Electroluminescent properties polymers

Since multiple electrical and optical functionality must be combined in the fabrication of an OLED, many workers have turned to the techniques of molecular self-assembly in order to optimize the microstructure of the materials used. In turn, such approaches necessitate the incorporation of additional chemical functionality into the molecules. For example, the successive dipping of a substrate into solutions of polyanion and polycation leads to the deposition of poly-ionic bilayers [59, 60]. Since the precursor form of PPV is cationic, this is a very appealing way to tailor its properties. Anionic polymers that have been studied include sulfonatcd polystyrene [59] and sulfonatcd polyanilinc 159, 60]. Thermal conversion of the precursor PPV then results in an electroluminescent blended polymer film. 

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-... 

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. 

H. Wang, L. Duan, Y. Qui, X. Wang, and D. Liu, Synthesis and electroluminescence properties of a novel poly(p-phenylene vinylene)-based copolymer with tri(ethylene oxide) segments on the backbone, J. Appl. Polym. Sci., 83 2195-2200, 2002. 

M. Remmers, D. Neher, J. Griiner, R.H. Friend, G.H. Gelinck, J.M. Warman, C. Quattrocchi, D.A. dos Santos, and J.-L. Bredas, The optical, electronic, and electroluminescent properties of novel poly(p-phcnylcnc)-rclatcd polymers, Macromolecules, 29 7432-7445, 1996. 

Various arylene dihalides and heteroarylene dihalides are applicable to the reaction of bisallene 163, and polymers 164 of various structures are available in good to excellent yields (M of 15 000-22000 with PDI of ca. 2.0). Photoluminescent and electroluminescent properties of the polymer 164 are also studied. 

Of much interest are the electroluminescence properties of conjugated polymers that allow the development of electrically switched light-emitting devices [8.257]. Electric field activated bistable molecules are expected to switch at a critical field strength [8.258]. 

Despite the extensive application of ruthenium complexes in DSSC, transition metal containing polymers have received relatively little attention in the fabrication of polymeric photovoltaic cells. Most of the early works on ruthenium containing polymers were focused on the light-emitting properties.58-60 Several examples of ruthenium terpyridine/bipyridine containing conjugated polymers and their photoconducting/electroluminescent properties were reported.61,62... 

High and low molecular weight electroactive polymers containing pendant 2-(7-benzothiazolyl-9,9 -dioctylfluorene) units have been prepared. These materials display electroluminescent properties that are useful in electronic devices. 

Conjugated polymers like poly(l,4-phenylene-vinylene), PPV, or more generally Poly(arylene-vinylenes), PAVs have evoked considerable interest as electrically conductive and nonlinear optical materials. More recently, electroluminescence properties of PPV have attracted substantial attention, since it was first reported in 1990. Direct synthesis of PPV has been limited by its insolubility. Hence, the most commonly used routes are based on soluble polymer precursors or soluble conjugated precursors. The latter process is also commonly referred to as the sulfonium-based polyelectrolyte precursor route. PPV thin films from these solution-based routes, however, have problems related to contamination by solvents and oxidative defects in the polymer. C VP is an alternate method for the deposition of high quality thin films of PPV. Reported first by Iwatsuki et al., it was investigated for electroluminescence applications by Staring et al. ... 

Remmers M, Neher D, Gruener J, Friend RH, Gelinck GH, Warman JM, Quattrocchi C, dos Santos DA, Bredas J-L. (1996) The optical, electronic, and electroluminescent properties of novel poly(p-phenylene)-related polymers. Macromol29 7432-7445. 

X. Wu, G. Shi, F. Chen, S. Han, and J. Peng. High-quality poly[2-meth-oxy-5-(2 -ethylhexyloxy)-p-phenylenevinylene] synthesized by a solid-liquid two-phase reaction Characterizations and electroluminescence properties. J. Polym. Set, Part A Polym. Chem., 42(12) 3049-3054, June 2004. 

R.-H. Lee, H.-E. Hsu, L.-H. Chan, and C.-T. Chen. Synthesis and electroluminescence properties of a novel tetraphenylsilane-oxadiazole-diphen-yl(para-tolyl)amine polymer. Polymer, 47(20) 7001-7012, September 2006. 

N.S., Hoppe, H., 2012. Charge carrier mobility, photovoltaic, and electroluminescent properties of anthracene-based conjugated polymers bearing randomly distributed side chains. J. Polym. Sci. Part A Polym. Chem. 50, 3425-3436. 

Unless the electrical properties of light emiting devices are first understood it seems most unlikely that their electroluminescent properties, which are dependent on the electrical properties, can be completely understood, llie possibility must be considered that under appropriate conditions, EB might act both as a good electron and as a good hole transporting material. It may be concluded that reduction in injection barriers for electrons or holes may possibly be optimized by judicious matching of electrode material which interacts chemically in a favorable manner with the polymer with which it is in contact and that the nature of the polymer/polymer interface may also play a critical role. 

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