https://doi.org/10.1351/goldbook.14040
Nonequilibrium free electron or free hole generated in a solid by ultraviolet, visible, or infrared absorption and occupying energy levels in the conduction band or the valence band, respectively.
Note: Electrons occupying energy levels near the bottom of the conduction band and holes occupying energy levels near the top of the valence band (thermalised carriers) are considered as quasi-chemical intermediates. Nonthermalised (hot) carriers can also be involved in photocatalysed reactions.