Gelderman, K., L. Lee, and S. W. Donne. "Flat-band potential of a semiconductor: using the Mott–Schottky equation." Journal of chemical education 84, no. 4 (2007): 685.
The flat band potential (Vf) is the potential required to bring back the semiconductor band edges to their flat band position from the bending position at the semiconductor/metal or semiconductor/electrolyte interface. Consequently, the Fermi levels of both the materials differ by an energy equal to ∼qVf. , where q is the charge of the carrier involved.