Nickel oxide sol-gel ink

1. A method for preparing a nickel oxide precursor ink comprising:

preparing a solvent comprising diols and alcohol amines;

adding nickel nitrate into the solvent to form a nickel nitrate containing solution;

adding at least one metal acetate into the nickel nitrate containing solution to form a nickel nitrate and metal acetate containing solution;

adding water to the nickel nitrate and metal acetate containing solution to form a nickel oxide precursor mixture;

heating the nickel oxide precursor mixture to 60 to 75° C.; and

cooling the nickel oxide precursor mixture to form the nickel oxide precursor ink.

2. The method of claim 1 , wherein the nickel nitrate is Ni(NO 3 ) 2 ·nH 2 O and n is 0, 4, 6 or 9.

3. The method of claim 1 , wherein the at least one metal acetate is Ni(CH 3 CO 2 ) 2 ·xH 2 O, and x is 0, 2 or 4.

4. The method of claim 1 , wherein the nickel nitrate is Ni(NO 3 ) 2 ·6H 2 O and the at least one metal acetate is Ni(CH 3 CO 2 ) 2 ·4H 2 O.

5. The method of claim 4 , wherein the nickel oxide precursor mixture has a concentration of Ni(NO 3 ) 2 ·6H 2 O between 0.7 M and 0.8 M and a concentration of Ni(CH 3 CO 2 ) 2 ·4H 2 O is between 50 mM and 110 mM.

6. The method of claim 5 , wherein the concentration of Ni(NO 3 ) 2 ·6H 2 O is 0.72 M and the concentration of Ni(CH 3 CO 2 ) 2 ·4H 2 O is 103 mM.

7. The method of claim 1 , wherein the at least one metal acetate comprises Ni(CH 3 CO 2 ) 2 ·xH 2 O and Cu(CH 3 CO 2 ) 2 ·bH 2 O, wherein x is 0, 2 or 4 and b is 0 or 1.

8. The method of claim 1 , wherein the nickel nitrate is Ni(NO 3 ) 2 ·6H 2 O and the at least one metal acetate comprises Ni(CH 3 CO 2 ) 2 ·4H 2 O and Cu(CH 3 CO 2 ) 2 ·1H 2 O.

9. The method of claim 8 , wherein the nickel oxide precursor mixture has a concentration of Ni(NO 3 ) 2 ·6H 2 O between 0.7 M and 0.8 M, a concentration of Ni(CH 3 CO 2 ) 2 ·4H 2 O between 50 mM and 110 mM, and a concentration of Cu(CH 3 CO 2 ) 2 ·1H 2 O between 20 mM and 41·3 mM.

10. The method of claim 1 , wherein the solvent comprises ethylene glycol and ethanolamine.

11. The method of claim 1 , wherein:

the solvent comprises ethylene glycol and ethanolamine; and

in the nickel oxide precursor mixture, the ethylene glycol, ethanolamine and water have a volume ratio of 12:1·46:1, respectively.

12. The method of claim 1 , wherein the method is performed under an inert atmosphere having less than 5 ppm water and less than 5 ppm oxygen.

13. The method of claim 1 , wherein the at least one metal acetate is selected from the group consisting of: nickel acetate tetrahydrate, copper acetate monohydrate, and any combination thereof.

14. The method of claim 1 , wherein the at least one metal acetate comprises nickel acetate tetrahydrate and copper acetate monohydrate.