Bandgap-tunable perovskite materials and methods of making the same

1. A mixed halide perovskite composition comprising:

a perovskite having the formula CsPb(A x B y ) 3 ,

wherein the perovskite is in the form of nanocrystals embedded in a non-perovskite matrix having the formula Cs 4 Pb(A x B y ) 6 ,

wherein A and B are each a halogen,

wherein x and y are non-zero and x+y=1,

wherein the mixed halide perovskite composition has a morphology which suppresses phase segregation of the mixed halide perovskite composition when subjected to optical or electrical stimuli to stabilize a tuned bandgap of the mixed halide perovskite composition, and

wherein at least a portion of the perovskite is in the form of a layer.

2. The composition of claim 1 , wherein A and B are selected from iodine and bromine.

3. The composition of claim 1 , wherein x is ⅓ and y is ⅔, or x is ⅔ and y is ⅓.

4. The composition of claim 1 , wherein the perovskite comprises a Cs(I x ) 3 layer and a Pb(Br y ) 3 layer.

5. The composition of claim 1 , wherein the perovskite comprises a Cs(Br y ) 3 layer and a Pb(I x ) 3 layer.

6. The composition of claim 1 , wherein the perovskite comprises a CsPb(I x Br y ) 3 layer.

7. The composition of claim 1 , which has a photoluminescence of from about 500 nm to about 650 nm.

8. The composition of claim 1 , which has a UV-vis absorption peak between from about 225 nm to about 600 nm.

9. A light-emitting diode comprising:

an electron injection layer;

a hole injection layer;

a metal electrode adjacent to the electron injection layer;

a transparent electrode adjacent to the hole injection layer; and

a perovskite layer comprising the mixed halide perovskite composition of claim 1 , disposed between the electron injection layer and the hole injection layer.

10. The light-emitting diode of claim 9 , wherein the perovskite comprises a Cs(I x ) 3 layer and a Pb(Br y ) 3 layer.

11. The light-emitting diode of claim 9 , wherein the perovskite comprises a Cs(Br y ) 3 layer and a Pb(I x ) 3 layer.

12. The light-emitting diode of claim 9 , wherein the perovskite comprises a CsPb(I x Br y ) 3 layer.

13. A solar cell comprising:

a hole transport layer;

an electron transport layer;

a metal electrode adjacent to the hole transport layer;

a transparent electrode adjacent to the electron transport layer; and

a perovskite layer comprising the mixed halide perovskite composition of claim 1 , disposed between the hole transport layer and the electron transport layer.

14. The solar cell of claim 13 , wherein the perovskite comprises a Cs(I x ) 3 layer and a Pb(Br y ) 3 layer.

15. The solar cell of claim 13 , wherein the perovskite comprises a Cs(Br y ) 3 layer and a Pb(I x ) 3 layer.

16. The solar cell of claim 13 , wherein the perovskite comprises a CsPb(I x Br y ) 3 layer.

17. A mixed halide perovskite composition comprising:

photo-active crystallites of a perovskite having the formula CsPb(I y Br x ) 3 , and

a host matrix of photo-inactive insulating crystallites of a non-perovskite having the formula Cs 4 Pb(A x B y ) 6 in which the photo-active crystallites are embedded, wherein A and B are each a halogen,

wherein A and B are each a halogen,

wherein x and y are non-zero and x+y=1,

wherein the host matrix is effective to suppress ion-migration when subjected to optical or electrical stimuli leading to the formation of iodine-rich and bromine-rich regions in the composition, and

wherein at least a portion of the perovskite is in the form of a layer.

18. The composition of claim 17 , which is in the form of a film formed by a physical deposition process.

19. The composition of claim 17 , wherein the photo-inactive insulating crystallites comprise crystallites of Cs 4 Pb(I x Br y ) 6 .