eng.)
Kim, Yeon-Ju (Dept. of Electronics and Electrical Eng.)
Park, Jong-Sun (Dept. of Electronics and Electrical Eng.)

Publication Information

KIEE International Transactions on Electrophysics and Applications / v.3C, no.1, 2003 , pp. 19-22 More about this Journal

Abstract

The co-evaporated cathodes composed of A1 and CsF is adopted to enhance the electrical and the optical properties of organic light emitting diodes (OLEDs). The hole transport layer (HTL), made of 50nm thick N,N-dipheny1-N,N-bis(3-methylphenyl)-1,1-bipheny14,4-diamine (TPD), and the electron transport layer (ETL), made of 50nm thick tris(8-hydroxy-quinoline) aluminum (A1q $_3$ ), were deposited under the base pressure of 1.6 $\times$ 10 $^{-6}$ Torr. In depositing A1-CsF, the mass ratio of CsF is varied between 1 and 10wt%. OLEDs with co-evaporated cathodes have luminance of about 35,000cd/ $m^2$ , and external quantum efficiency of about 1.38%. Cs tends to diffuse into the organic layer and then re-forms Cs $^{+}$ cation and free electron with the Cs-doped surface region.n.

Keywords

OLEDs; Co-evaporated cathodes; CsF;

Citations & Related Records

Reference

1	'Carrier tunneling and device characteristics in polymer light emitting diodes.' I. D. Parker, J. Appl. Phys., 75, p.1656 (1994)
2	'An experimental study of poly(9,9-dioctyl-fluorene) and its interfaces with Al, LiF and CsF.', G. Greczynski, W. R. Salaneck, M. Fahlman, Appl. Surface Science, 175-176, p.319 (2001)
3	'A lithium carboxylate ultrathin film on an aluminum cathode for enhanced electron injection in organic electroluminescent devices.' C. Ganzorig, M. Fujihara. Jpn. J. Appl. Phys. 38 p. L1348 (1999)
4	'Interfacial chemistry of $Alq_{3}$ and LiF with reactive metals.' M. G. Mason, C. W. Tang, L. -S. Hung, P. Raychaudhuri, J. Madathil, and D. J., Giesen, J. Appl. Phys. 89 p. 2756 (2001)
5	'Bright organic electroluminescent devices having a metal-doped electron-injecting layer.' J. Kido, T. Matsumoto , Appl. Phys. Lett., 73 p. 2866 (1998)
6	'Highly efficient and bright organic electroluminescent devices with an aluminum cathode.' G. E. Jabbour, Y. Kawabe, S. E. Shaheen, J. F. Wang, M. M. Morrell, B. Kippelen, and N. Peyghambarian, Appl. Phys. Lett., 71 p.1762 (1997)
7	'Electroluminescence of doped organic thin films.', C. W. Tang, S. A. VanSlyke, and C. H. Chen, J. Appl. Phys., 65, p.3610 (1989)
8	'Organic electroluminescent diodes.', C. W. Tang and S. A. VanSlyke, Appl. Phys. Lett. 51, p.913 (1987)
9	'Lithium-aluminum contacts for organic lightemitting devices.' E. I. Haskal, A. Curioni, P. F. Seidler, W. Andreoni, Appl. Phys. Lett., 71, p.1151 (1997)
10	'Lithium doping of semiconducting organic charge transport materials.' G. Parthasarathy, C. Shen, A. Kahn, and S. R. Forrest, J. Appl. Phys., 89, p.4986 (2001)
11	Kwan C. Kao, Wei Hwang, 'Electrical Transport in Solids' p. 159, (1981)
12	'Aluminum based cathode structure for enhanced electron injection in electroluminescent organic devices.' G. E. Jabbour, B. Kippelen, N. R. Armstrong, and N. Peyghambarian, Appl. Phys. Lett., 73, p.1185 (1998)
13	'Improvement in electron and hole injection at electrodes and in recombination at a two-organic-layer interface.', M. Fujihira, C, Ganzorig, Materials Science and Engineering B, 85, p.203 (2001)