Solution processable phenolic encapsulation of articles

Abstract

Disclosed herein are coatings comprising: at least one polyphenol optionally comprising a plurality of catechol and / or gallol groups; and at least one transition metal. Also disclosed herein are methods of forming said coatings and the use of said coatings on articles, for example a solar cell. Also disclosed herein is an array comprising a plurality of said articles, for example an array of solar cells.

Description

[0001] SOLUTION PROCESSABLE PHENOLIC ENCAPSULATION OF ARTICLES

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The present application claims priority from Australian Provisional Patent Application No. 2023902538 filed on 10 August 2023, the contents of which are incorporated herein by reference in their entirety.

[0004] TECHNICAL FIELD

[0005] The present disclosure relates to coatings comprising: at least one polyphenol, optionally comprising a plurality of catechol and / or gallol groups; and at least one transition metal. Also disclosed herein are methods of forming said coatings and the use of said coatings on articles, for example a solar cell. Also disclosed herein is an array comprising a plurality of said articles, for example an array of solar cells.

[0006] BACKGROUND

[0007] Modern photovoltaics (PV) for efficiently harnessing sunlight show considerable promise to mitigate our fossil fuel dependence and the impending energy crisis. Today, the hybrid lead (Pb) halide perovskite solar cell (PSC) is the fastest-growing PV technology with immense potential as evidenced by its certified efficiency elevated to 25.7% in just over a decade. Such a rapid improvement can be attributed to the exceptional features of perovskite materials including bandgap tunability, high absorption coefficient, and prolonged carrier lifetime. Additionally, the use of off-the- shelf chemicals and solution processability, have enabled the low-cost fabrication of PSC devices that can be readily scaled up. However, the poor stability and potential for toxic metal (e.g., Pb), contamination are the two major obstacles for PSCs, currently stifling their commercial prospects. While the intrinsic degradation of perovskite materials can originate from ion migration, hysteresis, and interface defects, they are also prone to be degraded by environmental factors such as humidity, heat, and light. In an aim to reduce these challenges, new perovskite formulations and various encapsulation techniques have been explored. Examples include the development of encapsulating tapes for on- device Pb sequestration, polymer / glass stack encapsulation, textured perovskite films, sandwiched internal encapsulants, and perfluoroalkyl-based superhydrophobic encapsulants. Despite the progress, these strategies suffer from complex synthesis and processing steps, the use of toxic chemicals, and poor long-term stability. More importantly, no existing strategy offers stability and Pb sequestration capacity at the same time. Therefore, the demand for a general encapsulating strategy capable of providing both long-term stability and Pb capture, while remaining synthetically facile and inexpensive, is extremely high.

[0008] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

[0009] SUMMARY

[0010] The inventors have identified that polyphenols can be used as a possible surface engineering strategy when using polyphenol assembly via coordination-crosslinking. This process can be a rapid (e.g., < 1 min), versatile, and adaptive method to functionalise one or more surfaces. This approach can benefit from the diverse physicochemical properties of polyphenols including universal adhesion, metal coordination, redox, and stimuli responsiveness. For example, based on the pH responsive coordination crosslinks, the synthesised coatings can potentially be used as protective encapsulants for living cells. Furthermore, utilising functional groups such as catechol and / or gallol groups can enable these coatings to trap hazardous metal ions via coordination interactions. The inventors have identified that polyphenol-based conformal coatings, based on various metal / polyphenol combinations could potentially provide a general encapsulation platform for articles such as perovskite materials.

[0011] Herein, the inventors demonstrate a polyphenol-based encapsulation strategy which may be used for long-term stabilization of PSCs with an inherent capacity to capture Pb ions. The coordination cross-linked encapsulating coatings may provide one or more advantages such as: be solution processable; require no special apparatus; and / or take less than a minute to prepare. The coatings described herein may improve the PSC stability in ambient and ambient conditions, for example by potentially retaining over 80% efficiency for an exceedingly long period of time (e.g., potentially about 2000 hours). In one embodiment, the coatings can capture Pb ions, for example from degrading perovskites, preventing Pb leakage.

[0012] In another embodiment, the coatings are hydrophilic, or substantially hydrophilic. The hydrophilicity or hydrophobicity may be measured by an appropriate test, for example ASTM D7334-08(2022) as updated 25 January 2022. In one embodiment one or more coatings, when tested using ASTM D7334-08(2022) as updated 25 January 2022 has a contact of less than about 45°, or in a range of about 45° to about 90°, or greater than about 90°, for example, less than about, about or greater than about (in °): 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150. In one embodiment, the coatings may inhibit or reduce the passage or movement of moisture / water through the coating, or a portion thereof. In a solar cell the coatings could reduce or prevent the passage of water through the coating to prevent contact with at least one layer, for example a perovskite layer.

[0013] It will be appreciated that the embodiments of each aspect of the present disclosure may equally be applied to each other aspect, mutatis mutandis.

[0014] In a first aspect, disclosed herein is a coating composition comprising: a polyphenol comprising a plurality of catechol and / or gallol groups; and at least one transition metal.

[0015] In a second aspect, disclosed herein is a coating composition formulated for a solar cell, the coating comprising: a polyphenol comprising a plurality of catechol and / or gallol groups; and at least one transition metal.

[0016] In a third aspect, disclosed herein is a coating composition when used on a solar cell, the composition comprising: a polyphenol comprising a plurality of catechol and / or gallol groups; and at least one transition metal.

[0017] In a fourth aspect, disclosed herein is a use of: a polyphenol comprising a plurality of catechol and / or gallol groups; and / or at least one transition metal, in the formation of the coating composition according to any one of the first to third aspects.

