Equilibrium
-There is no gradient in Fermi level ,that is fermi level is constant
Non equilibrium
there will be a gradient in Fermi level due to the drift and diffusion of holes and electrons
so we use a Quasi Fermi level concept
Quasi Fermi level
h**p://en.wikipedia.org/wiki/Quasi_Fermi_level
The new Fermi level that describes the population of each type of charge carrier (electrons and holes) in a semiconductor separately when their populations are displaced from equilibrium. This displacement could be caused by the application of an external electric potential, which injects electrons and holes, or by exposure to light
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h**p://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_2/backbone/r2_3_2.html