Role of Tartaric Acid on Structural, Morphological and Optical Properties of FeSxOyFilms Formed by Chemical Bath Deposition

Chemical bath deposition (CBD) was used to prepareFeSxOyfilms on fluorine-tin-oxide (FTO)-coated glass substrate. The deposition temperature and time were fixed to 75°C and 3 hours, respectively. In previous works, high concentration of tartaric acid (≥50 mM) led to improvement of the properties of the deposited films [1-2]. However,there is no workreported on CBD of FeSxOywith tartaric acid (C4H6O6) as the complexing agent. Thus, 50 mM tartaric acid wasselected and introduced into the deposition solution containing 100 mM Na2S2O3and 30 mM FeSO4. The pH of the solution with the complexing agent was adjusted close to the pH without the agent (~pH 5.1) using ammonia solution. Both depositedfilms were crystalline and showed n-type photoresponse.Thedeposition with tartaric acid resulted in film thickness reduction and containedless iron and larger oxygen and sulfur contents. In addition, the film with 50 mM tartaric acidalso showed better homogeneity, improved crystallinity, larger optical transmittance and less hematite peaks. The role of tartaric acid can be explained by considering the suppression of elemental Fe deposition and enhancement of sulfur reduction.