Influence of pH on structural, optical and electrical properties of solution processed Cu2ZnSnS4 thin film absorbers

Cu2ZnSnS4 (CZTS) films were obtained by the dip-coating method. The effect of different pH values 4.0, 4.5, and 5.0 on the structural, morphological, optical and electrical properties of samples was investigated by XRD, SEM, UV–vis and Hall Effect measurements. The XRD spectra showed that the characteristic peak intensity of CZTS semiconductor increased with increasing pH value of the precursor solution. It was also observed that increased pH values resulted in a significant reduction in the amount of impurity phases of the films. The UV–vis studies revealed a significant increase in the optical absorption of thin films in the visible region as the pH value of the solution was increased. The band gap of the samples shifted from 2.0 to 1.38 eV by increasing the pH value. The electrical resistivity of the films was found to vary from 2.8×10−2 to 3.1 Ω cm, depending on its pH value.