ELECTRODES | Semiconductor Electrodes

The basic concepts concerning formation and operation of a junction between a semiconductor and a solution are presented in this article. The behavior of semiconductor electrodes in the dark and under illumination, different from that of metallic electrodes, is explained with reference to the peculiar properties of semiconductors such as very low concentration of mobile electrons; presence of a gap of forbidden energies for electronic states; control by electrode potential, under appropriate conditions, of the surface concentration of carriers; and the ability of illumination to change drastically the population of minority carriers. The dependence of photoeffects on material properties and light intensity is discussed, considering also the role and effects of surface states. The relevance of interface energetics for the performances and stability of a photoelectrode in contact with different redox couples is pointed out.