Effect of copper concentration on physical properties of CZTS thin films deposited by dip-coating technique

Cu 2 ZnSnS 4 (CZTS) thin films have been prepared via sol–gel method and deposited on ordinary glass substrates by dip-coating technique. The chemical composition of Cu/(Zn + Sn) ratio was varied between 0.85, 0.95 and 1.05 to study its effect on structural, optical, morphological, compositional and electrical properties of deposited films. The films were investigated using different techniques such as X-ray diffractometer (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), UV–vis spectrophotometer and four-point probe method. The X-ray diffraction showed the single kesterite phase with the preferential orientation along (112) plane. The crystallites size was found to be between 6.95 and 9.30 nm. Raman scattering measurements for CZTS films deposited at Cu/(Zn + Sn) equal to 0.85 and 1.05 were confirmed the presence of pure CZTS phase by the characteristic peak at 332 cm −1 . The morphological properties show a dense surface morphology and the elemental composition indicates CZTS films with a near-stoichoimetric composition. The optical properties were calculated using transmittance and absorbance data in the wavelength range between 450 and 850 nm. The obtained band gap energy values were found to be between 1.41 and 1.47 eV. The electrical sheet resistance showed values between 0.68 and 1.07 × 10 3 Ω square −1 . A best sheet resistance and favorable optical band gap make our dip-coated CZTS thin films suitable to be used as an absorber layer for photovoltaic applications.