Structural, electronic and optical properties of Cu-doped ZnS thin films deposited by the ultrasonic spray method- DFT study

• DOI: 10.1007/s11082-021-02934-8
• Publication Date: 2021-06-12T14:14:30Z
• Authors: Hamza Shaili; El mehdi Salmani; Rida Essajai; Mustapha Beraich; Wafaa Battal; Mouad Ouafi; Abderrahim Elhat; Mustapha Rouchdi; Hamid Ez-Zahraouy; Najem Hassanain; Ahmed Mzerd
• Keywords: Wurtzite crystal structure

Herein, the modifications on the properties of the ZnS thin films by copper doping with various concentrations Zn1−xCuxS (x = 0, 1, 3, and 5 at %) have been studied. The properties of pure ZnS have been provided for the purpose of comparing different thin films. All samples have been synthesized using the simple ultrasonic spray method on glass substrates at 200 °C and characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and ultraviolet–visible (UV-Vis) spectroscopy. Structural analysis revealed that the films are polycrystalline fitting well with the ZnS hexagonal wurtzite structure with the (002) direction as a preferential orientation for all the films except for the (5 at%) concentration that preferred (100) orientation. An increase in the grain size was observed through surface scanning as the dopant percentage increased. The deposited films possessed an average optical transmittance in the range of 86% at the visible region combined with a high absorption coefficient (~ 105 cm−1), while a slight decrement was observed on the optical band gaps of Zn1−xCuxS films passing from 3.93 eV to 3.64 eV as dopant content increased. The ab initio calculations revealed a major enhancement in the properties of ZnS as the Cu content increased. The findings obtained in the current study display that when the copper percentage is highest, the Zn1−xCuxS thin film can be a suitable candidate as an absorber layer in thin film solar cells.