[0018] In a fifth aspect, disclosed herein is a method of forming a coating composition according to any one of the first to third aspects, the method comprising a step of: combining the polyphenol with at least one transition metal containing compound. In a sixth aspect, disclosed herein is a coating composition obtained by the method according to the fifth aspect.

[0019] In a seventh aspect, disclosed herein is a method of coating at least a portion of an article, the method comprising introducing the coating composition according to any one of the first to third or sixth aspect, to at least the portion of the article.

[0020] In an eighth aspect, disclosed herein is a method of encapsulating at least a portion of an article, the method comprising introducing the coating composition according to any one of the first to third or sixth aspect, to at least the portion of the article.

[0021] In a ninth aspect, disclosed herein is a method of sequestering at least one metal or metal ion released from an article, the method comprising introducing the coating composition according to any one of the first to third or sixth aspect, to at least a portion of the article.

[0022] In a tenth aspect, disclosed herein is a method of sequestering at least one metal or metal ion from a solar cell, the method comprising introducing the coating composition according to any one of the first to third or sixth aspect, to at least a portion of the solar cell.

[0023] In an eleventh aspect, disclosed herein is a use of the coating composition according to any one of the first to third or sixth aspect, on at least a portion of an article.

[0024] In a twelfth aspect, disclosed herein is an article comprising the coating composition according to any one of the first to third or sixth aspect.

[0025] In a thirteenth aspect, disclosed herein is a solar cell comprising the coating composition according to any one of the first to third or sixth aspect.

[0026] In a fourteenth aspect, disclosed herein is an array comprising a plurality of the article or solar cell comprising the coating composition according to the twelfth or thirteenth aspects. BRIEF DESCRIPTION OF DRAWINGS

[0027] Whilst it will be appreciated that a variety of embodiments disclosed herein may be utilised, described herein are a number of examples with reference to the following drawings:

[0028] Figure 1: Encapsulated device structure and characterisation: (A) 3D schematic illustration of the full device with the phenolic network of the tannic acid-Ti4+crosslinked coordination; (B) cross-section SEM image of the encapsulated device and schematic structures of the phenolic coating; (C)-(E) surface topography and thickness analyses of the tannic acid- Ti4+coating.

[0029] Figure 2: Photovoltaic characteristics data: (A) photovoltaic characteristics (current density versus voltage) of the control and coated device; (B) degradation characteristics of the control and coated device up to 175 days in terms of power conversion efficiency.

[0030] Figure 3: Device stability data: (A) photoluminescence (PL) spectra of the newly made and 135 days old control and coated devices; (B) time-resolved photoluminescence (TrPL) image of the freshly prepared and 20 days old devices; (C) normalised XRD pattern of the coated device; and (D) normalized XRD image of the control device.

[0031] Figure 4. Lead leaching data for encapsulated solar cell.

[0032] DETAILED DESCRIPTION

[0033] General Definitions and Terms

[0034] With regard to the definitions provided herein, unless stated otherwise, or implicit from context, the defined terms and phrases include the provided meanings. In addition, unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired by a person skilled in the relevant art. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims.

[0035] All publications discussed and / or referenced herein are incorporated herein in their entirety, unless described otherwise. Unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. Throughout this disclosure, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality ( / '.<?., one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. For example, reference to “a” includes a single as well as two or more; reference to “an” includes a single as well as two or more; reference to “the” includes a single as well as two or more and so forth.

[0036] Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the examples, steps, features, methods, compositions, formulations, and processes, referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features.

[0037] The term “and / or”, e.g., “X and / or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning.

[0038] Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to a “second” item does not require or preclude the existence of lower-numbered item (e.g., a “first” item) and / or a higher-numbered item (e.g., a “third” item).

[0039] As used herein, the phrase “at least one”, “one or more”, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one” or “one or more” means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example and without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

[0040] It is to be appreciated that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination.

[0041] Throughout the present specification, various aspects and components of the disclosure can be presented in a range format. The range format is included for convenience and should not be interpreted as an inflexible limitation on the scope of the present disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range, unless specifically indicated. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 5, from 3 to 5 etc., as well as individual and partial numbers within the recited range, for example, 1, 2, 3, 4, 4.5 and 5, unless where integers are required or implicit from context. This applies regardless of the breadth of the disclosed range. Where specific values are required, these will be indicated in the specification.

[0042] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0043] Throughout this specification, the term "consisting essentially of" is intended to exclude elements which would materially affect the properties of the claimed composition, method or process.

[0044] The terms "comprising", "comprise" and "comprises" herein are intended to be optionally substitutable with the terms "consisting essentially of", "consist essentially of", "consists essentially of", "consisting of", "consist of" and "consists of", respectively, in every instance.

[0045] Herein the term “about” encompasses a 10% tolerance in any value or values connected to the term. Herein “weight %” may be abbreviated to as “wt%” or “wt.%”. The weight % may be w / w or w / v, unless specifically indicated or clear from context.

[0046] Disclosed herein is a coating composition comprising:

[0047] • a polyphenol optionally comprising a plurality of catechol and / or gallol groups; and

[0048] • at least one transition metal.

[0049] Also disclosed herein is a coating composition formulated for a solar cell, the coating comprising:

[0050] • a polyphenol optionally comprising a plurality of catechol and / or gallol groups; and

[0051] • at least one transition metal.

[0052] Also disclosed herein is a coating composition when used on a solar cell, the composition comprising:

[0053] • a polyphenol optionally comprising a plurality of catechol and / or gallol groups; and

[0054] • at least one transition metal.

[0055] As used herein "coating" or “coating composition”, refers to any temporary, semipermanent or permanent layer, or layers, treating or covering a surface, or a portion thereof, or at least a portion of an article or object. In one embodiment the coating is intended as a permeant coating. The coating may be a chemical modification of the underlying substrate or may involve the addition of new materials to the surface of a substrate (for example one or more polyphenols and / or one or more transition metals). It may include any increase in thickness to the substrate or change in surface chemical composition of the substrate. A coating or coating composition, for example a polymer coating, may be applied as a liquid and solidified into a solid coating.

