Effect of sulfur amount during post-growth sulfurization process on the structural, morphological and thermoelectric properties of sol-gel grown quaternary chalcogenide Cu2ZnSnS4 thin films

Abstract

In this work, the CZTS thin films (TFs) have been grown using sol-gel spin coating method on Si substrate. The effect of sulfur concentration on the structural, morphological and thermoelectric properties was investigated using various amounts of sulfur (100–400 mg) during post growth sulfurization process. XRD data evident that the best crystallinity of the CZTS thin film was obtained when the sample was sulfurized using 400 mg amount of sulfur. The vibrational modes of CZTS thin films were observed using Raman spectroscopy with major A1 mode at 331 cm−1 and secondary B(TO) and B(LO) modes at 292 cm−1 and 367 cm−1 respectively. SEM images showed that higher amount of sulfur contents resulted in the compact and smooth surface when compared with the samples sulfurized at lower concentration of sulfur. The thermoelectric properties such as Seebeck coefficient, electrical conductivity and power factor have improved from (249–334 μV/°C), (69–117 S/cm) and (4.28 × 104–1.305 × 103 Wm−1C−2) respectively with increasing the amount of sulfur during sulfurization process. This behavior of thermoelectric properties explained in detail using standard formulas and available literature.