**5. References**


[11] W. Song, S. K. So, J. Moulder, Y. Qiu, Y. Zhu and L. Cao, Study on the interaction between Ag and tris(8-hydroxyquinoline) aluminum using x-ray photoelectron spectroscopy. Surf. Interface Anal. 32: 70 (2001).

The Advanced Charge Injection Techniques Towards the Fabrication of High-Power Organic Light Emitting Diodes 175

[26] V. Bulović, P. E. Burrows, S. R. Forrest, J. A. Cronin and M. E. Thompson, Study of localized and extended excitons in 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) I. Spectroscopic properties of thin films and solutions. Chem. Phys. 210: 1

[27] Y. H. Chen, J. S. Chen, D. G. Ma, D. H. Yan and L. X. Wang, Effect of organic bulk heterojunction as charge generation layer on the performance of tandem organic light-

[28] D. R. T. Zahn, G. N. Gavrila and G. Salvan, Electronic and Vibrational Spectroscopies

[29] Y. Yuan, D. Grozea, S. Han and Z. H. Lu, Interaction between organic semiconductors

[30] A. Kahn, W. Zhao, W. Y. Gao, H. Vazquez and F. Flores, Doping-induced realignment of molecular levels at organic–organic Heterojunctions. Chem. Phys. 325: 129 (2006). [31] G. Parthasarathy, C. Shen, A. Kahn and S. R. Forrest, Lithium doping of semiconducting organic charge transport materials. J. Appl. Phys. 89: 4986 (2001). [32] C. Tao, S. P. Ruan, X. D. Zhang, G. H. Xie, L. Shen, X. Z. Kong, W. Dong, C. X. Liu and W. Y. Chen, Performance improvement of inverted polymer solar cells with different top electrodes by introducing a MoO3 buffer layer. Appl. Phys. Lett. 93: 193307

[33] M. Kröger, S. Hamwi, J. Meyer, T. Riedl, W. Kowalsky and A, Kahn, Role of the deeplying electronic states of MoO3 in the enhancement of hole-injection in organic thin

[34] E. Tutiš, D. Berner and L. Zuppiroli, Internal electric field and charge distribution in

[35] S. W. Shi and D. G. Ma, Investigation on internal electric field distribution of organic light-emitting diodes (OLEDs) with Eu2O3 buffer layer. Phys. Status Solidi A 206: 2641

[36] Y. Shirota and H. Kageyama, Charge carrier transporting molecular materials and their

[37] H. Tachikawa, H. Kawabata, R. Miyamoto, K. Nakayama and M. Yokoyama, Experimental and Theoretical Studies on the Organic−Inorganic Hybrid Compound:

[38] P. Jeon, H. Lee, J. Lee, K. Jeong, J. W. Lee and Y. Yi, Interface state and dipole assisted hole injection improvement with 1,4,5,8,-naphthalene-tetracarboxylic-dianhydride in

[39] Y. M Koo and O. K. Song, Spontaneous charge transfer from indium tin oxide to organic

[40] L. S. Liao and K. P. Klubek, Power efficiency improvement in a tandem organic light-

Aluminum-NTCDA Co-Deposited Film. J. Phys. Chem. B 109: 3139 (2005).

molecules for effective hole injection. Appl. Phys. Lett. 94: 153302 (2009).

organic light-emitting devices. Appl. Phys. Lett. 99: 073305 (2011).

multilayer organic light-emitting diodes. J. Appl. Phys. 93: 4594 (2003).

Applied to Organic/Inorganic Interfaces. Chem. Rev. 107: 1161 (2007).

emitting diodes. J. Appl. Phys. 110: 074504 (2011).

and LiF dopant. Appl. Phys. Lett. 85: 4959 (2004).

films. Appl. Phys. Lett. 95: 123301 (2009).

applications in devices. Chem. Rev. 107: 953 (2007).

emitting diode. Appl. Phys. Lett. 92: 223311 (2008).

(1996).

(2008).

(2009).


[26] V. Bulović, P. E. Burrows, S. R. Forrest, J. A. Cronin and M. E. Thompson, Study of localized and extended excitons in 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) I. Spectroscopic properties of thin films and solutions. Chem. Phys. 210: 1 (1996).

174 Organic Light Emitting Devices

[11] W. Song, S. K. So, J. Moulder, Y. Qiu, Y. Zhu and L. Cao, Study on the interaction between Ag and tris(8-hydroxyquinoline) aluminum using x-ray photoelectron

[12] M. Thomschke, S. Hofmann, S. Olthof, M. Anderson, H. Kleemann, M. Schober, B.

[13] C. R. Cheng, Y. H. Chen, D. S. Qin, W. Quan and J. S. Liu, Inverted bottom-emission organic light emitting diode using two n-doped layers for the enhanced performance.

[14] D. S. Qin, J. S. Liu, Y. H. Chen, C. R. Cheng and W. Quan, Inverted bottom-emission organic light emitting diodes using MoO3 for both hole and electron injections. Phys.