[0056] Herein, "polyphenol" as used herein, can refer to a diverse group of compounds, which may be produced synthetically or naturally, wherein the compounds include a phenol ring to which at least two OH (hydroxy) groups are covalently attached. For example, representative polyphenols may include ellagic acid, tannic acid, vanillin, caffeic acid, CGA, ferulic acid, dehydroxy rosmarinic acid, coumaroylnepitrin, eupafolin, camosol, scutellarin, kaempferol, rosmarinic acid, rosmanol, cirsimaritin, luteolin, 6-methoxy- luteolin, 7-epirosmannol, quercetin, catechin, hesperidin, cyanidin, catechins (e.g., epicatechin gallate, epigallocatechin), flavonols (e.g., anthocyanidins, quercetin, kaempferol), and various other flavonoids, and optionally their glycosides and depsides. Furthermore, contemplated polyphenols may also be in oligomeric or polymeric form (e.g., oligomeric proanthocyanidins or condensed tannins).

[0057] In one embodiment the polyphenol comprises at least one catechol and / or gallol group. In another embodiment the polyphenol comprises a plurality of catechol and / or gallol groups. In another embodiment the polyphenol comprises a plurality of catechol groups, for example about or at least about: 2, 3, 4, 5, 6, 7, 8, 9, or 10 catechol groups. In another embodiment the polyphenol comprises a plurality of gallol groups, for example about or at least about: 2, 3, 4, 5, 6, 7, 8, 9, or 10 gallol groups. In another embodiment the polyphenol comprises a plurality of gallol groups and a plurality of catechol, for example about or at least about: 2, 3, 4, 5, 6, 7, 8, 9, or 10 gallol and / or catechol groups. In addition to one or more catechol and / or gallol groups, the coating and / or the polyphenol may comprise one or more additional functional groups. Examples of functional groups may be independently selected from, but not limited to one or more of: a,P-unsaturated carbonyl, acid, acyl halide, acylazide, haloimide, alcohol, aldehyde, alkene, alkyne, amide, amine, azide, aziridine, carbocyclic acid, disulfide, epoxide, ester, activated ester (e.g., N-hydroxysuccinimide ester, pentynoic acid STP ester), halide, heteroaryl group, heterocyclic or heteroaryl group, hydrazide, hydrazine, hydrazone, hydroxide, imidoester, imine, isocyanate, isothiocyanate, ketone, maleimide, nitrile, nitrone, oxime, phosphine, sulfhydryl, sulfinic acid, sulfonic acid, sulfonyl halide, tetrazine, tetrazole, thioester, triazolyl, and mixtures thereof. In one embodiment, in addition to one or more catechol and / or gallol groups, the coating and / or the polyphenol comprises one or more additional functional groups selected from: a,P-unsaturated carbonyl, acid, acyl halide, acylazide, haloimide, alcohol, aldehyde, alkene, alkyne, amide, amine, azide, aziridine, carbocyclic acid, disulfide, epoxide, ester, activated ester (e.g., N-hydroxysuccinimide ester, pentynoic acid STP ester), halide, heteroaryl group, heterocyclic or heteroaryl group, hydrazide, hydrazine, hydrazone, imidoester, imine, isocyanate, isothiocyanate, ketone, maleimide, nitrile, nitrone, oxime, phosphine, sulfhydryl, sulfinic acid, sulfonic acid, sulfonyl halide, tetrazine, tetrazole, thioester, triazolyl, and mixtures thereof.

[0058] In one embodiment, the polyphenol comprises about, or at least about: 2, 3, 4, 5, 6, 7, 8, 9 or 10 phenol groups. The polyphenol may comprise or be selected from, but not limited to at least one of: catechin, epicatechin, gallocatechin, catechin gallate, gallocatechin gallate, epicatechin gallate, epigallocatechin gallate, epigallocatechin, tannic acid, gallotannin, ellagitannin, and mixtures thereof.

[0059] In one embodiment the polyphenol comprises tannic acid. In another embodiment the polyphenol comprises catechin. In another embodiment the polyphenol comprises epicatechin. In another embodiment the polyphenol comprises gallocatechin. In another embodiment the polyphenol comprises catechin gallate. In another embodiment the polyphenol comprises gallocatechin gallate. In another embodiment the polyphenol comprises epicatechin gallate. In another embodiment the polyphenol comprises epigallocatechin gallate. In another embodiment the polyphenol comprises epigallocatechin. In another embodiment the polyphenol comprises gallotannin. In another embodiment the polyphenol comprises ellagitannin. In another embodiment the polyphenol comprises a mixture of polyphenols, for example two or more of the exemplified polyphenols as described herein.

[0060] Herein, one or more polyphenol may be a naturally occurring polyphenol, a synthetic version, a synthetic derivative of a polyphenol, or a plant extract containing at least one polyphenolic component. The polyphenol may be used in a substantially pure form, for example at a purity of about 80% or greater (e.g., a purity of about, or at least about (in %): 80, 85, 90, or 95), or they can be provided as a part of a plant extract.

[0061] In one embodiment the one or more polyphenols act as a ligand to one or more transition metals. The one or more transition metals may act as a crosslinker for one or more polyphenols. One potential advantage obtained from the crosslinking of coating is the stability of the resulting coating, for example crosslinking can reduce the solubility of the coating in comparison to similar compositions which are not crosslinked. In addition, the crosslinked nature of the coating may increase the chemical resistance of the composition. The application of a crosslinked coating to a surface of an article, for example a solar cell, may also yield a surface which has an increased heat tolerance, decreased permeability, better abrasion resistance and / or extend the life of the article.

