Effect of rapid thermal annealing on sprayed Cu₂SnS₃ thin films for solar-cell application

Ternary compound Cu₂SnS₃ (CTS) thin films were synthesized using two simple and non-vacuum processes: chemical spray pyrolysis and rapid thermal annealing (RTA). The crystal quality of CTS films improved and the band tailing, shown in Tauc's plot, tended to vanish after annealing in a nitrogen atmosphere using RTA. Although ethanol was used as a solvent in the spray pyrolysis, the CTS film was not contaminated by carbon and oxygen. The bandgap of CTS was changed via sulfurization. The optimization of the RTA process affected the composition of the CTS thin films, modifying material defects, and improving the crystal quality. These results represent the initial step toward the practical application of CTS solar cells using an inexpensive fabrication process.