Effect of the Ga-Content on the Microstructural Properties of Cu(In1-x,Gax)Se2 Thin Film and its Device Performance

Cu(In
1-x
,Ga
x
)Se
2
(CIGS) thin films were deposited on Molybdenum (Mo) coated soda lime glass (SLG/Mo) substrates, using physical vapor deposition (PVD). In order to study the impact of Ga content variations on the CIGS thin films’ microstructural and its device performance; single stage deposition process was applied to avoid any material grading and to maintain a uniform depth profile for each evaporated element throughout the film thickness. During the deposition, the Ga content x = Ga/(Ga+In) was varied from x = 0.0 (CIS) to x = 1.0 (CGS). High-Resolution Scanning Electron Microscopy (HRSEM) was used to examine the CIGS films’ morphology. Also, the X-Ray Diffraction (XRD) θ/2θ technique was applied to study the films’ texture, and lattice parameters as well as its lattice distortion. The chemical composition of the films was examined by Electron Probe Micro-Analyzer (EPMA) coupled with Wavelength Dispersive Spectrometer (WDS). Depth profiling survey for the elements and their relative concentrations were analyzed for the CIGS films by Auger Electron Spectroscopy (AES). Optical energy band gap (E
g
), and absorption coefficient (α) of the films were calculated from the transmission spectral data measured using UV-Vis-NIR spectrometer. The performance of the completed CIGS devices was evaluated under standard conditions of 1000W/m
²
and 25°C.