Synthesis of Wurtzite Cu2ZnGeSe4 Nanocrystals and their Thermoelectric Properties

An unusual wurtzite phase of Cu2ZnGeSe4 (CZGSe) has been discovered and its corresponding nanocrystals (NCs) were synthesized by using a facile hot-injection solution-phase synthesis method. Moreover, the formation mechanism of this new phase of CZGSe, instead of the typically observed stannite structure, has been investigated in detail, which indicates that wurtzite CZGSe, which represents the kinetic phase, could be prepared by using a kinetic growth process without phase transformation into the thermodynamically stable stannite structure during the colloidal synthesis. In addition, the potential of wurtzite CZGSe as a thermoelectric material is demonstrated by characterizing the thermoelectric properties of as-synthesized wurtzite CZGSe NCs. This work allows for a rational manipulation of the NCs with a desired crystal structure through adjusting the thermodynamics and kinetics without using any additives and, because of its simplicity and versatility, it may be extended to the phase-controlled synthesis of other chalcogenide NCs.