Photoconductive polymers based

Photoconductive polymers can be convenientiy classified into five categories based on thek stmctures and modes of photoconduction. 

The use of interpenetrating donor-acceptor heterojunctions, such as PPVs/C60 composites, polymer/CdS composites, and interpenetrating polymer networks, substantially improves photoconductivity, and thus the quantum efficiency, of polymer-based photo-voltaics. In these devices, an exciton is photogenerated in the active material, diffuses toward the donor-acceptor interface, and dissociates via charge transfer across the interface. The internal electric field set up by the difference between the electrode energy levels, along with the donor-acceptor morphology, controls the quantum efficiency of the PV cell (Fig. 51). 

New applications (e.g. demand for fluorescent, pearlescent and other brilliant pigments introduction of photoconductive elements in polymer-based electro-optical devices)... 

Another group of polyconjugated photoconductive polymers reported in the literature are poly(Schiff-bases)33, polycondensates of aromatic diamines and... 

To tune the sensitivity of a photorefractive polymer to a particular spectral region, the composite is doped with a sensitizer. Examples of widely used sensitizers are shown in Fig. 21. TNF was used in numerous polymers based on the photoconducting polymer PVK because mixtures of PVK/TNF were used in the first... 

Photoconductivity is based on the conversion of light to electricity. The reverse phenomenon, electroluminescence, is based on the conversion of electricity to light. Electroluminescence is useful for flat-panel display and 11-VI semiconductors such as ZnS are employed for this purpose [132], The current trend is toward the development of polymeric electroluminescent material for their processing flexibility [133,134]. It has already been demonstrated that properly doped semiconductor nanoclusters such as ZnIMn1 IS emits light efficiently [135], With the demonstration of photoconductivity [101 103] these nanocluster-doped polymers can become interesting candidates of electroluminescent materials. No experimental work has been performed yet. 

Very recently, the first metathesis reaction was utilized to synthesize a new type of photorefractive polymers, based on poly(1.6-heptadiyne) derivatives, that contain both a carbazole moiety as a hole transporter and NLO chromophores. attached to TT-conjugated backbones. Photorefractive polymers based on the previous works for the photoconductivity of poly(1.6-heptadiyne) derivatives containing a carbazole moiety and electrooptic activity of poly(1.6-heptadiyne) derivatives containing NLO chromophores were developed.Herein, all functional groups are covalently linked to the polymer backbone. 

A polymer composite with a low glass transition temperature has been described as based on layered photoconductive polymers, namely, poly(p-phenylene terephthalate carbazole)s. " These polymers consist of a rigid backbone of poly(pentylene terephthalate) with pendant oxyalkyl carbazole groups. When the host polymers are mixed with various dopants, the layers are preserved and their layer distance increases, indicating that all the guest molecules are confined to the nanoscale interlayer space. 

As regards photoconducting polymers, typical work has been carried out with poly(N-vinylcarbazole), PVK, and polysilylenes. The first commercial photoconductor was based on a 1 1 charge-transfer (CT) complex between PVK and trini-trofluorenone (TNF) [11]. Similar photoconductor properties were found with a 1 1 CT complex of TNF with poly[bis(2-naphthoxy)phosphazene] (see Chart 2.7), which is an insulator if dopant-free [54]. 

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. 

---