Enhanced perovskite materials for photovoltaic devices

1. A perovskite material comprising:

a perovskite crystal lattice having a formula of C x M y X z ; and

an alkyl polyammonium cations disposed within or at a surface of the perovskite crystal lattice; wherein:

x, y, and z, are real numbers;

C comprises one or more cations selected from the group consisting of Group 1 metals, Group 2 metals, ammonium, formamidinium, guanidinium, and ethene tetramine;

M comprises one or more metals each selected from the group consisting of Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr, and combinations thereof; and

X comprises one or more anions each selected from the group consisting of halides, pseudohalides, chalcogenides, and combinations thereof.

2. The perovskite material of claim 1 , wherein the alkyl polyammonium cations comprise 1,4-diammonium butane, 1,8 diammonium octane, bis(4-aminobutyl)amine, or tris(4-aminobutyl)amine.

3. The perovskite material of claim 1 , wherein the alkyl polyammonium cations have a concentration between 1 mol % and 20 mol % in the perovskite material.

4. The perovskite material of claim 1 , wherein the alkyl polyammonium cations have a concentration between 1 mol % and 5 mol % in the perovskite material.

5. The perovskite material of claim 1 , wherein the alkyl polyammonium cations have a concentration of approximately 5 mol % in the perovskite material.

6. The perovskite material of claim 1 , wherein C comprises formamidinium, M comprises lead, and X comprises iodide.

7. The perovskite material of claim 6 , wherein the perovskite material crystal lattice has a cubic structure.

8. The perovskite material of claim 6 , wherein the ammonium groups of the alkyl polyammonium cations substitute for formamidinium ions within the perovskite crystal lattice.

9. A perovskite material comprising:

a formamidinium lead iodide perovskite material; and

an alkyl polyammonium cations dispersed within or at a surface of the formamidinium lead iodide perovskite material.

10. The perovskite material of claim 9 , wherein the alkyl polyammonium cations comprise 1,4-diammonum butane, 1,8 diammonium octane, bis(4-aminobutyl)amine, or tris(4-aminobutyl)amine.

11. The perovskite material of claim 9 , wherein the ammonium groups of the alkyl polyammonium cations substitute for formamidinium ions within the formamidinium lead iodide perovskite material.

12. The perovskite material of claim 9 , wherein the alkyl polyammonium cations have a concentration between 1 mol % and 20 mol % in the perovskite material.

13. The perovskite material of claim 9 , wherein the alkyl polyammonium cations have a concentration between 1 mol % and 5 mol % in the perovskite material.

14. The perovskite material of claim 9 , wherein the alkyl polyammonium cations have a concentration of approximately 5 mol % in the perovskite material.

15. The perovskite material of claim 9 , wherein the formamidinium lead iodide perovskite material has a cubic crystal structure.

16. A method for depositing perovskite material comprising:

depositing a lead salt precursor onto a substrate to form a lead salt thin film, wherein the lead salt precursor comprises a lead salt and an alkyl polyammonium salt;

depositing a second salt precursor onto the lead salt thin film to form a perovskite precursor thin film; and

annealing the substrate and perovskite precursor thin film to form a perovskite material.

17. The method of claim 16 , wherein the alkyl polyammonium salt comprises 1,4-diammonum butane, 1,8 diammonium octane, bis(4-aminobutyl)amine, or tris(4-aminobutyl)amine.

18. The method of claim 16 , wherein the lead salt precursor has an alkyl polyammonium salt concentration between 1 mol % and 20 mol %.

19. The method of claim 16 , wherein the lead salt is selected from the group consisting of lead (II) iodide, lead (II) thiocyanate, lead (II) chloride, lead (II) bromide, and combinations thereof.

20. The method of claim 16 , wherein the lead salt comprises lead (II) iodide.

21. The method of claim 16 , wherein the second salt precursor comprises a salt selected from the group consisting of formamidinium iodide, formamidinium thiocyanate, guanidinium thiocyanate, and combinations thereof.

22. The method of claim 16 , wherein the second salt precursor comprises formamidinium iodide.

23. The method of claim 16 , wherein the lead salt precursor contains one or more additives selected from the group consisting of an amino acid, 5-aminovaleric acid hydroiodide, 1,8-diiodooctane, 1,8-dithiooctane, formamidinium halide, acetic acid, trifluoroacetic acid, a methylammonium halide, water, and combinations thereof.

24. The method of claim 16 , wherein the lead salt precursor comprises a 90:10 mole ratio of PbI 2 to PbCl 2 dissolved in anhydrous dimethylformamide.

25. The method of claim 16 , wherein annealing occurs at a temperature greater than or equal to 50° C. and less than or equal to 300° C.

26. The method of claim 16 , wherein annealing occurs at an absolute humidity greater than or equal to 0 g H 2 O/m 3 air and less than or equal to 20 g H 2 O/m 3 air.

27. The method of claim 16 , wherein annealing occurs at an absolute humidity between about 4 and 7 g H 2 O/m 3 air.

28. A method for depositing perovskite material comprising:

depositing a lead salt precursor onto a substrate to form a lead salt thin film;

depositing an alkyl polyammonium salt precursor onto the lead salt thin film;

depositing a third salt precursor onto the lead salt thin film to form a perovskite precursor thin film; and

annealing the substrate and perovskite precursor thin film to form a perovskite material.

29. The method of claim 28 , wherein:

the lead salt precursor comprises lead (II) iodide;

the third salt precursor comprises formamidinium iodide.

30. The method of claim 28 , wherein:

the lead salt precursor comprises a 90:10 mole ratio of PbI 2 to PbCl 2 dissolved in anhydrous dimethylformamide;

the lead salt precursor comprises as much as 10 mol % cesium; and

annealing occurs at a temperature greater than or equal to 50° C. and less than or equal to 300° C.