An Investigation on Structural, Morphological, Optical, and Electrical Properties of Copper Zinc Tin Sulfide (CZTS) Thin Films Prepared by SILAR Method

Copper zinc tin sulfide (CZTS) thin films have been synthesized by successive ionic layer adsorption and reaction (SILAR) technique for different concentrations of precursors. The as-prepared samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), UV-visible-NIR spectroscopy, and Raman spectroscopy. The electrical conductivity was measured by two-probe Keithley 2450 Source Meter. The XRD patterns confirmed the prominent kesterite phase in addition to the wurtzite phase of CZTS. The Raman spectra further confirmed the formation of the kesterite phase. The crystallite size was found to be in the range of 11 nmto 28 nm. The lattice constants measured were in good agreement with previous literature. The SEM images showed a non-uniform distribution of granular agglomerates along with nano-flakes almost homogeneous in size throughout the thin film. UV-Vis-NIR spectra showed high absorption in the visible region, and the optical band gap was found to be in the range of 1.5 eV to 2.31 eV. The sample with an optimum band gap of 1.5 eV is promising for the solar cell absorber layer. The sample with a band gap of 2.31 eV shows around 90% transmission in the visible region and is suitable for window layer in thin film solar cells, and the sample with a band gap of 1.55 eV shows low transmission in the UV region coupled with high reflection in NIR region can be used as solar control coating unit.