Solar cells on metallic substrates

Abstract

Disclosed are solar cells on a metallic substrate and methods for making such solar cells and substrates. For example, the disclosure can relate to perovskite solar cells on an aluminum substrate with a metal oxide layer on the surface of the substrate. The disclosure also relates to modifications to the surface topography of the substrate, for example to increase the surface area of the perovskite solar cell and increase overall efficiency.

Description

Attorney Docket No. 108050-1544781SOLAR CELLS ON METALLIC SUBSTRATESPriority Claim

[0001] This application claims priority to U.S. Provisional Application No.63 / 753,727 filed on February 4, 2025, the entirety of which is incorporated herein by reference.Technical Field

[0002] The disclosure relates generally to solar cells on a metallic substrate. For example, the disclosure can relate to perovskite solar cells on an aluminum substrate with a metal oxide layer on the surface of the substrate. The disclosure can also relate to modifications to the surface topography of the substrate, for example to increase the surface area of the perovskite solar cell and increase overall efficiency.Background

[0003] Innovation around solar cell technologies is increasing as the energy industry looks toward more sustainable solutions. For example, perovskite solar cells (PSCs) have shown enormous potential as a low-cost photovoltaic technology.

[0004] Perovskite solar cells utilize a light-absorbing layer composed of hybrid organic-inorganic lead or tin halide-based materials that crystallize in the perovskite structure (ABX3). When photons are absorbed by the perovskite layer, strong light-matter interaction leads to the generation of excitons with low binding energy, facilitating efficient charge separation into free electrons and holes. These carriers are subsequently transported through selective charge transport layers—typically an electron transport layer (ETL), and a hole transport layer (HTL)—that flank the perovskite absorber. The ETL and HTL provide energy band alignment and suppress recombination losses, directing electrons toward the cathode and holes toward the anode. The device architecture, which may be planar or mesoporous, can be optimized for interface engineering, defect passivation, and moisture stability to maximize power conversion efficiency and operational longevity. The tunable bandgap and solution-processability of perovskite materials further enable integration into tandem and flexible photovoltaic modules, positioning PSCs as a leading candidate for next-generation photovoltaic technologies.Attorney Docket No. 108050-1544781

[0005] However, glass substates for the PSCs have several drawbacks, including high cost, weight, complexity with multiple layers required, difficulty of transport, limited recyclability, and difficulty of manufacture, for example. Adding to the difficulty is that halide ions (e.g., iodide) within the perovskite layer are known to migrate to interfaces, potentially causing corrosion and loss of efficiency for some substrates.Summary

[0006] One or more embodiments of the disclosure relate to a solar cell, comprising: an aluminum substrate and a perovskite layer positioned on one side of the aluminum substrate. In one or more embodiments, the solar cell can further comprise a metal oxide layer between the aluminum substrate and the perovskite layer. In one or more embodiments, the solar cell can further comprise a hole / electron transport layer positioned on the perovskite layer on a side opposite the aluminum substrate. In one or more embodiments, the solar cell can further comprise a transparent conducting layer contacting the hole / electron transport layer on a side opposite the perovskite layer. In one or more embodiments, the transparent conducting layer comprises an oxide. In one or more embodiments, the solar cell can further comprise a lamination or moisture barrier on the transparent conducting layer. In one or more embodiments, the metal oxide layer comprises SnO2, TiO2, ZrO2, Cr2O3, or combinations thereof. In one or more embodiments, the metal oxide layer comprises SnO2or TiO2, or combinations thereof. In one or more embodiments, the metal oxide layer is not doped with a second metal. In one or more embodiments, the perovskite layer comprises at least one halide. In one or more embodiments, the aluminum substrate comprises a 1xxx series, 3xxx series, 5xxx, or 7xxx series aluminum. In one or more embodiments, the metal oxide layer has a weight of from 20 to 200 mg / m², for example as measured by x-ray fluorescence. In one or more embodiments, the aluminum substrate serves as a conductive layer for the solar cell. In one or more embodiments, the aluminum substrate is rigid. However, in other embodiments, the aluminum substrate can be flexible. In one or more embodiments, the aluminum substrate has a thickness of 1 mm or greater.

[0007] One or more embodiments of the invention relate to a process for making a solar cell, comprising: providing an aluminum sheet, optionally depositing or growing an electron transport layer on the aluminum sheet, depositing a halide perovskite layerAttorney Docket No. 108050-1544781on the aluminum sheet or the electron transport layer, depositing a hole / electron transport layer on the halide perovskite layer, depositing at least one transparent conductive material on the hole / electron transport layer. In one or more embodiments, the aluminum sheet has a metal oxide layer on a surface of the aluminum sheet. In one or more embodiments, the process can further comprise adding a lamination or moisture barrier on the transparent conductive material. In one or more embodiments, the aluminum sheet comprises a 1xxx series, 3xxx series, 5xxx, or 7xxx series aluminum. In one or more embodiments, the metal oxide layer comprises SnO2, TiO2, ZrO2, or Cr2O3. In one or more embodiments, the process is a roll-to-roll process.Brief Description of the Drawings

[0008] FIG. 1 illustrates an embodiment of the layered structure of a perovskite solar cell.

