Conjugated polymers Electroluminescence

Conjugated polymer electroluminescence R.H. Friend and N.C. Greenham Physical Properties of Polymers Handbook, J.E. Mark, Ed., AIP Press, New York, pp. 479-487... 

The apphcation of a high electric field across a thin conjugated polymer film has shown the materials to be electroluminescent (216—218). Until recentiy the development of electroluminescent displays has been confined to the use of inorganic semiconductors and a limited number of small molecule dyes as the emitter materials. Expansion to the broad array of conjugated polymers available gives advantages in control of emission frequency (color) and facihty in device fabrication as a result of the ease of processibiUty of soluble polymers (see Chromogenic materials,electrochromic). 

The enormous progress in the field of electroluminescent conjugated polymers has led to performances of oiganic light-emitting devices (LEDs) that are comparable and in some aspects superior to their inorganic counterparts 11). Quantum efficiencies in excess of 5% have been demonstrated [2] and show that a high fraction of the injected carriers in a polymeric electroluminescence (EL) device form electronic excitations which recombine radiatively. 

G. Leising, S. Tasch. W. Graupncr, Fundamentals of Electroluminescence in Paraphcnylene-Typc Conjugaled Polymers and Oligomers, in Handbook of Conducting Polymers (Eds. T. Skotheim, R. Elsenbaumer, J. Reynolds), Marcel Dekker, New York 1997. 

Light-emitting diodes (LEDs) based on the electroluminescent conjugated polymers (Fig. 47) have attracted significant attention, both in academic research and industrial development, and are now on the edge of commercialization (Burroughs et al. 1990, Barth and Bassler 1997). Polymer LEDs require properties such as shown in Table 11. Recently, ef-... 

In electroluminescent applications, electrons and holes are injected from opposite electrodes into the conjugated polymers to form excitons. Due to the spin symmetry, only the antisymmetric excitons known as singlets could induce fluorescent emission. The spin-symmetric excitons known as triplets could not decay radiatively to the ground state in most organic molecules [65], Spin statistics predicts that the maximum internal quantum efficiency for EL cannot exceed 25% of the PL efficiency, since the ratio of triplets to singlets is 3 1. This was confirmed by the performance data obtained from OLEDs made with fluorescent organic... 

B Grem, G Leditzky, B Ullrich, and G Leising, Blue electroluminescent device based on a conjugated polymer, Synth. Met., 51 383-389, 1992. 

A Kraft, AC Grimsdale, and AB Holmes, Electroluminescent conjugated polymers — seeing polymers in a new light, Angew. Chem. Int. Ed., 37 402-428, 1998. 

Optically detected magnetic resonance (ODMR) studies of -iT-conjugated polymer-based hght emitting diodes (LEDs) J. Shinar Organic Electroluminescent Materials and Devices, S. Miyata and H.S. Nalwa, Eds., Gordon and Breach, Amsterdam, pp.177-202... 

J.-H. Lee, J.-W. Park, and S.-K. Choi, Synthesis and electroluminescent property of a new conjugated polymer based on carbazole derivative poly(3,6-lV-2-ethylhexyl carbazolyl cyanoter-ephthalidene), Synth. Met., 88 31-35, 1997. 

P.L. Bum, A.B. Holmes, A. Kraft, D.D.C. Bradley, A.R. Brown, and R.H. Friend, Synthesis of a segmented conjugated polymer-chain giving a blue-shifted electroluminescence and improved efficiency, J. Chem. Soc., Chem. Commune. 32-34, 1992. 

J. Pei, W.-L. Yu, W. Huang, and A.J. Heeger, The synthesis and characterization of an efficient green electroluminescent conjugated polymer poly[2,7-h s(4-hexylthienyl)-9,9-dihexylfluorene], Chem. Commune. 1631-1632, 2000. 

M. Chen, E. Perzon, M.R. Andersson, S.K.M. Jonsson, M. Fahlman, and M. Berggren, 1 Micron wavelength photo- and electroluminescence from TT-conjugated polymer, Appl. Phys. Lett., 84 3570-3572, 2004. 

J. Huang, H. Zhang, W. Tian, J. Hou, Y. Ma, J. Shen, and S. Liu, Violet-blue electroluminescent diodes utilizing conjugated polymer blends, Synth. Met., 87 105-108, 1997. 

G. Grem and G. Leising, Electroluminescence of wide-bandgap chemically tunable cyclic conjugated polymers, Synth. Met., 57 4105-4110, 1993. 

Y. Zhu, M.M. Alam, and S.A. Jenekhe, Regioregular head-to-tail poly(4-alkylquinoline)s synthesis, characterization, self-organization, photophysics, and electroluminescence of new n-type conjugated polymers, Macromolecules, 36 8958-8968, 2003. 

X. Zhang and S.A. Jenekhe, Electroluminescence of multicomponent conjugated polymers. 1. Roles of polymer/polymer interfaces in emission enhancement and voltage-tunable multicolor emission in semiconducting polymer/polymer heterojunction, Macromolecules, 33 2069-2082, 2000. 

Y. Cui, X. Zhang, and S.A. Jenekhe, Thiophene-linked polyphenylquinoxaline a new electron transport conjugated polymer for electroluminescent devices, Macromolecules, 32 3824—3826,1999. 

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