Preparation and growth mechanism of centimeter-scale (AgxCu1−x)2ZnSnS4 single crystals via a molten salt method

Abstract

Kesterite Cu₂ZnSnS₄ (CZTS) is considered as one of the most promising thin-film solar cell and photocatalytic materials; however, its efficiency in practical photoelectric applications is often seriously limited by the presence of large numbers of Cu–Zn antisite defects. Alloying with Ag to fabricate Ag-alloyed CZTS ((Ag_xCu_1−x)₂ZnSnS₄, ACZTS) can reduce the Cu–Zn antisite defects in CZTS, but few research studies have been able to separately clarify the effect of Ag content and growth temperature on large-sized (Ag_xCu_1−x)₂ZnSnS₄ single crystals. In this study, centimeter-scale high-quality ACZTS single crystals were synthesized via an Ag-alloying strategy by a molten salt method for the first time. The results showed that the synthesized ACZTS have a high-quality single-crystal structure. A series of experiments was performed using various characterization techniques and it was found that Ag content and growth temperature were crucial in determining the size of ACZTS single crystals obtained through a molten salt method and that the associated CZTS base generated at high temperature was beneficial for further ACZTS single-crystal growth in this high-temperature environment. The experimental results showed that the growth mechanism of ACZTS crystals prepared using a molten salt method could be attributed to a type of epitaxial growth process. Our study provides a promising approach for growing large-sized ACZTS single crystals with high quality that can provide a potential single-crystal platform for the study of light-emitting diodes, photocatalytic hydrogen production, etc.