Radio frequency magnetron sputtered highly textured Cu2ZnSnS4 thin films on sapphire (0Â 0Â 0Â 1) substrates

This paper describes the growth of highly textured Cu2ZnSnS4 (CZTS) thin films on sapphire (0 0 0 1) substrate by radio frequency (RF) magnetron sputtering from a single CZTS target. Working pressure is one of the most important parameters for a one-step RF magnetron sputtering process. The influence of working pressure on the composition and the structural, morphological, and optical properties of CZTS thin films has been investigated is this paper. The properties of Zn-rich and Cu-poor and stoichiometric CZTS thin films are compared to study the effect of film composition. Using photoluminescence (PL) and time-resolved photoluminescence (TRPL) techniques, two PL bands are observed from the Zn-rich and Cu-poor highly textured CZTS. In addition to the band to band transition at 1.39 eV, a PL band at 1.26 eV is ascribed to the donor-acceptor recombination. The band edge transition exhibits a PL lifetime of 17.2 ns. In contrast, the band of donor-acceptor recombination exhibits a much longer lifetime of 177.3 ns. The understanding of the film formation mechanism from single target sputtering may improve the standard preparation method for high quality CZTS absorbers.