[0009] FIG. 2 illustrates an example of the efficiency over time of the solar cells described herein.Detailed Description

[0010] In some embodiments, the disclosure relates to solar cells comprising a metallic (e.g., aluminum) substrate, a perovskite layer positioned on at least one side of the metallic substrate (not necessarily contacting), optionally an additional layer on a top side of the metallic substrate, for example an indium tin oxide (ITO) layer, and an interface layer, e.g., a metal oxide layer between the metallic substrate and the perovskite layer. In some embodiments, the metal oxide layer can comprise more than one layer, for example a compact layer and a mesoporous layer. In some embodiments, the metallic substrate is rigid (e.g., not flexible). In some embodiments, the metallic substrate can serve as both the substrate and the bottom contact for the cell. In some embodiments, the metal oxide layer is not a metal doped layer. Some embodiments can further include a hole / electron transport layer on the perovskite layer on a side opposite the metallic substrate. Some embodiments can further include a transparent conducting layer contacting the hole / electron transport layer on a side opposite the perovskite layer. In some embodiments, the transparent conducting layer can be an indium tin oxide (ITO) layer. Some embodiments can further comprise an encapsulation layer, e.g., a lamination or moisture barrier on the transparentAttorney Docket No. 108050-1544781conducting layer. The encapsulation layer can, in some embodiments, serve to protect the solar cell from moisture and / or mechanical damage.

[0011] As used herein, the terms “invention,” “the invention,” “this invention” and “the present invention” are intended to refer broadly to all of the subject matter of this patent application and the claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below.

[0012] In this description, reference is made to alloys identified by aluminum industry designations, such as “series” or “7xxx.” For an understanding of the number designation system most commonly used in naming and identifying aluminum and its alloys, see “International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys” or “Registration Record of Aluminum Association Alloy Designations and Chemical Compositions Limits for Aluminum Alloys in the Form of Castings and Ingot,” both published by The Aluminum Association.

[0013] Aluminum alloys are described herein in terms of their elemental composition in weight percentage (wt. %) based on the total weight of the alloy. In certain examples of each alloy, the remainder is aluminum, with a maximum wt. % of 0.15 % for the sum of the impurities.

[0014] As used herein, terms such as “cast metal product,” “cast product,” “cast aluminum alloy product,” and the like are interchangeable and refer to a product produced by direct chill casting (including direct chill co-casting) or semi-continuous casting, continuous casting (including, for example, by use of a twin belt caster, a twin roll caster, a twin block caster, or any other continuous caster), electromagnetic casting, hot top casting, or any other casting method.

[0015] As used herein, a “continuous coil” or an “aluminum alloy continuous coil” refers to an aluminum alloy subjected to a continuous processing method on a continuous line without breaks in time or sequence (i.e., the aluminum alloy is not subjected to batch processing).

[0016] As used herein, a “coil-to-coil” line or “coil-to-coil processing” refers to a continuous processing method on a continuous line whereby the alloy, e.g., aluminum alloy, processed in the method is fed into the processing from a coil, uncoiled during the processing, and re-coiled after completing the processing.Attorney Docket No. 108050-1544781

[0017] Reference is made in this application to alloy condition or temper. For an understanding of the alloy temper descriptions most commonly used, see “American National Standards (ANSI) H35 on Alloy and Temper Designation Systems.” An F condition or temper refers to an aluminum alloy as fabricated. An 0 condition or temper refers to an aluminum alloy after annealing. A T1 condition or temper refers to an aluminum alloy cooled from hot working and naturally aged (e.g., at room temperature). A T2 condition or temper refers to an aluminum alloy cooled from hot working, cold worked, and naturally aged. A T3 condition or temper refers to an aluminum alloy solution heat treated, cold worked, and naturally aged. A T4 condition or temper refers to an aluminum alloy solution heat treated and naturally aged. A T5 condition or temper refers to an aluminum alloy cooled from hot working and artificially aged (at elevated temperatures). A T6 condition or temper refers to an aluminum alloy solution heat treated and artificially aged. A T7 condition or temper refers to an aluminum alloy solution heat treated and artificially overaged. A T8x condition or temper refers to an aluminum alloy solution heat treated, cold worked, and artificially aged. A T9 condition or temper refers to an aluminum alloy solution heat treated, artificially aged, and cold worked.

[0018] As used herein, the meaning of “a,” “an,” or “the” includes singular and plural references unless the context clearly dictates otherwise.

[0019] As used herein, the meaning of “room temperature” can include a temperature of from about 15 °C to about 30 °C, for example about 15 °C, about 16 °C, about 17 °C, about 18 °C, about 19 °C, about 20 °C, about 21 °C, about 22 °C, about 23 °C, about 24 °C, about 25 °C, about 26 °C, about 27 °C, about 28 °C, about 29 °C, or about 30 °C.

[0020] All ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1 to 10” should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more, e.g. 1 to 6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10.Metallic Substrate

[0021] The metallic substrate described herein is particularly well suited, but not limited, to an aluminum alloy. For example, any suitable aluminum alloy might beAttorney Docket No. 108050-1544781used, such as a continuous coil of an aluminum alloy. Suitable aluminum alloys include, for example, 1xxx series aluminum alloys, 2xxx series aluminum alloys, 3xxx series aluminum alloys, 4xxx series aluminum alloys, 5xxx series aluminum alloys, 6xxx series aluminum alloys, 7xxx series aluminum alloys, and 8xxx series aluminum alloys. In some embodiments, the substrate comprises a a 1xxx series, 3xxx series, 5xxx, or 7xxx series aluminum alloy. In some embodiments, the substrate comprises a (bright) 3104 or (mill) 3105 series aluminum alloy.

[0022] By way of non-limiting example, exemplary 1xxx series aluminum alloys for use as the metallic substrate can include AA1100, AA1100A, AA1200, AA1200A, AA1300, AA1110, AA1120, AA1230, AA1230A, AA1235, AA1435, AA1145, AA1345, AA1445, AA1150, AA1350, AA1350A, AA1450, AA1370, AA1275, AA1185, AA1285, AA1385, AA1188, AA1190, AA1290, AA1193, AA1198, or AA1199. In some cases, the aluminum alloy is at least 99.9 % pure aluminum (e.g., at least 99.91 %, at least 99.92 %, at least 99.93 %, at least 99.94 %, at least 99.95 %, at least 99.96 %, at least 99.97 %, at least 99.98 %, or at least 99.99 % pure aluminum).

