Читать книгу Perovskite Materials for Energy and Environmental Applications - Группа авторов - Страница 18

Many semiconductor devices work by producing charge carriers that exceed the thermal equilibrium values, such excess carriers can be generated either by optical excitation or by adding an electrical field.

Through producing excess carriers (electrons and holes), thermal equilibrium in the semiconductor is no longer maintained, and the Fermi energy is no longer strictly specified. For the nonequilibrium semiconductor, we can outline two novel parameters: the quasi-Fermi energy for electrons and holes respectively.

The electron and hole concentrations of for the nonequilibrium are then given by:

(1.29)

(1.30)

EFn and EFp are the quasi-Fermi levels for electron and hole.

When electrons and holes are at equilibrium, EFn and EFp coincide and this is known as EF.