Electrodeposition of tin sulfide (SnS) in a pyrophosphate bath: From electrochemical analysis to microstructure control

A C T SnS is increasingly studied due to its various domains of applications and especially in renewable energy. This work focused on the understanding of the electrochemical behavior of SnS from a bath containing pyrophosphates (PP). PP were used to stabilize the precursor of Sn(II) in solution. First, Sn-PP and thiosulfate, used as a sulfur precursor, electrochemical system were studied separately. Sn-PP system appears quite complex with multiple redox reactions related to the Sn-PP complex but also PP which are electroactives and the formation/ oxidation of AuSn. Voltammetries clearly show the advantage of using PP as stabilizing agent for Sn. Regarding thiosulfate, special attention must be paid to the preparation of the solution in order to obtain colloidal sulfur. Afterwards, the study of the electrochemical system allows the assignments of the redox reactions. Then, the binary system was studied through voltammetry and electrodeposition. The deposits were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Two major parameters were studied namely, the ratio S/Sn precursors in solution and the potential of deposition. Single-phase, wellcrystallized and oriented SnS films were obtained for a ratio of S/Sn of 4.2 and at -0.7 V vs Ag/AgCl.