Structure and transport behavior of hydrothermally grown phase pure Cu2ZnSn1-xGexS4 (x = 0.0, 0.3) nanoparticles

Abstract

Phase pure Cu2ZnSnS4 (CZTS) and Cu2ZnSn0.7Ge0.3S4 (CZTGS) kesterite nanoparticles of 10–35 nm size range were fabricated through a low-temperature hydrothermal process. Morphology, structure, and structural phase of the nanoparticles were determined utilizing field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectroscopy. Electrical transport behaviors of the pelletized nanostructures were studied in a physical properties measurement system (PPMS) in the 100–320 K temperature range. Obtained results indicate that both the CZTS and CZTGS nanostructures have p-type conductivity, with high room temperature hole concentration and carrier mobility. Substitution of 30% Sn by Ge enhances the electrical conductivity of CZTS about four times. While the room temperature hole mobility in the kesterite nanostructures reduces to about 60%, the hole concentration increases about one order on Ge incorporation. The limited substitution of Sn atoms by Ge does not affect the position of acceptor levels in the electronic band gap of the kesterite nanostructures. However, it increases the concentration of CuZn and ZnCu antisite defects and affects the transition temperature where the electrical transport of kesterite nanostructures changes from lattice scattering controlled to defect scattering controlled conduction.