Ionic-liquids Assisted Routes To Cu₂ZnSnS₄ Thin Films

Cu2Zn Sn S4(CZTS) thin film is a direct band-gap semiconductor material with a large absorption coefficient of over 104 cm-1 and a band-gap of 1.5e V. Moreover, all the constituents of CZTSthin films are earth abundant and low-cost. Therefore, CZTS thin film is considered as one of the promising materials for photovoltaic devices. However, the fabrications of CZTS thin films need either complex process and expensive equipment, or the use of lots of volatile, flammable or explosive solvents. Here, we attempt to develop a simple process for fabricating the CZTS thin films without volatile, flammable or explosive solvents. The main works are concluded as follows:1. High-quality CZTS thin films are grown on quartz substrates. We prepare the metal-ionic liquids precursors by adding metal chlorides into the ionic liquids such as 1-butyl-3-methylimidazolium chloride([Bmim][Cl]) at 80 oC. As-grown CZTS thin films are analyzed by X-ray diffraction(XRD), Raman, field-emission scanning electron microscopy(SEM) and ultraviolet-visible(UV-Vis) measurement, and X-ray photoemission spectroscopy(XPS).2. As-grown CZTS thin films could replace the high-cost Pt counter electrode in the dye-sensitized solar cells(DSSCs). Furthermore, we also investigate the effects of selenization time on the DSSCs’ performance.