Photoelectrochemistry of lamellar n- and p-type InSe in aqueous solution

The n- and p-type InSe single crystals have been grown by the Bridgman--Stockbarger method and characterized by their electronic transport properties. A photoelectrochemical study in aqueous media using the cleavage surface shows rectifying behavior in the dark, confirming diode behavior for both. InSe electrodes exhibit anodic and cathodic photocurrents. These photocurrents are related to a photoelectrochemical effect when a positive bias is applied to n-type InSe and when a negative bias is applied to p-type InSe, whereas the cathodic photocurrent for the n-type and the anodic photocurrent for the p-type are due to a photoconductive effect. Flatband potentials in acidic solution have been determined from the change of sign of the photocurrent and from Mott--Schottky plots of the capacitance (--0.6 V vs. SCE for n-type and +0.2 V vs. SCE for p-type). The flatband potential is not p H dependent. Photocurrent spectra indicate a 1.2 eV bandgap. The behavior of InSe electrodes is explained in terms of the location of the valence and conduction bands on the electrochemical scale. 15 ref.--AA