[0023] Non-limiting exemplary 2xxx series aluminum alloys for use as the metallic substrate can include AA2001, AA2002, AA2004, AA2005, AA2006, AA2007, AA2007A, AA2007B, AA2008, AA2009, AA2010, AA2011, AA2011A, AA2111, AA2111A, AA2111B, AA2012, AA2013, AA2014, AA2014A, AA2214, AA2015, AA2016, AA2017, AA2017A, AA2117, AA2018, AA2218, AA2618, AA2618A, AA2219, AA2319, AA2419, AA2519, AA2021, AA2022, AA2023, AA2024, AA2024A, AA2124, AA2224, AA2224A, AA2324, AA2424, AA2524, AA2624, AA2724, AA2824, AA2025, AA2026, AA2027, AA2028, AA2028A, AA2028B, AA2028C, AA2029, AA2030, AA2031, AA2032, AA2034, AA2036, AA2037, AA2038, AA2039, AA2139, AA2040, AA2041, AA2044, AA2045, AA2050, AA2055, AA2056, AA2060, AA2065, AA2070, AA2076, AA2090, AA2091, AA2094, AA2095, AA2195, AA2295, AA2196, AA2296, AA2097, AA2197, AA2297, AA2397, AA2098, AA2198, AA2099, and AA2199.

[0024] Non-limiting exemplary 3xxx series aluminum alloys for use as the metallic substrate can include AA3002, AA3102, AA3003, AA3103, AA3103A, AA3103B, AA3203, AA3403, AA3004, AA3004A, AA3104, AA3204, AA3304, AA3005, AA3005A, AA3105, AA3105A, AA3105B, AA3007, AA3107, AA3207, AA3207A, AA3307, AA3009, AA3010, AA3110, AA3011, AA3012, AA3012A, AA3013, AA3014, AA3015, AA3016, AA3017, AA3019, AA3020, AA3021, AA3025, AA3026, AA3030, AA3130, orAA3065.Attorney Docket No. 108050-1544781

[0025] Non-limiting exemplary 4xxx series aluminum alloys for use as the metallic substrate can include AA4004, AA4104, AA4006, AA4007, AA4008, AA4009, AA4010, AA4013, AA4014, AA4015, AA4015A, AA4115, AA4016, AA4017, AA4018, AA4019, AA4020, AA4021, AA4026, AA4032, AA4043, AA4043A, AA4143, AA4343, AA4643, AA4943, AA4044, AA4045, AA4145, AA4145A, AA4046, AA4047, AA4047A, and AA4147.

[0026] Non-limiting exemplary 5xxx series aluminum alloys for use as the metallic substrate can include AA5182, AA5183, AA5005, AA5005A, AA5205, AA5305, AA5505, AA5605, AA5006, AA5106, AA5010, AA5110, AA5110A, AA5210, AA5310, AA5016, AA5017, AA5018, AA5018A, AA5019, AA5019A, AA5119, AA5119A, AA5021, AA5022, AA5023, AA5024, AA5026, AA5027, AA5028, AA5040, AA5140, AA5041, AA5042, AA5043, AA5049, AA5149, AA5249, AA5349, AA5449, AA5449A, AA5050, AA5050A, AA5050C, AA5150, AA5051, AA5051A, AA5151, AA5251, AA5251 A, AA5351, AA5451, AA5052, AA5252, AA5352, AA5154, AA5154A, AA5154B, AA5154C, AA5254, AA5354, AA5454, AA5554, AA5654, AA5654A, AA5754, AA5854, AA5954, AA5056, AA5356, AA5356A, AA5456, AA5456A, AA5456B, AA5556, AA5556A, AA5556B, AA5556C, AA5257, AA5457, AA5557, AA5657, AA5058, AA5059, AA5070, AA5180, AA5180A, AA5082, AA5182, AA5083, AA5183, AA5183A, AA5283, AA5283A, AA5283B, AA5383, AA5483, AA5086, AA5186, AA5087, AA5187, orAA5088.

[0027] Non-limiting exemplary 6xxx series aluminum alloys for use as the metallic substrate can include AA6101, AA6101A, AA6101B, AA6201, AA6201A, AA6401, AA6501, AA6002, AA6003, AA6103, AA6005, AA6005A, AA6005B, AA6005C, AA6105, AA6205, AA6305, AA6006, AA6106, AA6206, AA6306, AA6008, AA6009, AA6010, AA6110, AA6110A, AA6011, AA6111, AA6012, AA6012A, AA6013, AA6113, AA6014, AA6015, AA6016, AA6016A, AA6116, AA6018, AA6019, AA6020, AA6021, AA6022, AA6023, AA6024, AA6025, AA6026, AA6027, AA6028, AA6031, AA6032, AA6033, AA6040, AA6041, AA6042, AA6043, AA6151, AA6351, AA6351 A, AA6451, AA6951, AA6053, AA6055, AA6056, AA6156, AA6060, AA6160, AA6260, AA6360, AA6460, AA6460B, AA6560, AA6660, AA6061, AA6061 A, AA6261, AA6361, AA6162, AA6262, AA6262A, AA6063, AA6063A, AA6463, AA6463A, AA6763, A6963, AA6064, AA6064A, AA6065, AA6066, AA6068, AA6069, AA6070, AA6081, AA6181, AA6181A, AA6082, AA6082A, AA6182, AA6091, orAA6092.Attorney Docket No. 108050-1544781

[0028] Non-limiting exemplary 7xxx series aluminum alloys for use as the metallic substrate can include AA7011, AA7019, AA7020, AA7021, AA7039, AA7072, AA7075, AA7085, AA7108, AA7108A, AA7015, AA7017, AA7018, AA7019A, AA7024, AA7025, AA7028, AA7030, AA7031, AA7033, AA7035, AA7035A, AA7046, AA7046A, AA7003, AA7004, AA7005, AA7009, AA7010, AA7011, AA7012, AA7014, AA7016, AA7116, AA7122, AA7023, AA7026, AA7029, AA7129, AA7229, AA7032, AA7033, AA7034, AA7036, AA7136, AA7037, AA7040, AA7140, AA7041, AA7049, AA7049A, AA7149, AA7204, AA7249, AA7349, AA7449, AA7050, AA7050A, AA7150, AA7250, AA7055, AA7155, AA7255, AA7056, AA7060, AA7064, AA7065, AA7068, AA7168, AA7175, AA7475, AA7076, AA7178, AA7278, AA7278A, AA7081, AA7181, AA7185, AA7090, AA7093, AA7095, or AA7099.

