Effect of electrolytes on photoelectrochemical performance of a CuS–CdS heterojunction

CdS–CuS heterojunction films have been grown successfully on a copper substrate using a chemical bath deposition (CBD) method. The obtained films are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical absorption, Raman spectroscopy and photoluminescence (PL) analysis and the photo-electrochemical (PEC) properties of the CdS–CuS heterojunction have been studied using different electrolytes. The XRD pattern of CuS–CdS shows peaks corresponding to CuS (hexagonal) and CdS (cubic) structures, while the optical absorption studies revealed the presence of an absorption edge corresponding to CuS–CdS (band gap of 1.85 eV). The Raman spectra of the CuS, CdS and CuS–CdS heterojunctions were recorded and are in good agreement with the results reported in the literature. TEM and cross-sectional SEM images show an overlap between CuS rods and CdS flasks. The charge transfer across the layers was studied by using PL spectra. The measurement of the photo-electrochemical properties using a conventional two electrode system for an iodine electrolyte showed the highest conversion efficiency of 1.40% as against for potassium ferro–ferricyanide (0.38%) and polysulphide electrolytes (0.02%).