Photocurrent is the

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...

through a

photosensitive Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicit ...

device, such as a

photodiode A photodiode is a light-sensitive semiconductor diode. It produces current when it absorbs photons. The package of a photodiode allows light (or infrared or ultraviolet radiation, or X-rays) to reach the sensitive part of the device. The packag ...

, as the result of exposure to

radiant power In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted, or received per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spec ...

. The photocurrent may occur as a result of the

photoelectric The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...

, photoemissive, or

photovoltaic effect The photovoltaic effect is the generation of voltage and electric current in a material upon exposure to light. It is a physical and chemical phenomenon. The photovoltaic effect is closely related to the photoelectric effect. For both phenomena, ...

. The photocurrent may be enhanced by internal

gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...

caused by interaction among ions and photons under the influence of applied fields, such as occurs in an

avalanche photodiode An avalanche photodiode (APD) is a highly sensitive semiconductor photodiode detector that exploits the photoelectric effect to convert light into electricity. From a functional standpoint, they can be regarded as the semiconductor analog of phot ...

(APD). When a suitable radiation is used, the photoelectric current is directly proportional to intensity of radiation and increases with the increase in accelerating potential till the stage is reached when photo-current becomes maximum and does not increase with further increase in accelerating potential. The highest (maximum) value of the photo-current is called

saturation current The saturation current (or scale current), more accurately the reverse saturation current, is the part of the reverse current in a semiconductor diode caused by diffusion of minority carriers from the neutral regions to the depletion region. This ...

. The value of retarding potential at which photo-current becomes zero is called cut-off voltage or stopping potential for the given frequency of the incident ray.

Photovoltaics

The generation of a photocurrent forms the basis of the

photovoltaic cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

Photocurrent spectroscopy

A characterization technique called photocurrent spectroscopy (PCS), also known as photoconductivity spectroscopy, is widely used for studying optoelectronic properties of semiconductors and other light absorbing materials. The setup of the technique involves having a semiconductor contacted with electrodes allowing for application of an electric bias, while at the same time a tunable light source incident with a given specific wavelength (energy) and power, usually pulsed by a mechanical chopper. The quantity measured is the electrical response of the circuit, coupled with the spectrograph obtained by varying the incident light energy by a

monochromator A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input. The name is from the Greek roots ''mono-'', ...

. The circuit and optics are coupled by use of a lock-in amplifier. The measurements give information related to the band gap of the semiconductor, allowing for identification of various charge transitions like

exciton An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids. ...

and trion energies. This is highly relevant for studying semiconductor nanostructures like quantum wells, and other nanomaterials like

transition metal dichalcogenide monolayers Transition-metal dichalcogenide (TMD or TMDC) monolayers are atomically thin semiconductors of the type MX2, with M a transition-metal atom ( Mo, W, etc.) and X a chalcogen atom ( S, Se, or Te). One layer of M atoms is sandwiched between two ...

. Furthermore, by using a piezo stage to vary the lateral position of the semiconductor with micron precision, one can generate a micrograph false color image of the spectra for different positions. This is called scanning photocurrent microscopy (SPCM).

References

* Electromagnetism {{electronics-stub

Photovoltaics

Photocurrent spectroscopy

See also

References