Photoelectrochemistry of the CuInS₂/S_n^2- system

Single crystal and thin film polycrystalline samples of n-CuInS₂ were studied as photoanodes in a polysulfide electrolyte-based photoelectrochemical cell. The I-V plots in the dark and under illumination show a strong dependence on the electronic properties of the electrode, explaining the large variations in photoelectrochemical behaviour of different electrodes. Short-circuit photocurrent spectra show a strong temperature dependence as do the I-V plots under illumination. The output stability of the electrodes depends both on electrolyte composition and temperature, and reaches a constant value after a period of some minutes-hours, depending on electrolyte composition. The flat-band potential in polysulfide solution, as derived from a plot of the square of the photocurrent vs. applied potential, is similar to that for Cd-chalcogenide photoelectrodes in this electrolyte, indicating possible pinning of the semiconductor bands by adsorbed sulfide, or by a surface or near-surface layer. Information on the effective hole diffusion length is obtained from analysis of monochromatic I-V curves.