From AMS Glossary
Any process in which illumination of a material by electromagnetic radiation causes electrons to be separated from atoms or molecules.
Photoelectric effect is often synonymous with surface photoelectric effect, "the release of electrons by light at the boundary between a solid or liquid . . . and usually a gas" (Hughes and Dubridge 1932). The photoelectric effect was discovered in 1887 by Heinrich Hertz. The fundamental law of photoelectricity is the Einstein law
where e is the (maximum) kinetic energy of the emitted photoelectron, ν is the frequency of the source of illumination, h is Planck's constant, and p is the (minimum) difference between the potential energy of an electron inside and outside the material to which it is bound. An implicit assumption underlying this equation is that the initial kinetic energy of the electron is negligible compared with its maximum kinetic energy. The Einstein law played a fundamental role in establishing the quantum theory of light (Leighton 1959).
Hughes, A. L., and L. A. DuBridge 1932. Photoelectric Phenomena. 1–2.
Leighton, R. B. 1959. Principles of Modern Physics. 67–69.