INFLUENCE OF DEPOSITION PARAMETERS ON THE MORPHOLOGY, STRUCTURAL AND OPTICAL PROPERTIES OF Cu2ZnSnS4 THIN FILMS GROWN BY SOLVOTHERMAL METHOD

In this study, the Cu2ZnSnS4 (CZTS) thin films have been directly grown on transparent conductive fluorine-doped tin oxide (FTO) substrates via a solvothermal synthetic route. The effects of deposition temperature and deposition time on the morphology, structure, composition and optical properties of CZTS thin films were investigated using scanning electronic microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, energy dispersive spectrometry (EDS) and UV-visible spectrophotometry, respectively. The results indicated that the deposition temperature obviously affect crystal structures, surface morphology and composition of CZTS thin films. The thin films are mainly composed of CZTS with kesterite phase, however it contains a little binary and ternary impurities phase especially for samples prepared at low temperatures of 140 degrees C and 170 degrees C. The CZTS thin films prepared at temperatures of 140 degrees C and 170 degrees C are composed of a large number of sphere-like particles with an average diameter of about 300-450 nm. The CZTS thin films grown at 200 degrees C are composed of vertically oriented nano-flakes which directly spread over the FTO substrates. The deposition time do not obviously affect crystal structures and morphology. The crystallite sizes of CZTS thin films increase gradually with deposition temperature raising or deposition time prolonging. The strong absorption in the visible light region and a band gap of approximately 1.5 eV suggest that the CZTS thin films can be used as an absorber layer of thin film solar cells.