Organic Light - Emitting Diodes and their Applications

Abstract:

Organic light emitting diodes (OLEDs) have been the focus of intense study since the late 1980s, when the low voltage organic electroluminescence in small organic molecules such as Alq3, and large organic molecules such as polymers (PPV), was reported. Since that time, research has continued to demonstrate the potential of OLEDs as viable systems for displays and eco-friendly lighting applications. OLEDs offer full colour display, reduced manufacturing cost, larger viewing angle, more flexible, lower power consumption, better contrast, slimmer, etc. which help in replacing the other technologies such as LCD. The operation of OLEDs involves injection of charge carriers into organic semiconducting layers, recombination of charge carriers, formation of singlet and triplet excitons, and emission of light during decay of excitons. The maximum internal quantum efficiency of fluorescent OLEDs consisting of the emissive layer of fluorescent organic material is 25% because in this case only the 25% singlet excitons can emit light. The maximum internal quantum efficiency of phosphorescent OLEDs consisting of the emissive layer of fluorescent organic material mixed with phosphorescent material of heavy metal complexes such as platinum complexes, iridium complexes, etc. is nearly 100% because in this case both the 25% singlet excitons and 75% triplet excitons emit light. Recently, a new class of OLEDs based on thermally activated delayed fluorescence (TADF) has been reported, in which the energy gap between the singlet and triplet excited states is minimized by design, thereby promoting highly efficient spin up-conversion from non-radiative triplet states to radiative singlet states while maintaining high radiative decay rates of more than 10⁶ decays per second. These molecules harness both singlet and triplet excitons for light emission through fluorescence decay channels and provides an intrinsic fluorescence efficiency in excess of 90 per cent and a very high external electroluminescence efficiency of more than 19 per cent, which is comparable to that achieved in high-efficiency phosphorescence-based OLEDs.The OLED technology can be used to make screens large enough for laptop, cell phones, desktop computers, televisions, etc. OLED materials could someday be applied to plastic and other materials to create wall-size video panels, roll-up screens for laptops, automotive displays, and even head wearable displays. Presently, the OLEDs are opening up completely new design possibilities for lighting in the world of tomorrow whereby the offices and living rooms could be illuminated by lighting panels on the ceiling. The present paper describes the salient features of OLEDs and discusses the applications of OLEDs in displays and solid state lighting devices. Finally, the challenges in the field of OLEDs are explored. Contents of Paper

• Periodical: Defect and Diffusion Forum (Volume 357)
• Pages: 29-93
• DOI: https://doi.org/10.4028/www.scientific.net/DDF.357.29
• Online since: July 2014
• Authors: V.K. Chandra*, B.P. Chandra, Piyush Jha
• Keywords: Displays, Electroluminescence, Organic Electronics, Organic Light Emitting Diodes (OLEDs), Solid State Lighting Devices

References

[1] C. W. Tang and S. A. VanSlyke, Organic electroluminescent diodes, Appl. Phys. Lett. 51 (1987) 913 - 915.

DOI: 10.1063/1.98799

[2] J.H. Burroughes, D.D.C. Bradley, A.R. Brown, R.N. Marks, K. Mackey, R.H. Friend, P.L. Burns, A.B. Holmes, Light-emitting diodes based on conjugated polymers, Nature 347 (1990)539 -541.

DOI: 10.1038/347539a0

[3] A. Bernanose, M. Comte, P. Vouaux, Blue emission from light-emitting diodes based on lithium complex, Journal of Chemical Physicsique 50 (1953) 64-69 (in French).

[4] A. Bernanose, G. Marquet, Electroluminescence du carbazol par les champs electriques alternatives carecterisation de lelectrophotoluminescence organique, J. Chim. Phys. 51 (1954) 255-259(in French).

DOI: 10.1051/jcp/1954510255

[5] A. Bernanose, Electroluminescence of organic compounds, Br. J. Appl. Phys. 6 (1955) S54-S56.

[6] G. D. Short, D. M. Herucles, Electroluminescence of organic compounds. the role of gaseous discharge in the excitation process, J. Am. Chem. Soc. 87 (1965) 1439 -1442.

DOI: 10.1021/ja01085a005

[7] M. Pope, H. Kallmann, P. Magnate, Electroluminescence in organic crystals, J. Chem. Phys. 38 (1963) 2042 - 2043.

[8] M. Sano, M. Pope, H. Kallmann, Electroluminescence and band gap in anthracene, J. Chem. Phys. 43 (1965) 2920-2921.

DOI: 10.1063/1.1697243

[9] W. Helfrich, W. G. Schneider, Recombination radiation in anthracene crystals, Phys. Rev. Lett. 14 (1965) 229 -229.

DOI: 10.1103/physrevlett.14.229

[10] W. G. Schneider, W. Helfrich, Transient volume-controlled current and of recombination radiation in anthracene, J. Chem. Phys. 44 (1966) 2902-2909.

DOI: 10.1063/1.1727152

[11] J. Kalinowski, J. Godlewski, R. Signerski, Electroluminescence in tetracene crystals, Mol. Cryst. Liq. Cryst. 33 (1976) 247 -259.

DOI: 10.1080/15421407608084300

[12] T. C. Werner, J. Chang, D. M. Hercules, Electrochemiluminescence of perylene. The role of direct excimer formation, J. Am. Chem. Soc. 92 (1970) 763.

DOI: 10.1021/ja00722a005

[13] D. F. Williams, M. Schadt, DC and pulsed electroluminescence in anthracene and doped anthracene crystals, J. Chem. Phys. 53 (1970) 3480-3487.

DOI: 10.1063/1.1674521

[14] H. P. Schwob, D. Weitz, D. F. Williams, The variation of the carrier recombination region with carrier density in anthracene crystals, Mol. Cryst. Liq. Cryst. 24 (1973) 271-282.

