Method for making a perovskite layer at high speed
A method for making a perovskite layer includes providing a substrate; providing a perovskite solution comprising first and second polar, protic solvents each having a boiling point less than 135 degrees Celsius, an inorganic perovskite precursor, and an organic perovskite precursor, wherein the first solvent is an alcohol-based glycol ether capable of dissolving the inorganic Perovskite precursor material, the second solvent is an aliphatic alcohol, and the perovskite solution has a total initial amount of solvent greater than 30 percent by weight and a total solids concentration that is between 30 percent and 70 percent by weight of the Perovskite solution's saturation concentration: depositing the perovskite solution at a temperature of from 20 to 40 degrees Celsius on the substrate at a first location; removing a first portion of the initial amount of solvent from the deposited perovskite solution with a first drying step having a first drying step dwell time at a second location wherein the temperature of the first drying step is maintained between 20 and 40 degrees Celsius and the first drying step increases the total solids concentration of the perovskite solution to at least 75 percent of its saturation concentration; and removing a second portion of the initial amount of solvent from the deposited perovskite solution with a second drying step having a higher rate of solvent evaporation than the first drying step during a second drying step dwell time at a third location that causes saturation and a conversion reaction in the deposited perovskite solution resulting in perovskite crystal formation or formation of a perovskite intermediate phase, wherein the substrate is moved at a constant speed from the first location to the second location, and from the second location to the third location. A continuous inline method for production of photovoltaic devices at high speed, and a perovskite solution for use in making a uniform Perovskite layer at high speed to enable low cost production of high efficiency Perovskite devices are also described.
1. A method for making a perovskite layer, comprising: providing a substrate; providing a perovskite solution comprising first and second polar, protic solvents each having a boiling point less than 135 degrees Celsius, an inorganic perovskite precursor, and an organic perovskite precursor, wherein the first solvent is an alcohol-based glycol ether capable of dissolving the inorganic Perovskite precursor material, the second solvent is an aliphatic alcohol, and the perovskite solution has a total initial amount of solvent greater than 30 percent by weight and a total solids concentration that is between 30 percent and 70 percent by weight of the Perovskite solution's saturation concentration; depositing the perovskite solution at a temperature of from 20 to 40 degrees Celsius on the substrate at a first location; removing a first portion of the initial amount of solvent from the deposited perovskite solution with a first drying step having a first drying step dwell time at a second location wherein the temperature of the first drying step is maintained between 20 and 40 degrees Celsius and the first drying step increases the total solids concentration of the perovskite solution to at least 75 percent of its saturation concentration; and removing a second portion of the initial amount of solvent from the deposited perovskite solution with a second drying step having a higher rate of solvent evaporation than the first drying step during a second drying step dwell time at a third location that causes saturation and a conversion reaction in the deposited perovskite solution resulting in perovskite crystal formation or formation of a perovskite intermediate phase, wherein the substrate is moved at a constant speed from the first location to the second location, and from the second location to the third location.
2. The method of claim 1 , wherein the first drying step removes between 40 percent and 75 percent of the initial amount of solvent.
3. The method of claim 2 , wherein the removal of the second portion of solvent in the second drying step results in less than 10 percent of the initial amount of solvent remaining.
4. The method of claim 1 , wherein the conversion reaction changes the color or optical density of the perovskite solution.
5. The method of claim 4 wherein the percent transmission of visible light through the perovskite solution is reduced by at least a factor of 2 in the second drying step.
6. The method of claim 5 further comprising performing the second drying step with a drying device that causes the change in percent transmission of visible light in less than 0.5 seconds after the drying device first acts on the perovskite solution.
7. The method of claim 6 wherein the drying device is an air knife or plenum that blows gas on the perovskite solution.
8. The method of claim 1 , wherein the substrate is a flexible multilayer substrate.
9. The method of claim 8 wherein the flexible multilayer substrate comprises a flexible support, a first conducting layer, and a carrier transport layer.
10. The method of claim 9 wherein the flexible support comprises a material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyimide, polysulfone, metal foil, or glass.
11. The method of claim 9 wherein the carrier transport layer comprises material selected from the group consisting of poly(triaryl amine), poly-(N-vinyl carbazole), PEDOT complex, Poly(3-hexylthiophene), Spiro-MeOTAD, fullerene, graphene, reduced graphene oxide, copper(I) thiocyanate, cuprous iodide, or metal oxide and their derivatives.
12. The method of claim 1 further comprising annealing the perovskite solution with an annealing device in an annealing step at a fourth location wherein the annealing device is selected from the group consisting of a convection oven, a Rapid Thermal Processor, a photonic device, a heated roller, and a stationary heated curved surface.
13. The method of claim 12 wherein the annealing device heats an area around the substrate to between 90 and 125 degrees Celsius during the annealing step and the substrate comprises a material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polycarbonate.
14. The method of claim 12 wherein the annealing device heats an area around the substrate to between 120 and 300 degrees Celsius during the annealing step and the substrate comprises a material selected from the group consisting of polyimide, polysulfone, metal foil, or glass.
