Investigation of single phase Cu2ZnSnxSb1−xS4 compounds processed by mechanochemical synthesis

Abstract

The copper zinc tin sulfide (CZTS) compound is a promising candidate as an alternative absorber material for thin-film solar cells. In this study, we investigate the direct formation of $\mathrm{C}{\mathrm{u}}_{1.92}\mathrm{ZnS}{\mathrm{n}}_{x}(\mathrm{S}{\mathrm{b}}_{1\ensuremath{-}x}){\mathrm{S}}_{4}$ compounds $\text{[CZT}(A)\text{S]}$, with $x=1$, 0.85, 0.70, and 0.50, via a mechanochemical synthesis (MCS) approach, starting from powders of the corresponding metals, zinc sulfide, and sulfur. The thermal stability of the $\text{CZT}(A)\text{S}$ compounds was evaluated in detail by in situ synchrotron high-energy x-ray diffraction measurements up to 700 \ifmmode^\circ\else\textdegree\fi{}C. The $\text{CZT}(A)\text{S}$ compounds prepared via MCS revealed a sphalerite-type crystal structure with strong structural stability over the studied temperature range. The contribution of the MCS to the formation of such a structure at room temperature is analyzed in detail. Additionally, this study provides insights into the MCS of CZTS-based compounds: the possibility of a large-scale substitution of Sn by Sb and the production of single phase $\text{CZT}(A)\text{S}$ with a Cu-poor/Zn-poor composition. A slight increase in the band gap from 1.45 to 1.49--1.51 eV was observed with the incorporation of Sb, indicating that these novel compounds can be further explored for thin-film solar cells.