[15] D. S. Qin, L. Chen, Y. H. Chen, J. S. Liu, G. F. Li, W. Quan, J. D. Zhang and D. H. Yan, Enhanced performance in inverted organic light emitting diode assisted by an interlayer of crystalline and n-doped 1,4,5,8-naphthalene-tetracarboxylic-dianhydride,

[16] J. S. Liu, Y. H. Chen, D. S. Qin, C. R. Cheng, W. Quan, L. Chen and G. F. Li, Improved interconnecting structure for a tandem organic light emitting diode. Semicond. Sci.

[18] C. Rost, S. Karg, W. Riess, M. A. Loi, M. Murgia and M, Muccini, Ambipolar light-

[19] J. Wang, H. B. Wang, J. X. Yan, H. C. Huang and D. H. Yan, Organic heterojunction and its application for double channel field-effect transistors. Appl. Phys. Lett. 87: 093507

[20] L. Chkoda, C. Heske, M. Sokolowski and E. Umbach, Improved band alignment for hole injection by an interfacial layer in organic light emitting devices. Appl. Phys. Lett.

[21] P. E. Burrows and S. R. Forrest, Electroluminescence from trap-limited current transport in vacuum deposited organic light emitting devices, Appl. Phys. Lett. 64: 2285

[22] I. G. Hill, A. Rgjagopal, A. Kahn and Y. Hu, Molecular level alignment at organic

[23] S. R. Forrest, W. Y. Yoon, L. Y, Leu and F. F. So, Optical and electrical properties of isotype crystalline molecular organic heterojunctions. J. Appl. Phys. 66: 5908 (1998). [24] B. P. Rand, J. Xue, S. Uchida and S. R, Forrest, Mixed donor-acceptor molecular heterojunctions for photovoltaic applications. I. Material properties. J. Appl. Phys. 98:

[25] P. Liu, Q. Li, M. S. Huang and W. Z. Pan, High open circuit voltage organic photovoltaic cells based on oligothiophene derivatives. Appl. Phys. Lett. 89: 213501

semiconductor-metal interfaces. Appl. Phys. Lett. 73: 662 (1998).

[17] C. W. Tang, Two-layer organic photovoltaic cell. Appl. Phys. Lett. 48: 183 (1986).

emitting organic field-effect transistor. Appl. Phys. Lett. 85: 1613 (2004).

spectroscopy. Surf. Interface Anal. 32: 70 (2001).

Chin. Phys. Lett. 27: 117801 (2010).

Solidi Status A 208: 1976 (2011).

Phys. Solidi Status A 209: 790 (2012).

Technol. 26: 095011 (2011).

(2005).

(1994).

77: 1093 (2000).

124902 (2005).

(2006).

Lüssem and K. Leo, Appl. Phys. Lett. 98: 083304 (2011).

	- [41] C. W. Chen, Y. J. Lu, C. C. Wu, E. H. E. Wu, C. W. Chu and Y. Yang, Effective connecting architecture for tandem organic light-emitting devices. Appl. Phys. Lett. 87: 241121 (2005).

**Chapter 7** 

© 2012 Kaplunov et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 Kaplunov et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**Exciplex Electroluminescence of the New** 

M.G.Kaplunov, S.N. Nikitenko and S.S. Krasnikova

Additional information is available at the end of the chapter

quinolines, benzothiazoles and related ligands [4-6].

relative to the emissions of the individual acceptor or donor [7-10].

http://dx.doi.org/10.5772/51799

acceptor blends [10,12-15].

OLEDs. [16-19].

**1. Introduction** 

**Organic Materials for Light-Emitting Diodes** 

In typical organic light emitting devices (OLEDs), light originates from radiative recombination of molecular excited states formed by electrons and holes injected from electrodes and localized on individual molecular sites. That is, the results are interpreted as due to Frenkel exciton generation and recombination [1,2]. In particular, this is applied to the bilayer OLEDs composed of metal 8-hydroxyquinolates Mq3 (M = Al, Ga, In, or Sc) as an electron-transporting and emitting layer and amines like triphenylamine derivative (TPD) as a hole-transporting layer. The electroluminescence (EL) spectra of these devices are close to the photoluminescence (PL) spectra of corresponding Mq3 molecules [1-3]. The similarity of the EL and PL spectra was also observed for zinc complexes with hydroxy-substituted

In some bilayer devices, interactions of donor and acceptor molecules at the organic/organic interface can lead to formation of an exciplex state. Exciplex is a kind of excited state complex formed between donor and acceptor, with one in the excited state and the other in the ground state. Exciplex usually leads to the red shifted emission and broadened spectrum

Exciplex formation at the solid interface between Alq3 and the electron-rich multiple triarylamine hole-transporting materials m-MTDATA and t-Bu-TBATA was observed in a study by Itano et al., [11]. Exciplexes can also be observed in the PL spectra of donor-

Sometimes, another sort of bimolecular excited complex called electroplex can be generated around heterojunction. Unlike exciplex emission which can be observed under both photoexcitation and electric field excitation, electroplex emission can not be typically observed under photo-excitation and can be formed only in the presence of high electric field in some

[42] C. R. Cheng, Y. H. Chen, D. S. Qin, W. Quan and J. S. Liu, Lithium carbonate doped 3, 4, 9, 10 perylenetetracarboxylic dianhydride for enhanced performance in organic light emitting diode Chin. J. Lumin. 32: 387 (2011).
