Effect of substrate temperature on structural and optical properties of the new high absorbent Sn3Sb2S6 thin films

• Synthesis of ternary high absorbent Sn3Sb2S6 thin films by thermal evaporation route.
• Pure phase of Sn3Sb2S6 was confirmed with XRD analysis.
• Absorption coefficient higher than 105 cm−1 in visible and NIR range (2.5·105 cm−1 at 2.2 eV).
• Optical investigation leads to a direct energy gap ranging 1.18–1.47 eV depending on substrate temperature.
• The material is a potential candidate for flexible solar cells.

In this paper we present the influence of substrate temperature on structural and optical characteristics of the ternary Sn3Sb2S6. The samples were deposited by vacuum thermal evaporation onto glass substrates at various substrate temperatures (30–60–100–140–160) °C. The films were analyzed by X-ray diffraction, atomic force microscopy (AFM) and spectrophotometric measurements. The XRD analysis showed the presence of only homogenous Sn3Sb2S6 phase. The surface roughness of the deposited films varied between 3.6 and 16 nm with decreasing the substrate temperature from 160 to 30 °C. We found that by increasing the substrate temperature from 30 to 160 °C, the optical band gap decreased from 1.47 to 1.18 eV. The absorption coefficients of the films are in the range of 105–106 cm−1. The refractive index n has been analyzed according to the Wemple–Di Domenico single oscillator model and the values of E0 and Ed were determined.