CuAgSe nanocrystals: colloidal synthesis, characterization and their thermoelectric performance

CuAgSe is a promising thermoelectric (TE) material for its superior carrier mobility and ultralow lattice thermal conductivity. Herein, we present a scalable colloidal method to prepare monodisperse CuAgSe nanocrystals with high yield. The collected powder sample was washed by a sulfur-free reagent of NaNH₂ to remove the surface organic ligands (CuAgSe-W) and then annealed (CuAgSe-W-A). Both kinds of ligand-free samples were then hot pressed into dense pellets to measure the TE property. The results revealed that the crystal structure of both samples changed from low-temperature β-phase to high-temperature α-phase at around 465 K. Sample CuAgSe-W shows interesting temperature-dependent transition from N-type to P-type, which could be potentially used as thermal control transistor. Sample CuAgSe-W-A does not display this transition state but it exhibits potential for intermediate temperature TE applications with a figure-of-merit zT reaching 0.68 at 566 K.