Production of Cu2(Zn,Fe)SnS4 powders for thin film solar cell by high energy ball milling

Copper zinc tin sulfide (Cu2ZnSnS4, CZTS) is nowadays one of the most promising materials as an alternative to the well known absorber in the CIGS thin film solar cells. Additionally to the non toxicity of the single species; the material suitable bandgap and large absorption coefficient, low-cost and large-area deposition techniques are already under development in order to avoid expensive vacuum-based processes. In this work high energy ball milling was used to obtain Cu2(Zn,Fe)SnS4 powders for solar-inks production. Optimal conditions for the milling and for the following annealing process are described in detail. Substitution of zinc by iron, either as an effect of contamination from the milling vials and/or as an addition in controlled quantity, was studied by structural (XRD) and chemical (SEM-EDX) techniques. XPS measurements provided further information on the oxidation state of iron, whereas in-situ high temperature synchrotron radiation XRD was used to follow the evolution of the system, and in particular the transformation of iron from the starting metallic condition to the alloying in the final kesterite powders.

► Cu2(Zn,Fe)SnS4 powders were successfully produced using high energy ball milling.
► Iron substitution in the Zn site of the kesterite structure, was studied.
► XPS measurements revealed the proper oxidation state of iron.
► In-situ SXRD was used to follow the system evolution into final CZTS structure.
► Solar-inks were successfully obtained and deposited via spin-coating technique.