[0062] In one embodiment at least one transition metal is selected from: group III or group IV, or a mixture thereof, from the periodic table. In one embodiment at least one transition metal may be selected from, but not limited to: Sc, Y, Ti, Zr, and mixtures thereof. In an alternative embodiment, at least one transition metal may be selected from, but not limited to: Fe, V and mixtures thereof. In one embodiment the at least one transition metal is a group III transition metal. In one embodiment the at least one transition metal is a group IV transition metal. In another embodiment the at least one transition metal is selected from titanium, zirconium, and mixtures thereof. In one embodiment the coating comprises two or more different transition metals from the same or different group(s) of the periodic table.

[0063] The oxidation state of the one or more transition metals may be: +3, +4, or mixture thereof. In one embodiment at least one transition metal with a +3 and / or +4 oxidation state is present. In another embodiment at least one of titanium and zirconium is present with a +4 oxidation state. In another embodiment the coating comprises two or more metal ions with different oxidation states, wherein the metal per se may be the same or different.

[0064] Herein, the molar ratio between one or more polyphenols and at least one transition metal may be in a range of: about 1: 1 to about 1:5, about 1: 1 to about 1:4.5, about 1: 1 to about 1:4, about 1: 1 to about 1:3.5, about 1: 1 to about 1:3, about 1: 1 to about 1:2.5, or about 1: 1 to about 1:2. In another embodiment, the molar ratio between one or more polyphenols and at least one transition metal may be in a range of: about 1: 1 to about 1: 1.9, about 1: 1 to about 1: 1.8, about 1: 1 to about 1: 1.7, about 1: 1 to about 1: 1.6, about 1: 1 to about 1: 1.5, about 1: 1 to about 1: 1.4, about 1: 1 to about 1: 1.3, about 1: 1 to about 1: 1.2, or about 1: 1 to about 1: 1.1. Alternatively, the molar ratio between the polyphenol an at least one transition metal is in a range of about 1: 1 to about 5: 1, about 1: 1 to about 4.5: 1, about 1: 1 to about 4: 1, about 1: 1 to about 3.5: 1, about 1: 1 to about 3: 1, about 1: 1 to about 2.5: 1, or about 1: 1 to about 2: 1.

[0065] The transition metal may be introduced in any appropriate form known in the art. For example, the metals may be introduced in the form of a salt. Herein “salt” includes both inorganic and organic acid addition salts and basic addition salts. Nonlimiting examples include, but are not limited to: metal salts (including: alkali metal salts, for example lithium, sodium or potassium salts; alkaline earth metal salts, for example calcium or magnesium salts; or zinc salts); organic amine salts (including triethylamine, pyridine, picoline, ethanolamine, triethanolamine, dicylohexylamine, or N,N'- dibenzylethylenediamine salts); inorganic acid salts (including hydrochloride, hydrobromide, phosphate, nitrate, carbonate, bicarbonate or sulphate salts); organic acid salts (including citrate, lactate, malonate, succinate, benzoate, ascorbate, a-ketoglutarate, a-glycerophosphate tartrate, maleate, hydroxymaleate, gluconate, oxalate, phenylacetate, salicylate, edetate, stearate, palmate, oleate, laurate, fumarate, mandelate, acetate, propanoate, butanoate, dichloroacetate, trifluoroacetate, oxalate, or formate salts); sulfonate salts (including methanesulfonate, benzenesulfonate, or para-toluenesulfonate salts); amino acid salts (including arginate or glutamate salts); and mixtures thereof.

[0066] The coating composition may further comprise at least one additive and / or excipient. The at least one additive and / or excipient may assist in changing and / or tailoring at least one chemical, physical and / or electrical characteristic of the coating composition.

[0067] The coating composition may be transparent, substantially transparent, translucent or substantially translucent.

[0068] Herein the coating composition, or one or more layers of the coating composition, may have a thickness from about 50 nm to about 500 nm. In some embodiments, the thickness can be from about 100 nm to about 400 nm, for example from about 200 to about 400 nm. In some embodiments the coating composition, or one or more layers of the coating composition, may have a thickness of about, or at least about (in nm): 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, or 500. The coating composition may be applied as a single layer, or as a plurality of layers. An article may comprise one or more layers of a coating composition on one or more portions of the article. The thickness of a layer of a coating may be tailored, e.g., the number of layers, based on the specific article and / or intended use.

[0069] Herein the defined coating composition may be used or applied to at least a portion of an article. The coating may be applied directly to at least a portion of the article, or the coating may be applied to an intermediate layer which may or may not be in direct contact with at least one surface of an article. In another embodiment the coating may be applied directly or indirectly to at least a portion of a surface on an article, such as solar cell or part thereof. The coating may be contiguous over at least a portion or all of a surface of an article. In one embodiment the coating may be applied directly or indirectly to at least one surface of an article (optionally 2, 3 or 4 surfaces or portions thereof), for example a solar cell, and independently cover about or at least about (in %): 10, 20, 30, 40, 50, 60, 70, 80 or 90 of the surface area of the one or more surface. In some embodiments the article is a solar cell. In some embodiments the article is a perovskite solar cell. For example, the article may be a lead halide perovskite solar cell. Herein, the perovskite has a mixed cation and mixed halide structure. For example, and without intending to limit the scope of the present disclosure, the perovskite may have a formula of Cs0.06Rb0.04FA0.77MA0.13PbI2.55Br0.45. Without being bound by theory, any suitable mixture of FA (formamidinium) and MA (methylammonium) (or alternatively, Cs / Rb can be added), which is typically used for solar cell applications, can be used herein. In addition, the composition of iodine and bromine can be tuned if required. Alternative examples include, but are not limited to: FAo.6MAo.4Pbl2.4Bro.6 and Cso.1FAo.9Pbh.

