Properties of Cu₂ZnSnS₄ (CZTS) thin films prepared by plasma assisted co-evaporation

Abstract

In this work, Cu₂ZnSnS₄ (CZTS) in thin film form has been prepared on soda-lime glass by sulfurization of Cu–Zn–Sn (CZT) metal precursors. Different from traditional methods, precursor films were synthesized using elemental Cu, Zn and Sn metal wire by inductively coupled plasma (ICP) assisted co-evaporation. The composition, microstructure and properties of CZTS thin films were investigated using energy dispersive X-ray spectrometers (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Vis spectrophotometer. SEM study showed that the grain size of the CZT and CZTS films prepared by ICP assisted were larger than that no plasma assisted, however, an increasing of discharge power resulted in the increase of grain number, the decrease of grain size and exhibiting denser morphology. XRD analysis indicated the plasma assisted could improve the properties of films crystallinity. EDS revealed loss of Zn in films by traditional method, especially in CZT films. The plasma assistive technology could alleviate the lack of Zn, moreover, the content of Zn increased with the increasing of plasma discharge power. The values measured by UV–Vis spectrophotometer obtained for the optical band gap energy of the films both were about 1.50 eV, which was not affected by plasma assisted.