Effect of film thickness on some physical properties of sol-gel spin-coated Cu2ZnSnS4 thin films

Abstract

In this paper, Cu2ZnSnS4 (CZTS) thin films were deposited on glass substrates at 325 °C with different thicknesses (200, 300, 450, 550, 600, 700 and 750 nm) using spin coating technique. The aim of this research is to study effect of the thickness on the structural, morphological, optical and electrical properties. The crystal structure of CZTS films has been investigated by using low angle XRD which showed that all CZTS films are polycrystalline in nature and have kesterite structure of the tetragonal system. It found the crystallite size increasing from 5.9 to 19.5 nm with increasing thickness of the films from 200 to 750 nm. Raman spectroscopy showed strong peak at 338 cm−1 for all samples, which indicated the presence of CZTS quaternary compound. The morphological characteristics of CZTS films had been carried out by using FESEM imaging, which showed that all CZTS films formed as intertwined thorny twigs like texture beautifully organized at the nano-scale range. The optical properties have been studied using UV-Visible spectrophotometry,. It was observed that the calculated values of optical energy gap decreased from 2.0 to 1.55 eV with increasing thickness of films from 200 to 750 nm. The values of absorption coefficient for all samples in the visible region were greater than 104 cm−1 which may indicate direct electronic transition. The results of Hall effect measurements showed p-type conductivity, and the maximum value of conductivity had recorded 55.578(Ω.cm) −1 at the Thickness 550 nm.