[0070] Methods of synthesis

[0071] Disclosed herein is a use of:

[0072] • a polyphenol optionally comprising a plurality of catechol and / or gallol groups; and / or

[0073] • at least one transition metal, in the formation the coating composition as defined herein.

[0074] Also disclosed herein is a method of forming a coating composition as defined herein, wherein the method comprising a step of:

[0075] • combining at least one polyphenol with at least one transition metal containing compound.

[0076] In one embodiment, the at least one polyphenol with at least one transition metal containing compound are mixed in an appropriate ratio.

[0077] In some embodiments, following contacting the at least one polyphenol with at least one transition metal containing compound results in a complex in a short time period. In some instances, to reduce or minimise the formation of a gel, an appropriate solvent is added. Suitable solvents will be known to persons skilled in the art. An exemplified, nonlimiting method may comprise one of the following steps, wherein the regents are replaced with appropriate alternatives:

[0078] 1. Mixing a tannic acid (TA) solution and a Ti4+precursor solution (for example a Ti4+metal salt) in an appropriate ratio.

[0079] 2. Noting any physical changes, for example a colour change. In some embodiments with the TA and Ti4+precursor an orange-red complex solution can be immediately formed while mixing.

[0080] 3. Extracting, for example aliquoting a portion of this mix (e.g., 50 pL) by a pipette, and depositing on a solar cell device attached to a spin coater.

[0081] 4. Undertaking a spin coating step. This step may be performed at 5000 rpm for 30 seconds. 5. Following the spin coating step, the encapsulated device is detached from the spin coater, and may be dried. The period any time can be tailored, for example for 3 minutes at 120 °C on a hot plate.

[0082] In some embodiments, for the methods disclosed herein, aliquots of a mixture of the at least one polyphenol with at least one transition metal containing compound are deposited on an article, for example a solar cell device. In some embodiments the article is attached to a spin coater. Spin coating may be used at an appropriate rpm or range of rpm values. The time for the spin coating will be dependent on the article, the coating composition and the intended use of the article.

[0083] Herein, appropriate transition metal containing compounds, or precursors include, but are not limited to metal salts. For example, and without intending the limit the scope of the present disclosure, titanium (IV) bis(ammonium lactato)dihydroxide solution, 50 wt% in water, commercially available and / or zirconyl chloride octahydrate, dissolved in water, could be used.

[0084] In one embodiment the at least one polyphenol and at least one transition metal compound is diluted in a solvent. Appropriate solvents are known in the art. In one embodiment the solvent is an alcohol, which may be selected from, but not limited to: methanol, ethanol, isopropanol and mixtures thereof.

[0085] In one embodiment the coating composition is formulated as a sol prior to application to at least a portion of an article.

[0086] Also disclosed here is a coating composition obtained by one or more methods as defined herein.

[0087] Uses and Applications

[0088] Also disclosed herein is a method of coating at least a portion of an article, the method comprising introducing or disposing a coating composition as defined herein, to at least the portion of the article. In some embodiments that coating composition is applied to at least a portion of a complete article. In another embodiment the coating composition is applied to a component which is or will be used on the article.

[0089] Also disclosed herein is a method of encapsulating at least a portion of an article, the method comprising introducing the coating composition as defined herein to at least a portion of the article. In some embodiments, the article is a solar cell. Also disclosed herein is a method of sequestering at least one metal or metal ion, released from an article. The method may comprise introducing or disposing a coating composition as defined herein to at least the portion of the article. In some embodiments that coating composition is applied to at least a portion of a complete article. In another embodiment the coating composition is applied to a component which is or will be used on a solar cell.

[0090] Also disclosed herein is a method of sequestering at least one metal or metal ion, for example lead and / or lead ions from a solar cell. The method may comprise introducing or disposing a coating composition as defined herein to at least a portion of a solar cell. In some embodiments that coating composition is applied to at least a portion of a complete solar cell. In another embodiment the coating composition is applied to a component which is or will be used on a solar cell.

[0091] The at least one metal or metal ion may comprise one or more of: a precious metal (for example one or more of: Au, Ag, Pd, In, Ru, and / or Os); a toxic metal (for example one or more of: Pb, Hg, and / or Cd); a transition metal (for example one or more of : Ti, Ni, Fe, Cu, Zr, Mn, Zn, and / or Ga); rare earth metals (for example one or more of: Ce, Tb, Gd, Eu, La, Ho, Tm, Yb, Nd, DI, and / or Er); and mixtures thereof. The metal ions may have an oxidation state / charge of +1, +2, +3 or +4, or a mixture thereof wherein a plurality of metal ions are present. In one embodiment the metal or the metal ion comprises lead.

[0092] Herein, the article or solar cell may be a lead halide perovskite solar cell. The solar cell may take any form known in the art.

[0093] In one embodiment of the methods disclosed herein, the coating composition is formulated as a sol prior to application to at least a portion of an article.

[0094] In one embodiment, the coating composition is applied to at least a portion of an article or the solar cell via an appropriate method known in the art, for example a method selected from, but not limited to: spray coating, dip coating, spin coating, or mixtures thereof.

[0095] In one embodiment, the coating composition is annealed following application to at least a portion of the article or the solar cell. The annealing may be undertaken at an appropriate temperature, for example a temperature in a range of about 100 °C to about 150 °C, for example about or at least about (in °C): 100, 105, 110, 115, 120, 125, 130, 135, 140, 145 or 150. The annealing may be undertaken for an appropriate period of time, for example in a range of about 2 minutes to about 5 minutes.

