The Effect of Annealing on Structural, Optical, and Electrical Properties of Cu3SnS4 Thin Films Prepared by Spin Coat Method

Abstract

Cu3SnS4 films were grown on glass substrates via method of spin coating, followed by annealing at 550 degrees C in a furnace under H2S:Ar (1:9) sulfur rates of 30 and 40 sccm for 15, 30, and 60 minutes. The effect of the sulfur rate and annealing time on the structural, morphological, and optical behaviors of the samples was systematically investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL), Hall effect, and UV-Vis spectroscopy. The XRD patterns revealed that all the Cu3SnS4 samples had a polycrystalline structure. The crystallite size, dislocation density, interplaner distance, micro-strain, and crystallite number of the Cu3SnS4 samples were calculated from the XRD spectra. Among all the samples, the CTS sample annealed for 15 minutes under a 30 sccm H2S:Ar (1:9) gas flow showed the best crystalline structure. The surface morphology of the samples showed spherical micro-crystal formations. Analysis of the Cu3SnS4 samples indicated that the surfaces were composed of valley and peak regions. The valley regions appeared relatively smooth, while the peak regions displayed a crystal structure with specific orientations. When examining the energy band gap values, it is observed that the energy band gap of the films increases significantly with the increase in sulfur flow rate. PL analysis revealed emission peaks at approximately 1.41 eV and 1.80 eV, along with broad emission bands at 549 nm, 567 nm, 689.42 nm, and 882.6 nm. An increase in sulfur content led to a reduction in peak intensity, which is attributed to conduction band fluctuations and the formation of structural defects. The carrier concentration of the samples is found to be on the order of 1017 cm-3 and 1018 cm-3, which is more appropriate for thinfilm solar cells (TFCSs).