Large-grain crystallized metal chalcogenide film, colloidal solution of amorphous particles, and preparation methods

A method for preparing a colloidal aqueous, or hydro-alcoholic solution of amorphous nanoparticles of metal chalcogenides of formula M-C wherein:

• M represents first metals consisting of Cu, Zn, and Sn, and
• C represents at least one chalcogenide element selected from S and Se,
• the method comprising the following successive steps being performed at a room temperature from 0° C. to 50° C., wherein:
• a) a first solution of precursors of said first metals M is prepared in a solvent consisting of pure acetonitrile, or a mixture of acetonitrile with water and/or an alcohol other than methanol, and
• b) a second aqueous or hydro-alcoholic solution of precursors of the at least one chalcogenides C consisting of one or two chalcogenide salts of second metals, other than said first metals M, is prepared, the alcohol of said second solution, if any, being an alcohol other than methanol, and
• c) both of said first and second solutions of precursors are mixed at atmospheric pressure and at room temperature until a crude colloidal solution is obtained, including a solid portion comprising primary amorphous nanoparticles containing all of the first metals Cu, Zn, and Sn, with sizes of less than 30 nm, and a liquid supernatant, and
• d) the solid portion is separated from said colloidal solution of step c), in order to obtain a solid residue after removal of the liquid supernatant, and
• e) the solid residue obtained in step d) is rinsed by pouring onto it an aqueous or hydro-alcoholic solution in order to form a subsequent colloidal solution including a solid portion and a liquid supernatant, the alcohol of said hydro-alcoholic colloidal solution being other than methanol, and
• f) again, the solid portion is separated from said subsequent colloidal solution of step e), in order to obtain, after removal of the liquid supernatant, a rinsed solid residue as a humid paste, and
• g) said humid paste of step f) is re-dispersed in a dispersion solvent consisting of an aqueous or hydro-alcoholic solution, the alcohol of said hydro-alcoholic solution, if any, being a non-toxic alcohol, so as to obtain a dispersion of nanoparticles of chalcogenides of Cu, Zn, and Sn.