Patent ID: 8236146

Claim:
A photoelectrochemical cell comprising: a semiconductor electrode including a conductor and an n-type semiconductor layer disposed on the conductor; a counter electrode connected electrically to the conductor; an electrolyte in contact with surfaces of the n-type semiconductor layer and the counter electrode; and a container accommodating the semiconductor electrode, the counter electrode and the electrolyte, wherein the photoelectrochemical cell generates hydrogen by irradiation of the n-type semiconductor layer with light, and relative to a vacuum level, (I) band edge levels of a conduction band and a valence band in a surface near-field region of the n-type semiconductor layer, respectively, are equal to or higher than band edge levels of a conduction band and a valence band in a junction plane near-field region of the n-type semiconductor layer with the conductor, (II) a Fermi level of the junction plane near-field region of the n-type semiconductor layer is higher than a Fermi level of the surface near-field region of the n-type semiconductor layer, and (III) a Fermi level of the conductor is higher than the Fermi level of the junction plane near-field region of the n-type semiconductor layer.