DOI: 10.1080/15421407308084237

[15] L. L. T. Bradrey, H. P. Schwob, D.Weitz, D. F.Williams, Delayed electroluminescence quenching in anthracene, Mol. Cryst. Liq. Cryst. 23 (1973) 271-282.

DOI: 10.1080/15421407308083377

[16] W. Hwang, K. C. Kao, On the theory of filamentary double injection and electroluminescence in molecular crystals, J. Chem. Phys.60 (1974) 3845-3855.

DOI: 10.1063/1.1680828

[17] M. Witter, I. Zschokke-Granacher, Exciton–charge carrier interactions in the electroluminescence of crystalline anthracene, J. Chem. Phys. 63 (1975) 4187-4194.

DOI: 10.1063/1.431177

[18] F. Lohmann, W. Mehl, Dark injection and radiative recombination of electrons and holes in naphthalene crystals,J. Chem. Phys. 50 (1969) 500-506.

DOI: 10.1063/1.1670827

[19] N.E. Geacintov, M.Binder, C. E. Swenberg, M. Pope, Exciton dynamics in –particle tracks in organic crystals: magnetic field study of the scintillation in tetracene crystals, Phys. Rev. B12 (1975) 4113-4134.

DOI: 10.1103/physrevb.12.4113

[20] J. Kalinowski, J. Godlewski, Magnetic field effects on recombination radiation in tetracene crystal, Chem. Phys. Lett.36 (1975) 345-348.

DOI: 10.1016/0009-2614(75)80252-1

[21] J. Glinski, J. Godlewski, J. Kalinowski, Spatial distribution of the distribution of the electroluminescence and the recombination process in tetracene single crystals, Mol. Cryst. Liq. Cryst. 48 (1977) 1-25.

DOI: 10.1080/00268947808083749

[22] G. G. Roberts, B. S. Keating, P. S. Vincett, W. A. Barlow, Electroabsorption in disordered solids. II. Anthracene crystals and thin films, J. Phys. C: Solid StatePhys. 11(1978)3847-3855.

DOI: 10.1088/0022-3719/11/18/020

[23] P. S. Vincett, W. A. Barlow, R. A. Hann, G. G. Roberts, Electrical conduction and low voltage blue electroluminescence in vacuum-deposited organic films, Thin Solid Films 94 (1982)171-183.

DOI: 10.1016/0040-6090(82)90509-0

[24] N. P. Sinha, Y. Misra, L. N. Tripathi, M. Misra, Electro-optical properties of doped anthracene films, Solid State Commun. 39 (1981) 89 -91.

DOI: 10.1016/0038-1098(81)91053-x

[25] R. M. Burgess, M. Gouterman, G. E. Khalil, Novel ultraviolet electroluminescence from Al/octaethylporphyrin/Ag film sandwich cells, J. Lumin. 28 (1983) 377-384.

DOI: 10.1016/0022-2313(83)90006-6

[26] G. G. Roberts, M. McGinnity, P. S. Vincett, W. A. Barlow, Electroluminescence, photoluminescence and electroabsorption of a lightly substituted anthracene langmuir film, Solid State Commun.32 (1979) 683-686.

DOI: 10.1016/0038-1098(79)90728-2

[27] C.Adachi, T. Tsutsui, Molecular LED: Design Concept of Molecular Materials for High-Performance OLED, in:J. Shinar (Ed.), Organic Light-Emitting Diodes, Springer, Berlin 2004, pp.43-70.

DOI: 10.1007/978-0-387-21720-8_2

[28] P. H. Partridge, Electroluminescence from polyvinylcarbazole films. 1.Carbazole cations, Polymer 24 (1983)733-738.

DOI: 10.1016/0032-3861(83)90012-5

[29] P. H. Partridge, Electroluminescence from polyvinylcarbazole films. 2. Polyvinylcarbazole films containing antimony pentachloride, Polymer 24 (1983) 739- 747.

DOI: 10.1016/0032-3861(83)90013-7

[30] P. H. Partridge, Electroluminescence from polyvinylcarbazole films.3. Electroluminescent devices, Polymer 24 (1983) 748-754.

DOI: 10.1016/0032-3861(83)90014-9

[31] P. H. Partridge, Electroluminescence from polyvinylcarbazole films. 4.Electroluminescence using higher work function cathodes, Polymer 24 (1983) 755-762.

DOI: 10.1016/0032-3861(83)90015-0

[32] S. Hayashi, H. Etoh, S. Saito, Electroluminescence of perylene films with a conducting polymer as an anode, Jpn. J. Appl. Phys. 25 (1986) L773-L775.

DOI: 10.1143/jjap.25.l773

[33] N.C. Greenham, R.H. Friend, In Solid State Physics, Academic Press, New York, London, 1995, 2-150.

[34] M.A. Baldo, D.F.O'Brien, Y. You, A. Shoustikov, S. Sibley, M.E. Thompson, S.R. Forrest, Highly efficient phosphorescent emission from organic electroluminescent devices, Nature 395 (1998)151 - 154.

DOI: 10.1038/25954

[35] C Adachi, M.A. Baldo, M.E. Thompson, S.R. Forrest, Nearly 100% internal phosphorescence efficiency in an organic light emitting device, J. Appl. Phys. 90 (2001) 5048 -5051.

DOI: 10.1063/1.1409582

[36] M. Hack, R. Hewitt, K. Urbanik, A. Chwang, J.J. Brown, Full colour top emission AMOLED displays on flexible metal foil, Proceedings of the IMID/IDMC'06 Digest Conference, Daegu, South Korea, 2006, 305-307.

[37] H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, Highly efficient organic light-emitting diodes from delayed fluorescence, Nature 492 (2012)234 -238.

DOI: 10.1038/nature11687

[38] J. Kalinowski, Electroluminescence in organics, J. Phys. D: Appl. Phys.32 (1999) R179 – R250.

DOI: 10.1088/0022-3727/32/24/201

[39] L. S. Hung, C. H. Chen, Recent progress of molecular organic electroluminescent materials and devices, Materials Science and Engineering R39 (2002) 143 - 222.

