Chemical bath deposition (CBD) of iron sulfide thin films for photovoltaic applications, crystallographic and optical properties

A low temperature chemical deposition method has been developed to deposit iron/sulfur thin films onto soda lime glass substrates. The chemical bath deposition (CBD) consists of aqueous solution ferrous sulphate, disodium salt of ethylenediaminetetra-acetic acid (Na2EDTA), sodium thiosulphate and organic solutions of ethylenediamine and methanol. The experiments were performed at room temperature and under two different conditions. The films were uniform and adhered well to the soda lime glass substrates. The deposited films were additionally processed in a sulfur and nitrogen atmosphere at a variety of different temperatures to form the pyrite phase of FeS2. The as-deposited and annealed thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption, auger electron spectroscopy (AES), and resistivity. The optimization of the FeS2 pyrite growth parameters was determined using XRD. Although both methods appeared to form FeS2 the second method is the preferable one where additional sulfurization at 450 °C for one hour yielded the films with the maximum crystalline order and stoichiometry.