[0029] Non-limiting exemplary 8xxx series aluminum alloys for use as the metallic substrate cane include AA8005, AA8006, AA8007, AA8008, AA8010, AA8011, AA8011 A, AA8111, AA8211, AA8112, AA8014, AA8015, AA8016, AA8017, AA8018, AA8019, AA8021, AA8021A, AA8021 B, AA8022, AA8023, AA8024, AA8025, AA8026, AA8030, AA8130, AA8040, AA8050, AA8150, AA8076, AA8076A, AA8176, AA8077, AA8177, AA8079, AA8090, AA8091, and AA8093.

[0030] Aluminum can offer a potential weight savings over glass or steel (e.g., up to 50 % weight savings). Aluminum can also be more formable that glass, enabling the shaping of the solar cells such as for shaped solar cell roofing panels. In addition, aluminum can be more thermally and / or electrically conductive than glass or steel, enabling a lower operating temperature for a solar panel to be maintained during operation, potentially extending the lifetime of the solar panel.

[0031] While aluminum alloy products are described throughout the disclosure, the methods and products apply to any metallic substrate. In some embodiments, the metallic substrate is aluminum, an aluminum alloy, magnesium, a magnesium-based material, titanium, a titanium-based material, copper, a copper-based material, steel, a steel-based material, bronze, a bronze-based material, brass, a brass-based material, a composite, a sheet used in composites, or any other suitable metal or combination of materials. The product may include monolithic materials, as well as non-monolithic materials such as roll-bonded materials, clad materials, composite materials, or various other materials. In some examples, the metal article is a metal coil, a metal strip, a metal plate, a metal sheet, a metal billet, a metal ingot, or the like.Attorney Docket No. 108050-1544781

[0032] The metallic substrate can be prepared from an alloy of any suitable temper. In certain examples, the alloys can be used in F, 0, T3, T4, T6, T8x, H24, H34, H291, or HS3 tempers. The alloys can be produced by direct chill casting (including direct chill co-casting) or semi-continuous casting, continuous casting (including, for example, by use of a twin belt caster, a twin roll caster, a block caster, or any other continuous caster), electromagnetic casting, hot top casting, or any other casting method.

[0033] In some embodiments, the metallic substrate is a rigid layer. Thus, in some embodiments, the metallic substrate is not flexible (e.g., not easily bent at normal handling pressures). In some of these embodiments, the thickness of the metallic substrate is sufficient for it to be rigid (e.g., not flexible). Thus, in some embodiments, the metallic substate has a thickness of at least 0.01 mm (e.g., at least 0.05 mm, at least 0.1 mm, at least 0.2 mm, at least 0.3 mm, at least 0.4 mm, at least 0.5 mm, at least 0.7 mm, at least 0.8 mm, at least 1 mm, at least 1.5 mm, at least 2 mm, at least 2.5 mm, at least 3 mm, at least 4 mm, at least 5 mm, at least 7 mm, at least 8 mm, at least 1 cm, from 0.1 mm to 5 cm, from 0.2 mm to 4 cm, from 0.5 mm to 3 cm, from 0.7 mm to 2 cm, or from 0.8 mm to 15 mm). In some embodiments, the metal substrate is not a foil. In some embodiments, the metal substrate has a Young’s Modulus (average of tension and compression moduli) of 68 GPA or greater (e.g., 69 GPa or greater, 70 GPa or greater, 71 GPa or greater, 72 GPa or greater, from 68 GPa to 75 GPa, or from 69 GPa to 73 Gpa).

[0034] In some embodiments, the metallic substrate can serve as a conductive layer. This can eliminate the need for separate conductive contacts or layers and simplify the overall solar cell.Oxide Layer

[0035] In some embodiments, the metallic substrate has an interfacial layer, such as an oxide layer on at least one surface of the substrate. In some embodiments, the oxide layer is between the metallic substrate and the perovskite layer. In some embodiments, the metallic substrate is optionally covered by a bottom ITO layer between the metallic substrate and the oxide layer. In such embodiments the bottom ITO layer can overcome any resistive native oxide on the surface of the metallic substrate and / or planarize the substrate surface. Whether or not the bottom ITO layer is used, the oxide layer can protect the substrate and / or allow electrons to flow freelyAttorney Docket No. 108050-1544781to the substrate. In some embodiments, the oxide layer can comprise a metal oxide layer, including, but not limited to SnO2, TiO2, Cr2O3, ZrO2, MgO, α-MnO2, β-MnO2, Al2O3, and combinations thereof. In some embodiments, the oxide layer is not metal doped. For example, in some embodiments, the metal oxide layer consists of the metal oxide without an additional metal doped into the oxide layer.