DOI: 10.1016/s0927-796x(02)00093-1

[40] S. Reineke, M. Thomschke, B. Lussem, K.Leo, White organic light-emitting diodes: Status and perspective, Rev. Modern Phys. 85 (2013) 1245 -1293.

DOI: 10.1103/revmodphys.85.1245

[41] J. Shinar, Organic Light-Emitting Diodes, Springer Berlin 2004.

[42] J. Kalinowski, Organic Light Emitting Diodes, Principles, Characteristics and Processes, Marcel Dekker, New York, 2005.

[43] M. Pfeiffer, S. R. Forrest, in Nanoelectronics and Information Technology: Advanced Materials and Novel Devices, (edited by Rainer Waster). Wiley – VCH GmbH & Co. KGaA Weinheim, (2003), pp.917-931.

[44] H. Yersin (Ed.), Highly Efficient OLEDs with Phosphorescent Materials, Wiley-VCH, Weinheim, 2009.

[45] I.H. Chambell, B.K. Crone, D.L. Smith, Physics of Organic Light Emitting Diodes, in: G. Hadiziioannou, G.G. Malliaras (Eds.), Semiconducting Polymers, Wiley-VCH, Weinheim, 2007.

[46] Z. Kafafi (Ed.), Organic Electroluminescence, CRC Press Taylor & Francis Group, Boca Raton, Fluorida, USA (2005).

[47] M. Mazzeo, Organic Light Emitting Diode, SciyoJaneza Trdine, Rijeka, Croatia (2010).

[48] S. J. Martin, "Simulations of Charge Transport in Organic Light Emitting Diodes" (University of Bath, PhD Thesis, Bath, 2002).

[49] K. Müllen, U. Scherf, "Organic Light-Emitting Devices: Synthesis, Properties and Applications" (WILEY-VCH, Singapore, 2006).

[50] J. Shinar, Organic Light-Emitting Devices, AIP press (2002).

[51] Deepak, Organic electronics: successes in organic light emitting diodes and display technology, Materials Science Forum736 (2013) 241 -249.

DOI: 10.4028/www.scientific.net/msf.736.241

[52] N. G. Pillow, M. Halim, J. M. Lupton, P. L Burn, I. D. W. Samuel, A facile iterative procedure for the preparation of dendrimers containing luminescent cores and stilbene dendrons, Macromolecules 32 (1999) 5985-5993.

DOI: 10.1021/ma981871k

[53] P.R. Emtage, J.J. O'Dwyer, Richardson-Schottky effect in insulators, Phys. Rev. Lett. 16 (1966) 356-358.

DOI: 10.1103/physrevlett.16.356

[54] Y. Gartstein, E.M. Conwell, Field-dependent thermal injection into a disordered molecular insulator, Chem. Phys. Lett. 255 (1996) 93-98.

DOI: 10.1016/0009-2614(96)00359-4

[55] M. Abkowitz, H. Mize, K. Facci, Emission limited injection by thermally assisted tunneling into a trap-free transport polymer, Appl. Phys. Lett. 66 (1995)1288-1290.

DOI: 10.1063/1.113272

[56] P. He, S. D. Wang, W. K. Wong, C. S Lee, S. T. Lee, Vibrational and photoemission study of the interface between phenyl diamine and indium tin oxide, Appl. Phys. Lett. 79 (2001) 1561-1563.

DOI: 10.1063/1.1399314

[57] G. Greczynski, M. Fahlman, W. R. Salaneck, Hybrid interfaces of poly(9,9-dioctylfluorene) employing thin insulating layers of CsF: A photoelectron spectroscopy study, J. Chem, Phys. 114 (2001) 8628-8636.

DOI: 10.1063/1.1367260

[58] Y. Yang, A.J. Heeger, Polyaniline as a transparent electrode for polymer light-emitting diodes: Lower operating voltage and higher efficiency, Appl. Phys. Lett. 64 (1994) 1245-1247.

DOI: 10.1063/1.110853

[59] J. Godlewski, J. Kalinowski,Injection limited currents in insulators, Japan. J. Appl. Phys.28(1989) 24-38.

DOI: 10.1143/jjap.28.24

[60] I. Esaki,Tunnelling Phenomena in Solids ed E Burnstein and C Lundqvist (New York: Plenum)1969, p.47–48

[61] D. F. Blossey, One dimensional Onsager theory for carrier injection in metal – insulator systems, Phys. Rev. B 9 (1974) 5183-87.

DOI: 10.1103/physrevb.9.5183

[62] R.H. Parmeter, W. Ruppel, Two carrier space charge limited current in a trap free insulator, J. Appl. Phys. 30 (1959) 1548-1558.

DOI: 10.1063/1.1734999

[63] J. Godlewski, Currents and photocurrents in organic materials determined by the interface phenomena, Adv. Colloid and Interface Science 116 (2005) 227-243.

DOI: 10.1016/j.cis.2005.04.004

[64] D. Braun, A.J. Heeger, Visible light emission from semiconducting po;ymer diodes, Appl. Phys. Lett. 58 (1991) 1982- 1984.

DOI: 10.1063/1.106423

[65] I. D. Parker, Carrier tunneling and device characteristics in polymer light emitting diodes, J. Appl. Phys. 75 (1994) 1656-1666.

DOI: 10.1063/1.356350

[66] N. Huby, L. Hirsch, G. Wantz, L. Vignau, A. S. Barriere, J.P. Parneix, L. Aubouy, P. Gerbier, Injection and transport processes in organic light emitting diodes based ona silole derivative, J. Appl. Phys. 99 (2006) 084907-1-084907-6.

DOI: 10.1063/1.2190714

[67] H. A. Méndez-Pinzón, D. R. Pardo-Pardo, J.P. Cuéllar-Alvarado, J. C. Salcedo-Reyes, R. Vera, B. A. Páez-Sierra, Analysis of the current-voltage characteristics of polymer-basedorganic light-emitting diodes (OLEDs) deposited by spin coating, Universitas Scientiarum, 15 (2010) 68-76.

