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

[Display omitted] • Kesterite CZTS and CZTGS nanoparticles are synthesize by low-temperature hydrothermal process. • Substitution of 30% Sn by Ge in the kesterite lattice does not induce any impurity phase. • Ge incorporation in kesterite lattice increases the concentration of (V Cu + Zn Cu) defect complex. • Incorporation of Ge in kesterite lattice decreases [2Cu Zn + Sn Zn ] defect concentration. • Formation of V Cu enhances carrier concentration and conductivity of kesterite nanoparticles. Phase pure Cu 2 ZnSnS 4 (CZTS) and Cu 2 ZnSn 0.7 Ge 0.3 S 4 (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 Cu Zn and Zn Cu antisite defects and affects the transition temperature where the electrical transport of kesterite nanostructures changes from lattice scattering controlled to defect scattering controlled conduction. [ABSTRACT FROM AUTHOR]