One step synthesis of Cu2ZnSnS4 nanoflakes by microwave irradiation technique and effect of Cu concentration

The influence of cyclic microwave irradiation and effect of Cu concentration has been investigated for synthesis of pure phase Cu2ZnSnS4 powder. It has been observed that Cu concentration plays a vital role to get pure phase Cu2ZnSnS4. The optical properties, phase purity, crystallographic structure and morphology have been investigated by spectroscopic and microscopic techniques. The results reveal that single phase kesterite Cu2ZnSnS4 with no other secondary phase can be obtained by precisely controlling the cyclic microwave irradiation time and the precursor concentrations. The optical band gap of prepared Cu2ZnSnS4 powder, estimated from UV-Visible spectroscopy has been found to be ~ 1.45 eV which is superlative for photovoltaic application. Systematic Raman study confirms the formation of Cu2ZnSnS4 phase and suppression of CuS peak with proper control in copper concentration. TEM image shows nanoflakes kind of morphology having thickness of flakes between 25 nm to 45 nm. Further the crystal inter-planer spacing is found to be 0.32 nm, which is consistent with the XRD data and ascribed to (112) plane