Abstract
There is an ongoing interest in organic materials due to their application in various organic electronic devices. However stability of organic materials limits their potential use. They are prone to degradation both during the working life and storage. One of the main causes is extrinsic degradation, under the influence of oxygen and moisture. This problem can be solved by encapsulation of devices. However no encapsulation is perfect. This paper presents a study of interaction of thin films of well-known organic blue emitters, namely N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPD) and 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi), with UV light in air. Films of both materials are stable in vacuum, but readily degrade in the presence of oxygen. Thus, the necessary condition for interaction (degradation) is the simultaneous presence of UV light and oxygen. Chemical analysis of irradiated films by mass and infrared spectroscopy revealed presence of oxidized species (impurities). These impurities are responsible for increased morphological stability of irradiated films and quenching of photoluminescence (PL). Only small amount of impurities, 0.4 % (0.2 %) for TPD (DPVBi), causes 50 % decrease of PL. This implies a non-trivial mechanism of quenching. For both molecules it was found that distance between impurities is smaller or equal to exciton diffusion length, which is the necessary condition for quenching. Following mechanism of quenching is proposed: exciton diffuses by hopping form one host molecule (DPVBi or TPD) to another through Förster resonant energy transfer in a random walk manner. If, during its lifetime, it comes to proximity of an impurity, a PL quenching process occurs. Findings of this study are important because they show that even a small amount of oxygen that penetrates a blue emitter layer would impair luminescence efficiency of a device. Moreover, the absorption of its own radiation would additionally contribute to the rate of degradation of a device. It is reasonable to expect that transport properties would also be affected when materials are used as a hole-transporting layer in OLEDs.
This work was supported by the Serbian Ministry of Education, Science and Technological Development, projects nos. 171033 and 41028.
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H. Neugebauer, C. Brabec, J.C. Hummelen, N.S. Sariciftci, Stability and photodegradation mechanisms of conjugated polymer/fullerene plastic solar cells. Sol. Energy Mater. Sol. Cells 61, 35–42 (2000)
K. Kawano, R. Pacios, D. Poplavskyy, J. Nelson, D.D.C. Bradley, J.R. Durrant, Degradation of organic solar cells due to air exposure. Sol. Energy Mater. Sol. Cells 90, 3520–3530 (2006)
R. Pacios, A.J. Chatten, K. Kawano, J.R. Durrant, D.D.C. Bradley, J. Nelson, Effects of photo-oxidation on the performance of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene]:[6]-phenyl C61-butyric acid methyl ester solar cells. Adv. Funct. Mater. 16, 2117–2126 (2006)
S. Cook, A. Furube, R. Katoh, Matter of minutes degradation of poly(3-hexylthiophene) under illumination in air. J. Mater. Chem. 22, 4282–4289 (2012)
S. Schmidbauer, A. Hohenleutner, B. König, Studies on the photodegradation of red, green and blue phosphorescent OLED emitters. Beilstein J. Org. Chem. 9, 2088–2096 (2013)
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, 2922–2924 (1994)
