Colloidal synthesis and functional properties of quaternary Cu-based semiconductors: Cu₂HgGeSe₄

Herein, a colloidal synthetic route to produce highly monodisperse Cu₂HgGeSe₄ (CHGSe) nanoparticles (NPs) is presented in detail. The high yield of the developed procedure allowed the production of CHGSe NPs at the gram scale. A thorough analysis of their structural and optical properties is shown. CHGSe NPs displayed poly-tetrahedral morphology and narrow size distributions with average size in the range of 10–40 nm and size dispersions below 10 %. A 1.6 eV optical band gap was measured by mean of UV–Vis. By adjusting the cation ratio, an effective control of their electrical conductivity is achieved. The prepared NPs are used as building blocks for the production of CHGSe bulk nanostructured materials. The thermoelectric properties of CHGSe nanomaterials are studied in the temperature range from 300 to 730 K. CHGSe nanomaterials reached electrical conductivities up to 5 × 10⁴ S m⁻¹, Seebeck coefficients above 100 μV K⁻¹, and thermal conductivities below 1.0 W m⁻¹ K⁻¹ which translated into thermoelectric figures of merit up to 0.34 at 730 K.