Influence of copper concentration on sprayed CZTS thin films deposited at high temperature

In this study, Cu2ZnSnS4 (CZTS) thin films were deposited by spray pyrolysis technique at constant substrate temperature. The effects of the copper concentration on the structural, morphological and optical properties of the films were investigated. The copper concentration was varied from 0.15 to 0.25 M in the steps of 0.05 M. The structural studies revealed that the Cu poor film shows low intense peaks, but as Cu concentration increases a relatively more intense and sharper diffraction peaks (112), (200), (220), and (312) of the kesterite crystal structure were observed. Raman spectroscopy analysis confirmed the formation of phase-pure CZTS films. From the morphological studies, it is found that the grain size increased as the Cu concentration increases from 0.15 to 0.25 M. The optical band-gap values were estimated to be 1.61, 1.52 and 1.45 eV for copper concentration 0.15, 0.20 and 0.25 M, respectively. Photoelectrochemical cells using films of different copper concentrations were fabricated and the best cell exhibited an efficiency of 1.09% for 0.25 M of copper concentration.