DOI: 10.11144/javeriana.sc15-1.aotc

[68] J. C. Scott, Metal–organic interface and charge injection in organic electronic devices, J. Vac. Sci. Technol. A 21 (2003) 521-531.

[69] Y. Shen, G. G. Malliaras, Charge injection into organic semiconductors, The Spectrum 13 (2000) 1–4.

[70] F. Gutmann, L. E. Lyons, Organic Semiconductors. John Wiley & Sons, Inc.,1967.

[71] W. D. Gill, Drift mobilities in amorphous charge-transfer complexes of trinitrofluorenone and poly-n-vinylcarbazole, J. Appl. Phys. 43 (1972) 5033–5040.

DOI: 10.1063/1.1661065

[72] P. W. M. Blom, M. J. M. de Jong, and M. G. van Munster, Electric-field and temperature dependence of the hole mobility in poly(p-phenylene vinylene), Phys.Rev. B55 (1997) 656–659.

DOI: 10.1103/physrevb.55.r656

[73] T. Mori, T. Ogawa, D. Cho, T. Mizutani, A discussion of conduction in organic light-emitting diodes, Appl. Sur. Sci. 212-213 (2003)458-463.

DOI: 10.1016/s0169-4332(03)00465-3

[74] A. J. Campbell, D. Bradley, H. Antoniadis, M. Inbasekaran, W. Wu, E. Woo, Transient and steady-state space-charge-limited currents in polyfluorene copolymer diode structures with ohmic hole injecting contacts, Appl. Phys. Lett. 76 (2000) 1734-1736.

DOI: 10.1063/1.126182

[75] C. Giebeler, H. Antoniadis, D. Bradley, Y. Shirota, Space-charge-limited charge injection from indium tin oxide into a starburst amine and its implications for organic light-emitting diodes, Appl. Phys. Lett. 72 (1998)2448-2450.

DOI: 10.1063/1.121392

[76] P.E. Burrows, Z. Shen, V. Bulovic, D.M. McCarty, S.R. Forrest, J.A. Cronin, M.E. Thompson, Relationship between electroluminescence and current transport in organic heterojunction light‐emitting devices, J. Appl. Phys.79 (1996)7991-8006.

DOI: 10.1063/1.362350

[77] P. Langevin, Recombinaison et mobilites des ions dans les gaz, Ann. Chem. Phys. 28 (1903) 433-450.

[78] J.J. Thomson, Recombination of gaseous ions, the chemical combination of gases, and mono-molecular reactions, Phil. Mag. 47 (1924) 337-378.

[79] M. Lax, Cascade capture of electrons in solids, Phys. Rev. 119 (1960) 1502.

DOI: 10.1103/physrev.119.1502

[80] R. Morris, M. J. Silver, Direct electron-hole recombination in anthracene, Chem. Phys. 50 (1969) 2969-2973.

DOI: 10.1063/1.1671492

[81] M. Pope, C.E. Swenberg, Electronic Processes in Organic Crystals; Clarendon: Oxford, New York, 1982.

[82] O. Mikhnenko, Singlet and Triplet Excitons in Organic Semiconductors, PhD Thesis, University of Groningen, the Netherlands, 2012.

[83] D. L. Dexter, A theory of sensitized luminescence in solids, J. Chem. Phys.21 (1953) 836-850.

[84] D. L. Dexter, R. S. Knox, T. Förster, The radiationless transfer of energy of electronic excitation between impurity molecules in crystals, Phys. Status Solidi B34 (1969) K159-K162.

DOI: 10.1002/pssb.19690340264

[85] G. D. Scholes, Long-range resonance energy transfer in molecular systems, Ann. Rev. Phys. Chem. 54 (2003) 57-87.

DOI: 10.1146/annurev.physchem.54.011002.103746

[86] W. A. Luhman, R. J. Holmes, Investigation of energy transfer in organic photovoltaic cells and impact on exciton diffusion length measurements, Adv. Funct. Mater. 21 (2011) 764-771.

DOI: 10.1002/adfm.201001928

[87] V. Cleave, G. Yahioglu, P. L. Barny, R. H. Friend, N. Tessler, Harvesting singlet and triplet energy in polymer LEDs, Adv. Mater. 11(1999) 285-288.

DOI: 10.1002/(sici)1521-4095(199903)11:4<285::aid-adma285>3.0.co;2-n

[88] J. Kalinowski, W. Stampor, M. Cocchi, D. Virgili, V. Fattori, P. Di Marco, Triplet energy exchange between fluorescent and phosphorescent organic molecules in a solid state matrix, Chem.Phys. 297 (2004) 39-48.

DOI: 10.1016/j.chemphys.2003.09.041

[89] A. Köhler, H. Bässler, Triplet states in organic semiconductors, Mater. Sci. Eng. R 66 (2009) 71-109.

[90] R. Wyckhoff, Crystal Structures, New York: Wiley 1963, 1 - 28.

[91] M. Schwoerer, H.C. Wolf, Organic Molecular Solids, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2007.

[92] T. Ishida, H. Kobayashi, Y. Nakato. Structures and properties of electron-beam-evaporated indium tin oxide films as studied by x-ray photoelectron spectroscopy and work-function measurements, J. Appl. Phys. Lett. 73 (1993) 4344 -4350.

DOI: 10.1063/1.352818

[93] T. Osada, T. Kugler, P. Broms, W. Salaneck. Polymer-based light-emitting devices: investigations on the role of the indium—tin oxide (ITO) electrode, Synth. Met. 96 (1998) 77-80.

DOI: 10.1016/s0379-6779(98)00069-1

[94] J. Kim, M. Granstrom, R. Friend, N. Johansson, W. Salaneck. Indium–tin oxide treatments for single- and double-layer polymeric light-emitting diodes: The relation between the anode physical, chemical, and morphological properties and the device performance, J. Appl. Phys. 84 (1998) 6859-6870.

