Photoconducting materials

Nanoclusters/Polymer Composites. The principle for developing a new class of photoconductive materials, consisting of charge-transporting polymers such as PVK doped with semiconductor nanoclusters, sometimes called nanoparticles, Q-particles, or quantum dots, has been demonstrated (26,27). 

This new optical data storage device is reported to be robust and nonvolatile. The response time for the write—read beam is in the subnanosecond range, and no refreshing is requked for long-term retention of trapped charges (95). The basic principle may be appHed to other, similar photoconductive materials. 

Another interesting applications area for fullerenes is based on materials that can be fabricated using fullerene-doped polymers. Polyvinylcarbazole (PVK) and other selected polymers, such as poly(paraphcnylene-vinylene) (PPV) and phenylmethylpolysilane (PMPS), doped with a mixture of Cgo and C70 have been reported to exhibit exceptionally good photoconductive properties [206, 207, 208] which may lead to the development of future polymeric photoconductive materials. Small concentrations of fullerenes (e.g., by weight) lead to charge transfer of the photo-excited electrons in the polymer to the fullerenes, thereby promoting the conduction of mobile holes in the polymer [209]. Fullerene-doped polymers also have significant potential for use in applications, such as photo-diodes, photo-voltaic devices and as photo-refractive materials. 

Heterocycles as photoconductive materials used for electrophotographic organic photoreceptors 99YGK541. 

Possible ways in which polysilanes may be useful include, 1. As precursors to silicon carbide ceramics 2. As photoinitiators in radical reactions 3. As photoconductive materials, and 4. As photoresists in microelectronics. The last of these uses will be treated in the chapter by Miller,(31) and so will not be covered here. 

The synthesis of oxo-squaraines and related compounds, including their spectral properties and applications as biomedical probes, photoconducting materials, and photosensitizers are provided in a recent review [56]. 

KY Law, Organic photoconductive materials recent trends and developments, Chem. Rev., 93 449-486, 1993. 

The traditional source in IR absorption spectroscopy is a glowing rod or wire heated by the passage of an electric current the hot body emits radiation over a continuous frequency range. The radiation is dispersed using a prism NaCl, which is transparent over much of the IR region, is commonly used for IR prisms and windows. The sample may be a solid, liquid, or gas. Various detectors are used the most common are thermocouples, photoconductive materials such as PbS, bolometers (which are temperature-dependent resistors), and the Golay cell (which uses the thermal expansion of a gas contained in a chamber). 

Addition polymers of pyrrole derivatives have attracted considerable interest. This interest has centered largely around two areas, the relationship of these materials to biological systems and the preparation of photoconductive materials. 

The oxadiazole (169) and the pyrazoline (170) are charge transport compounds in photoconductive materials (81GEP2715714, 81JAP56080051). 

The most useful of the known photorefractives are LiNbC>3 and BaTiC>3. Both are ferroelectric materials. Light absorption, presumably by impurities, creates electron/hole pairs within the material which migrate anisotropically in the internal field of the polar crystal, to be trapped eventually with the creation of new, internal space charge fields which alter the local index of refraction of the material via the Pockels effect. If this mechanism is correct (and it appears established for the materials known to date), then only polar, photoconductive materials will be effective photorefractives. However, if more effective materials are to be discovered, a new mechanism will probably have to be discovered in order to increase the speed, now limited by the mobility of carriers in the materials, and sensitivity of the process. 

The photoconductive properties of the fluorene-derived polymers 19, 23, and 24 were studied by the single-layer photocells in the configuration of ITO/Pt polyyne/Al. These polymers show moderate photoconductivity. A PCQE of 0.01 % was estimated in these cases, which does not vary much with variation of the central fluorene ring.26,30 Likewise, polymer 44 was also shown to be a photoconducting material in a similar architecture with a PCQE of 0.01 % in the forward bias mode. 

Considerable effort has been expended upon investigating the electronic absorption and fluorescence properties of carbazole derivatives or molecules containing a carbazole moiety/substructure, due to the interest of these compounds for application as nonlinear optical chromophores and as photoconducting materials. In the following, selection of papers is guided mainly by criteria of structural relevance, omitting very bulky molecules in which the carbazole unit is not prominent, or studies of luminescence properties. An overview of the electronic absorption spectra of carbazole derivatives is provided in Table 24. 

In conventional xerography, an electrostatic latent image is created on the surface of a photoconducting material, made visible by toner particles, transferred to a paper receiver, then made permanent by a fusing process. In a... 

---