[0036] In some embodiments, the oxide layer can be present at a weight (for example as measured by XRF) of from 10 mg / m² to 200 mg / m² (e.g., from 20 mg / m² to 150 mg / m², from 30 mg / m² to 120 mg / m², from 40 mg / m² to 100 mg / m², from 50 mg / m² to 100 mg / m², or from 60 mg / m² to 80 mg / m²). In some embodiments, the oxide layer (e.g., TiO2) can be at a thickness of from 50 mg / mL to 500 mg / mL (e.g., from 100 mg / mL to 450 mg / mL, from 120 mg / mL to 400 mg / mL, from 140 mg / mL to 300 mg / mL, or from 150 mg / mL to 250 mg / mL. In some embodiments, the oxide layer can have a thickness of from 1 nm to 200 nm (e.g., from 5 nm to 200 nm, from 8 nm to 180 nm, from 10 nm to 150 nm, from 10 nm to 125 nm, from 20 nm to 100 nm, from 20 nm to 80 nm, or from 20 nm to 50 nm).

[0037] The oxide layer can be deposited by several methods, including, but not limited to, conversion coating and flame aerosol deposition (or aerosol flame spraying). In some embodiments, the oxide layer can be grown on the metallic substrate. In some embodiments, the method of depositing or growing the oxide layer can comprise a method to improve the wettability of chemicals on the substrate (e.g., metal substrate) surface. In some embodiments, this can involve degreasing, for example. Thus in some embodiments, the method can involve solvent degreasing, surfactant degreasing, plasma treatment (degreasing), or any combination thereof.

[0038] Thus, in some embodiments, the metallic substrate may be subjected to a conversion coating process to create a conversion coating over a surface of the metallic substrate. Example conversion coatings include, but are not limited to, an anodized coating, a chromate conversion coating, a phosphate conversion coating, a titanium conversion coating, a zirconium conversion coating, and rare earth metal conversion coatings.

[0039] In some embodiments, the conversion coating can be applied by chromate coating. Chromium conversion coatings are corrosion resistant and can provide retention of subsequent coatings. In some embodiments, different types of subsequent coatings can be applied to the chromate conversion coating to produce an acceptable surface. Properly pre-treated aluminum surfaces become highlyAttorney Docket No. 108050-1544781protected against corrosion even if the surface is exposed to external impacts (e.g., damage, high temperature, humidity) as a solar cell might be exposed to. In some embodiments, the coating weight on the substrate surface varies between 0.2 - 2.0 g / m² when a coating solution is applied to surface by immersion or spraying. The coating weight is variable according to concentration, application time, temperature and pH of the coating solution, for example. In some embodiments, the coating quality can be affected positively when surface treated with deionized water after chromating. In some embodiments, refinishing of the rinsing baths can also improve the quality of the coating. Chromated and rinsed aluminum substrates can be dried in driers or ovens with drying temperatures above 70°C, for example. Exemplary process line of chromate conversion coating can be set up as follows:Simple Process1. Acidic Degreasing2. Water Rinsing3. Water Rinsing4. Chromating5. Water Rinsing6. DryingAdvanced Process1. Degreasing2. Water Rinsing3. Caustic Treatment4. Water Rinsing5. Nitric Acid Treatment6. Water Rinsing7. Chromating8. Water Rinsing9. DryingAttorney Docket No. 108050-1544781

[0040] In some cases, a chemical conversion coating may be achieved by an ion bound to phosphorus-containing organic acid on a surface of the metallic substrate like an aluminum alloy product, such as when the phosphorus-containing organic acid comprises an ionic group as a tail group, such as a phosphonato group (-PO32-) or a hydrogen phosphonato group (-PO3H-). Optionally a coating may comprise a phosphorus containing organic acid having a formula of: X-(CR1R2)n-PO(OH)2or X-(CR1R2)n-PO(OH)H, where n is an integer from 3 to 30, where each R1and R2is independently a hydrogen or a substituted or unsubstituted alkyl, alkenyl, or alkynyl group, and where X is a -PO3M group (e.g., -PO32’M2+group), -PO3MIM2 group (e.g., -PO32’M1+M2+group), a -PO3HM group (e.g., -POsH’ M+group), a -PO2(OH)M (e.g., -PO2(OH)’ M+group), where M, M1, and M2 represents a metal atom, such as Ti, Zr, Mo, Na, K, Mg, Ca, Zn, Cr, etc., or a rare earth metal atom, such as Ce, Y, Tb, La, etc.

[0041] In practice, the conversion coating can be applied by passing the metallic substrate through a conversion layer applicator, for example. The conversion layer applicator can pre-treat the metallic substrate with a conversion layer. In some cases, as mentioned above, this conversion layer can include compounds of trivalent chromium (Cr(III)) and phosphates. In some cases, this conversion layer can include compounds of titanium and / or zirconium (Ti-Zr). In some examples, the metallic substrate is heated to a temperature of from about 80 °C to about 120 °C after the conversion layer is applied. For example, the metallic substrate can be heated to about 90 °C, about 100 °C, or about 110 °C. Any suitable technique for applying a conversion layer can be used by the conversion layer applicator, such as applying conversion solutions (e.g., via spray nozzle, dipping, or other techniques) based on desired parameters (e.g., for desired amounts of times, at desired temperatures, at desired thicknesses, and / or with desired amounts of drying time).

[0042] In some embodiments, the oxide layer can serve as a hole / electron transport layer. This can eliminate the need for additional layer(s) and simplify the overall solar cell. However, some embodiments involve an additional hole / electron transport layer positioned on the surface of the metal oxide layer.

[0043] In some embodiments, the conductivity of the oxide layer and the metallic substrate can be from 20 % to 65 % of the International Annealed Copper Standard (IACS) (e.g, from 25 % to 65 % IACS, from 30 % to 60 % IACS, from 35 % to 60 % IACS, from 40 % to 60 % IACS, of from 45 % to 55 % IACS.Attorney Docket No. 108050-1544781Perovskite Layer

[0044] Halide perovskites are a family of materials that have shown potential for high performance and low production costs in solar cells. The name “perovskite” comes from the nickname for their crystal structure. Other types of non-halide perovskites (such as oxides and nitrides) are utilized in other energy technologies, such as fuel cells and catalysts.

