The investigation of structural, electrical, and optical properties of thermal evaporated AgGaS₂ thin films

AgGaS₂ (AGS) thin films were deposited onto glass substrates by sequential thermal evaporation of AgGaS₂ single crystalline powder and excess silver (Ag) interlayer. Systematic optimization to obtain single phase AgGaS₂ thin films was carried out by changing the thickness of the excess silver layer. The structure and composition of as-grown and annealed films were studied by means of X-ray diffraction and energy dispersive X-ray analysis, respectively. The optical properties of AGS thin films determined by transmittance and reflection measurements showed that they had quite high absorption coefficient with the values around 10⁴ (cm^-1). The calculated band gap values were found to be between 2.30 and 2.75 eV depending on annealing temperature. The refractive index (n) and extinction coefficient (k) of the films were determined by the envelope method. Finally, photo-electrical measurements under different illumination intensities were carried out, and different sensitizing and recombination centers were defined.