Poly photo conductivity

The properties are very sensitive to composition and the charge carriers are apparently positive. Other studies have shown poly(acenaph-thalene) to be only slightly photo-conductive while the nitrated polymer exhibits a photocurrent dependent upon the degree of nitration (100). Since the number of mobile n electrons is the same as in poly (vinyl naphthalene), the authors conclude that some form of stereoregularity is required for enhanced conductivity. Complexes of poly(vinyl anthracene) with halogen molecules show enhanced conductivity and reduced activation energy which is thought to be typical of an electronic semiconductor (101). 

The enhanced flow of current under the influence of an apphed electric field that occurs when a semiconductor is exposed to visible light or other electromagnetic radiation is known as photoconduction. Poly (N-vinyl carbazole) (VII) and various other vinyl derivatives of polynuclear aromatic compounds such as poly(2-vinyl carbazole) (Vin) and poly(vinyl pyrene) (DC) have high photo-conductive efficiencies. The excellent photoconductivities of these polymers are believed to be due to their helical condormation with successive aromatic side chins lying parallel to each other in a stack along which electron transfer takes place relatively easily. 

These dyes were then shown to sensitize photo-conductivity of poly(W-vinyl carbazole). Polyacetylene derivatives exhibit unique characteristics such as semiconductivity, high gas permeability, helix inversion, and nonlinear optical properties [253]. Attempts were made, therefore, to incorporate carbazole into polyacetylene in hope of attaining enhance properties [253]. 

Since the photoconductive properties of poly(A-vinylcarbazole) (PVK) were revealed, carbazole-based polymeric materials have been extensively studied [264-266]. Recently, there has been a renewed interest in the study of photo-conductive polymer composites. Photoactive dopants capable of charge injection into the polymer matrix are normally employed. Of these photoactive dopants, C60 and CNTs as well as inorganic SCs have been shown to be among the most efficient to date [267]. 

In single layer devices the low efficiency frequently is due to the imbalance of electrons and holes. Inserting a hole-transport (electron-blocking) or electron transport (hole-blocking) layer provides a means to enhance minority carriers and block the majority carriers and confine them to the emitter layer, which increases the probability of recombination. Poly(N-vinylcarbazole) (PVK) has been used as a hole transport layer and occasionally in blends with the emitter polymer. PVK is a well-studied photo-conductive polymer which often forms exciplexes with organic molecules, e.g., dimethyl terephthalate. An exciplex is a transient donor-acceptor complex between the excited state of the donor and the ground state of the acceptor. ... 

Electriad and dielectric behaviour of polymers reflect macromolecular structure and motion, both in solution and the solid state. Some polymers whidt have special electrical properties may have commaical potential. Mention need ordy be made of polymer electrets, pyro-electrk polymers, photo-conductive polymers as used In ctro-imaging, and conductive poly mas to indicate tR expansion of use over that of insulators. The separation of electrical behaviour into didectric and btdk conductive properties is convenient and has been followed in this review. 

Binh, N. T., Gailberger, M., and Bassler, H., Photo-conduction in poly(3-alkylthiophene) I. Charge carrier generation, Synth. Met., 47, 77, 1992. 

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. 

Meijer, F.W., Nijhuis, S., and Vroonhoven, F.C.B.M. (1988) Poly-1,2-azepines by the photo-polymerization of phenyl azides. Precursors for conducting polymer films./. Am. Chem. Soc. 110, 7209-7210. 

Irradiations were conducted at 366 nm (Corning 7-83 filter combination) in a merry-go-round apparatus in which the samples rotated about a stationary 450-Watt Hanovia medium pressure lamp for constant light exposure. The samples consisted of degassed 5 ml solutions of the photo initiators in neat MMA contained in Pyrex tubes. Two initiator concentrations were utilized 1.05 x 10 3 and 4.11 x 10 2 M, which corresponded to 16 and > 99% light absorption, respectively. Samples were irradiated to about 7% monomer conversions which required 15 min for the optically dense solutions and 30 min for the tubes with low initiator concentration. The resulting poly-... 

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