Effect of copper content on optostructural, morphological and photoelectrochemical properties of MoBi2−x Cu x Se4 thin films

In the present investigation we have reported a facile chemical route for the deposition of MoBi2−x Cu x Se4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) thin films at room temperature by using a simple and self-organised arrested precipitation technique. The deposited samples were characterised for their structural, morphological, optical and photoelectrochemical properties. X-ray diffraction patterns revealed that, undoped MoBi2Se5 shows a rhombohedral crystal structure, while mixed rhombohedral and orthorhombic crystal structures were observed with shifting of diffraction peaks after copper doping. The scanning electron microscopy and transmission electron microscopy images revealed that the surface morphology was improved with copper content. Compositional analysis of all samples was carried out by using energy dispersive X-ray spectroscopy. The direct band gap energy of all the samples estimated from absorbance spectra varies from 1.26 to 1.60 eV. The photoelectrochemical properties of all samples were studied in I−/I3 − redox electrolyte which demonstrated that the electrical conductivity was transformed from n-type to p-type after copper doping and photoelectrochemical response of p-type MoBi2−x Cu x Se4 thin film electrode was improved with increasing copper content. The mechanism of change in the type of electrical conductivity and augmentation in photoelectrochemical response after copper doping are discussed.