Kesterite material of CZTS, CZTSe or CZTSSe type

1. A method of producing a kesterite material of CZTS, CZTSe or CZTSSe type, comprising the steps of:

a) preparing an acidic solution and dissolving copper salt and zinc salt in water in desired molar ratio,

b) preparing a basic solution by dissolving an alkali metal stannate together with an alkali metal carbonate or an alkali metal hydrogen carbonate or an alkali metal hydroxide or a combination thereof, and optionally with an alkali metal selenate or an alkali metal selenite or a mixture thereof,

c) carrying out a precipitation reaction by mixing said acidic and said basic solution, thereby obtaining a precipitate,

d) washing and heat treating said precipitate thereby providing a precursor for the kesterite material, and

e) sulfurizing the precursor of step d to provide the kesterite material.

2. The method according to claim 1 , wherein the salts used for the acidic solution are nitrates, halides, sulfates, carboxylates or combinations thereof.

3. The method according to claim 1 , wherein the copper salt is copper (II) nitrate and the zinc salt is zinc (II) nitrate.

4. The method according to claim 1 , wherein said acidic solution further comprises nitric acid.

5. The method according to claim 1 , wherein said alkali metal stannate comprises Na 2 SnO 3 and/or K 2 SnO 3 in hydrated or anhydrous form.

6. The method according to claim 1 , wherein said basic solution further comprises selenium in the form of an alkali metal selenate and/or an alkali metal selenite.

7. The method according to claim 1 , wherein the step of sulfurizing comprises subjecting the precursor to a sulfur comprising gas at a temperature above room temperature.

8. The method according to claim 7 , wherein said sulfur comprising gas is one or more of the following: H 2 S, elemental sulfur in gaseous state (S 2 -S 8 ), COS, CS 2 , organic sulfur compounds.

9. The method according to claim 8 , wherein said organic sulfur compounds are CH 3 SH and/or CH 3 SSCH 3 .

10. The method according to claim 1 , wherein said sulfur comprising gas further comprises selenium.

11. The method according to claim 1 , further comprising the following steps between steps d) and e):

grinding the precursor for the kesterite material obtained by step d),

dispersing said grinded precursor in a liquid, thereby obtaining a slurry,

depositing a thin layer of the slurry onto a substrate, and

optionally, drying said thin layer.

12. The method according to claim 11 , wherein the step of dispersing said grinded precursor in a liquid comprises wetting and dispersing said grinded precursor in a liquid using polymeric wetting and/or dispersion agents.

13. The method according to claim 1 , further comprising the following steps subsequent to step e):

grinding said kesterite material,

dispersing said grinded kesterite material in a liquid, thereby obtaining a slurry,

depositing a thin layer of the slurry onto a substrate,

optionally, drying said thin layer, and

optionally, heat treating such thin layer.

14. The method according to claim 13 , wherein the step of dispersing said grinded kesterite material in a liquid comprises wetting and dispersing said grinded kesterite material in a liquid using polymeric wetting and/or dispersion agents.

15. A precursor material for a kesterite material of CZTS, CZTSe or CZTSSe type, where said precursor material is obtained by a process comprising the steps of:

a) preparing an acidic solution and dissolving copper salt and zinc salt in water in a desired molar ratio,

b) preparing a basic solution by dissolving an alkali metal stannate together with an alkali metal carbonate or an alkali metal hydrogen carbonate or an alkali metal hydroxide or a combination thereof,

c) carrying out a precipitation reaction by mixing the acidic and the basic solutions, thereby obtaining a precipitate, and

d) washing and heat treating the precipitate thereby providing a precursor for the kesterite material.