DOI: 10.1063/1.368981

[95] T. H. Han, Y. Lee, M. R. Choi, S. H. Woo, S.H. Bae, B H Hong, J.H. Ahn, T.W. Lee, Extremely efficient flexible organic light – emitting diodes with modified grapheme anode, Nat. Photonics 6 (2012) 105-110.

DOI: 10.1038/nphoton.2011.318

[96] L. Duan, L. Hou, T. W. Lee, J. Qiao, D. Zhang, G. Dong, L. Wang, Y. Qiu, Solution processable small molecules for organic light emitting diodes, J. Mat. Chem. 20 (2010) 6392-6407.

DOI: 10.1039/b926348a

[97] C.W. Tang, S. A. VanSlyke, C. H. Chen. Electroluminescence of doped organic thin films, J. Appl. Phys. 65 (1989) 3610-3616.

DOI: 10.1063/1.343409

[98] T. Wakimoto, Y. Fukuda, K. Nagayama, A. Yokoi, H. Nakada, M. Tsuchida. Organic EL cells using alkalinemetal compounds as electron injection material, IEEE Trans. Electron Dev. 44 (1997) 1245-1248.

DOI: 10.1109/16.605462

[99] G. E. Jabbour, B. Kippelen, N. R. Armstrong, N. Peyghambarian. Aluminium based cathode structure for enhanced electron injection in electroluminescent organic devices, Appl. Phys. Lett. 73 (1998) 1185-1187.

DOI: 10.1063/1.122367

[100] F. Li, H. Tang, J. Anderegg, J. Shinar.Fabrication and electroluminescence of double-layered organic light-emitting diodes with the cathode, Appl. Phys. Lett. 70 (1997)1233-1235.

DOI: 10.1063/1.118539

[101] S. J. Kang, D.S. Park, S. Y. Kim, C. N. Whang, K. Jeong, S. Im, Enhancing the electroluminescent properties of organic light-emitting devices using a thin NaCl layer, Appl. Phys. Lett. 81 (2002) 2581.

DOI: 10.1063/1.1511817

[102] L. S. Hung, R.Q. Zhang, P. He, G. Mason, Contact formation of LiF/Al cathodes in Alq-based organic light-emitting diodes, J. Phys. D: Appl. Phys. 35 (2002) 103-107.

DOI: 10.1088/0022-3727/35/2/302

[103] Z. Y. Zhong, Y. D. Jiang.The effect of electrode materials on the performance of OLEDs, Proc. SPIE 6030 (2006)122-129.

[104] W. Brutting, S. Berleb, A.G. Muckl, Device physics of organic light-emitting diodes based on molecular materials, Organic Electronics 2 (2001) 1-36.

DOI: 10.1016/s1566-1199(01)00009-x

[105] M. Ikai, S. Tokito, Y. Sakamoto, T. Suzuki and Y. Taga, Highly efficient phosphorescence from organic light-emitting devices with an exciton-block layer, Appl. Phys. Lett. 79 (2001) 156 -158.

DOI: 10.1063/1.1385182

[106] S. Kappaun, C. Slugovc,E. J. W. List, Phosphorescent organic light-emitting devices: working principle and iridium based emitter materials, Int. J. Mol. Sci. 9 (2008) 1527-1547.

DOI: 10.3390/ijms9081527

[107] M. A. Baldo, S. Lamansky, P. E. Burrows, M. E., Thompson, S. R. Forrest, Very high-efficiency green organic light-emitting devices based on , Appl. Phys. Lett. 75 (1999) 4 -6.

DOI: 10.1063/1.124258

[108] A. Kohle, J. S. Wilson, R. H. Friend, Fluorescence and phosphorescence in organic materials,Advanced Materials14 (2002) 701-707.

[109] Y. Kawamura, S. Yanagida, S. R. Forrest, Energy transfer in polymer electrophosphorescent light emitting devices with single and multiple doped luminescent layers,J. Appl. Phys., 92 (2002) 87-93.

DOI: 10.1063/1.1479751

[110] K. M. Vaeth, C. W. Tang, Light emitting diodes based on phosphorescent guest/polymeric host systems, J. Appl. Phys. 92 (2002) 3447 - 3453.

DOI: 10.1063/1.1501748

[111] M.A. Baldo, C. Adachi, S.R. Forrest, Transient analysis of organic electrophosphorescence. II. Transient analysis of triplet-triplet annihilation, Phys. Rev. B: Condensed Matter 62 (2000)10967-10977.

DOI: 10.1103/physrevb.62.10967

[112] M.A. Baldo, M.E. Thompson, S.R. Forrest, High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer, Nature 403 (2000) 750 -753.

DOI: 10.1038/35001541

[113] C. Adachi, M.A. Baldo, S.R. Forrest, M.E. Thompson, High-efficiency organicelectrophosphorescent devices with tris.2-phenylpyridine.iridium doped into electron-transporting materials,Appl. Phys. Lett. 77 (2000) 904 -906.

DOI: 10.1063/1.1306639

[114] A.Endo, K. Sato, K. Yoshimura, T. Kai, A. Kawada, H. Miyazaki, C. Adachi, Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes, Appl. Phys. Lett. 98 (2011) 083302-1-083302-3.

DOI: 10.1063/1.3558906

[115] Optoelectronics Industry Development Association (OIDA) 2002 Organic light emitting diodes (OLEDs) for general illumination, update Report August2002.

[116] K.T. Kamtekar, A.P. Monkman, M.R. Bryce, Recent advances in white organic light emiting materials and devices (WOLEDs), Advanced Materials22 (2010) 572-582.

DOI: 10.1002/adma.200902148

[117] R.J. Holmes, S. R. Forrest, Y. J. Tung, R.C. Kwong, J. J. Brown, S. Garon, M.E. Thompson. Blue organic electrophosphorescence using exothermic host–guest energy transfer, Appl. Phys. Lett. 82 (2003) 2422 -2424.

