Electroluminescence Subject

The use of luminescent materials, the subject of Chapter 3, which was at one time confined largely to the production of fluorescent lamps and cathode ray tubes has spread further into everyday life. It is a common sight to see phosphorescent safety signage in low-light environments, to wear fluorescent garments, to look at electroluminescent displays and to use light emitting diodes in trafhc control and vehicle... 

An important application of polydimethylsilane is as a source of silicon carbide (SiC) fibres, which are manufactured under the trade-name Nicalon by Nippon Carbon in Japan. Heating in an autoclave under pressure converts polydimethylsilane to spinnable polycarbosilane (-Me2Si-CH2-) with elimination of methane. The spun fibres are then subjected to temperatures of 1200-1400 °C to produce silicon carbide fibres with very high tensile strengths and elastic moduli." As a result of their conductivity, polysilanes have also been used as hole transport layers in electroluminescent devices. In addition, the photoconductivity of polymethylphenylsilane doped with Cgo has been found to be particularly impressive. ... 

Electroluminescence (EL) spectra of P-l-P-4 are given in Fig. 6 [29,30]. The EL spectra of the polymers were obtained for the light-emitting diodes (LEDs) fabricated between the indium-tin oxide (ITO) coated glass anode and the aluminum cathode. For P-l-P-3, their organic soluble precursor polymers were coated onto the ITO-coated glass and they were subjected to thermolysis at 270 °C for 12 h to convert them into the final polymers. And then aluminum cathode was vacuum deposited on the polymer films. P-4 obtained by base-catalyzed polymerization of the bis-bromomethyl monomer was organic soluble and, thus,... 

DNA is said to be the molecular memory of living things. DNA is expected as electro-conductive [2] and ion conductive [3] materials, base materials for electroluminescence [4], and so on. There is wide number of trials of DNA reported in electrochemistry. We have been trying to solubihze DNAs in several organic solvents including ELs [5]. J. Davis and coworkers have also pursued this subject, and both groups have determined some ELs to be good solvents for DNA [6]. 

Another factor which determines the efficiency of LEDs is the photoluminescence (PL) efficiency, i.e. the fraction of photoexcited states which recombine radiatively. Since the radiative lifetime of most conjugated polymers is less than 1 ns and there are relatively few non-radiative channels for relaxation, the PL efficiency can be quite high. Many conjugated polymers have photoluminescence efficiencies higher than 60%. A subject of substantial debate is whether or not the electroluminescence (EL) efficiency can be as high as the photoluminescence (PL) efficiency. As summarized in Section IVB, EL efficiency as high as 50% of the PL efficiency has been demonstrated [158]. 

PLECs represent a dynamic research subject toward their promising applications in future lighting and display devices. Unlike PLEDs, the active materials of PLECs are composed of ionically conductive species and the electroluminescent conjugated polymer. 

Organic electroluminescent (EL) devices are the subject of study by many researchers because of their potential application as light-emitting devices which operate at low drive voltages. These devices are injection-type, in which carriers, such as electrons (radical anions) and holes (radical cations), are injected into the organic emitter layer where they recombine. It is, therefore, necessary for the component organic materials to possess carrier-transporting properties as well as fluorescence properties. 

Organic polymers that emit light on the imposition of an electric field have commanded increasing attention in the last decade both for their scientific interest and as potential materials for electrooptical and optoelectronic applications. A number of reviews on electroluminescent polymers focusing the basic physics [1-5], synthesis and properties [6,7], device operation and materials [8-11], design and synthesis [12] blue emitting structures [13] have been published. Some books are also out on the subject [14—18]. 

Although silane-based pol5miers are wcU-documented, the corresponding germanium-based materials have only recently been subjected to detailed investigation. This interest is a consequence of the physical properties of these materials common to the group 14 based polymers, namely their electroluminescence and conductivity when doped, typi-... 

Organic electroluminescent devices have been the subject of intense research for almost a decade. These organic molecule-based devices use a multilayer cell structure composed of emitted layers and carrier transport layers as shown by Tang et al. [264-5]. The next advance in these devices was the construction of a three-layer cell by Adachi et al. [266] in which the emitter layer was sandwiched between a hole transport layer and an electron transport layer in the belief that these layers would increase electroluminescent efficiency. The device has the type of constmction shown in Figure 12.25. Adachi et al. reported that with a 500 A° emitter thickness, the luminescence was 1000 Cd cm. ... 

Soluble 3.4-disubstituted polythiophenes have found application as antistaticcomponents for film materials and are on the market electrochromic and electroluminescent devices are subject to intensive research and surely will be effective in the near future. Biosensor devices with functionalized polythiophene carrier systems for immobilizing enzymes are also applicable for the electro-analytical determination of analytes in micromolar concentrations. 

The fabrication of polymer analogs of 8-hydroxyquinoline-based metal chelates (such as Alq3, etc.) for electroluminescence applications has been a challenging task. These metal chelate polymers are nontraditional polymers and are usually associated with considerable handling difficulties. Their major intricacy arises from complexation-decomplexation dynamics, which are very sensitive to the pH and ionic strength of the solute.(75) For linear metal chelate polymers, solubilization typically occurs only in polar aprotic solvents,(79) which are difficult to remove from spun films. The insoluble and intractable nature of these polymers makes them amenable to the self-assembly growth which is the subject of this paper. 

Therefore, in the year 2000, it is timely to publish The Handbook of Advanced Electronic and Photonic Materials and Devices. The editor, Hari Singh Nahva, is well known for his original work on nonlinear optics of organic molecules and polymers. Together with Seizo Miyata, he edited a comprehensive volume under this title that provides a broad overview of this particular subject. The same authors also edited a volume on organic electroluminescent materials and devices. 

Electroluminescent diodes are not the only way of practical appUcadon of luminescence. Luminescence of materials subjected to action of various types of electromagnetic radiation is used for its detection, for road signs visible at dusk and at night, and many other applications. 

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