Structural, optical and morphological characteristics of sprayed ZnS thin films for solar cells

Abstract

Zinc sulfide (ZnS) thin films were deposited on glass substrate by spray pyrolysis technique, which appears as an unusual method for preparing ZnS thin films. Indeed, this technique is interesting because it is inexpensive, simple and capable of deposition of optically smooth, uniform and homogeneous layers. The starting solution is a mixture of 0.01 M zinc chloride as source of Zn and 0.01 M thiourea as source of S. The glass substrate temperature was varied in the range of 250–400 °C to check on the influence of substrate temperature on the structure and optical properties of ZnS films. The X-ray diffraction analyses indicated that ZnS films is polycrystalline under mixture of hexagonal (H) and cubic (C) phase with a prevalence of the hexagonal phase and grain size varied from 120.88 to 160.26 nm, which is decreasing with the deposition time. The optical films characterization was carried out by the UV–visible transmission. Optical measurements analysis showed that these binary films had more than 85 % transmittance in the visible region and they had a relatively high absorption coefficient (≈106 cm−1) in the visible spectrum with a direct band gap varied from 3.65 to 3.77 eV; which is quite to the optimum value for the solar cells.