DOI: 10.1063/1.1568146

[118] M. A. Baldo, D. F. O'Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson, S.R. Forest,Highly efficient phosphorescent emission from organic electroluminescent devices, Nature 395 (1998) 151 -154.

DOI: 10.1038/25954

[119] G. Gu, D. Z. Garbuzov, P. E. Burrows, S. Vankatsh, S. R. Forrest, M. E. Thompson. High-external-quantum-efficiency organic light-emitting devices, Opt. Lett. 22 (1997) 396-398.

DOI: 10.1364/ol.22.000396

[120] C. F. Madigan, M. H. Lu, J. C. Sturm, Improvement of output coupling efficiency of organic light emitting diodes by backside substrate modification, Appl. Phys. Lett. 76 (2000) 1650 - 1652.

DOI: 10.1063/1.126124

[121] S. Moller, S. R. Forrest, Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays, J. Appl. Phys.91 (2002) 3324-3327.

DOI: 10.1063/1.1435422

[122] B W. D'Andrade, J. Brooks, V. Adamovich, M. E. Thompson, S. R. Forrest,White light emission using triplet excimers in electrophosphorescent organic light-emitting devices, Adv. Mater. 15 (2002) 1032 -1036.

DOI: 10.1002/1521-4095(20020805)14:15<1032::aid-adma1032>3.0.co;2-6

[123] J. Lim, S. S. Oh, D. Y. Kim, S. H. Cho, I. T. Kim, S. H. Han, H. Takezoe, E.H. Choi, G.S. Cho, Y.H. Seo, S.O. Kang, B. Park, Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array, Opt. Exp. 14 (2006) 6564-6571.

DOI: 10.1364/oe.14.006564

[124] H. Peng, Y. L. Ho,X. J. Yu, M. Wong, H. S. Kwok, Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment, J. Displ. Technol. 1(2005) 278-282.

DOI: 10.1109/jdt.2005.858944

[125] T. Yamasaki, K. Sumioka, T. Tsutsui,Organic light-emitting device with an ordered monolayer of silica microspheres as a scattering medium, Appl. Phys. Lett. 76 (2000) 1243-1245.

DOI: 10.1063/1.125997

[126] K. Neyts, A. U. Nieto,Importance of scattering and absorption for the outcoupling efficiency in organic light-emitting devices, J. Opt. Soc. Am. A 23 (2006) 1201-1206.

DOI: 10.1364/josaa.23.001201

[127] M. H. Lu, C. F. Madigan, J. C. Strurm,Improved external coupling efficiency in organic light-emitting devices on high-index substrates, International Electron Devices Meeting 2000 (IEDM) 007, 607-610.

DOI: 10.1109/iedm.2000.904393

[128] T. Tsutsui, M. Tahiro, H. Yokogawa, K. Kawano, M. Yokoyama,Doubling coupling-out efficiency in organic light-emitting devices using a thin silica aerogel layer, Adv. Mater. 13 (2001)1149-1152.

DOI: 10.1002/1521-4095(200108)13:15<1149::aid-adma1149>3.0.co;2-2

[129] C. Liu, V. Kamaev, Z. V. Vardeny,Efficiency enhancement of an organic light-emitting diode with a cathode forming two-dimensional periodic hole array, Appl. Phys. Lett. 86 (2005)143501-1-143501-2.

DOI: 10.1063/1.1895481

[130] C. Adachi, R. C. Kwong, P. Djurovich, V. Adamovich, M. A. Baldo, M. E. Thompson, S. R. Forest, Endothermic energy transfer. A mechanism for generating very efficient high-energy phosphorescent emission in organic materials, Appl. Phys. Lett. 79 (2001) 2082-2084.

DOI: 10.1063/1.1400076

[131] L. Do, E. Han, N. Yamamoto, M. Fujihira. Thermal stabilities of organic layer in electroluminescent devices, Mol. Cryst. Liq. Cryst. 280 (1996) 373-378.

[132] P. Tyagi, R. Srivastava, A. Kumar, V. K. Rai, R. Grover, M. N. Kamalasanan, White electroluminescence from stacked organic light emitting diode,Synthetic Metals 160 (2010) 756-761.

DOI: 10.1016/j.synthmet.2010.01.016

[133] Q. Y. Zhang, K. Pita, W. Ye, W.X. Que, Influence of annealing atmosphere and temperature on photoluminescence of Tb 3+ or Eu 3+-activated zinc silicate thin film phosphors via sol-gel method, Chem. Phys. Lett. 351 (2002) 163-170.

DOI: 10.1016/s0009-2614(01)01370-7

[134] Q.Y. Zhang, K. Pita, S. Buddhudu, C. H. Kam, Luminescent properties of rare-earth ion doped yttrium silicate thin film phosphors for a full-colour display, J. Phys. D 35 (2002) 3085-3090.

DOI: 10.1088/0022-3727/35/23/308

[135] W. R. Stevens, Building Physics : Lighting. London : Pergamon Press, 1969, 66.

[136] J. E. Kaufman, J. F. Christensen, Lighting hand book. Maryland: Waverly Press, 1972, 48.

[137] G. Wyszelki, W.S. Stiles, Color Science, 2nd ed., Wiley, New York (1982).

[138] C. Adachi, M. A. Baldo, S. R. Forrest,M. E. Thompson, High efficiency organic electrophosphorescent devices with tris (2-phenylpyridine) iridium doped into electron – transporting materials, Appl. Phys. Lett. 77 (2000) 904-906.

DOI: 10.1063/1.1306639

[139] S.T. Lee, Z.Q. Gao, L.S. Hung, Metal diffusion from electrodes in organic light-emitting diodes, Appl. Phys. Lett. 75 (1999) 1404-1406.

DOI: 10.1063/1.124708

[140] K. A. Higginson, X.M. Zhang, F. Papadimitrakopoulos, Thermal and morphological effects on the hydrolytic stability of aluminum tris(8-hydroxyquinoline) (Alq3), Chem. Mater. 10 (1998) 1017-1020.

