The choice of the copper concentration favoring the production of stoichiometric CuSbS2 and Cu12Sb4S13 thin films co-electrodeposited on FTO

Abstract

In order to elaborate stoichiometric CuSbS 2 and Cu 12 Sb 4 S 13 (CAS) thin films by co-electrodeposition on FTO substrates, the copper concentration was varied between 0.015 M and 0.030 M at − 0.98 mV co-electrodeposition potential (vs. saturated calomel electrode (SCE)). After a sulfurization step in a quartz tube at 410 °C under an argon flow for 45 min, the samples formed are analyzed by different techniques: The XRD technique has shown the existence of characteristic peaks of the CuSbS 2 phase at 28.53, 28.79, 29.73 and 29.99° clearly for the 0.015 M concentration, but this XRD spectrum has shifted to that of Cu 12 Sb 4 S 13 phase when the copper concentration increases to 0.030 M. Likewise the Raman spectroscopy has indicated the principal peak of CuSbS 2 located at 337 cm −1 on the spectrum of the 0.015 M concentration, but this peak have disappeared for the 0.030 M concentration and was replaced by a new principal peak of Cu 12 Sb 4 S 13 at 317 cm −1 . This effect was confirmed by the UV-Visible spectrophotometry technique which shows an increase of optical gap from 1.46 eV (CuSbS 2 ) to 1.81 eV (Cu 12 Sb 4 S 13 ) when the copper concentration passes from 0.015 M to 0.030 M. The morphological study and EDS analysis have proved that the layers CuSbS 2 and Cu 12 Sb 4 S 13 were elaborated with good stoichiometry. • Stoichiometric CuSbS 2 and Cu 12 Sb 4 S 13 thin films were synthesized for the first time by co-electrodeposition in aqueous medium. • XRD and Raman analysis shows a transition from CuSbS 2 to Cu 12 Sb 4 S 13 when Cu passes from 0.015 M to 0.030 M. • An increase of the optical gap was estimated from 1.46 to 1.58 eV for CuSbS 2 and from 1.71 to 1.81 eV for Cu 12 Sb 4 S 13 .