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Structural characteristics of iridium dual-emitter organometallic compound

Published online by Cambridge University Press:  24 November 2014

Silviu Polosan*
Affiliation:
National Institute for Materials Physics, Bucharest-Magurele 077125, Romania
Iulia Corina Ciobotaru
Affiliation:
National Institute for Materials Physics, Bucharest-Magurele 077125, Romania
Ionut Enculescu
Affiliation:
National Institute for Materials Physics, Bucharest-Magurele 077125, Romania
Constantin Claudiu Ciobotaru
Affiliation:
National Institute for Materials Physics, Bucharest-Magurele 077125, Romania
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

By combining two types of ligands, phenylpyridine and quinoline, a new type of organometallic IrQ(ppy)2 compound has been synthesized, which exhibits two phosphorescences: green and red. Using an appropriate catalyst, the final IrQ(ppy)2 compound has a good chemical yield up to 60% and becomes a stable dual emitter at room temperature. This compound is important because it exhibits stable red emission which is limited by the quantum yield due to the low energy band gap. As a result, an overlap between the ground state and the excited state occurs due to the vibrations that increase the nonradiative transitions, destroying the red emissions. Structural characteristics of the IrQ(ppy)2 powder reveal a triclinic structure confirmed by x-ray diffraction and scanning electron microscopy images. Thermal analysis of the final compound confirms a good stability against decomposition and structural changes up to 350 °C. X-ray photoelectron spectroscopy reveals Ir–O chemical bonds and several differences between the intermediate and final compounds, such as Ir–Cl bonds. Cathodoluminescence patterns show a phosphorescent triclinic structure with a higher efficiency for the red color. Backscattering electron images prove that there is a uniform distribution of iridium ions in the IrQ(ppy)2 nanocrystals.

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Articles
Copyright
Copyright © Materials Research Society 2014 