[0045] Perovskite solar cells are thin-film devices built with layers of materials, either printed or coated from liquid inks or vacuum-deposited. A perovskite solar cell is a type of solar cell that employs a metal halide perovskite compound as a light absorber. As the core material of a perovskite solar cell, perovskite compounds can have a general chemical formula of ABX3, where A and B are cations with various atomic radii (A is larger than B), and X is an anion. The crystal structure of organic- inorganic hybrid metal halide perovskites shares the same type with the calcium titanium oxide (CaTiO3). Particularly, in the metal halide perovskite, A-site cation is a monovalent cation, such as methylammonium (CH3NH3+, MA+), formamidinium ((NH2)2CH+, FA+) or Cs+or combinations among them. B-site cations are bivalent metallic cations from Group IV (e.g., Pb2+or Sn2+) in the periodic table and X site is a halide anion (Cl Br, k). In the crystal structure, the B-site cation is in the center of corner-linked octahedral of X-site anion.

[0046] Another benefit of perovskite solar cells is that they can be easily deposited, adapted and optimized via solution processing. One way of depositing perovskite thin films is to dissolve the precursors in a solution, then coat the substrate using any chosen thin film coating method. Perovskites solar cells fabrication methods can be compatible with roll-to-roll processing (R2R processing) methods as described herein for the substrate and oxide layers, which is useful for large scale manufacturing. Examples of these methods include slot-die coating or inkjet printing.

[0047] In some embodiments, perovskites can be incorporated into a standard OPV (or other thin-film) architecture. The first perovskite solar cells were based on solid state dye-sensitized solar cells (DSSCs), and so used a mesoporous TiO2 scaffold. Some cells since have followed this template or used an Al2O3scaffold in a ‘meso-superstructured’ architecture, but the high temperature steps required for manufacture, and UV instability of TiO2, led to introduction of a ‘planar’ architecture similar to other thin-film cells.Attorney Docket No. 108050-1544781

[0048] The perovskite film itself is typically processed by either vacuum or solution methods. Film quality is very important. Initially, vacuum-deposited films gave the best devices, but this process requires the co-evaporation of the organic (methylammonium) component at the same time as the inorganic (lead halide) components, necessitating specialist evaporation chambers. As a result, there have been significant efforts into improving solution-processed devices, as these are simpler and allow for low-temperature processing.

[0049] In some embodiments, the active layer of a perovskite solar cell is deposited via either a one or two-step process. In the one-step process, a precursor solution (such as a mix of CH3NH3I and PbI2) is coated that then converts to the perovskite film upon heating. A variation on this is the ‘antisolvent’ method, in which the precursor solution is coated in a polar solvent, and then quenched during the spin coating process by a non-polar solvent. Precise timings of the quench and volumes of the quenching solvents give the optimal performance.

[0050] In the two-step process, the metal halide (such as PbI2) and organic components (such as CH3NH3I) are spin-coated in separate, subsequent films. Alternatively, metal halide films can be coated and annealed in a chamber filled with the organic component vapour, known as ‘vacuum-assisted solution process’ (VASP).Electron / Hole Transfer Layers

[0051] In some embodiments, the architectural configuration of the photovoltaic cells based on perovskite is either of the n-i-p type or the p-i-n type. Specifically, the layer of perovskite material can be positioned between an electron transport material and a hole transport material. The perovskite material functions as a layer that absorbs light, resulting in the generation of charge carriers through the process of photogeneration. The charge carriers created by light are collected and delivered to their corresponding electrodes by the use of electron and hole transport layers. Therefore, some embodiments of the perovskite solar cells are based on a transparent conducting oxide / ETL (or HTL) / Perovskite / HTL (or ETL) / metal substrate structure, where ETL and HTL refer to electron-transport and hole-transport layers respectively. Typical hole-transport layers include Spiro-OMeTAD or PEDOT: PSS, and typical electron-transport layers include TiO2 or SnO2.Attorney Docket No. 108050-1544781Thin Protective Layer and Transparent Conducting Layer

[0052] In some embodiments, the upper layer of the solar cell can be thin protective layer such as an Au buffer layer, for example evaporated Au, scraping tape, Au paint, or any combinations thereof. In some embodiments, a transparent conducting electrode and / or layer (e.g., a transparent conducting oxide) can cover the thin protective layer and / or serve as an outer layer of the solar cell. Transparent Conductive Oxides (TCOs) are a unique class of materials that combine two essential properties: optical transparency and electrical conductivity.Solar Cells

[0053] FIG. 1 shows an embodiment of a perovskite solar cell 100. An aluminum alloy 101 serves as the substrate for the cell. Suitable aluminum alloys include, for example, 1xxx series aluminum alloys, 2xxx series aluminum alloys, 3xxx series aluminum alloys, 4xxx series aluminum alloys, 5xxx series aluminum alloys, 6xxx series aluminum alloys, 7xxx series aluminum alloys, and 8xxx series aluminum alloys. As disclosed, an oxide layer 102 can be used on a surface of the aluminum substrate to protect the substrate and to allow electrons to flow freely to the substrate. A hole / electron transport layer 103 can be positioned on the oxide layer. An electron transport layer (ETL) is a layer which has high electron mobility and high electron affinity. Thus, in this layer holes are blocked and cannot go through while electrons can flow through. A hole transport layer (HTL) does the opposite of the ETL by blocking electrons from flowing through. In some embodiments, (not shown) the oxide layer 102 can serve as a hole / electron transport layer for the solar cell. A perovskite layer 104 positioned on the oxide layer 102 serves as the active layer (e.g., performs solar energy capture) for the cell. The majority of efficient perovskites are based on Group IV (e.g, lead) metal halides. Lead-based perovskite-based solar cells are particularly good because of a range of factors, including strong absorption in the visible regime, long charge-carrier diffusion lengths, a tuneable band gap, and easy manufacture (due to the high defect tolerance and the ability to process at low temperatures). An electron / hole transport layer 106 is positioned on the opposite side of the perovskite layer 104 as the hole / electron transport layer 104 and can perform the opposing function as the hole / electron transport layer 104. A transparent conducting layer 108 can cover the surface of the electron / hole transport layer 106. T ransparent conducting layers or films are thin layers / films used as electrodes when a situation calls for lowAttorney Docket No. 108050-1544781resistance electrical contacts without blocking light. In some embodiments, these materials possess wide bandgaps whose energy value is greater than those of visible light.

