Semiconductor Electrodes. 24. Behavior and Photoelectrochemical Cells Based on p-Type GaAs in Aqueous Solutions

摘要

The electrochemical Behavior of single crystal p-type GaAs in aqueous solutions containing several redox couples (I3(-)/I(-), Fe(III)/Fe(II), Sn(IV)/Sn(II), Eu(III)/Eu(II)) in the dark and under irradiation is described. The observation that the difference in potential between that for the onset of photocurrent and the standard potential for the redox couple was 0.4 to 0.5 V, independent of the couple, leads to a revised model for semiconductor/electrolyte solution interface with semiconductors having a high density of surface states with energies within the band gap region. In such a surface controlled system, the Fermi level of the semiconductor is pinned at the surface state level. Several solar cells in which p-GaAs shows stable behavior are described.