Production of a voltage difference across a p-n junction resulting from the absorption of photon energy. The voltage difference is caused by internal drift of holes and electrons.
The generation of electricity when radiant energy, such as sunlight, falls on the boundary between two different substances(e.g. two different semiconductors).
This is the effect caused when a photon is absorbed by a semiconductor detector and it generates an electrical charge, measured as voltage, across an =n junction of that semiconductor.