15. The method of claim 1 further comprising treating the substrate with a surface treatment device prior to deposition of the perovskite solution where the surface treatment device is selected from the group consisting of corona discharge, ozone, and plasma.
16. The method of claim 1 wherein the constant speed is greater than 15 meters per minute.
17. The method of claim 1 wherein the substrate is a flexible substrate and further comprising conveying the flexible substrate from a roll to the first location.
18. The method of claim 1 wherein the first solvent is selected from 2-methoxyethanol, 2-ethoxyethanol, or 1-methoxy-2-propanol.
19. The method of claim 1 wherein the first solvent is 2-methoxyethanol.
20. The method of claim 19 , wherein the second solvent is selected from 2-methyl-1-propanol, methanol, propanol, butanol, and ethanol.
21. The method of claim 20 , wherein the second solvent is ethanol.
22. The method of claim 1 wherein the layer of perovskite solution is deposited on the substrate with a deposition device selected from slot die, gravure, spray, flexographic, dip, inkjet, rod, or blade.
23. The method of claim 1 wherein the perovskite solution has a total solids concentration between 25 and 60 weight percent of precursor materials.
24. The method of claim 1 wherein the thickness of the perovskite solution deposited on the substrate is less than 10 microns.
25. The method according to claim 1 wherein the amount of the second solvent is from 10 to 50 percent by volume of the total solvent volume.
26. The method according to claim 1 wherein the amount of the second solvent is from 10 to 30 percent by volume of the total solvent volume.
27. The method according to claim 1 wherein the second solvent is selected from the aliphatic alcohol group consisting of 2-methyl-1-propanol, methanol, propanol, butanol, and ethanol.
28. The method according to claim 27 wherein the second solvent is ethanol.
29. The method according to claim 1 wherein the sum of the first and second solvent is greater than 50 percent by weight of the Perovskite solution and the total solids concentration is less than 40 percent by weight of the Perovskite solution.
30. The method according to claim 1 wherein the inorganic Perovskite precursor material comprise a material selected from the group consisting of lead (II) iodide, lead (II) acetate, lead (II) acetate trihydrate, lead (II) chloride, lead (II) bromide, lead (II) halide, lead nitrate, lead thiocyanate, tin (II) halide, rubidium halide, potassium halide, cesium halide, an cesium thiocyanate.
31. The method according to claim 1 wherein the organic Perovskite precursor material comprise a material selected from the group consisting of methylammonium iodide, methylammonium bromide, methylammonium chloride, methylammonium acetate, formamidinium acetate, formamidinium bromide, formamidinium chloride, formamidinium iodide, guanidinium iodide, methylammonium thiocyanate, and formamidinium thiocyanate.
32. The method according to claim 1 wherein the organic Perovskite precursor material has a purity greater than 99 percent by weight.
33. The method according to claim 1 wherein the inorganic Perovskite precursor contains a metal cation and has a purity greater than 99.9 percent by weight.
34. The method according to claim 1 wherein the perovskite solution further comprises a crystal growth modifier selected from the group consisting of gamma-butyrolactone, tetramethylsulfone, 1,8-diiodooctane, N-cyclohexyl-2-pyrrolidone, cyclohexanone, water, alkyl diamines, potassium thiocyanate, copper thiocyanate, acetic acid, and hydrogen iodide, acetonitrile, urea, tetrahydrofuran, isoamyl acetate, and methyl acetate.
35. The method according to claim 34 wherein the crystal growth modifier has a concentration from 0.01 to 10 percent by weight of the perovskite solution.
36. The method according to claim 1 wherein the perovskite solution further comprises a crystal grain boundary modifier selected from the group consisting of choline chloride, phenethylamine, hexylamine, l-α-phosphatidylcholine, polyethylene glycol sorbitan monostearate, sodium dodecyl sulfate, Poly(methyl methacrylate), Polyethylene glycol, phenethylammonium halide, pyridine, thiophene, ethylene carbonate, propylene carbonate, fullerenes, poly(propylene carbonate), potassium hexafluorophosphate, carbohydrazide, and didodecyldimethylammonium bromide.
37. The method according to claim 36 where in the crystal grain boundary modifier has a concentration from 0.01 to 2 percent by weight of the perovskite solution.
38. The method according to claim 19 wherein the amount of 2-methoxyethanol is greater than 20 percent by weight of the total solvent volume.
39. The method according to claim 21 , wherein the amount of the 2-methoxyethanol and the ethanol are together greater than 30 percent by weight of the provided perovskite solution, the inorganic Perovskite precursor material comprises a lead cation, and the molar ratio of organic Perovskite precursor material to inorganic Perovskite precursor material is between one and three.
40. The method according to claim 1 , wherein the perovskite solution is deposited at a temperature of from 20 to 30 degrees Celsius on the substrate at the first location, and wherein the temperature of the first drying step is between 20 and 30 degrees Celsius.