[0054] In some embodiments, the solar cells as described herein can achieve 15 mW / cm² power under 1 Sun illumination or greater. In some embodiments, the solar cells as described herein can achieve 10 % efficiency or greater (e.g., 15 % power conversion efficiency or greater, or 20 % power conversion efficiency or greater), depending on layer optimization. In some embodiments, the solar cells as described herein can exhibit 80 % retention of original efficiency after 3 years. Two issues for practical device fabrication of perovskite solar cells are film quality and thickness. In some embodiments, the light-harvesting (active) perovskite layer is several hundred nanometers thick (e.g., from 200 nm to 800 nm) - several times more than for standard organic photovoltaics, and creating such thick layers with high uniformity can be difficult. Unless the deposition conditions and annealing temperature are optimized, rough surfaces with incomplete coverage will form. Even with good optimization, there will still be a significant surface roughness remaining. Therefore, some embodiments use thicker interface layers than might normally be used. In some embodiments, improvements to film quality can be achieved through the addition of small amounts of acids, such as hydroiodic or hydrobromic acid or excess of lead iodide precursor.

[0055] In some embodiments, the process for making solar cells as described herein can include a surface preparation step, for example a chemical (e.g., acid) and / or laser etch of the metallic substrate. Some embodiments can involve a rising step to follow the etching.

[0056] In some embodiments, the process can also involve a step of RF or magnetron sputtering to produce a bottom ITO layer on the substrate. In some embodiments, a metal oxide layer (e.g., comprising TiO2) can be prepared by a step of heating at from 350 °C to 550 °C (e.g., from 400 °C to 500 °C or about 450 °C) for from 10 minutes to 2 hours (e.g., 20 minutes to 1.5 hours, from 20 minutes to 1 hour, or about 30 minutes).

[0057] In some embodiments that involve a compact metal oxide layer, a metal oxide precursor can then be applied (e.g., sprayed) on the metallic substrate and / or ITO layer, for example. In some embodiments, the metal oxide precursor can be in a solvent (e.g., IPA and / or ethanol). In some embodiments, the metal precursor can beAttorney Docket No. 108050-1544781annealed for from 10 minutes to 2 hours (e.g., 20 minutes to 1.5 hours, from 20 minutes to 1 hour, or about 30 minutes). This can be followed by cooling, for example, to from 10 °C to 200 °C (e.g., from 20 °C to 150 °C, from 50 °C to 150 °C, or to around 100 °C) to produce the metal oxide layer.

[0058] In some embodiments, a mesoporous layer can then be applied. In some embodiments, this can involve applying a metal oxide paste (for example metal oxide (e.g., TiO2) in ethanol or in IPA can be applied (for example by spin coating, doctor blade, or spraying) and ramping the temperature to from 350 °C to 550 °C (e.g., from 400 °C to 500 °C or about 450 °C) for from 10 minutes to 2 hours (e.g., 20 minutes to 1.5 hours, from 20 minutes to 1 hour, or about 30 minutes). In some embodiments, the material can then be cooled to from 10 °C to 200 °C (e.g., from 50 °C to 180 °C, from 80 °C to 170 °C, or to around 150 °C) and held for from 1 minute to 1 hour (e.g., from 5 minutes to 45 minutes, or around 15 minutes).

[0059] In some embodiments, the perovskite layer can then be deposited on the metal oxide layer, for example, by spin coating, doctor blade, or spraying. In some embodiments this can be followed with a coating (e.g., spin coating of chlorobenzene solution). In some embodiments, the perovskite layer can be annealed at 10 °C to 200 °C (e.g., from 50 °C to 180 °C, from 80 °C to 170 °C, or to around 150 °C) for from 1 minute to 1 hour (e.g., from 5 minutes to 45 minutes, or around 10 minutes).

[0060] In some embodiments, a hole transport layer, for example comprising a spiro compound (e.g., 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD) or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA)), can be added on the perovskite layer by spin coating, doctor blade, or spraying. In some embodiments, the spiro or PTAA can be in a solvent (e.g., chlorobenzene).

[0061] In some embodiments, a top ITO layer can be prepared by RF or magnetron sputtering on the hole transport layer and annealed, for example.

[0062] Some examples of embodiments are listed below:

[0063] Embodiment 1 is a solar cell, comprising:an aluminum substrate;a perovskite layer positioned on one side of the aluminum substrate.

[0064] Embodiment 2 is the solar cell of embodiment 1, further comprising a metal oxide layer between the aluminum substrate and the perovskite layer.Attorney Docket No. 108050-1544781

[0065] Embodiment 3 is the solar cell of any of the preceding embodiments, further comprising a hole / electron transport layer positioned on the perovskite layer on a side opposite the aluminum substrate.

[0066] Embodiment 4 is the solar cell of any of the preceding embodiments, further comprising a transparent conducting layer contacting the hole / electron transport layer on a side opposite the perovskite layer.

[0067] Embodiment 5 is the solar cell of any of the preceding embodiments, wherein the transparent conducting layer comprises an oxide.

[0068] Embodiment 6 is the solar cell of any of the preceding embodiments, further comprising a lamination or moisture barrier on the transparent conducting layer.

[0069] Embodiment 7 is the solar cell of any of the preceding embodiments, wherein the metal oxide layer comprises SnO2, TiO2, ZrO2, Cr2O3, or combinations thereof.

