Effect of annealing under various atmospheres on the properties of electrodeposited CIGS thin films on ITO coated glass substrates

This work aims to evaluate the effects of two different annealing atmospheres such as vacuum and N₂ + Se vapor on the structural, morphological, optical and electrical properties of electrodeposited Cu (In_1−xGa_x) Se₂ CIGS thin films. All films are electrodeposited from an aqueous-based solution at room temperature in a three-electrode cell configuration, with platinum plate as the counter electrode and a glass/ITO substrate as the working electrode, and the reference electrode was saturated calomel. X-ray diffraction measurements indicate the films are crystallized in a single phase with the chalcopyrite structure and a preferred orientation along the (112) plane without unwanted secondary CIGS phases. The annealing atmospheres affected the crystallinity, morphology and grain size of the prepared films. Optical analysis by means of transmission T (λ) and reflection R (λ) measurements allow us to determine the direct band gap energy value which decreases with increasing the annealing temperature and it is in the range 1.12–1.32 eV. Electrical measurements show that CIGS compound exhibits p-type conductivity and resistivity was improved when CIGS films annealed in nitrogen + Se vapor.