Precursor-mediated colloidal synthesis of compositionally tunable Cu−Sb−M−S (M = Zn, Co, and Ni) nanocrystals and their transport properties

The solution-based colloidal synthesis of multinary semi-conductor compositions has allowed the design of new inorganic materials impacting a large variety of applications. Yet there are certain compositions that have remained elusive--particularly quaternary structures of transition metal-based (e.g., Co, Zn, Ni, Fe, Mn, and Cr) copper antimony chalcogenides. These are widely sought for tuning the electrical and thermal conductivity as a function of the size, composition, and crystal phase. In this work, a facile hot injection approach for the synthesis of three different tetrahedrite-substituted nanocrystals (NCs) (Cu10Zn2Sb4S13, Cu10Co2Sb4S13, and Cu10Ni1.5Sb4S13) and their growth mechanisms are investigated. We reveal that the interplay between the Zn, Ni, and Co precursors on the basis of thiophilicity is key to obtaining pure phase NCs with controlled size and shape. While all of the synthesized crystal phases display outstanding low thermal conductivity, the Cu10.5Sb4Ni1.5S13 system shows the most enhanced electrical conductivity compared to Cu10Zn2Sb4S13 and Cu10Co2Sb4S13. This study highlights an effective synthesis strategy for the growth of complex quaternary nanocrystals and their high potential for application in thermoelectrics.