Processing of perovskite films using inks with complexing agents

1. A method, comprising:

providing an ink comprising reactants, a complexing agent, and a solvent, wherein:

the reactants comprise a first and a second cation, a first metal, and a first and a second anion, wherein the first and second cations are different from each other, and the first and second anions are different from each other;

the complexing agent comprises a heterocyclic donor material;

depositing the ink onto a substrate to form a wet film;

drying the wet film to form a precursor layer; and

annealing the precursor layer to form a perovskite film, wherein:

the perovskite film comprises a mixed-cation mixed-halide perovskite material;

the perovskite film comprises less than 5% by mass of the complexing agent; and

the perovskite film is formed using a one-step process.

2. The method of claim 1 , wherein the heterocyclic donor material is selected from the group consisting of oxygen donors, nitrogen donors, nitrogen-oxygen donors, phosphorous donors, sulfur donors, and selenium donors.

3. The method of claim 1 , wherein the heterocyclic donor material is selected from the group consisting of a material listed in Table 1.

4. The method of claim 1 , wherein the heterocyclic donor material is selected from the group consisting of pyridine, 4-substituted pyridines, quinoline, and iso-quinoline derivatives.

5. The method of claim 1 , wherein the first and second cations are each selected from the group consisting of methylammonium, formamidinium, Cs, K, and Rb.

6. The method of claim 1 , wherein the first metal is selected from the group consisting of lead and tin.

7. The method of claim 1 , wherein:

the reactants further comprises a second metal;

the first metal is lead; and

the second metal is tin.

8. The method of claim 1 , wherein the first and second anions are each selected from the group consisting of bromide, iodide and chloride.

9. The method of claim 1 , wherein:

the first cation comprises formamidinium and the second cation comprises Cs;

the first metal comprises Pb; and

the first anion comprises bromide and the second anion comprises iodide.

10. The method of claim 1 , wherein the mixed-cation mixed-halide perovskite material comprises:

the first and the second cation, wherein each are selected from the group consisting of methylammonium, formamidinium, Cs, K and Rb;

the first metal selected from the group consisting of Pb and Sn; and

the first and the second anion, wherein each are selected from the group consisting of bromide, iodide, and chloride.

11. The method of claim 1 , wherein the mixed-cation mixed-halide perovskite material comprises formamidinium cesium lead iodide bromide.

12. The method of claim 1 , wherein the mixed-cation mixed-halide perovskite material comprises FA 0.85 Cs 0.15 Pb(I 0.85 Br 0.15 ) 3 , where FA is formamidinium.

13. The method of claim 1 , wherein each of the first and second anions, the metal, and the first and second cations have concentration ratios in the ink that are less than 5% different from targeted concentration ratios in the perovskite film.

14. The method of claim 1 , wherein each of the first and second anions, the first metal, and the first and second cations have concentration ratios in the ink that are less than 5% different from concentration ratios in a stoichiometric perovskite film.

15. The method of claim 1 , wherein:

the complexing agent has greater than 0.05 molar solubility relative to the reactants;

the complexing agent has a complex binding strength to the first metal greater than that of dimethylformamide (DMF) and less than that of dimethylsulfoxide (DMSO); and

the complexing agent has a boiling point less than 200° C.

16. The method of claim 1 , wherein the solvent is selected from the group consisting of an anhydrous solvent, a polar solvent, dimethylformamide (DMF), dimethylacetamide (DMAC), and combinations thereof.

17. The method of claim 1 , wherein the depositing, drying or annealing steps, or the depositing, drying and annealing steps, are performed in dehumidified air with less than 5% RH.

18. The method of claim 1 , wherein the depositing, drying or annealing steps, or the depositing, drying and annealing steps are performed in an atmosphere comprising less than 1% oxygen.

19. The method of claim 1 , wherein the drying step is performed in an environment of nitrogen forced convection, an environment of air forced convection, or a low-pressure environment with pressure from 0.01 Pa to 3000 Pa.

20. The method of claim 1 , wherein the drying step is performed in an environment with a controlled partial pressure of the solvent.

21. The method of claim 1 , wherein the annealing step is performed at a temperature from 70° C. to 350° C.

22. The method of claim 1 , wherein the perovskite film is formed without the use of any anti-solvents.

23. The method of claim 1 , wherein an equivalent ratio of the complexing agent relative to the first metal concentration in the ink is from 0.5 to 5.

24. The method of claim 1 , wherein the first metal molarity in the ink is from 0.25 to 1.5 moles of the first metal per liter of the ink.

25. The method of claim 1 , wherein the perovskite film comprises an undetectable amount of the complexing agent when measured by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), or Fourier transform infrared spectroscopy (FTIR).

26. A method, comprising:

providing an ink comprising reactants, a complexing agent, and a solvent, wherein:

the reactants comprise a first and a second cation, a first metal, and a first and a second anion, wherein the first and second cations are different from each other, and the first and second anions are different from each other;

depositing the ink onto a substrate to form a wet film, wherein the depositing step is performed using spin-coating, slot-die coating, blade coating, dip coating, spraying, screen printing, ink-jet printing, gravure printing, offset printing, or waterfall coating;

drying the wet film to form a precursor layer; and

annealing the precursor layer to form a perovskite film, wherein:

the perovskite film comprises a mixed-cation mixed-halide perovskite material;

the perovskite film comprises less than 5% by mass of the complexing agent; and

the perovskite film is formed using a one-step process.

27. The method of claim 26 , wherein the complexing agent comprises:

a molar solubility greater than 0.05 to at least one of the reactants;

a complex binding strength to the first metal greater than that of dimethylformamide (DMF) and less than that of dimethylsulfoxide (DMSO); and

a boiling point less than 200° C.

28. A method, comprising:

providing an ink comprising reactants, a complexing agent, and a solvent, wherein:

the reactants comprise a first and a second cation, a first metal, and a first and a second anion, wherein the first and second cations are different from each other, and the first and second anions are different from each other;

the complexing agent comprises:

a molar solubility greater than 0.05 to at least one of the reactants;

a complex binding strength to the first metal greater than that of dimethylformamide (DMF) and less than that of dimethylsulfoxide (DMSO); and

a boiling point less than 200° C.;

depositing the ink onto a substrate to form a wet film, wherein the depositing step is performed using spin-coating, slot-die coating, blade coating, dip coating, spraying, screen printing, ink jet printing, gravure printing, offset printing, or waterfall coating;

drying the wet film to form a precursor layer: and

annealing the precursor layer to form a perovskite film, wherein the perovskite film comprises:

a mixed-cation mixed-halide perovskite material: and

less than 5% by mass of the complexing agent.