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References

REFERENCES

Yang, Q., Hao, Y., Wang, Z., Li, Y., Wang, H., and Xu, B.: Double-emission-layer green phosphorescent OLED based on LiF-doped TPBi as electron transport layer for improving efficiency and operational lifetime. Synth. Met. 162, 398 (2012).CrossRefGoogle Scholar
Rosselli, F.P., Quirino, W.G., Legnani, C., Calil, V.L., Teixeira, K.C., Leităo, A.A., Capaz, R.B., Cremona, M., and Achete, C.A.: Experimental and theoretical investigation of tris-(8-hydroxy-quinolinate) aluminum (Alq3) photo degradation. Org. Electron. 10, 1417 (2009).CrossRefGoogle Scholar
Shinar, J. and Shinar, R.: Organic light-emitting devices (OLEDs) and OLED-based chemical and biological sensors: An overview. J. Phys. D: Appl. Phys. 41, 133001 (2008).CrossRefGoogle Scholar
Mao, C.H., Hong, J.L., and Yeh, A.C.: Influence of aggregation on the phosphorescence of iridium complex in poly(methyl methacrylate) matrix. J. Polym. Sci. B 46, 631 (2008).CrossRefGoogle Scholar
Polosan, S. and Radu, I.C.: Mechanisms of the charge transfer in IrQ(ppy)2–5Cl dual-emitter compound. J. Nanosci. Nanotechnol. 13, 5203 (2013).CrossRefGoogle ScholarPubMed
Polosan, S., Radu, I.C., and Tsuboi, T.: Photoluminescence and magnetic circular dichroism of IrQ(ppy)2-5Cl. J. Lumin. 132, 998 (2012).CrossRefGoogle Scholar
Sengottuvelan, N., Yun, S.J., Kim, D.Y., Hwang, I.H., Kang, S.K., and Kim, Y.I.: Highly efficient red emissive heteroleptic cyclometalated iridium(III) complexes bearing two substituted 2-phenylquinoxaline and one 2-pyrazinecarboxylic acid. Bull. Korean Chem. Soc. 34, 167 (2013).CrossRefGoogle Scholar
Bera, N., Cumpustey, N., Burn, P.L., and Samuel, I.D.W.: Highly branched phosphorescent dendrimers for efficient solution-processed organic light-emitting diodes. Adv. Funct. Mater. 17, 1149 (2007).CrossRefGoogle Scholar
Sengottuvelan, N., Seo, H.J., Kang, S.K., and Kim, Y.I.: Tuning photophysical and electrochemical properties of heteroleptic cationic iridium(III) complexes containing substituted 2-phenylquinoxaline and biimidazole. Bull. Korean Chem. Soc. 31, 2309 (2010).CrossRefGoogle Scholar
Jung, N., Lee, E., Kim, J., Park, H., Park, K.M., and Kang, Y.: Synthesis and crystal structure of blue phosphorescent mer-tris(2',6'-difluoro-2,3'-bipyridinato-N,C4')iridium(III). Bull. Korean Chem. Soc. 33, 183 (2012).CrossRefGoogle Scholar
Rothmann, M.M., Fuchs, E., Schildknecht, C., Langer, N., Lennartz, C., Munster, I., and Strohriegl, P.: Designing a bipolar host material for blue phosphorescent OLEDs: Phenoxy-carbazole substituted triazine. Org. Electron. 12, 1192 (2011).CrossRefGoogle Scholar
Huang, D.F., Chow, T.J., Wu, C.Y., Sun, S.S., Tsai, S.H., Wen, Y.S., Polosan, S., and Tsuboi, T.: The preparation of (8-hydroxyquinolinato)bis(2-phenylpyridyl)iridium complexes and their photophysical properties. J. Chin. Chem. Soc. 55, 439 (2008).CrossRefGoogle Scholar
Yi, C., Yang, C.J., Liu, J., Xu, M., Wang, J.H., Cao, Q.Y., and Gao, X.C.: Red to near-infrared electrophosphorescence from an iridium complex coordinated with 2-phenylpyridine and 8-hydroxyquinoline. Inorg. Chim. Acta 360, 3493 (2007).CrossRefGoogle Scholar
Rachinger, W.A.: A correction for the α1 α2 doublet in the measurement of widths of x-ray diffraction lines. J. Sci. Instrum. 25, 254 (1948).CrossRefGoogle Scholar
Laetsch, T. and Downs, R.: Software for identification and refinement of cell parameters from powder diffraction data of minerals using the RRUFF project and American Mineralogist Crystal Structure Databases. Abstracts from the 19th General Meeting of the International Mineralogical Association, Kobe, Japan, 23–28 July (2006).Google Scholar
Lee, J., Park, K.M., Yang, K., and Kang, Y.: Blue phosphorescent Ir(III) complex with high color purity: fac-tris(2′,6′-difluoro-2,3′-bipyridinato-N,C4′)iridium(III). Inorg. Chem. 48, 1030 (2009).CrossRefGoogle Scholar
Wagner, C.D., Riggs, W.M., Davis, L.E., and Moulder, J.F.: Handbook of X-ray Photoelectron Spectroscopy, Muilenberg, G.E. ed.; Perkin Elmer, Physical Electronics Division: Eden Prairie, MN, 1978.Google Scholar
El-Issa, B.D., Katrib, A., Ghodsian, R., Salsa, B.A., and Addassi, S.H.: A comparative study of the bonding in different halides of iridium. Int. J. Quantum Chem. 33, 195 (1988).CrossRefGoogle Scholar
Atanasoska, L., Atanasoska, R., and Trassati, S.: XPS and AES study of mixed layers of RuO2 and IrO2 . Vaccum 40, 91 (1990).CrossRefGoogle Scholar
Atanasoska, L., Gupta, P., Deng, C., Warner, R., Larson, S., and Thompson, J.: XPS, AES, and electrochemical study of iridium oxide coating materials for cardiovascular stent application. ECS Trans. 16, 37 (2009).CrossRefGoogle Scholar
García de Abajo, F.J.: Optical excitations in electron microscopy. Rev. Mod. Phys. 82, 209 (2010).CrossRefGoogle Scholar
Radu, I.C., Polosan, S., Enculescu, I., and Iovu, H.: Cathodoluminescence and Raman analysis of the finite-size effects in mer-Alq3 structure. Opt. Mater. 35, 268 (2012).CrossRefGoogle Scholar