ABSTRACT Organic Light-Emitting diodes (OLEDs) are extremely sensitive to water vapour and oxygen, which causes rapid degradation. Epoxy and cover glass with large amount of desiccant are commonly applied to encapsulate bottom emitting OLEDs which is not a viable option for flexible as well as top emitting OLEDs. This paper reports a completely organic encapsulating layer consisting of four periods of alternate stacks of two organic materials with different morphologies deposited by simple vacuum thermal evaporation technique. Standard green OLED structures with and without encapsulation were fabricated and investigated using structural, optical and electrical studies. Moreover, the encapsulation presented being organic is safe for underlying organic layers in OLEDs and is ultrathin, transparent and without any cover glass and desiccant, ensuring its application in flexible and top emitting OLEDs.
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nullR. Grover, R. Srivastava, O. Rana, D. Mehta and M. Kamalasanan, "New Organic Thin-Film Encapsulation for Organic Light Emitting Diodes," Journal of Encapsulation and Adsorption Sciences, Vol. 1 No. 2, 2011, pp. 23-28. doi: 10.4236/jeas.2011.12003.
 S. R. Forrest, “The Road to High Efficiency Organic Light Emitting Devices,” Organic Electronics, Vol. 4, No. 2-3, 2003, pp. 45-48. doi:10.1016/j.orgel.2003.08.014
P. E. Burrows, G. L. Graff, M. E. Gross, P. M. Martin, M. K. Shi, M. Hall, E. Mast, C. Bonham, W. Bennet and M. B. Sullivan, “Ultra Barrier Flexible Substrates for Flat Panel Displays,” Displays, Vol. 22, No. 2, 2001, pp. 65-69. doi:10.1016/S0141-9382(00)00064-0
G. Gu, P. E. Burrows, S. Venkatesh, et al., “Vacuum Deposited Nonpolymeric Flexible Organic Light Emitting Devices,” Optics Letters, Vol. 22, No. 3, 1997, pp. 172-174. doi:10.1364/OL.22.000172
A. Kunio, M. Atsushi, F. Hisayoshi, et al., “Flexible Oled for Automobiles Using Sinx/Cnx:H Multi-Layer Barrier Films and Epoxy Substrates,” Journal of Photopolymer Science and Technology, Vol. 19, No. 2, 2006, pp. 203-208. doi:10.2494/photopolymer.19.203
L. D. Wang, Y. Li, C. Chang, et al., “Research on the Adhesive Ability between ITO Anode and PET Substrate Improved by Polyimide Buffer Layer,” Chinese Science Bulletin, Vol. 50, No. 1, 2005, pp. 1-4.
Y. Qiu, L. Duan and L. D. Wang, “Flexible Organic Light-Emitting Diodes with Poly-3, 4-Ethylene-Dioxy- thiophene as Transparent Anode,” Chinese Science Bulletin, Vol. 47, No. 23, 2002, pp. 1979-1982.
J. Shen, D. Wang, E. Langlois, W. A. Barrow, P. J. Green and C. W. Tang, “Degradation Mechanism in Organic Light Emitting Diodes,” Synthetic Metals, Vol. 111-112, 2000, pp. 233-236. doi:10.1016/S0379-6779(99)00370-7
S. T. Lee, Z. Q. Gao and L. S. Hung, “Metal Diffusion From Electrodes in Organic Light Emitting Diodes,” Applied Physics Letters, Vol. 75, No. 10, 1999, pp. 1404-1406. doi:10.1063/1.124708
Z. D. Popovic, H. Aziz, N. X. Hu, A. M. Hor and G. Xu, “Long-Term Degradation Mechanism of Tris (8-Hydrox- yq-Uinoline) Aluminium-Based Organic Light-Emitting Devices,” Synthetic Metals, Vol. 111-112, 2000, pp. 229-232. doi:10.1016/S0379-6779(99)00353-7
Y. C. Luo, H. Aziz, Z. D. Popovic and G. Xu, “Degradation Mechanisms in Organic Light-Emitting Devices: Metal Migration Model versus Unstable Tris (8-Hydroxy- quinoline) Aluminium Cationic Model,” Journal of Applied Physics, Vol. 101, 2007, pp. 034510-1-4.
