LAUSR

Abstract Se-rich CZTSSe absorbers with large grains are important contributors to the performances of CZTSSe solar cells and can be fabricated by the selenization of as-sputtered CZTS precursors. To explore the effects of the H2Se concentration in the annealing atmosphere on the growth of CZTSSe phases, sputtered CZTS precursors were subjected to annealing with a mixed gas of Ar and H2Se at different concentrations. A series of characterization techniques were employed to investigate the morphologies, phase structures, surface states, and elemental compositions of the annealed samples. The results demonstrate that the H2Se concentration in the annealing atmosphere can significantly affect the grain size, suppressing the decomposition of CZTSSe absorbers. When the H2Se concentration in the annealing atmosphere reaches 4.5 vol%, a selenium-enriched CZTSSe absorber that is composed of the pure kesterite structure and that has densely packed large grains and a high concentration of selenium was obtained. The highest efficiency of 10.12% of CZTSSe solar cells was achieved herein.