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

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

• M represents one or several first metals, either identical or different selected from Cu, Zn, Sn, Ge, Sb and Bi, and
• C represents one or more chalcogenide elements either identical or different selected from S, Se and Te,
• characterized in that the following successive steps are performed at a temperature from 0° C. to 50° C., preferably from 20° to 40° C. wherein:
• a) a first solution of precursor(s) of said first metal(s) M, other than one (or more) chalcogenide salt(s) C in solution, is prepared in a solvent consisting in pure acetonitrile or a mixture with water and/or an alcohol other than methanol, and
• b) a second aqueous, alcoholic or hydro-alcoholic solution of precursor(s) of chalcogenide(s) C consisting in one (or more) chalcogenide salts of second metal(s), other than one (or more) first metal(s) M, is prepared, the alcohol of said second solution being 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 quasi-instantaneously, comprising primary amorphous nanoparticles with sizes of less than 30 nm, preferably 3 to 20 nm, 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, alcoholic or hydro-alcoholic solution in order to form a colloidal solution, the alcohol of said aqueous, alcoholic or hydro-alcoholic colloidal solution being other than methanol, and
• f) again the solid portion is separated from said colloidal solution of step e), preferably by centrifugation, 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 comprising, an aqueous, alcoholic or hydro-alcoholic solution, the alcohol of said alcoholic or hydro-alcoholic solution, if any, being a non-toxic alcohol.