Surface band energy shifts of a p-type Si electrode in the presence of redox couples: Study of anthraquinone derivatives in the dark and under illumination

Abstract

Surface band energy shifts of a p-type Si electrode have been observed, in the presence of various redox couples, in the dark and in dry acetonitrile solution. These results are reinforced by the study of the reduction of a large series of anthraquinone derivatives at the mercury electrode and at illuminated p-type Si and p-type GaAs electrodes (in acetonitrile solution and in the presence or absence of acetic acid). The two semiconducting materials exhibit the Fermi level pinning phenomenon, giving a constant photovoltage output independent of the E s 0 of the anthraquinone derivatives. Unexpectedly, the anthraquinones used in the present work do not show any trend towards sluggish kinetics in reduction, even in the presence of acetic acid and a slight amount of water. This result indicates that the choice of the best anthraquinone derivative for photoelectrochemical devices using p-type Si or p-type GaAs will be mainly dictated by stability properties of the depolarizer in the chemistry one seeks to develop.