[0070] Embodiment 8 is the solar cell of any of the preceding embodiments, wherein the metal oxide layer comprises SnO2 or TiO2, or combinations thereof.

[0071] Embodiment 9 is the solar cell of any of the preceding embodiments, wherein the metal oxide layer is not doped with a second metal.

[0072] Embodiment 10 is the solar cell of any of the preceding embodiments, wherein the perovskite layer comprises at least one halide.

[0073] Embodiment 11 is the solar cell of any of the preceding embodiments, wherein the aluminum substrate comprises a 1xxx series, 3xxx series, 5xxx, or 7xxx series aluminum.

[0074] Embodiment 12 is the solar cell of any of the preceding embodiments, wherein the metal oxide layer has a weight of from 20 to 200 mg / m² as measured by XRF.

[0075] Embodiment 13 is the solar cell of any of the preceding embodiments, wherein the aluminum substrate serves as a conductive layer for the solar cell.

[0076] Embodiment 14 is the solar cell of any of the preceding embodiments, wherein the aluminum substrate is rigid.

[0077] Embodiment 15 is the solar cell of any of the preceding embodiments, wherein the aluminum substrate has a thickness of 1 mm or greater.

[0078] Embodiment 16 is a process for making a solar cell, comprising:providing an aluminum sheet,Attorney Docket No. 108050-1544781optionally depositing or growing an electron transport layer on the aluminum sheet,depositing a halide perovskite layer on the aluminum sheet or the electron transport layer,depositing a hole / electron transport layer on the halide perovskite layer,depositing at least one transparent conductive material on the hole / electron transport layer.

[0079] Embodiment 17 is the process of any of the preceding embodiments, wherein the aluminum sheet has a metal oxide layer on a surface of the aluminum sheet.

[0080] Embodiment 18 is the process of any of the preceding embodiments, further comprising adding a lamination or moisture barrier on the transparent conductive material.

[0081] Embodiment 19 is the process of any of the preceding embodiments, wherein the aluminum sheet comprises a 1xxx series, 3xxx series, 5xxx, or 7xxx series aluminum.

[0082] Embodiment 20 is the process of any of the preceding embodiments, wherein the metal oxide layer comprises SnO2, TiO2, ZrO2, or Cr2O3.

[0083] Embodiment 21 is the process of any of the preceding embodiments, wherein the process is a roll-to-roll process.Examples

[0084] Accelerated stability testing was carried out using solar cells prepared as disclosed above using aluminum substrates under one sun illumination at 65 °C under dry N2with a metal oxide layer of 150 mg / mL TiO2. This was compared to similar cells using a traditional glass substrate under identical conditions. The solar cells were exposed to ambient conditions and indoor illumination during measurements (approximately 2 hours). Testing was carried out manually. The results in terms of efficiency over time are shown in FIG. 2. The aluminum devices performed both close to the initial efficiency over time and also close to the glass control (upper line) as demonstrated by the trend line (lower line) shown in FIG. 2.

[0085] The foregoing description of certain examples including the illustrated examples above, has been presented only for the purpose of illustration andAttorney Docket No. 108050-1544781description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Numerous modifications, adaptations, and uses thereof will be apparent to those skilled in the art without departing from the scope of the disclosure. For instance, any examples described herein can be combined with any other examples to yield further examples.

Claims

Attorney Docket No. 108050-1544781Claims1. A solar cell, comprising:an aluminum substrate;a perovskite layer positioned on one side of the aluminum substrate.

2. The solar cell of claim 1, further comprising a metal oxide layer between the aluminum substrate and the perovskite layer.

3. The solar cell of claim 2, further comprising a hole / electron transport layer positioned on the perovskite layer on a side opposite the aluminum substrate.

4. The solar cell of claim 3, further comprising a transparent conducting layer contacting the hole / electron transport layer on a side opposite the perovskite layer.

5. The solar cell of claim 4, wherein the transparent conducting layer comprises an oxide.

6. The solar cell of claim 5, further comprising a lamination or moisture barrier on the transparent conducting layer.

7. The solar cell of claim 2, wherein the metal oxide layer comprises SnO2, TiO2, ZrO2, Cr2O3, or any combinations thereof.

8. The solar cell of claim 7, wherein the metal oxide layer is not doped with a second metal.

9. The solar cell of claim 1, wherein the perovskite layer comprises at least one halide.

10. The solar cell of claim 1, wherein the aluminum substrate comprises a 1xxx series, 3xxx series, 5xxx, or 7xxx series aluminum.Attorney Docket No. 108050-154478111. The solar cell of claim 7, wherein the metal oxide layer has a weight of from 20 to 200 mg / m² as measured by XRF.

12. The solar cell of claim 1, wherein the aluminum substrate serves as a conductive layer for the solar cell.

13. The solar cell of claim 1, wherein the aluminum substrate is rigid.

14. The solar cell of claim 13, wherein the aluminum substrate has a thickness of 1 mm or greater.

15. A process for making a solar cell, comprising:providing an aluminum sheet,optionally depositing or growing an electron transport layer on the aluminum sheet,depositing a halide perovskite layer on the aluminum sheet or the electron transport layer,depositing a hole / electron transport layer on the halide perovskite layer, depositing at least one transparent conductive material on the hole / electron transport layer.

16. The process of claim 15, wherein the aluminum sheet has a metal oxide layer on a surface of the aluminum sheet.

17. The process of claim 15, further comprising adding a lamination or moisture barrier on the transparent conductive material.

18. The process of claim 15, wherein the aluminum sheet comprises a 1xxx series, 3xxx series, 5xxx, or 7xxx series aluminum.

19. The process of claim 16, wherein the metal oxide layer comprises SnO2, TiO2, ZrO2, or Cr2O3.

20. The process of claim 16, wherein the process is a roll-to-roll process.

Images