Organo-metal halide perovskites films and methods of making the same

1. A method comprising:

applying a solution comprising a first solvent, a halogen-containing precursor, and a metal halide to a substrate to form a coating of the solution on the substrate;

contacting the coating with a second solvent to form a first plurality of organo- metal halide perovskite crystals on the substrate; and

thermally treating the first plurality of organo-metal halide perovskite crystals, such that at least a portion of the first plurality of organo-metal halide perovskite crystals is converted to a second plurality of organo-metal halide perovskite crystals on the substrate, wherein:

the halogen-containing precursor consists of a cation and a halide,

the metal halide consists of a metal and the halide,

the halogen-containing precursor is provided in the solution in stoichiometric excess,

the first plurality of organo-metal halide perovskite crystals have an average crystal size between 30 nm and 200 nm,

the second plurality of organo-metal halide perovskite crystals have an average crystal size between 1 μm and 2 μm, and

the second plurality of organo-metal halide perovskite crystals consists essentially of the cation, the metal, and the halide.

2. The method of claim 1 , wherein the first plurality of organo-metal halide perovskite crystals form as a film on the substrate.

3. The method of claim 1 , wherein the first solvent has a boiling point temperature greater than about 150° C.

4. The method of claim 1 , wherein the first solvent comprises at least one of 1-methyl-2-pyrrolidinone, γ-butyrolactone, or dimethyl sulfoxide.

5. The method of claim 1 , wherein the halogen-containing precursor comprises at least one of a methylammonium halide, a formamidinium halide, or a cesium iodide.

6. The method of claim 5 , wherein the methylammonium halide consists of methylammonium iodide (MAI).

7. The method of claim 6 , wherein:

the stoichiometric excess corresponds to a molar ratio of the MAI to the metal halide between greater than about 1.01:1.0 and equal to 2.0:1.0.

8. The method of claim 7 , wherein the molar ratio is between 1.2:1.0 and 2.0:1.0.

9. The method of claim 1 , wherein the metal halide comprises at least one of PbI 2 , SnI 2 , BiI 3 , or InI 3 .

10. The method of claim 1 , wherein the second solvent has a boiling point temperature below about 150° C.

11. The method of claim 1 , wherein the second solvent comprises at least one of diethyl ether, toluene, chlorobenzene, or hexane.

12. The method of claim 1 , wherein the applying comprises at least one of spin-coating, curtain-coating, dip-coating, or spraying the solution onto a surface of the substrate.

13. The method of claim 1 , wherein the applying is performed at a temperature between about 0° C. and about 35° C.

14. The method of claim 1 , wherein the applying is performed over a period of time between about 1 second and about 1 hour.

15. The method of claim 1 , wherein the contacting comprises immersing the coating and the substrate in the second solvent.

16. The method of claim 15 , wherein the immersing is performed for a period of time between about 30 seconds and about 1 hour.

17. The method of claim 1 , wherein the thermally treating comprises heating the first plurality of organo-metal halide perovskite crystals to a temperature between about 35° C. and about 200° C.

18. The method of claim 17 , wherein the thermally treating is performed for a period of time between about 5 seconds and about 1 hour.

19. The method of claim 1 , wherein the thermally treating is performed in an oxygen-containing environment.

20. The method of claim 1 , wherein the second plurality of organo-metal halide perovskite crystals comprises an alkylammonium metal halide crystal.

21. The method of claim 20 , wherein the alkylammonium metal halide crystal comprises a methylammonium lead iodide crystal.