A.B. Chwang, M.A. Rothman, S.Y. Mao, R.H. Hewitt, M.S. Weaver, J.A. Silvernail, K. Rajan, M. Hack, J.J. Brown, X. Chu, L. Moro, T. Krajewski, N. Rutherford, Thin film encapsulated flexible organic electroluminescent displays. Appl. Phys. Lett. 83, 413–415 (2003)
J.-S. Park, H. Chae, H.K. Chung, S.I. Lee, Thin film encapsulation for flexible AM-OLED: a review. Semicond. Sci. Technol. 26, 034001 (2011)
F. So, D. Kondakov, Degradation mechanisms in small-molecule and polymer organic light emitting diodes. Adv. Mater. 22, 3762–3777 (2010)
R. Siefert, S. Scholz, B. Lüssem, K. Leo, Comparison of ultraviolet- and charge-induced degradation phenomena in blue fluorescent organic light emitting diodes. Appl. Phys. Lett. 97, 013308 (2010)
A. Maliakal, K. Raghavachari, H. Katz, E. Chandross, T. Siegrist, Photochemical stability of pentacene and a substituted pentacene in solution and in thin films. Chem. Mater. 16, 4980–4986 (2004)
A.B. Djurišić, T.W. Lau, C.Y. Kwong, L.S.M. Lam, W.K. Chan, Evolution of optical properties of tris (8-hydroxyquinoline) aluminum (Alq3) with atmosphere exposure. Proc. SPIE 4800, 200–207 (2003)
V.K. Shukla, S. Kumar, D. Deva, Light induced effects on the morphology and optical properties of tris-(8-hydroxyquinoline) aluminium (Alq3) small molecular thin film. Synth. Metals 156, 387–391 (2006)
T. Zyung, J.-J. Kim, Photodegradation of poly(p-phenylenevinylene) by laser light at the peak wavelength of electroluminescence. Appl. Phys. Lett. 67, 3420–3422 (1995)
H. Hintz, H.-J. Egelhaaf, L. Lüer, J. Hauch, H. Peisert, T. Chassé, Photodegradation of P3HT—a systematic study of environmental factors. Chem. Mater. 23, 145–154 (2011)
L. Lüer, H.-J. Egelhaaf, D. Oelkrug, G. Cerullo, G. Lanzani, B.-H. Huisman, D. de Leeuw, Oxygen-induced quenching of photoexcited states in polythiophene films. Org. Electron. 5, 83–89 (2004)
K.W. Von Benz, H.C. Wolf, Die konzentrationsabhängigkeit der energie-übertragung in anthracen-tetracen-mischkristallen. Z. Naturforschg. 19a, 177–181 (1964)
M. Pope, C.E. Swenberg, Electronic processes in organic crystals and polymers, 2nd edn. (Oxford University Press, New York, 1999)
S. Winter, S. Reineke, K. Walzer, K. Leo, Photoluminescence degradation of blue OLED emitters. Proc. SPIE 6999, 69992N (2008)
G. Nenna, M. Barra, A. Cassinese, R. Miscioscia, T. Fasolino, P. Tassini, C. Minarini, D. della Sala, Insights into thermal degradation of organic light emitting diodes induced by glass transition through impedance spectroscopy. J. App. Phys. 105, 123511 (2009)
H. Mattoussi, H. Murata, C.D. Merritt, Y. Iizumi, J. Kido, Z.H. Kafafi, Photoluminescence quantum yield of pure and molecularly doped organic solid films. J. App. Phys. 86, 2642–2650 (1999)
T. Fukuda, B. Wei, M. Ichikawa, Y. Taniguchi, Transient characteristics of organic light-emitting diodes with efficient energy transfer in emitting material. Thin Solid Films 518, 567–570 (2009)
K. Naito, A. Miura, Molecular design for non-polymeric organic dye glasses with thermal stability: relations between thermodynamic parameters and amorphous properties. J. Phys. Chem. 97, 6240–6248 (1993)
S. Wang, W.J. Oldham Jr., R.A. Hudack Jr., G.C. Bazan, Synthesis, morphology, and optical properties of tetrahedral oligo(phenylenevinylene) materials. J. Am. Chem. Soc. 122, 5695–5709 (2000)
WSxM software can be downloaded from the following address http://www.wsxmsolutions.com/
