Cu2SnS3 thin films deposited by spin coating route: a promise candidate for low cost, safe and flexible solar cells

Abstract

Thin films of Cu2SnS3 (CTS) was successfully grown on glass substrates by sol–gel spin coating technique. In this work, the effect of drying time on structural, morphological and optical characteristics is investigated while drying temperature was kept at 300 °C. The samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–Vis–NIR spectroscopy and four probe analysis. The XRD patterns of the samples proved the polycrystalline nature and the formation of pure cubic Cu2SnS3 structure with (111) preferential orientation. No peak referring to other binary or ternary phases were detected in the patterns. The average crystallite sizes calculated using the Debye–Scherrer formula was about 7.5 nm. The AFM and SEM images revealed that the CTS films have continuous and dense morphology. The films roughness increases from 8 to 68 nm with increasing drying time from 2 to 10 min. The thin films absorption coefficients were in the range 0.66 × 105–1.38 × 105 cm−1 at 2.14 eV. We found that by increasing the drying time, the sheet resistance increased from 22 to 574 kΩ and the direct optical band gap increased from 1.19 to 1.65 eV. The synthesised material seems to be a good candidate for flexible, cheap and friendly environment solar cells applications.