عنوان المقالة:Effect of Substrate Temperature on Structural and Optical Properties of Cu2ZnSnS4 (CZTS) Films Prepared by Chemical Spray Pyrolysis Method
In this work Copper zinc tin sulfide (CZTS) films were prepared by using chemical spray pyrolysis technique. Copper chloride CuCl, Zinc chloride ZnCl2, Tin chloride pentahydrate SnCl4.5H2O and Thiourea SC(NH2)2 were used as sources of Copper ions, Zinc ions, Tin ions and Sulfur ions respectively. CZTS thin films have been grown on clean preheated glass at different substrate temperatures of (200, 250, 300, 350, 400 and 450) oC. The structural and optical properties of these films have been studied using XRD, AFM, and UV-Visible spectroscopy. The XRD results showed that all films are polycrystalline in nature with tetragonal structure and preferred orientation along (112) plane. The crystallite size was calculated using Scherrer’s formula and it is found that the CZTS thin films have maximum crystallite size of (34.401 nm) at substrate temperature of 450 oC. Williamson-Hall analysis was carried out for all samples and the crystallite size along with microstrains were estimated. AFM results showed homogenous and smooth thin films. The absorbance and transmittance spectra have been recorded in the wavelength range of (300- 900) nm in order to study the optical properties. The optical energy gap for allowed direct electronic transition was calculated using (Tauc’s equation). It is found that the band gap decreases as the substrate temperature increases and the optical allowed energy gap for the direct electronic transitions was in the range of (2.3 -1.85) eV. Urbach energy values range between (477 - 643) meV. The optical constants including (absorption coefficient, real and imaginary parts of dielectric constant) were also calculated as a function of photon energy. Refractive index and extinction coefficient were estimated as a function of wavelength.
نبيل علي بكر | Nabeel A. Bakr | 5250