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.