Role of tartaric acid on structural, morphological and optical properties of fesxoy films formed by chemical bath deposition

Abstract

Chemical bath deposition (CBD) was used to prepare FeSxOy films 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 work reported on CBD of FeSxOy with tartaric acid (C4H6O6) as the complexing agent. Thus, 50 mM tartaric acid was selected and introduced into the deposition solution containing 100 mM Na2S2O3 and 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 deposited films were crystalline and showed n-type photoresponse. The deposition with tartaric acid resulted in film thickness reduction and contained less iron and larger oxygen and sulfur contents. In addition, the film with 50 mM tartaric acid also 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.