Structural and optical properties of CuIn1−xGaxS2 absorber layer for solar cells synthesized by spray pyrolysis

In this study, we investigated the effect of the chemical ratios (x=Ga/In+Ga) on the structural and optical properties of the chalcopyrite Cu(In
x−1
, Ga
x
)S
2
thin films made by spray pyrolysis. Structural analysis by X-ray diffraction revealed that the CIGS crystallizes in a polycrystalline structure with chalcopyrite phase and a preferential growth orientation [112]. The best crystallinity was observed for the film prepared with the chemical ratio x = 0.9. The grain size of the films of CIGS decreases with chemical ratio (Ga+In)/Ga increases. The Optical properties was calculate from the measured spectral transmittance T
λ
and reflectance R
λ
allow us to determine the direct band gap energy value which increases by increasing the x ratios and it is in the range 1.64–1.70 eV, indicating that Cu(In
1−x
Ga
x
)S
2
compound has an absorbing property favorable for photovoltaic applications.