Synthesis and characterization of CZTS thin-film as absorber layer for solar cells

Cu2ZnSnS4 (CZTS) thin films were deposited on glass substrates at temperature 350°C using chemical spray pyrolysis technique. The structural, optical and electrical properties of the CZTS films were studied using X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FESEM), UV-visible spectrophotometry and Hall Effect measurements. The X-ray diffraction results showed that the prepared films have a polycrystalline structure of the tetragonal type, kesterite phase. The size of the crystals was calculated using Scherer's method and it was found that the crystal size increased with the increase of the thickness. Raman spectroscopy showed the main peak around (324, 338, 330, 325, 334 cm-1) for all samples, which confirms the formation of tetragonal (CZTS) compound. The results of the field emission scanning electron microscope (FESEM) showed that the prepared films were formed as beautifully and homogeneously intertwined twigs. The optical properties were studied using UV-visible spectrophotometry, and the optical energy gap values were calculated using the (Tauc plot) and it was found that it decreases from (1.72 to 1.56 eV) with the increase in thickness. High values of the absorption coefficient (α>104 cm-1) are obtained which is suitable for the solar cell applications. The measurements of Hall coefficients showed that the prepared films are p-type. As the thickness increased from 0.59 to 3.3 μm, the mobility of charged particles increased from 1.33 to 30.5 cm2V-1s-1, and the conductivity of CZTS samples increased from 0.015 to 0.069 (Ω.cm)-1.