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Photoconductivity
 
 
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Photoconductivity is an optical
Optical phenomenon

An optical phenomenon is any observable event which results from the interaction of light and matter. See also list of optical topics and optics....
 and electrical phenomenon in which a material becomes more conductive due to the absorption of electro-magnetic radiation such as visible light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
, ultraviolet
Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 400 nanometer to 10 nm, and energies from 3 Electron volt to 124 eV....
 light, infrared
Infrared

Infrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves ....
 light, or gamma radiation. When light is absorbed by a material like a semiconductor
Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
, the number of free electrons and electron hole
Electron hole

An electron hole is the conceptual and mathematical opposite of an electron, useful in the study of physics and chemistry. The concept describes the lack of an electron....
s changes and raises the electrical conductivity of the semiconductor. To cause excitation, the light that strikes the semiconductor must have enough energy to raise electrons across the forbidden band gap
Band gap

In solid state physics and related applied fields, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states exist....
, or by exciting the impurities within the band gap.






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Encyclopedia


Photoconductivity is an optical
Optical phenomenon

An optical phenomenon is any observable event which results from the interaction of light and matter. See also list of optical topics and optics....
 and electrical phenomenon in which a material becomes more conductive due to the absorption of electro-magnetic radiation such as visible light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
, ultraviolet
Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 400 nanometer to 10 nm, and energies from 3 Electron volt to 124 eV....
 light, infrared
Infrared

Infrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves ....
 light, or gamma radiation. When light is absorbed by a material like a semiconductor
Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
, the number of free electrons and electron hole
Electron hole

An electron hole is the conceptual and mathematical opposite of an electron, useful in the study of physics and chemistry. The concept describes the lack of an electron....
s changes and raises the electrical conductivity of the semiconductor. To cause excitation, the light that strikes the semiconductor must have enough energy to raise electrons across the forbidden band gap
Band gap

In solid state physics and related applied fields, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states exist....
, or by exciting 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 varies the current flowing through the circuit. Two classic examples of photoconductive materials are the polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 polyvinylcarbazole, which is used extensively in photocopying (xerography
Xerography

Xerography is a photocopying technique developed by Chester Carlson in 1938 and patented on October 6, 1942. He received for his invention. Although dry electrostatic printing processes had been invented as far back as 1778 by Georg Christoph Lichtenberg, Carlson's innovation combined electrostatic printing with photography....
); and lead sulfide
Lead(II) sulfide

Lead sulfide is a chemical compound , most often purified from the mineral galena. PbS, lead selenide and lead telluride lead salts are semiconductors of the IV-VI family....
, used in infrared detection applications, such as the U.S. Sidewinder and Russian Atoll
Vympel K-13

The K-13 , was one of the world's most proliferated air-to-air missiles. Developed by the Soviet Union as a reverse-engineered copy of the AIM-9 Sidewinder, it saw widespread service in many nations....
 heat-seeking missile
Missile

A guided missile is a self-propelled projectile used as a weapon. Missiles are typically propelled by rockets or jet engines. Missiles generally have one or more explosive warheads, although other weapon types may also be used....
s and selenium
Selenium

Selenium is a chemical element with the atomic number 34, represented by the chemical symbol Se, an atomic mass of 78.96. It is a nonmetal, chemically related to sulfur and tellurium, and rarely occurs in its elemental state in nature....
, as employed in early television and xerography
Xerography

Xerography is a photocopying technique developed by Chester Carlson in 1938 and patented on October 6, 1942. He received for his invention. Although dry electrostatic printing processes had been invented as far back as 1778 by Georg Christoph Lichtenberg, Carlson's innovation combined electrostatic printing with photography....
.

See also, photoconductor and photodiode
Photodiode

A photodiode is a type of photodetector capable of converting light into either electric current or voltage, depending upon the mode of operation....
.

Application

solar cell
Solar cell

A solar cell or photovoltaic cell is a device that converts sunlight directly into electricity by the photovoltaic effect. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the source is unspecified....

photoconductive antenna