Photoelectrochemical study of ZnIn ₂Se ₄ electrodes fabricated using selenization of RF magnetron sputtered Zn-In metal precursors

Polycrystalline ZnIn ₂Se ₄ samples are grown on glass substrates and fluorine-doped tin oxide coated glass substrates using the selenization of radio-frequency magnetron sputtered Zn-In metal alloys. The effect of the [Zn]/[Zn + In] molar ratio in the metal alloys on the physical and photoelectrochemical properties of the samples is investigated. X-ray diffraction patterns of samples reveal that the samples are polycrystalline tetragonal ZnIn ₂Se ₄. The thicknesses and direct band gaps of the samples are in the ranges of 1.15-1.44 μm and 1.68-1.81 eV, as obtained from surface profile measurements and transmittance/reflectance spectra, respectively. The flat-band potentials of the samples in 0.6 M K ₂SO ₃ electrolyte are in the range of -0.41 to -0.95 V vs. an Ag/AgCl reference electrode. The highest photoelectrochemical response of samples was 1.84 mA/cm ² at an external potential of +1.0 V vs. an Ag/AgCl electrode in 0.6 M K ₂SO ₃ solution under illumination from a 300 W Xe lamp system with the light intensity set at 100 mW/cm ². Highlights: ZnIn ₂Se ₄ is deposited on substrates using selenization of of Zn-In precursors. All samples are polycrystalline tetragonal ZnIn ₂Se ₄. The direct energy band gaps of the samples were in the range of 1.68-1.81 eV. Sample with [Zn]/[Zn + In] ratio of 0.24 has a maximum PEC response.