We developed a facile hydrothermal method for synthesizing ultrafine size-controllable earth-abundant Cu 2 ZnSnS 4 (CZTS) nanocrystals using simple Cu(II), Zn(II) and Sn(II) inorganic salts and thiourea in a mixed ethylenediamine and di-water solution as precursors. X-ray diffraction, Raman scattering and transmission electron microscopy confirm that pure kesterite structure CZTS nanocrystals have been synthesized at temperatures as low as 180 C. Broadening of Raman peaks and blue-shift of the absorption edge is attributed to quantum confinement within the nanocrystals. The hydrophilism and tunable band-gap of the CZTS nanocrystals show the potential applications of the nanocrystals for biological labelling and quantum dot based solar cells.

The fabrication of environmental-friendly Cu2ZnSnS4 (CZTS) thin films with pure kesterite phase is always a challenge to researchers in the field of solar cells. We introduce a simple non-vacuum sol-gel method to fabricate kesterite CZTS films. Ethylenediamine is used as the chelating agent and stabilizer and plays an important role in preparing stable precursor. X-ray diffraction, Raman and scanning electron microscopy studies suggest that the microstructure and optical properties of CZTS films depend strongly on annealing temperatures. The temperature dependence of conductivity of 500 °C annealed CZTS film shows that the Mott law dominates in the low temperature region and thermionic emission is predominant at high temperatures.