Characterization of Cu2ZnSnS4 Thin Films Prepared by Vapor Phase Sulfurization

Abstract

Cu₂ZnSnS₄ (CZTS) thin films could be successfully formed by vapor phase sulfurization of electron-beam-evaporated precursors on a soda-lime glass substrate. This film is an interesting material for absorber layer in a solar cell because all the constituents are readily available in the earth's crust. In this study, using a new type of precursors containing ZnS, we could achieve the strong adhesion of CZTS films to a glass substrate. From the result of scanning electron microscope (SEM) observation, it was confirmed that the surface morphology of CZTS films is much improved by using this new type of precursor. The X-ray diffraction pattern revealed that CZTS thin films have kesterite structures. From the measurement of transmittance and reflectance, the optical band-gap energy was estimated as 1.40–1.45 eV, which is very close to the optimum value for a solar-cell absorber. The highest open-circuit voltage of our cells based on CZTS films is 735 mV, which is a higher value than that reported in numerous other studies on CZTS.