Etude des propriétés optiques des couches minces de CuInS2 et d'In-S " Airless spray "

Abstract

In this work we have studied the optical properties of the thin CuInS 2 and In-S layers prepared by airless spray P.S.A.. The study of the optical properties from the ellipsometric measure realized in the interval energy of incident photons [1.5-4] eV, has showed that the refraction index n, and the extinction coefficient k l vary in the interval [1.8-2.3] and [0.45-0.80] respectively. The absorption coefficient a of the thin CuInS 2 layers realized for different ratios x of the concentrations in the spray solution (x=[CuI]/[InIII]) is high with values varied between (5×10 4 and 18×10 4 cm -1 ). The direct gap energy of the thin CuInS 2 layers of the order of 1.38 eV. In the same way, we study the spectrum variation of n l (λ) and k l (λ) of the thin In-S layers, realized for two values of ratio y of the concentration in the spray solution (y=[In 3+ ]/[S -2 ]) shows that for the value of y=0.6 (material β-In 2 S 3 ) the refraction index is higher than that of teh thin layer obtained for the value of y=0.75 (material In 6 S 7 ) [1], and that the extinction coefficient is lower than that of In 6 S 7 . For In-S thin layers, α is also high with values varing between 2×10 4 and 12×10 4 cm -1 . The direct band gap of materials β-In 6 S 7 and In 6 S 7 are 2.22 eV and 1.94 eV respectively. The heat treatment under vacuum at 573 K during two hours improves the optical quality of the thin p type CuInS 2 layers