Photoconducting polymers

FURNACES,ELECTRIC - INDUCHON FURNACES] (Vol 12) -photoconductivity [PHOTOCONDUCTIVE POLYMERS] (Vol 18) for papermaking [PAPER] (Vol 18)... 

Photochemical technology Photoconductive polymers Photography Printing processes Radioactive tracers Radiopaques... 

Photoconductive polymers are widely used in the imaging industry as either photosensitive receptors or carrier (electron or hole) transporting materials in copy machines and laser printers. This is still the only area in which the photoelectronic properties of polymers are exploited on a large-scale industrial basis. It is also one electronic appHcation where polymers are superior to inorganic semiconductors. 

There are many excellent reviews of photoconductive polymers (4—10). This article emphasizes results obtained after 1980, up to early 1994. 

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

Fig. 2. Molecular structures of selected photoconductive polymers with pendent groups (1) poly(A/-vinylcarba2ole) [25067-59-8] (PVK), (2) A/-polysiloxane carbazole, (3) bisphenol A polycarbonate [24936-68-3] (4) polystyrene [9003-53-6] (5) polyvin5i(l,2-/n7 j -bis(9H-carba2ol-9-yl)cyclobutane) [80218-52-6]...

Liquid Crystalline Systems. Conventional photoconductive polymers are amphorous or systems withlow order. In the case of PVK, the hole moves by hoppiag between the pendent carba2ole groups. The hole mobilities are usuaUylow, cm /Vs, due to a trap-dominated hoppiag... 

The most important industrial appHcation of photoconductive polymers is electrophotography (qv). This is a biUion doUar industry and one of the few electronic areas where polymeric material excels. The principles and practices of electrophotography have been reviewed in detail elsewhere (9,85) and are not repeated here. 

The avaHabihty of photoconductive polymers opens up many areas for research, in addition to electrophotography. These are relatively unexplored areas and represent promising future directions. 

Recently photorefractivity in photoconductive polymers has been demonstrated (92—94). The second-order nonlinearity is obtained by poling the polymer doped with a nonlinear chromophore. Such a polymer may or may not be a good photoconductor. Usually sensitizers have to be added to enhance the charge-generation efficiency. The sensitizer function of fuUerene in a photorefractive polymer has been demonstrated (93). 

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