H. Aziz and Z. D. Popovic, “Degradation Phenomena in Small-Molecule Organic Light-Emitting Devices,” Chemistry of Materials, Vol. 16, No. 23, 2004, pp. 4522-4532. doi:10.1021/cm040081o
D. Kolosov, D. S. English, V. Bulovic, P. F. Barbara, S. R. Forrest and M. E. Thompson, “Direct Observation of Structural Changes in Organic Light Emitting Devices During Degradation,” Journal of Applied Physics, Vol. 90, No. 7, 2001, pp. 3242-3247. doi:10.1063/1.1389760
H. Aziz, Z. Popovic, S. Xie, A. M. Hor, N. X. Hu, C. Tripp and G. Xu, “Humidity-Induced Crystallization of Tris (8-Hydroxyquinoline)Aluminum Layers in Organic Light-Emitting Devices,” Applied Physics Letters, Vol. 72, No. 7, 1997, pp. 756-758. doi:10.1063/1.120867
M. Schaer, F. Niisch, D. Berner, W. Leo and L. Zuppiroli, “Water Vapor and Oxygen Degradation Mechanisms in Organic Light Emitting Diodes,” Advanced Functional Materials, Vol. 11, No. 2, 2001, pp. 116-121.
A. P. Ghosh, L. J. Gerenser, C. M. Jarman and J. E. Fornalik, “Thin-Film Encapsulation of Organic Light-Emitt- ing Devices,” Applied Physics Letters, Vol. 86, No. 22, 2005, pp. 223503-1-3. doi:10.1063/1.1929867
M. S. Weaver, L. A. Michalski, K. Rajan, M. A. Rothman, J. A. Silvernail, J. J. Brown, P. E. Burrows, G. L. Graff, M. E. Gross, P. M. Martin, M. Hall, E. Mast, C. Bohnam, W. Bennett and M. Zurnhoff, “Organic Light-Emitting Devices with Extended Operating Lifetimes on Plastic Substrates,” Applied Physics Letters, Vol. 81, No. 16, 2002, pp. 2929-2931. doi:10.1063/1.1514831
J. S. Lewis and M. S. Weaver, “Thin-Film Permeation-Barrier Technology for Flexible Organic Light-Emit- ting Devices,” IEEE Journal of Selected Topics in Quantum Electronics, Vol. 10, No. 1, 2004, pp. 45-57.
J. D. Affinito, M. E. Gross, C. A. Coronado, G. L. Graff, I. N. Greenwell and P. M. Martin, “A New Method for Fabricating Transparent Barrier Layers,” Thin Solid Films, Vol. 290-291, 1996, pp. 63-67.
M. A. Reddy, G. Mallesham, A. Thomas, K. Srinivas, V. J. Rao, K. Bhanuprakash, L. Giribabu, R. Grover, A. Kumar, M. N. Kamalasanan and R. Srivastava, “Synthesis and Characterization of Novel 2, 5-Diphenyl-1, 3, 4- Oxadiazole Derivatives of Anthracene and its Application in Electron Transporting Blue Emitters in Oleds,” Synthetic Metals, In Press.
K. Yamashita, T. Mori, T. Mizutani, H. Miyazaki and T. Takeda, “El Properties of Organic Light-Emitting-Diode Using TPD Derivatives with Diphenylstylyl Groups as Hole Transport Layer,” Thin Solid Films, Vol. 363,No. 1-2, 2000, pp. 33-36.
L. Song, Z. D. Qiang, L. Yang, D. Lian, D. Guifang, W. Liduo and Q. Yong, “New Hybrid Encapsulation for Flexible Organic Light-Emitting Devices on Plastic Substrates,” Chinese Science Bulletin, Vol. 53, No. 6, pp. 958-960.
J. Meyer, D. Schneidenbach, T. Winkler, S. Hamwi, T. Weimann, P. Hinze, S. Ammermann, H. -H. Johannes, T. Riedl and W. Kowalsky, “Reliable Thin Film Encapsulation for Organic Light Emitting Diodes Grown by Low-Temperature Atomic Layer Deposition,” Applied Physics Letters, Vol. 94, No. 23, 2009, pp. 233305-1-3.
S. -H. K. Park, J. -I. Lee, Y. S. Yang and S. J. Yun, “Characterization of Aluminum Oxide Thin Film Grown by Atomic Layer Deposition for Flexible Display Barrier Layer Application,” Proceedings of the 2nd Int’l Meetings Information Display, 2002, pp. 746-749.