Applications, photoconductors

A rapidly increasing number of publications on polysilanes documents current interest in these polymers (JJ. Polysilanes are potentially applicable in microlithography as high resolution UV-resists (2J, imageable etch barriers ), or contrast enhancement layers (4). They have been successfully used as precursors to Si-C fibers (5J and ceramic reinforcing agents ((L). Polysilanes have also initiated polymerization of vinyl monomers (J ). Doping of polysilanes have increased their conductivity to the level of semiconductors (8). Very recently polysilanes were used as photoconductors (9) and non-linear optical materials (10b... 

Soluble polydiorganosilane homo and copolymers have recently shown great potential in such areas as precursors for the preparation of silicon carbide fibers (1), as photoinitiators in alkene polymerization (2), as photoconductors (3), and as positive or negative self-developing photoresists for photolithographic applications (4). A number of copolydiorganosilane copolymers have been reported recently (5) in which the copolymer contained equal amounts of both monomers in the feed. 

The related metastable material ZnIn2S4, which has potential applications as a photoconductor material, was deposited using LP-MOCVD at 400 °C from the indium-zinc precursor [(Et)2In(S2CNEt2)Zn(Et)(S2CNEt2)].335... 

As with the triarylamines, the triphenylmethanes were first developed for xerographic and photoconductor applications [103], The prototypical example of a material of this type is MPMP (58) shown in Scheme 3.22. 

PBO polymers, 13 377. See also Poly(p-phenylene benzobisoxazole) (PBO) applications of, 13 379 degradation of, 13 379 early syntheses of, 13 378 PB resin, properties of, 20 419t PbSe photoconductors, 19 157 PbS photoconductors, 19 157 PBT molding resins, 20 62-64. See also Poly(butyleneterephthalate) (PBT) PBT polymer... 

The chemical modification of fullerenes has received considerable attention in the last decade in order to achieve new applications to material sciences [27]. Fuller-ene-bonded polysilane derivatives might be expected to show high conductivity since Ceo-doped polysilane is found to be a good photoconductor [28]. Therefore, a variety of silylated derivatives have been obtained to date, although the available methods are limited to the photoinduced addition of various silanes to Ceo-... 

Coloured materials find application in both toners and organic photoconductors fused in electrophotography. Photoconductors will be covered in detail in Chapter 4 (section 4.4) and only toner resins will be considered in this section. 

The energy associated with one photon of visible light ranges from 2.4 to 5.0x10 J. The band gap in selenium is 2.9x10 J. Explain why selenium is a good material to use as a photoconductor in applications such as photocopiers. 

Tetrapyrroles contain an extended jt-conjugated system which is responsible for their use in a wide range of applications ranging from technical (pigments, catalysts, photoconductors) to medicinal (photodynamic therapy) uses. The electronic absorption spectra are governed by the aromatic 18 tt-electron system and typically consist of two main bands. In phthalocyanines the Q band around 660-680 nm is the most intense one accompanied by a weaker Soret band near 340 nm . In porphyrins the situation is reversed with an... 

The present position as regards the industrial application of the dark- and photoconductor properties of organic dyes is outlined in this paper. 

As in inorganic photoconductors, with organic dyes and other organic compounds, too, photocurrents and photovoltages may be observed without the application of auxiliary voltages. The following effects may be mentioned. 

Polymers with saturated bonds, heteroatoms, heterostructures and poly-conjugated ones are available now as photosensitive materials. Really one cannot expect a single mechanism to be reponsible for photoconductivity in so many diverse systems. However, there are a lot of verified factors which permit us to explain the main features of the photoconductive processes in polymers. The status and prospects of the application of polymeric photoconductors as prospective new electronic materials will be also analyzed for various types of photoconductors. 

As already shown, the sensitized spectra follow the dye absorption. Most of the dyes have sufficiently narrow absorption bands. This does not permit us to obtain the panchromatic sensitivity in the sufficiently broad spectral range. It was proposed to use the polymers with conjugated bonds as sensitizers [21]. The broad diffuse absorption spectra are inherent to such compounds. One can expect higher thermal stability from such sensitizers. In addition the application of binder may be omitted from the preparation of the photosensitive layers, for example, in electrophotography. Polymers with triple bonds, polyphenylenes and polyoxiphenylenes were used as sensitizers [10, 14, 278-280]. The typical results are shown in Fig. 47. The main rules for photoconductivity sensitized by polymers were the same as for the dyes. Optimum sensitization was obtained at the concentration of the sensitizer of 10 1-10-2 g/cm3 relative to the polymeric photoconductor weight. 

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