Aqueous-based method of forming semiconductor film and photovoltaic device including the film
View Patent ↗A method with enhanced safety characteristics of depositing a kesterite film, which includes a compound of the formula: Cu 2−x Zn 1+y Sn(S 1−z Se z ) 4+q , wherein 0≤x≤1; 0≤y≤1; 0≤z≤1; −1≤q≤1. The method includes contacting an aqueous solvent, ammonia, a source of hydrazine, a source of Cu, a source of Sn, a source of Zn, a source of at least one of S and Se, under conditions sufficient to form an aqueous dispersion which includes solid particles; applying the dispersion onto a substrate to form a thin layer of the dispersion on the substrate; and annealing at a temperature, pressure, and length of time sufficient to form the kesterite film. An annealing composition and a photovoltaic device including the kesterite film formed by the above method are also provided.
1. A method of depositing a kesterite film comprising a compound of the formula:
Cu 2 ZnSn(Se,S) 4
said method consisting of:
contacting a first amount of hydrazine, Cu 2 S, and S to form a solution;
contacting a second amount of hydrazine, SnSe, Se, and Zn to form a dispersion including Zn-containing solid particles;
mixing the solution with the dispersion forming, in situ, an dispersion containing Zn-containing solid particles and dissolved components;
mixing the dispersion with an additional amount of ammonium hydroxide;
applying said dispersion with the additional amount of ammonium hydroxide onto a substrate to form a layer, wherein the dissolved components function as a binder; and
annealing at a temperature, pressure, and length of time sufficient to form said kesterite film.
2. The method of claim 1 , wherein the additional amount of the ammonium hydroxide provides a nominal ammonia content of about from 0.1 weight % to about 25 weight % of the dispersion.
3. The method of claim 1 , wherein the zinc containing solid particles have a particle size from about 2 nm to about 2000 nm and ranges there between.
4. The method of claim 1 , wherein the dissolved components contain at least one of S, Se, Cu and Sn.
5. The method of claim 1 , wherein said substrate is selected from the group consisting of: metal foil, glass, ceramics, aluminum foil coated with a layer of molybdenum, a polymer, and a combination thereof.
6. The method of claim 1 , wherein said substrate is coated with a transparent conductive coating.
7. The method of claim 1 , wherein the step of applying is carried out by a method selected from the group consisting of: spin coating, dip coating, doctor blading, curtain coating, slide coating, spraying, slit casting, meniscus coating, screen printing, ink jet printing, pad printing, flexographic printing, and gravure printing.
8. The method of claim 1 , wherein the step of annealing is carried out at a temperature from about 200° C. to about 800° C. and ranges there between.
9. The method of claim 8 , wherein said annealing is carried out in an atmosphere which further comprises vapors of at least one of: sulfur, selenium, and a compound thereof.
10. The method of claim 1 , wherein said annealing is carried out in an atmosphere comprising: at least one of: N 2 , Ar, He, forming gas, and a mixture thereof.