In SCEs, however, the electrons are more tightly bound and localized in the valence band. Therefore, the concentration of free charge carriers in semiconductors is low and this leads to low conductivity and poor screening of interfacial charges and electrostatic potential differences. Due to their widely different screening properties, metallic and semiconducting electrodes behave very differently when brought into contact with an electrolyte and when an electrostatic potential difference across the interface is created. On metallic electrodes, the potential drop takes place almost entirely on the electrolyte side because the electrostatic potential is efficiently screened by the metal.