Facile hydrothermal synthesis of hydrotropic Cu2ZnSnS4 nanocrystal quantum dots: band-gap engineering and phonon confinement effect

We developed a facile hydrothermal method for synthesizing ultrafine size-controllable earth-abundant Cu2ZnSnS4 (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.