|This article needs additional citations for verification. (January 2010) (Learn how and when to remove this template message)|
Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation.
When light is absorbed by a material such as a semiconductor, the number of free electrons and electron holes increases and raises its electrical conductivity. To cause excitation, the light that strikes the semiconductor must have enough energy to raise electrons across the band gap, or to excite the impurities within the band gap. When a bias voltage and a load resistor are used in series with the semiconductor, a voltage drop across the load resistors can be measured when the change in electrical conductivity of the material varies the current through the circuit.
Classic examples of photoconductive materials include :
- the conductive polymer polyvinylcarbazole, used extensively in photocopying (xerography);
- lead sulfide, used in infrared detection applications, such as the U.S. Sidewinder and Soviet (now Russian) Atoll heat-seeking missiles;
- selenium, employed in early television and xerography.
When a photoconductive material is connected as part of a circuit, it functions as a resistor whose resistance depends on the light intensity. In this context, the material is called a photoresistor (also called light-dependent resistor or photoconductor). The most common application of photoresistors is as photodetectors, i.e. devices that measure light intensity. Photoresistors are not the only type of photodetector—other types include charge-coupled devices (CCDs), photodiodes and phototransistors—but they are among the most common. Some photodetector applications in which photoresistors are often used include camera light meters, street lights, clock radios, and infrared detectors.
Some materials exhibit deterioration in photoconductivity upon exposure to illumination. One prominent example is hydrogenated amorphous silicon (a-Si:H) in which a metastable reduction in photoconductivity is observable (see Staebler–Wronski effect). Other materials that were reported to exhibit negative photoconductivity include molybdenum disulfide, graphene, and metal nanoparticles.
- Photoresistor (LDR)
- Photo conductive polymers
- Infrared detector
- DeWerd, L. A.; P. R. Moran (1978). "Solid-state electrophotography with Al2O3". Medical Physics. 5 (1): 23–26. Bibcode:1978MedPh...5...23D. doi:10.1118/1.594505. PMID 634229.
- Saghaei, Jaber; Fallahzadeh, Ali; Saghaei, Tayebeh (June 2016). "Vapor treatment as a new method for photocurrent enhancement of UV photodetectors based on ZnO nanorods". Sensors and Actuators A: Physical. 247: 150–155. doi:10.1016/j.sna.2016.05.050.
- Law, Kock Yee (1993). "Organic photoconductive materials: recent trends and developments". Chemical Reviews, American Chemical Society. 93: 449–486. doi:10.1021/cr00017a020.
- N V Joshi (25 May 1990). Photoconductivity: Art: Science & Technology. CRC Press. ISBN 978-0-8247-8321-1.
- Staebler, D. L.; Wronski, C. R. (1977). "Reversible conductivity changes in discharge-produced amorphous Si". Applied Physics Letters. 31 (4): 292. Bibcode:1977ApPhL..31..292S. doi:10.1063/1.89674. ISSN 0003-6951.
- Serpi, A. (1992). "Negative Photoconductivity in MoS2,". Physica Status Solidi (a). 133 (2): K73–K77. Bibcode:1992PSSAR.133...73S. doi:10.1002/pssa.2211330248. ISSN 0031-8965.
- Heyman, J. N.; Stein, J. D.; Kaminski, Z. S.; Banman, A. R.; Massari, A. M.; Robinson, J. T. (2015). "Carrier heating and negative photoconductivity in graphene". Journal of Applied Physics. 117 (1): 015101. arXiv:. Bibcode:2015JAP...117a5101H. doi:10.1063/1.4905192. ISSN 0021-8979.
- Nakanishi, Hideyuki; Bishop, Kyle J. M.; Kowalczyk, Bartlomiej; Nitzan, Abraham; Weiss, Emily A.; Tretiakov, Konstantin V.; Apodaca, Mario M.; Klajn, Rafal; Stoddart, J. Fraser; Grzybowski, Bartosz A. (2009). "Photoconductance and inverse photoconductance in films of functionalized metal nanoparticles". Nature. 460 (7253): 371–375. Bibcode:2009Natur.460..371N. doi:10.1038/nature08131. ISSN 0028-0836.
|This Condensed Matter Physics-related article is a stub. You can help Wikipedia by expanding it.|