Non-hydrolytic metal oxide films for perovskite halide overcoating and stabilization

1. A method of protecting a perovskite halide film from moisture and temperature, comprising:

positioning the perovskite halide film in a chamber;

maintaining the chamber at a temperature of less than 200 degrees Celsius;

inserting a first organo-metal compound into the chamber;

subsequently inserting a non-hydrolytic oxygen source into the chamber;

repeating the inserting of the first organo-metal compound and subsequent inserting of the non-hydrolytic oxygen source into the chamber for a predetermined number of cycles,

wherein, the non-hydrolytic oxygen source and the first organo-metal compound interact in the chamber to deposit a non-hydrolytic metal oxide film on the perovskite halide film, the non-hydrolytic metal oxide film protecting the perovskite halide film from relative humidity of greater than 35% and a temperature of greater than 150 degrees Celsius;

inserting a second organo-metal compound into the chamber;

subsequently inserting a hydrolytic oxygen source into the chamber; and

repeating the inserting of the organo-metal compound and subsequent inserting of the hydrolytic oxygen source into the chamber for a second predetermined number of cycles,

wherein, the second organo-metal compound and hydrolytic oxygen source interact in the chamber to deposit a hydrolytic metal oxide film on the non-hydrolytic metal oxide film.

2. The method of claim 1 , wherein the non-hydrolytic oxygen source includes a carboxylic acid.

3. The method of claim 2 , wherein the carboxylic acid includes at least one of acetic acid and formic acid.

4. The method of claim 1 , wherein the first organo-metal compound includes at least one of aluminum isopropoxide, aluminum triisopropoxide, titanium isopropoxide, titanium tetraisopropoxide, trimethylaluminum, dimethylaluminum isopropoxide, titanium phenyltriisopropoxide, titanocene dichloride, methyltitanium trichloride, aluminum trichloride, titanium tetrachloride or methyltriisopropoxytitanium.

5. The method of claim 4 , wherein the non-hydrolytic metal oxide film includes at least one of aluminum oxide, titanium dioxide, zirconium oxide, hafnium oxide or silicon oxide.

6. The method of claim 1 , wherein the hydrolytic oxygen source includes at least one of water or ozone.

7. The method of claim 1 , wherein the perovskite halide film includes a compound of formula I:

ABX 3   (I)

wherein,

A is organic or inorganic cation,

B is a metal cation, and

X is a halide.

8. The method of claim 7 , wherein the perovskite halide film includes a compound of formula II:

ABY 3-x Z x   (II)

wherein,

A is methylammonium or formamidinium,

B is Pb or Sn,

Y is I, Cl or Br,

Z is I, Cl or Br, and

x is 0, 1, 2 or 3.

9. A method of fabricating a photovoltaic cell, comprising:

depositing a perovskite halide film on a substrate;

positioning the substrate in a chamber;

maintaining the chamber at a temperature of less than 200 degrees Celsius;

inserting a titanium isopropoxide gas into the chamber;

subsequently inserting a non-hydrolytic oxygen source into the chamber; and

repeating the inserting of titanium isopropoxide gas and subsequent inserting of the non-hydrolytic oxygen source into the chamber for a predetermined number of cycles,

wherein, the non-hydrolytic oxygen source and the titanium isopropoxide gas interact in the chamber to deposit a non-hydrolytic titanium dioxide film on the perovskite halide film, the non-hydrolytic titanium dioxide film protecting the perovskite halide film from relative humidity of greater than 35% and a temperature of greater than 150 degrees Celsius, the non-hydrolytic titanium dioxide film transporting charges created in the perovskite halide film to an electrode in contact with the non-hydrolytic titanium dioxide film;

inserting an organo-metal compound into the chamber;

subsequently inserting a hydrolytic oxygen source into the chamber; and

repeating the inserting of the organo-metal compound and subsequent inserting of the hydrolytic oxygen source into the chamber for a predetermined number of cycles,

wherein, the hydrolytic oxygen source and the organo-metal compound interact in the chamber to deposit a hydrolytic metal oxide film on the non-hydrolytic titanium dioxide film.

10. The method of claim 9 , wherein the substrate includes a conductive substrate or an electronically conducting film positioned on the substrate.

11. The method of claim 10 , wherein the method further comprises:

prior to depositing the perovskite halide film on the substrate, positioning the substrate in the chamber;

inserting the titanium isopropoxide gas into the chamber;

subsequently inserting the non-hydrolytic oxygen source into the chamber; and

repeating the inserting of the titanium isopropoxide gas and subsequent inserting of the non-hydrolytic oxygen source into the chamber for a predetermined number of cycles,

wherein, the non-hydrolytic oxygen source and the titanium isopropoxide interact on the substrate to deposit a base non-hydrolytic titanium dioxide film on the substrate, the perovskite halide film coated on the base non-hydrolytic titanium dioxide film.

12. The method of claim 9 , wherein the non-hydrolytic oxygen source includes a carboxylic acid.

13. The method of claim 9 , wherein the organo-metal compound includes at least one of a aluminum isopropoxide, aluminum triisopropoxide, titanium isopropoxide, titanium tetraisopropoxide, trimethylaluminum, dimethyl aluminum isopropoxide, titanium phenyltriisopropoxide, titanocene dichloride, methyltitanium trichloride, aluminum chloride, titanium chloride or methyltriisopropoxytitanium.

14. The method of claim 9 , wherein the hydrolytic oxygen source includes at least one of water or ozone.

15. The method of claim 9 , wherein the perovskite halide film includes a compound of formula I:

ABX 3   (I)

wherein,

A is organic or inorganic cation,

B is a metal cation, and

X is a halide.

16. The method of claim 1 , wherein the first organo-metal compound and the second organo-metal compound are the same.