DOI: 10.1021/cm970599a

[141] D.Y. Kondakov, J.R. Sandifer, C.W. Tang, R.H. Young, Nonradiative recombination centres and electrical aging of organic light-emitting diodes: direct connection between accumulation of trapped charge and luminance loss, J. Appl. Phys. 93 (2003) 1108-1119.

DOI: 10.1063/1.1531231

[142] P.E. Burrows, V. Bulovic, S.R. Forrest, L.S. Sapochak, D.M. McCarty, M. E. Thompson, Reliability and degradation of organic light emitting devices, Appl. Phys. Lett. 65 (1994)2922 -2924.

DOI: 10.1063/1.112532

[143] H. Aziz, Z. Popovic, S. Xie, A.M. Hor, N. X. Hu, C. Tripp, G. Xu, Humidity-induced crystallization of tris(8-hydroxyquinoline) aluminum layers in organic light emitting devices, Appl. Phys. Lett. 72 (1998) 756 -758.

DOI: 10.1063/1.120867

[144] B. H. Cumpston, K.F. Jensen, Electromigration of aluminum cathodes in polymer-based electroluminescent devices, Appl. Phys. Lett. 69 (1996) 3941 -3943.

DOI: 10.1063/1.117577

[145] J. S. Kim, P. K. H. Ho, N. C. Greenham, R. H. Friend, Electroluminescence emission pattern of organic light-emitting diodes: Implications for device efficiency calculations, J. Appl. Phys. 88 (2000) 1073– 1081.

DOI: 10.1063/1.373779

[146] B. E. A. Saleh and M. C. Teich, Fundamentals of Photonics, 2nd ed. New York:Wiley-Interscience, 2007.

[147] G. Gu, D. Z. Garbuzov, P. E. Burrows, S. Venkatesh, S. R. Forrest, M. E.Thompson, High-external-quantum-efficiency organic light-emitting devices, Optics Letters 22 (1997) 396 -398.

DOI: 10.1364/ol.22.000396

[148] W. Holzer, A. Penzkofer, T. Tsuboi, Absorption and emission spectroscopic characterization of Ir(ppy)3, Chem. Phys. 308 (2005) 93-102.

DOI: 10.1016/j.chemphys.2004.07.051

[149] L. H. Smith, J. A. E. Wasey, I. D. W. Samuel, W. L. Barnes, Light out-coupling efficiencies of organic light – emitting diode structures and the effect of photoluminescence quantum yield, Adv. Funct. Mat. 15 (2005) 1839-1844.

DOI: 10.1002/adfm.200500283

[150] J. Kalinowski, N. Camaioni, P. Di Marco, V. Fattori, A. Martelli, Kinetics of charge carrier recombination in organic light-emitting diodes, Appl. Phys. Lett. 72 (1998) 513 -515.

DOI: 10.1063/1.120805

[151] D.G. Moon, R.B. Pode, C.J. Lee, J.I. Hars, Transient electrophosphorescence in red top-emitting organic light-emitting devices, Appl. Phys. Lett. 85 (2004) 4771-4773.

DOI: 10.1063/1.1815372

[152] A. Teramura, Y. Nanko, Y. Sakuma, Y. Satoh, S. Kojima, K. Kasahara, T.Ohatsuka, N. Miyura, Markedly different rise and fall times in transient electroluminescence of 4,4'-N,N'-dicarbazolylbiphenyl:fac-tris(2-phenylpyridinate) iridium(III)-based organic light emitting diodes, Jpn. J. Appl. Phys. 48 (2009)111505-1-111505-5.

DOI: 10.1143/jjap.48.111505

[153] V.R. Nikitenko, V. I.Arkhipov, Y. H. Tak, J. H. Pommerehne, H. Bassler, H, Horhold, The overshoot effect in transient electroluminescence from organic bilayer light emitting diodes: Experiment and theory, J. Appl. Phys. 81 (1997) 7514-7525.

DOI: 10.1063/1.365293

[154] J. M.Lupton, V. R.Nikitenko, I. D. W. Samuel, H.Bassler, Time delayed electroluminescence overshoot in single layer polymer light – emitting diodes due to electrode luminescence quenching, J. Appl. Phys. 89 (2001) 311-317.

DOI: 10.1063/1.1331066

[155] V. K. Chandra, M. Tiwari, B.P. Chandra, M. Ramrakhiani, Electroluminescence overshoot effect in single layer pulsed organic light emitting diodes, Synthetic Met. 161 (2011) 460 -465.

DOI: 10.1016/j.synthmet.2010.12.029

[156] V.K. Chandra, B.P. Chandra, M. Tiwari, R.N. Baghel, M. Ramrakhiani, Modeling of transient electroluminescence overshoot in bilayer organic light-emitting diodes using rate equations, J. Lumin. 132 (2012)1532 -1539.

DOI: 10.1016/j.jlumin.2012.01.033

[157] M. Tiwari, V.K. Chandra, B.P. Chandra, M. Ramrakhiani, Delayed electroluminescence in organic light emitting diodes, Int. J. Pure and Appl. Phys. 6 (2010)251 -256.

[158] B.P. Chandra, V.K. Chandra, Proceedings of the National Conference on Luminescence and its Application (NCLA-2006), held at Amravati University, Amravati(Maharastra), India, (February 7-9, 2006, pp.27-32).

[159] V.K. Chandra, B.P. Chandra, Transient electroluminescence in heavy metal complex-based phosphorescent organic light-emitting diodes, Organic Electronics 13 (2012)329 -334.

DOI: 10.1016/j.orgel.2011.11.003

[160] G. Parthasarathy, J. Liu, A. R. Duggal, Organic light emitting devices from displays to lighting, The Electrochemical Society Interface, Summer 2003, pp.42-47.