[0096] Also disclosed herein is use of a coating composition as described herein on at least a portion of an article as described herein. In one embodiment the article is a solar cell. In another embodiment, the article is a lead halide perovskite solar cell.

[0097] Also disclosed herein is an article comprising a coating composition as described herein. In one embodiment the article is a solar cell. In another embodiment, the article is a lead halide perovskite solar cell.

[0098] Also described herein is a solar cell comprising a coating composition as described herein. In one embodiment the solar cell is a lead halide perovskite solar cell.

[0099] In one or more embodiments, following application of a coating composition as described herein, the efficiency of the solar cell may be reduced by no more than about 5, 10, 15, 20, 25, 30, 35 or 40% of the initial power conversion efficiency, measured prior to application of the coating composition. This retention of efficiency may occur over a period of time, for example for up to about 650 hours (27 days), about 1400 hours (58 days), about 2050 hours (86 days), or about 3600 hours (150 days), respectively.

[0100] Herein the coating composition may be added to an article as a single layer or as a plurality of layers. In one embodiment an article or solar cell, as described herein, has about, or at least about: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, of the article or solar cell covered with one or more layers of the coating composition. In another embodiment about, or at least about: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, of the active portion of the article or solar cell is covered with one or more layers of the coating composition. In another embodiment, all or essentially all of the article or solar cell is covered with one or more layers of a coating composition as described herein. In another embodiment, all or essentially all of the active portion of the article or solar cell is covered with one or more layers of a coating composition as described herein.

[0101] Also described herein is an array comprising a plurality of any one of the solar cells described herein. A person skilled in the art will appreciate that solar cells of an array:

[0102] (i) may optionally be located on a supporting substrate, non-limiting examples of which include titanium, steel, coated steel, aluminium or alloys thereof; and / or

[0103] (ii) may be of varying dimensions and / or areas; and / or

[0104] (iii) may be provided in a range of shapes including circles, trapezoids, rectangles, or squares. The cells may be electrically interconnected by a circuit board, printed circuit board (PCB) or a continuous substrate such as the working electrode (WE) or counter electrode (CE).

[0105] The PCB may be flexible. The PCB design may allow for inclusion of diodes. The array may include an external connection point which is attached to the PCB via a knitted, solder paste adhered, rivet, pin, eyelet and / or soldered positive and negative contacts, or a combination thereof. The array may be formed by joining cells via any one of conductive adhesive coated tape, wire, cable, metal braid, polyimide strip, rivets, eyelets, pins, spade clips, crimp terminals or a combination thereof. The cells may use metal substrates for one of their electrodes. Furthermore, it will be appreciated that the array may be encapsulated in a substantially transparent cover which is of low light reflectivity. Furthermore, it will be appreciated that the array may be encapsulated by hot lamination, cold lamination and / or vacuum sealing or a combination thereof.

[0106] EXAMPLE EMBODIMENTS

[0107] The present disclosure may be defined by one or more example embodiments.

[0108] 1. A coating composition comprising:

[0109] • a polyphenol comprising a plurality of catechol and / or gallol groups and

[0110] • at least one transition metal.

[0111] 2. A coating composition formulated for a solar cell, the coating comprising:

[0112] • a polyphenol comprising a plurality of catechol and / or gallol groups and

[0113] • at least one transition metal.

[0114] 3. A coating composition when used on a solar cell, the composition comprising: a polyphenol comprising a plurality of catechol and / or gallol groups and at least one transition metal.

[0115] 4. The coating composition according to any one of the preceding example embodiments, wherein the polyphenol comprises: a plurality of catechol and gallol groups and / or optionally one or more functional groups selected from: a,P-unsaturated carbonyl, acid, acyl halide, acylazide, haloimide, alcohol, aldehyde, alkene, alkyne, amide, amine, azide, aziridine, carbocyclic acid, disulfide, epoxide, ester, activated ester (e.g., N-hydroxysuccinimide ester, pentynoic acid STP ester), halide, heteroaryl group, heterocyclic or heteroaryl group, hydrazide, hydrazine, hydrazone, hydroxide, imidoester, imine, isocyanate, isothiocyanate, ketone, maleimide, nitrile, nitrone, oxime, phosphine, sulfhydryl, sulfinic acid, sulfonic acid, sulfonyl halide, tetrazine, tetrazole, thioester, triazolyl, and mixtures thereof.

[0116] 5. The coating composition according to any one of the preceding example embodiments, wherein the polyphenol comprises at least one of: catechin, epicatechin, gallocatechin, catechin gallate, gallocatechin gallate, epicatechin gallate, epigallocatechin gallate, epigallocatechin, tannic acid, gallotannin, ellagitannin, and mixtures thereof.

[0117] 6. The coating composition according to any one of the preceding example embodiments, wherein the polyphenol comprises tannic acid.

[0118] 7. The coating composition according to any one of the preceding example embodiments, wherein the at least one transition metal is a group III or a group IV transition metal.

[0119] 8. The coating composition according to any one of the preceding example embodiments, wherein the at least one transition metal is a group IV transition metal, optionally selected from titanium and zirconium.

[0120] 9. The coating composition according to any one of the preceding example embodiments, wherein the at least one transition metal comprises titanium.

[0121] 10. The coating composition according to any one of the preceding example embodiments, wherein the at least one transition metal comprises Ti4+ions. 11. The coating composition according to any one of the preceding example embodiments, wherein the molar ratio between the polyphenol and the at least one transition metal is in a range of about 1: 1 to about 1:5, optionally about 1: 1 to about 1:3.

[0122] 12. The coating composition according to any one of the preceding example embodiments, wherein the molar ratio between the polyphenol and the at least one transition metal is in a range of about 1: 1 to about 1: 1.5, or optionally in a range of about 1: 1.4 or about 1: 1.

