Crystalline organic-inorganic halide perovskite thin films and methods of preparation
A film comprising a crystalline halide perovskite composition having the following formula: AMX 3 (1) wherein: A is an organic cation selected from the group consisting of methylammonium, tetramethylammonium, formamidinium, and guanidinium; M is at least one divalent metal; and X is independently selected from halide atoms; wherein the crystalline film of the halide perovskite composition possesses at least one of an average grain size of at least 30 microns, substantial crystal orientation evidenced in an ordering parameter of at least 0.6, and a level of crystallinity of at least 90%. Methods for producing films of these halide perovskite compositions using ionic liquids instead of volatile organic solvents are also described herein.
1. A film comprising a crystalline halide perovskite composition having the following formula:
AMX 3 (1)
wherein:
A is an organic cation selected from the group consisting of methylammonium, tetramethylammonium, formamidinium, and guanidinium;
M is at least one divalent metal; and
X is independently selected from halide atoms;
wherein the crystalline film of the halide perovskite composition possesses at least one of an average grain size of at least 30 microns, substantial crystal orientation evidenced in an ordering parameter of at least 0.6, and a level of crystallinity of at least 90%.
2. The film of claim 1 , wherein the film of the crystalline halide perovskite composition possesses an average grain size of at least 30 microns.
3. The film of claim 1 , wherein the film of the crystalline halide perovskite composition possesses an average grain size of at least 50 microns.
4. The film of claim 1 , wherein the film of the crystalline halide perovskite composition possesses an average grain size of at least 100 microns.
5. The film of claim 1 , wherein the at least one divalent metal is selected from lead, tin, and germanium.
6. The film of claim 1 , wherein the film has a thickness of at least 200 nm.
7. A method for producing a film of a crystalline halide perovskite composition, the method comprising:
i) forming a film of a perovskite precursor solution onto a substrate, the perovskite precursor solution comprising a) a metal-containing compound of the formula MX′ 2 , where M is at least one divalent metal and X′ is a monovalent anion; b) an organic salt of the formula AX, wherein A is selected from methylammonium, tetramethylammonium, formamidinium, and guanidinium, and X is independently selected from halide atoms; and c) an ionic liquid; wherein components a) and b) are dissolved in component c); and
ii) annealing the film of the perovskite precursor solution at a temperature of at least 30° C. for a time period effective to convert perovskite precursor components in the perovskite precursor solution to a film of a crystalline halide perovskite composition having the following formula:
AMX 3 (1)
wherein A, M, and X are as defined above; and
wherein the crystalline film of the halide perovskite composition possesses at least one of an average grain size of at least 30 microns, substantial crystal orientation evidenced in an ordering parameter of at least 0.6, and a level of crystallinity of at least 90%.
8. The method of claim 7 , wherein the at least one divalent metal (M) is selected from lead, tin, and germanium.
9. The method of claim 7 , wherein the film of the crystalline halide perovskite composition has a thickness of at least 200 nm.
10. The method of claim 7 , wherein the ionic liquid is selected from the group consisting of an alkylammonium ionic liquid, formamidinium ionic liquid, and guanidinium ionic liquid.
11. The method of claim 7 , wherein the ionic liquid possesses a cation that is equivalent to the cation A in the organic salt.
12. The method of claim 7 , wherein the ionic liquid possesses an anion other than halide.
13. The method of claim 7 , wherein the ionic liquid possesses a carbon-containing anion.
14. The method of claim 7 , wherein MX′ 2 and AX in the precursor are present in a relative amount such that the ratio of M:X is about 1:3.
15. The method of claim 7 , wherein a temperature of at least 30° C. and up to 150° C. is used in the annealing step (ii).
16. The method of claim 7 , wherein the film of the crystalline halide perovskite composition possesses an average grain size of at least 30 microns.
17. The method of claim 7 , wherein the film of the crystalline halide perovskite composition possesses an average grain size of at least 50 microns.
18. The method of claim 7 , wherein the film of the crystalline halide perovskite composition possesses an average grain size of at least 100 microns.
19. The method of claim 7 , further comprising removing the ionic liquid by rinsing said film of the crystalline halide perovskite composition with a solvent in which the ionic liquid is soluble.