Metal halide perovskites, light-emitting diodes, and methods

1. A composite material comprising:

a metal halide perovskite crystal comprising a unit cell according to formula (I)—

(RNH 3 ) 2 (IC) n-1 M n X 3n+1   (I),

wherein IC is an inorganic cation comprising a monovalent metal,

R is a monovalent C 1 -C 20 hydrocarbyl,

M is a metal selected from the group consisting of Pb, Sn, Cu, Ge, Mn, Co, and Eu,

X is a halide selected from the group consisting of Cl, Br, and I, and

n is an integer equal to or greater than 2; and

a polymeric matrix material in which the metal halide perovskite crystal is dispersed;

wherein the composite material is a film having a thickness of about 10 nm to about 250 nm, and

wherein the metal halide perovskite crystal has a quasi-2D structure.

2. The composite material of claim 1 , wherein the polymeric matrix material comprises poly(ethylene oxide).

3. The composite material of claim 1 , wherein the metal halide perovskite crystal is dispersed substantially evenly in the polymeric matrix material.

4. The composite material of claim 1 , wherein the film has a thickness of about 25 nm to about 75 nm.

5. An electronic device comprising:

an electrode,

a counterelectrode, and

the composite material of claim 1 ;

wherein the composite material is arranged between the electrode and the counterelectrode.

6. The electronic device of claim 5 , wherein the electronic device is a light-emitting diode (LED), and the composite material is configured to emit light.

7. The device of claim 5 , further comprising at least one of a layer selected from the group consisting of a hole transporting layer, a hole injecting layer, a hole blocking layer, an electron transporting layer, an electron injecting layer, and an electron blocking layer.

8. The device of claim 5 , further comprising:

a hole transporting layer, and

a hole injecting layer;

wherein the hole transporting layer is arranged between the composite material and the electrode, and the hole injecting layer is arranged between the hole transporting layer and the electrode.

9. The device of claim 5 , further comprising an electron transporting layer arranged between the composite material and the counterelectrode.

10. The device of claim 5 , wherein (i) the electrode is an anode, (ii) the counterelectrode is a cathode, (iii) the composite material is configured to emit light, and (iv) the device further comprises:

a hole injecting layer arranged adjacent to and in contact with the anode;

a hole transporting layer arranged between and in contact with both the hole injecting layer and the composite material; and

an electron transport layer arranged between and in contact with both the composite material and the cathode;

wherein the hole injecting layer comprises PEDOT:PSS, the hole transporting layer comprises poly-TPD, and the electron transport layer comprises TPBi.

11. A method of forming a composite material, the method comprising:

providing a precursor liquid comprising (i) (IC)X, (ii) MX 2 , (iii) an organic ammonium halide salt, (iv) a polymeric matrix material, and (v) a polar organic liquid; and

depositing the precursor liquid on a surface to form a film;

wherein M is a metal selected from the group consisting of Pb, Sn, Cu, Ge, Mn, Co, and Eu,

IC is an inorganic cation comprising a monovalent metal, and

X is a halide selected from the group consisting of Cl, Br, and I.

12. The method of claim 11 , further comprising annealing the film.

13. The composite material of claim 1 , wherein n is 2 to 9.

14. The composite material of claim 1 , wherein the monovalent metal comprises an alkali metal.

15. The composite material of claim 1 , wherein the alkali metal is Cs.

16. The composite material of claim 1 , wherein the monovalent C 1 -C 20 hydrocarbyl is a benzyl moiety.

17. The composite material of claim 1 , wherein M is Pb.

18. The composite material of claim 1 , wherein X is I.