Solution Processed Cu2ZnSnS4 Thin Films for Solar Cell Applications

Abstract

This thesis concerns with the growth and characterization of Cu2ZnSnS4 (CZTS) thin films for solar cell application. In the last few years, thin films of CZTS have attracted significant research interest owing to its earth-abundant constituents, high absorption coefficients in the visible region of solar radiation, fairly high tolerance to stoichiometric deviations and presence of native defects which are actually beneficial. The CZTS thin films were prepared using the chemical bath deposition (CBD) technique from non-toxic solutions in contrast to the hydrazine - a very toxic and carcinogenic compound - based solution based techniques, which have yielded the record efficiency. In this work, the bath solution was prepared from copper chloride as a source of copper ions (Cu2+), zinc chloride as a source of zinc ions (Zn2+), tin chloride as a source of tin ions (Sn2+) and thioacetamide (TAA) as a source of sulfur ions (S2+) and MEA as a complexing agent. The as-deposited films were ex-situ sulfurized at different temperatures to obtain good quality films. The prepared samples were characterized by several techniques such as X-ray diffraction, scanning electron microscopy and UV-visible spectroscopy. The results show that post-deposition sulfurization at 450 C results in the formation of a single phase polycrystalline CZTS. However, the films were discontinuous with the film surface consisting of sub-micrometer size particles. It shows that although a single dip coating followed by sulfurization at 450 C yields polycrystalline CZTS, further processing in the form of multiple coating is required for developing microstructure suitable for photovoltaic applications.