What is "photoluminescence"

Photoluminescence \Pho`to*lu`mi*nes"cence\, a. [Photo- + luminescence.] (Physics) luminescence induced by exposure to light waves in the infrared to ultraviolet range.

n. (context physics English) luminescence following the absorption of a photon.

Photoluminescence (abbreviated as PL) is light emission from any form of matter after the absorption of photons (electromagnetic radiation). It is one of many forms of luminescence (light emission) and is initiated by photoexcitation (excitation by photons), hence the prefix photo-. Following excitation various relaxation processes typically occur in which other photons are re-radiated. Time periods between absorption and emission may vary: ranging from short femtosecond-regime for emission involving free-carrier plasma in inorganic semiconductors up to milliseconds for phosphorescent processes in molecular systems; and under special circumstances delay of emission may even span to minutes or hours.

Observation of photoluminescence at a certain energy can be viewed as indication that excitation populated an excited state associated with this transition energy.

While this is generally true in atoms and similar systems, correlations and other more complex phenomena also act as sources for photoluminescence in many-body systems such as semiconductors. A theoretical approach to handle this is given by the semiconductor luminescence equations.