Browse > Article
http://dx.doi.org/10.4313/TEEM.2005.6.5.233

Efficiency Improvement of Organic Light-emitting Diodes depending on Thickness of Hole Injection Materials  

Kim, Weon-Jong (Department of Electrical Engineering, Kawngwoon University)
Yang, Jae-Hoon (Department of Electrical Engineering, Kawngwoon University)
Kim, Tag-Yong (Department of Electrical Engineering, Kawngwoon University)
Jeong, Joon (Department of Electrical Engineering, Kawngwoon University)
Lee, Young-Hwan (Department of Electrical Engineering, Kawngwoon University)
Hong, Jin-Woong (Department of Electrical Engineering, Kawngwoon University)
Park, Ha-Yong (Department of Electrical Engineering, Samcheok National University)
Kim, Tae-Wan (Department of Physics, Hongik University)
Publication Information
Transactions on Electrical and Electronic Materials / v.6, no.5, 2005 , pp. 233-237 More about this Journal
Abstract
In the device structure of ITO/hole injection layer/N, N'-biphenyl-N, N'-bis-(1-naphenyl)-[1,1'-biphenyl]4,4'-diamine(NPB)/tris(8-hydroxyquinoline) aluminum$(Alq_3)/Al$, we investigated an effect of hole-injection materials (PTFE, PVK) on the electrical characteristics and efficiency of organic light-emitting diodes. A thermal evaporation was performed to make a thickness of NPB layer with a evaporation rate of $0.5\~1.0\;\AA/s$ in a base pressure of $5\times10^{-6}$ Torr. We measured current-voltage characteristics and efficiency with a thickness variation of hole-injection layer. The PTFE and PVK hole-injection layer improve a performance of the device in several aspects, such as good mechanical junction, reducing the operating voltage and energy band adjustment. Compared with the devices without a hole-injection layer, we have obtained that an optimal thickness of NPB was 20 nm in the device structure of $ITO/NPB/Alq_3/Al$. And using the PTFE or PVK hole-injection layer, the external quantum efficiencies of the devices were improved by $24.5\%\;and\;51.3\%$, respectively.
Keywords
Hole injection layer(PTFE, PVK); OLEDs; External quantum efficiency;
Citations & Related Records
연도 인용수 순위
  • Reference
1 H. S. Lee, K. W. Jang, M. K. Choi, S. I. Lee, T. W. Kim, M. Iwamoto, arid J. U. Lee, 'Inelastic electron tunneling in Au/polymide/monolayer organic film/Pb structures using a polyimide barrier', J. of KIEEME(in Korean), Vol. 17, No.2, p. 196, 2004
2 G. B. Blanchet, Y. L. Loo, J. A. Rogers, F. Gao, and C. R. Fincher, 'Large area, high resolution, dry printing of conducting polymers for organic electronics', Applied Physics Letters, 82, p. 463, 2003
3 Y. Qiu, Y. Gao, Liduo, and D. Zhang, 'Efficient emitting diodes with Teflon buffer layer', Synthetic Metals, Vol. 130, p. 235, 2002
4 A. Tsuchida, A. Nagata, M. Yamamoto, H. Fukui, M. Sawamoto, and T. Higashimura, 'Hole resonance among more than two carbazole chromophores in poly(N-vinylcarbazole)', macromolecules, 28, p. 1285, 1995
5 K. Kudo, 'Organic light emitting transistors', Current Applied Physics, Vol. 5, p. 337, 2005
6 S. Tokito, H. Tanaka, K. Noda, A. Okada, and Y. Taga, 'Thermal stability in oligomeric triphenylamine /tris(8-quinolinolato) aluminum electroluminescent', IEEE Trans. Electron Devices, 44, p. 1239, 1997   DOI   ScienceOn
7 W. Helfrich and W. G. Schneider, 'Recombination radiation in anthracene crystals', Phys. Rev. Lett., 14, p.229, 1965
8 H. E. A. Huitema, G. H. Gelinck, J. B. P. H. Vander, K. M. Hart, E. Cantatore, and D. M. de Leeuw, 'Active-matrix displays driven by solution processed polymeric transistors', Advanced Materials, 14, p. 201, 2002
9 L. S. Hung and C. H. Chen, 'Recent progress of molecular organic electroluminescent materials and devices', Materials Science and Engineering, R. 39, p. 143, 2002
10 M. Pope, H. P. Kallmann, and P. Magnante, 'Electroluminescence in organic crystals', J. Chem. Phy., 38, p. 2042, 1963
11 R. H. Friend, R. W. Gymer, A. B. Holmes, J. H. Burroughes, R. N. Marks, C. Taliani, D. C. Bradley, D. A. Dos Santos, J. L. Bredas, M. Logdlund, and W. R. Saraneck, 'Electroluminescence in conjugated polymer', Nature, Vol. 397, p. 121, 1999
12 S. K. Kim, D. H. Chung, J. W. Hong, T. G. Chung, T. W. Kim, W. J. Lee, and K. U. Jang, 'Effects of buffer layer in organic light-emitting diodes', Mol. Cryst. Liq. Cryst., Vol. 377, p. 129, 2002
13 C. Jiang, W. Yang, J. Peng, S. Xiao, and Y. Caoet, 'High-efficiency, saturated red-phosphorescent polymer light-emitting diodes based on conjugated and non-conjugated polymers doped with an Ir complex', Advanced Materials, Vol. 16, No.6, p. 537, 2004
14 D. H. Chung, S. W. Hur, S. K. Kim, J. U. Lee, C. H. Kim, J. W. Hong, and T. W. Kim, ''Temperature-dependent electrical properties of organic light-emitting diodes depending on cathodes', Current Applied Physics, Vol. 4, Iss. 6, p. 667, 2004
15 D. H. Chung, S. W. Hur, S. K. Kim, J. U. Lee, M. J. Song, K. U. Jang, S. K. Kim, H. N. Cho, and T. W. Kim, 'Frequency-dependent response in ITO/$Alq_3$ 120/Al organic light-emitting diodes', Current Applied Physics, Vol. 4, p. 543, 2004
16 S. K. Kim, D. H. Chung, J. W. Hong, T. G. Chung, H. S. Lee, J. W. Park, T. W. Kim, M. J. Song, and W. S. Choi, 'Current-voltage characteristics of organic light-emitting' diodes depending on the application of forward-reverse bias voltage', Mol. Cryst. Liq. Cryst., Vol. 377, p. 133, 2002
17 S. K. Kim, D. H. Chung, H. S. Lee, H. N. Cho, J. W. Park, J. W. Hong, and T. W. Kim, 'Temperature dependent electrical properties in ITO/TPD/ $Alq_3$/ Al organic light-emitting diodes', Synthetic Metals, Vol. 137, p. 1041, 2003