Controlled synthesis of high efficiency Cu2BaSnS4 solar cells via a solution processed method

High purity Cu2BaSnS4 thin films with high qualities were synthesized by a low-cost solution processed method. The obtained Cu2BaSnS4 thin films were systematically studied via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-Ray photoelectron spectroscopy (XPS), and so on. The characterized results indicate high purity and fully coverage of Cu2BaSnS4, determined by the sequential annealing step under chalcogen vapor. The efficiency of the Cu2BaSnS4 solar cells is 1.99%, which is the highest efficiency obtained by a solution processed method. The high efficiency may be related to the high purity Cu2BaSnS4 phase. Our work provides an efficient way to obtain high efficiency Cu2BaSnS4 solar cells.