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Photocurrent is the electric current through a photosensitive device, such as a photodiode, as the result of exposure to radiant power.

The photocurrent may occur as a result of the photoelectric, photoemissive, or photovoltaic effect.

The photocurrent may be enhanced by internal gain caused by interaction among ions and photons under the influence of applied fields, such as occurs in an avalanche photodiode (APD).

As a characterization technique, photocurrent is commonly used to study charge properties such as excitons of semiconductor nanostructutres and other light absorbing materials [1]

When a suitable radiation is used, the photoelectric current

  • is directly proportional to intensity of radiation.
  • 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 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.


  1. ^ O. D. D. Couto; J. Puebla; E.A. Chekhovich; I. J. Luxmoore; C. J. Elliott; N. Babazadeh; M.S. Skolnick; A.I. Tartakovskii; A. B. Krysa (2011). "Charge control in InP/(Ga,In)P single quantum dots embedded in Schottky diodes" (PDF). Phys. Rev. B. 84 (12): 7. Bibcode:2011PhRvB..84d5306P. doi:10.1103/PhysRevB.84.125301.