Photo-conducting polymers

A major improvement was the usage of the photo-conductive polymer PVK. This allowed the concentration of the charge transport agent to be increased, while completely excluding crystallization of the carbazole groups [154], As chromophore, an azo dye 2,5-dimethyl-4-(p-nitrophenylazo)anisole (DMNPAA) was used, and TNF as a sensitizer. The compositions showed almost 100% diffraction efficiency at a laser intensity of 1 W cm and 90 V p,m biased voltage. However, the response time was slow, >100 ms. 

Photo-Conducting Polymers That Are Not Based on Carbazole. 771... 

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. 

Charge-carrier mobilities in amorphous disordered organic photo-conductive polymers that include molecularly doped polymers are typically near or below 10" m V s at E 10 Vm and T 295K. a-Conjugated silicon backbone polymers under similar conditions display hole mobilities around 1 m V s [40, 41]. 

Recently more attention has been paid to photo-conductive polymers having photoactive groups in the polymer backbone. The most widely studied polymers from this group are polyimides. Polyimides as well as... 

Electrode potentials components of, 9 energy scales and, 7 photo currents as a function of, 473 Electrode polymerization of conducting polymers, 314 and degradation, 325 degradation reactions simultaneous with, 326... 

This volume contains six chapters and a cumulative index for numbers 1-33. The topics covered include the potential of zero charge nonequilibrium fluctuation in the corrosion process conducting polymers, electrochemistry, and biomimicking processes microwave (photo)-electrochemistry improvements in fluorine generation and electronically conducting polymer films. 

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. 

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). 

A wide variety of methods exist for the immobilisation of enzymes on a sensor surface. Screen-printed carbon electrodes are often the favourite base for these sensors due to their inexpensiveness and ease of mass production. Methods used for the construction of AChE-containing electrodes include simple adsorption from solution [22], entrapment within a photo-crosslinkable polymer [20,23], adsorption from solution onto microporous carbon and incorporation into a hydroxyethyl cellulose membrane [24], binding to a carbon electrode via Concanavalin A affinity [25,26] and entrapment within conducting electrodeposited polymers [27]. 

Polaron Pair State. There are a number of experimental observations which can be interpreted neither by invoking charged excitations injected or photo-generated in the polymer, nor by excitons. However, it may happen that the singlet exciton is broken, as described above, and a pair of charges, negative P and positive P+ polarons, are separated onto adjacent chains, but still bound by the Coulomb attraction. These pairs will be referred to as polaron pairs. Polaron pairs are intermediate states between electronic molecular excitations and free charge carriers. They are formed by excitation of the photo-conductivity in polymers and other molecular solids, as well as... 

Nalwa HS, "Handbook of Organic Conductive Molecules and Polymers", Vol. 1, "Charge-Transfer Salts, Fullerenes and Photoconductors" Vol. 2, "Conductive Polymers Synthesis and Electrical Properties" Vol. 3, "Conductive Polymers Spectroscopy, Photo-Physics and Applications" Vol. 4, "Conductive Polymers Transport and Physical Properties", Wiley, Chichester, 1997. 

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