Optoelectronic Properties of CuSbS₂ and Cu₁₂Sb₄S₁₃ Thin Films for Thermoelectric Applications

This work presents a two-step procedure to obtain thin films with a combination of CuSbS₂ and Cu₁₂Sb₄S₁₃ phases for study in thermoelectric applications. The procedure consisted of the physical evaporation of sulfides layers (Sb₂S₃ and CuS) on glass substrates and the subsequent annealing of the samples in a N₂ atmosphere. The characterizations by Raman spectroscopy and XRD revealed that the samples presented a varied percentage of Cu₁₂Sb₄S₁₃ and CuSbS₂. The results indicated that the percentage of phases depended on the initial thickness of the sulfide layers and the annealing temperature. The lower initial ratio between sulfide thicknesses and annealing temperature above 300 °C favored the formation of Cu₁₂Sb₄S₁₃. However, the thermoelectric properties were improved when the phases coexisted in the thin film compared to samples with high percentages of Cu₁₂Sb₄S₁₃. In this way, a sample with a power factor of 2.30 μW /cm∙ K² at 60 ºC was identified.

Keywords:
CuSbS₂ chalcostebite; Cu₁₂Sb₄S₁₃ tetrahedrite; thin films; thermoelectric