Phase-controlled synthesis of Cu2ZnSnS4 powders via the microwave-assisted solvothermal route

Cu2ZnSnS4 was successfully prepared via the microwave-assisted solvothermal route at the reaction temperature as low as 180 °C. In comparison with the conventional solution process for preparing Cu2ZnSnS4 powders, the reaction time was significantly reduced to 1 h, and the preparation procedures were simplified with the incorporation of microwave irradiation technique. The mobility of ions and dipoles are suggested to have been accelerated via the microwave, thereby enhancing the reaction rates. Kesterite and wurtzite Cu2ZnSnS4 powders were formed via adjusting the volume fraction of ethylenediamine in the microwave-solvothermal process. The amount of ethylenediamine affected the morphology of the derived powders due to the selective passivation of ethylenediamine on Cu2ZnSnS4. The microscopic analysis revealed that the samples prepared with high ethylenediamine concentrations had large particle sizes. The enhanced grain size reduced the surface recombination and increased the photoluminescence intensity of Cu2ZnSnS4 particles. During the microwave-assisted solvothermal process, Cu2S was formed first and reacted with the constituent ions and hydrogen sulfide ions to form Cu2ZnSnS4 powders.