DOI: 10.1149/2.f10032if

[161] R. H. Friend, R. W. Gymer, A. B. Holmes, J. H. Burroughes, R. N. Marks, C. Taliani, D. D. C. Bradley, D. A. Dos Santos, J. L. Bre das, M. LoÈ gdlund, W. R. Salaneck, Electro-luminescence in conjugated polymers, Nature 397 (1999) 121-128.

DOI: 10.1038/16393

[162] S.R. Forest, The path to ubiquitous and low-cost organic electronic appliances on plastic, Nature 428 (2004) 911-918.

DOI: 10.1038/nature02498

[163] J. Zmija, M.J. Malachowski , Organic light emitting diode: Operation and application in displays, Archives of Materials Science and Engineering 40 (2009) 5 -12.

[164] C. D. Muller, A. Falcou, N. Reckefuss, M. Rojahn, V. Wiederhirn, P. Rudati, H. Frohne, O. Nuyken, H. Becker, K. Meerholz, Multi-colour organic light-emitting displays by solution processing, Nature 421 (2003) 829-833.

DOI: 10.1038/nature01390

[165] K. Chung, J. Choi, J. Jung, B. Choi, J. Chung, B.-W. Lee, Ch. Chu, Is AMOLED TV to enter the battle for large-screen, FPD dominance, Information Display 2/6 (2006) 12-17.

[166] "Sony Launches World's First OLED TV" on-line press release. Sony Corp. [Online]. Available:http://www.sony.net/SonyInfo/News/Press/200710/07-1001E/

[167] I. Yagi, N. Hirai, M. Noda, A. Imaoka, Y. Miyamoto, N. Yoneya, K. Nomoto, J. Kasahara, A. Yumoto, T. Urabe, SID Symposium Digest of Technical Papers 38 (2007) 1753.

DOI: 10.1889/1.2785666

[168] I. Yagi, N. Hirai, Y. Miyamoto, M. Noda, A. Imaoka, N. Yoneya, K. Nomoto, J. Kasahara, A. Yumoto, T. Urabe, A flexible full-colour AMOLED display driven by OTFTs, Journal of SID 16/1 (2008) 15 -19.

DOI: 10.1889/1.2835023

[169] A. R. Duggal, D. F. Foust, W. F. Nealon, C. M. Heller, Organic Light-Emitting Materials and Devices VII, edited by Zakya H. Kafafi, Paul A. Lane, Proceedings of SPIE Vol. 5214 (SPIE, Bellingham, WA, 2004) pp.241-247.

DOI: 10.1117/12.511477

[170] K. T. Kamtekar, A. P. Monkman, M. R. Bryce, Recent advances in white organic light-emitting materials and devices (WOLEDs), Adv. Mater. 21 (2009) 1–11.

DOI: 10.1002/adma.200902148

[171] M.N. Kamalasanan, R. Srivastava, G. Chauhan, A. Kumar, P. Tayagi, A. Kumar, Organic Light Emitting Diodes for White Light Emission, in Organic Light Emitting Diode, Marco Mazzeo (Ed.), InTech Europe University Campus STeP Ri Slavka Krautzeka 83/A 51000 Rijeka, Croatia. (2010). pp.179-224.

DOI: 10.5772/9892

[172] J. J. Shiang, Organiclight emitting devices for lighting,The Electrochemical Society Interface,Winter 2009, pp.37-41.

[173] B.W. D'Andrade, S.R. Forrest, Efficient organic electrophosphorescent white-light-emitting device with a triple doped emissive layer, Advanced Materials 16 (2004)624-628.

DOI: 10.1002/adma.200306670

[174] N. Ide, H. Tsuji, N. Ito, H. Sasaki, T. Nishimori, Y. Kuzuoka, K. Fujihara, T. Miyai, T. Komoda, High-performance OLEDs and their application to lighting, Proc. of SPIE , 7051 (2008) 705119-1-705119-10.

DOI: 10.1117/12.798190

[175] H. Sasabe, J. Kido, Multifunctional materials in high-performance OLEDs: challenges for solid –state lighting, Chem. Mater. 23 (2011) 621–630.

DOI: 10.1021/cm1024052

[176] P. Loebl, V. Elsbergena, H. Boernera, C. Goldmanna, S. Grabowskia, Organic Light Emitting Materials and Devices XIII, edited by Franky So, Chihaya Adachi, Proc. of SPIE Vol. 7415 (2009) 74151A ·

DOI: 10.1117/12.846115

[177] R. Pode, B. Diouf, Solar Lighting, Springer, London Dordrecht Heidelberg, New York, 2011, pp.97-150.

[178] N. Thejo Kalyani, S.J. Dhoble, Novel approaches for energy efficient solid state lighting by RGB organic light emitting diodes – A review, Renewable and Sustainable Energy Reviews 32 (2014) 448 - 467.

DOI: 10.1016/j.rser.2014.01.013

[179] N. Thejo Kalyani, S.J. Dhoble, Organic light emitting diodes: Energy saving lighting technology—A review, Renewable and Sustainable Energy Reviews 16 (2012) 2696 - 2723.

DOI: 10.1016/j.rser.2012.02.021

[180] A. De Almeida, B. Santos, B. Paolo, M. Quicheron, Solid state lighting review – Potential and challenges in Europe, Renewable and Sustainable Energy Reviews 34 (2014) 30-48.

DOI: 10.1016/j.rser.2014.02.029

[181] P. Kopola, M. Tuomikoski, R. Suhonen, A. Maaninen, Gravure printed organic light emitting diodes for lighting applications, Thin Solid Films 517 (2009) 5757–5762.

DOI: 10.1016/j.tsf.2009.03.209

[182] K.Hong, J.L. Lee, Review paper: Recent developments in light extraction technologies of organic light emitting diodes, Electronic Materials Letters 7 (2011) 77-91.

DOI: 10.1007/s13391-011-0601-1

[183] www.lumiblade.com

[184] R. Ma, M. Weaver, Maximizing OLED Lighting Efficacy, DOE Workshop, Long Beach, LA, January 30, 2013.