Photoelectric Effect, Internal

the redistribution of electrons with respect to energy states that occurs in a condensed medium when electromagnetic radiation is absorbed.

In nonmetallic solids, such as semiconductors and dielectrics, the internal photoelectric effect is exhibited as a change in the conductivity (see) or the dielectric constant (see) of a medium or as the generation of an electromotive force at the boundaries of a medium (see). In metals, the effect is imperceptible because of the high conductivity of metals.

The internal photoelectric effect is used to study the electrical properties of substances and nonequilibrium electronic processes in substances. The investigation of the internal photoelectric effect makes it possible to determine, for example, the width of the forbidden band in substances, the lifetimes of conduction electrons and holes, the mechanisms and parameters of recombination processes for nonequilibrium charge carriers, and the properties of impurities. The effect is also used in photoelectric devices (seePHOTOCONDUCTIVE CELL, PHOTOCELL, PHOTODIODE, and ) and in equipment for the conversion of solar energy into electrical energy (seeSOLAR BATTERY).