[0123] 13. The coating composition according to any one of the preceding example embodiments, wherein the molar ratio between the polyphenol an at least one transition metal is in a range of about 1: 1 to about 5: 1.

[0124] 14. The coating composition according to any one of the preceding example embodiments, further comprising at least one other excipient or additive.

[0125] 15. The coating composition according to any one of the preceding example embodiments, when used or applied to at least a portion of an article.

[0126] 16. The coating composition according to example embodiment 15, wherein the article is a solar cell.

[0127] 17. The coating composition according to example embodiment 15 or example embodiment 16, wherein the article is a perovskite solar cell.

[0128] 18. The coating composition according to any one of example embodiments 15 to 17, wherein the article is a lead halide perovskite solar cell.

[0129] 19. The coating composition according to example embodiment 17 to example embodiment 18, wherein the perovskite has a mixed cation and mixed halide structure.

[0130] 20. The coating composition according to any one of example embodiments 17 to 19, wherein the perovskite has a formula of Cs0.06Rb0.04FA0.77MA0.13PbI2.55Br0.45, wherein FA is formamidinium and MA is methylammonium.

[0131] 21. Use of:

[0132] • a polyphenol comprising a plurality of catechol and / or gallol groups; and / or

[0133] • at least one transition metal. in the formation the coating composition according to any one of the preceding example embodiments.

[0134] 22. A method of forming a coating composition according to any one of example embodiments 1 to 20, the method comprising a step of:

[0135] • combining the polyphenol with at least one transition metal containing compound.

[0136] 23. The method according to example embodiment 22, wherein the combined polyphenol and at least one transition metal containing compound is diluted in a solvent.

[0137] 24. The method according to example embodiment 23, wherein the solvent is an alcohol, optionally selected from: methanol, ethanol, isopropanol and mixtures thereof.

[0138] 25. The method according to any one of example embodiments 22 to 24, wherein the coating composition is formulated as a sol prior to application to at least a portion of an article.

[0139] 26. A coating composition obtained by the method according to any one of example embodiments 22 to 25.

[0140] 27. A method of coating at least a portion of an article, the method comprising introducing the coating composition according to any one of example embodiments 1 to 20, or 25, to at least the portion of the article.

[0141] 28. A method of encapsulating at least a portion of an article, the method comprising introducing the coating composition according to any one of example embodiments 1 to 20, or 25, to at least the portion of the article.

[0142] 29. The method according to example embodiment 27 or example embodiment 28, wherein the article is a solar cell.

[0143] 30. A method of sequestering at least one metal or metal ion released from an article, the method comprising introducing the coating composition according to any one of example embodiments 1 to 20, or 25, to at least the portion of the article.

[0144] 31. A method of sequestering at least one metal or metal ion from a solar cell, the method comprising introducing the coating composition according to any one of example embodiments 1 to 20, or 25, to at least the portion of the solar cell. 32. The method of example embodiment 30 or example embodiment 31, wherein the at least one metal or metal ion comprises lead.

[0145] 33. The method according to any one of example embodiments 27 to 32, wherein the article or solar cell is a lead halide perovskite solar cell.

[0146] 34. The method according to any one of example embodiments 27 to 33, wherein the coating composition is formulated as a sol prior to application to at least a portion of an article.

[0147] 35. The method according to any one of example embodiments 27 to 34, wherein the coating composition is applied to at least a portion of the article or the solar cell via a method selected from: spray coating, dip coating, spin coating, or mixtures thereof.

[0148] 36. The method according to any one of example embodiments 27 to 35, wherein the coating composition is annealed following application to at least a portion of the article or the solar cell, optionally at a temperature range of about 100 °C to about 150 °C, and optionally for a period of about 2 minutes to about 5 minutes.

[0149] 37. The method according to any one of example embodiments 27 to 36, wherein the efficiency of the solar cell is reduced by no more than about 5, 10, 15, 20, 25, 30, 35 or 40% of the initial power conversion efficiency measured prior to application of the coating, optionally for up to about 650 hours (27 days), about 1400 hours (58 days), about 2050 hours (86 days), or about 3600 hours (150 days), respectively.

[0150] 38. Use of the coating composition according to any one of example embodiments 1 to 20 or 25, on at least a portion of an article.

[0151] 39. The use according to example embodiment 38, wherein the article is a solar cell.

[0152] 40. The use according to example embodiment 38 or example embodiment 39, wherein the article is a lead halide perovskite solar cell.

[0153] 41. An article comprising a coating composition according to any one of example embodiments 1 to 20 or 25.

[0154] 42. The article according to example embodiment 41, wherein the article is a solar cell. 43. The article according to example embodiment 40 or example embodiment 41, wherein the article is a lead halide perovskite solar cell.

[0155] 44. A solar cell comprising a coating composition according to any one of example embodiments 1 to 20 or 25.

[0156] 45. The solar cell according to example embodiment 44, wherein the solar cell is a lead halide perovskite solar cell.

[0157] 46. The solar cell according to example embodiment 44 or example embodiment 45, wherein the solar cell retains at least 75, 80, 85 or 90% of the initial power conversion efficiency measured prior to application of the coating, optionally for up to about 650 hours (27 days), about 1400 hours (58 days), about 2050 hours (86 days), or about 3600 hours (150 days), respectively.

[0158] 47. The article or solar cell according to any one of example embodiments 41 to 46, wherein about, or at least about: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, of the article or solar cell is covered with one or more layers of the coating composition.

[0159] 48. The article or solar cell according to any one of example embodiments 41 to 47, wherein all or essentially all of the article or solar cell is covered with one or more layers of the coating composition.

[0160] 49. An array comprising a plurality of the article or solar cell according to any one of example embodiments 41 to 48.

