Photoelectrochemical performance of Cu-doped ZnIn2S4 electrodes created using chemical bath deposition

A solution growth method for the deposition of Cu-doped zinc-indium-sulfide (ZnIn₂S₄) semiconductor film electrodes is presented. The structural, optical, and photoelectrochemical (PEC) properties of samples were studied as a function of Cu content in samples. The X-ray diffraction pattern of the cubic ZnIn₂S₄ phase of an undoped sample was obtained. No Cu alloys or other binary compounds that included the Cu element were present in Cu-doped ZnIn₂S₄ samples. Images from a scanning electron microscope and atomic ratios of elements in samples obtained from the energy dispersion analysis of X-ray reveal a change in surface morphology and composition for Cu-doped ZnIn₂S₄ samples. The direct energy band gaps, indirect energy band gaps, and thicknesses of samples prepared in this study varied in the ranges 2.07-2.58 eV, 1.60-2.06 eV, and 521-879 nm, respectively. The maximum photoelectrochemical response of samples in 0.5 M K₂SO₄ aqueous solution reached 1.15 mA cm⁻² at an external potential of +1.0 V vs. an Ag/AgCl reference electrode under illumination using a 300-W Xe lamp with light intensity kept at 100 mW cm⁻². The experimental results show that Cu doping with Cu/(Cu+Zn) atomic ratio of 0.08 in samples improves the performance of the ZnIn₂S₄ photoabsorber for PEC applications.