Photoanodic Behavior of n-InSe Single Crystal

Abstract

The electrochemical behavior of van der Waals face of n-InSe single crystals in acidic and alkaline solutions with and without illumination was investigated.
Photovoltage, Vph, depended linearly on the redox potential of the solution, Vr, when Vr was more positive than -0.35 V (vs. SCE) but Vo, was nearly zero when Vr was more negative than -O.35 V. These results suggest that the flat band potential, VFB, of n-InSe is fixed at -O.35 V. However, large Vph was observed in solutions containing S2-/S2couple, although Vr of these solutions were much more negative than -O.35 V, suggesting the negative shift of V_FB. Impedancp analysis confirmed the shift and AES measurements showed that sulfur was adsorbed on InSe surface. Thus, the specific adsorption of S^2- (or SH^-) onto InSe causes the negative shift of the conduction band edge, i. e., V_FB:
Photoanodic dissolution process was studied based on AES measurement, detection of dissolved species by in situ monitor electrode and UV spectra of solution. S^2- suppresses the dissolution quite significantly.