M. Valiev, E.J. Bylaska, N. Govind, K. Kowalski, T.P. Straatsma, H.J.J. van Dam, D. Wang, J. Nieplocha, E. Apra, T.L. Windus, W.A. de Jong, NWChem: a comprehensive and scalable open-source solution for large scale molecular simulations. Comput. Phys. Commun. 181, 1477–1489 (2010)
E.M. Han, J.J. Yun, G.C. Oh, S.M. Park, N.K. Park, Y.S. Yoon, M. Fujihira, Enhanced stability of organic thin films for electroluminescence by photoirradiation. Opt. Mater. 21, 243–248 (2003)
Y. Qiu, J. Qiao, Photostability and morphological stability of hole transporting materials used in organic electroluminescence. Thin Solid Films 372, 265–270 (2000)
E. Suljovrujić, M. Mićić, S. Demic, V.I. Srdanov, Combinatorial approach to morphology studies of epitaxial thin films. Appl. Phys. Lett. 88, 121902 (2006)
X. Zhang, Z. Wuan, B. Jiao, D. Wang, D. Wang, X. Hou, W. Huang, Solution-processed white organic light-emitting diodes with mixed-host structures. J. Lumin. 132, 697–701 (2012)
P.M. Borsenberger, J.J. Fitzgerald, Effects of the dipole moment on charge transport in disordered molecular solids. J. Phys. Chem. 97, 4815–4819 (1993)
R. Blossey, Thin film rupture and polymer flow. Phys. Chem. Chem. Phys. 10, 5177–5183 (2008)
D. Kondakov, Role of chemical reactions of arylamine hole transport materials in operational degradation of organic light-emitting diodes. J. Appl. Phys. 104, 084520–084528 (2008)
S.-Z. Wang, X. Fan, A.-L. Zheng, Y.-G. Wang, Y.-Q. Dou, X.-Y. Wei, Y.-P. Zhao, R.-Y. Wang, Z.-M. Zong, W. Zhao, Evaluation of atmospheric solids analysis probe mass spectrometry for the analysis of coal-related model compounds. Fuel 117, 556–563 (2014)
I. Reva, L. Lapinski, N. Chattopadhyay, R. Fausto, Vibrational spectrum and molecular structure of triphenylamine monomer: a combined matrix-isolation FTIR and theoretical study. Phys. Chem. Chem. Phys. 5, 3844–3850 (2003)
J. Workman Jr., The Handbook of Organic Compounds (Academic Press, San Diego, 2000)
F.-C. Wu, H.-L. Cheng, W.-Y. Chou, Studies of blue organic electroluminescent devices using the polymer/dopant systems as a light-emitting layer. Proc. SPIE 6655, 66551P (2007)
R. Scholz, L. Gisslén, C. Himcinschi, I. Vragović, E.M. Calzado, E. Louis, E.S.F. Maroto, M.A. Díaz-García, Asymmetry between absorption and photoluminescence line shapes of TPD: spectroscopic fingerprint of the twisted biphenyl core. J. Phys. Chem. A 113, 315–324 (2009)
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, 7991–8006 (1996)
D.L. Dexter, A theory of sensitized luminescence in solids. J. Chem. Phys. 21, 836–850 (1953)
Th Förster, 10th Spiers memorial lecture. Transfer mechanisms of electronic excitation. Discuss. Faraday Soc. 27, 7–17 (1959)
J.R. Lakowicz, Principles of Fluorescence Spectroscopy, 3rd edn. (Springer Science+Business Media, New York, 2006)
T. Tsuboi, A.K. Bansal, A. Penzkofer, Fluorescence and phosphorescence behavior of TPD doped and TPD neat films. Thin Solid Films 518, 835–838 (2009)
K.O. Cheon, J. Shinar, Förster energy transfer in combinatorial arrays of selective doped organic light-emitting devices. Appl. Phys. Lett. 84, 1201–1203 (2004)
W. Holzer, A. Penzkofer, H.-H. Horhold, Travelling-wave lasing of TPD solutions and neat films. Synth. Met. 113, 281–287 (2000)
