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Definitions

Photoconductivity is an optical and electrical phenomenon, which material’s electrical conductivity increase by absorption of electromagnetic radiation (e.g. visible light, ultraviolet light, infrared light). Photoconductive polymers can serve as good insulators when the electricity, free electrons and holes are absent. When light is absorbed by a material, the number of free electrons and electron holes increases and raises its electrical conductivity. To cause excitation, the light that strikes to the materials must have enough energy to raise electrons across the band gap, or to excite the impurities within the band gap. And this process will involve four kinds of processes: charge-carrier generation, charge injection, charge trapping, charge carrier transport. The most important process is charge carrier transport. Photoconductive polymers have been developed into different types, there are two mainly types, one is negative photoconductivity, another one is magnetic photoconductivity. The photoconductive polymers have been greatly enriched the photoconductive material, and there are many applications (e.g. xerography, laser printers)

poly(vinylcarbazole)(PVK), a conductive polymer, in which conductivity is photon-dependent. The compound is used in the photoreceptors of photocopiers. The development of organic polymeric photoconductors was stimulated by the discovery of PVK.

This is a schematic representation of the flow of photocurrent in a photoconductive insulator. When insulators exposed under light, it will increase the number of free electrons and electron holes and raise its electrical conductivity.

References

1. J.A. Chilton; M.T. Goosey (1995) Special Polymers for Electronics and Optoelectronics 2. Haarer, Dietrich (1990). PHOTOCONDUCTIVE POLYMERS: STRUCTURE, MECHANISMS AND PROPERTIES. 3. Norio Ise; Iwao Tabushi (1983). An Introduction to Speciality Polymers 4. Ha Ngoc Giang; Kenji Kinashi; Wataru Sakai; Naoto Tsutsumi; Triphenylamine photoconductive polymers for high performance photorefractive devices 5. N. C. Greenham; Xiaogang Peng; and A. P. Alivisatos; Charge separation and transport in conjugated-polymer/semiconductor-nanocrystal composites studied by photoluminescence quenching and photoconductivity 6. N V Joshi (1990). Photoconductivity: Art: Science & Technology. CRC Press. ISBN 978-0-8247-8321-1 7. Roy A. Allan (1 October 2001). A History of the Personal Computer: The People and the Technology. Allan Publishing. pp. 13–. ISBN 978-0-9689108-3-2.