Colloidal synthesis of the mixed ionic-electronic conducting NaSbS₂ nanocrystals

Solution-based synthesis of mixed ionic and electronic conductors (MIECs) has enabled the development of novel inorganic materials with implications for a wide range of energy storage applications. However, many technologically relevant MIECs contain toxic elements (Pb) or are prepared by using traditional high-temperature solid-state synthesis. Here, we provide a simple, low-temperature and size-tunable (50-90 nm) colloidal hot injection approach for the synthesis of NaSbS₂ based MIECs using widely available and non-toxic precursors. Key synthetic parameters (cationic precursor, reaction temperature, and ligand) are examined to regulate the shape and size of the NaSbS₂ nanocrystals (NCs). FTIR studies revealed that ligands with carboxylate functionality are coordinated to the surface of the synthesized NaSbS₂ NCs. The synthesized NaSbS₂ nanocrystals have electronic and ionic conductivities of 3.31 × 10^-10 (e^-) and 1.9 × 10^-5 (Na⁺) S cm^-1 respectively, which are competitive with the ionic and electrical conductivities of perovskite materials generated by solid-state reactions. This research gives a mechanistic understanding and post-synthetic evaluation of parameters influencing the formation of sodium antimony chalcogenides materials.