M.P. Joshi, S. Raj Mohan, T.S. Dhami, B. Jain, M.K. Singh, H. Ghosh, T. Shripathi, U.P. Deshpande, Enhanced optoelectronic properties of UV-light-induced photodegraded TPD. Appl. Phys. A 90, 351–358 (2008)
S. Raj Mohan, M.P. Joshi, S.K. Tiwari, V.K. Dixit, T.S. Dhami, Electrical and optical characterization of photooxidized TPD. J. Mater. Chem. 17, 343–348 (2007)
H.-N. Liu, G. Zhang, L. Hu, P.-F. Su, Y.-F. Li, 4,4′-Bis(2,2-diphenylvinyl)-1,1′-biphenyl. Acta Cryst. E67, o220 (2011)
T. Virgili, D.G. Lidzey, D.D.C. Bradley, Efficient energy transfer from blue to red in tetraphenylporphyrin-doped poly(9,9-dioctylfluorene) light-emitting diodes. Adv. Mater. 12, 58–62 (2000)
E. Suljovrujic, A. Ignjatovic, V.I. Srdanov, T. Mitsumori, F. Wudl, Intermolecular energy transfer involving an iridium complex studied by a combinatorial method. J. Chem. Phys. 121, 3745–3750 (2004)
W. Klöpffer, Transfer of electronic excitation energy in polyvinyl carbazole. J. Chem. Phys. 50, 2337–2343 (1969)
D.C. Northrop, O. Simpson, Electronic properties of aromatic hydrocarbons. II Fluorescence transfer in solid Solutions. Proc. R. Soc. Lond. A 234, 136–149 (1956)
C. Madigan, V. Bulović, Modeling of exciton diffusion in amorphous organic thin films. Phys. Rev. Lett. 96, 046404 (2006)
T.-S. Ahn, N. Wright, C.J. Bardeen, The effects of orientational and energetic disorder on Forster energy migration along a one-dimensional lattice. Chem. Phys. Lett. 446, 43–48 (2007)
S.M. Menke, R.J. Holmes, Exciton diffusion in organic photovoltaic cells. Energy Environ. Sci. 7, 499–512 (2014)
H. Choukri, A. Fischer, S. Forget, S. Chénais, M.-C. Castex, D. Adès, A. Siove, B. Geffroy, White organic light-emitting diodes with fine chromaticity tuning via ultrathin layer position shifting. Appl. Phys. Lett. 89, 183513 (2006)
O.V. Mikhnenko, M. Kuik, J. Lin, N. van der Kaap, T.-Q. Nguyen, P.W.M. Blom, Trap-limited exciton diffusion in organic semiconductors. Adv. Mater. 26, 1912–1917 (2014)
Z. Zhang, E. Burkholderb, J. Zubieta, Non-merohedrally twinned crystals of N, N′-bis(3-methylphenyl)-N, N′-bis(phenyl)benzidine: an excellent triphenylamine-based hole transporter. Acta Cryst. C60, o452–o454 (2004)
Z.H. Kafafi, H. Murata, L.C. Picciolo, H. Mattoussi, C.D. Merritt, Y. Iizumi, J. Kido, Electroluminescent properties of functional π-electron molecular systems. Pure Appl. Chem. 71, 2085–2094 (1999)
G.J. Kavarnos, Fundamentals of photoinduced electron transfer (VCH Publishers, New York, 1993)
G. Schwartz, Novel concepts for high-efficiency white organic light-emitting diodes (PhD thesis), Dresden: Technischen Universität Dresden, 2007
J.B. Birks, The photophysics of aromatic excimers, in The exciplex, ed. by M. Gordon, W.R. Ware (Academic Press, New York, 1975), pp. 39–73
Acknowledgment
We thank Vojislav I. Srdanov for generous donation of his PVD apparatus and fruitful discussion. We acknowledge Zoran Velikić and Dragan Dramlić for UV−Vis spectroscopy, Suzana Veličković and Branislav Nastasijević for mass spectroscopy and Katarina Radulović for IR spectroscopy.
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Tomović, A.Ž., Đurišić, I., Žikić, R., Pejić, M., Jovanović, V.P. (2017). Interaction of UV Irradiation with Thin Films of Organic Molecules. In: Lee, B., Gadow, R., Mitic, V. (eds) Proceedings of the IV Advanced Ceramics and Applications Conference. Atlantis Press, Paris. https://doi.org/10.2991/978-94-6239-213-7_23
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