[0161] EXAMPLES

[0162] The present disclosure will now be described with reference to the following non-limiting examples and with reference to the accompanying Figures (where relevant).

[0163] Example 1: Perovskite Solar Cell Fabrication

[0164] ITO substrates and 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'- spirobifluorene (spiro-OMeTAD), were purchased from Luminescence Technology Corp. (Lumtec). All solvents, caesium iodide (CsI), rubidium iodide (Rbl), tannic acid (TA) and titanium(IV) bis(ammonium lactato)dihydroxide solution (50 wt% in H2O; Ti- BALDH) were purchased from Sigma Aldrich and used as received. Perovskite precursors formamidinium iodide (FAI) and methylammonium bromide (MABr) were purchased from GreatCell Solar Materials. SnOi 15% dispersion solution in H2O was purchased from Thermo Fisher Scientific. Lead iodide (PbE) and lead bromide (PbBn) were purchased from TCI. Silver shots were bought from ESPI Metals.

[0165] Patterned ITO on glass substrates (12 cm x 12 cm) were cleaned sequentially with Hellmanex III, deionized water, acetone, and 2-propanol. Each clean was performed in an ultrasonic bath for 10 minutes. Cleaned substrates were heated at 70 °C for 30 minutes and UV-ozone treated 20 minutes.

[0166] To form the electron transport layer, aqueous 3.75 wt% SnO2 nano-particle dispersion solution was stirred for one hour and spin-coated at 3500 rpm for 35 seconds on the clean ITO substrates. The ITO samples were subsequently transferred to an open-air hot plate and annealed for 30 min at 150 °C to form a mesoporous SnO2 layer.

[0167] Cs0.06Rb0.04FA0.77MA0.13PbI2.55Br0.45 perovskite solution (1.3 M) was prepared by mixing three solutions. The first solution contained 189.2 mg of formamidinium iodide (FAI), 22.4 mg of methylammonium bromide (MABr), 553.2 mg of PbE, and 73.4 mg of PbB dissolved in 1 mL solution of DMF and DMSO in a 4: 1 ratio. The first solution contained 169 mg of CsI dissolved in 500 mL DMSO. The third solution contained 138 mg of Rbl dissolved in 500 mL DMSO. After rigorous stirring for 2 hours, 70 mL of the second solution and 30 mL of the third solution were added to the first solution to make the final perovskite solution. The final perovskite solution was stirred for 1 hour. The solution was spin-coated on top of SnCh layer at a rate of 1000 rpm for 10 seconds, followed by 4000 rpm for 40 seconds. The perovskite film was immediately annealed at 110 °C for 10 minutes.

[0168] 72.3 mg Spiro-OMeTAD solution was prepared in 1 mL chlorobenzene. To increase the conductivity, 28.8 pL 4-tBP and 17.5 pL Li-TFSI salt were added and rigorously stirred for 2 hours. The solution was then spin-coated on the perovskite thin film at a rate of 3500 rpm for 30 seconds.

[0169] Electrodes of the device were thermally evaporated using a shadow mask at a rate of 0.1 nm / sec under 10’5m-bar pressure. The electrodes were 100 nm thick. For the first 10 nm, the rate was maintained at 0.01 nm / sec. The cells had an active area of 0.045 cm2each.

[0170] The devices were scratched at all sides so that the encapsulant could cover the edges.

[0171] Example 2: Preparation of the TA-Ti4+coating as the encapsulant laver

[0172] Tannic acid (TA) solution (200 pL, 25 wt.% in methanol, 250 mg mL-1) and Ti4+precursor solution (titanium- bis(ammonium lactate)dihydroxide (Ti-BALDH); 50 pL, 50 wt.% aqueous solution) were mixed in a 1.5-mL tube under vortex to achieve a TA / Ti4+molar ratio of ~ 1 : 1.4. This mixture was immediately diluted (under vortex) with 400 pL of methanol. 50 pL of the resulting solution was spread over a complete perovskite device (1.44 cm2), and the device was spin-coated at 5000 rpm for 30 seconds, followed by annealing at 120 °C for 3 minutes.

[0173] Example 3: Encapsulating laver characterisation

[0174] A Nano SEM 450 field-emission scanning electron microscopy (FE-SEM) with a Bruker SDD-EDS detector was used to capture surface topology and device cross-sectional images. A 3D schematic illustration and a cross-section SEM image of the encapsulated device are shown in Figure 1A and Figure IB, respectively. The encapsulating layer is clearly observed as the top layer with a thickness of around 200 nm. Moreover, the coatings displayed a crack-free, homogeneous structure with no pinholes. The thickness of the underlying perovskite layer was found to be -500 nm.

[0175] The surface roughness and thickness of encapsulation layer were measured with Bruker Dimension ICON SPM Atomic Force Microscopy (AFM) with a scan size of “1 x 1 pm” at a scan rate of 0.512 Hz. when AFM was performed on a scratched coating section, the TA-Ti4+coating thickness was found to be ~233 nm, as shown in Figure IE. The surface topography of the coatings was observed to be smooth with a RMS roughness of 1.9 nm, as shown in Figure 1C.

[0176] Example 4: Photovoltaic (J-V) characterizations and stability

[0177] The photovoltaic (J-V) characterizations were performed with an NREL calibrated Keithley 2400 Source Meter under 100 mW / cm2(AM 1.5G) simulated sunlight. Current density vs voltage (J-V) characteristics of the freshly prepared encapsulated and control devices are shown in Figure 2A. The control device had a PCE of 21.3% and the encapsulated device had a PCE of 20.7%, corresponding to 96.8% PCE retention after encapsulation.

[0178] The degradation of the encapsulated and control devices was monitored by PCE as a function of time. The PCE of the control device dropped to zero in less than 10 days. In contrast, the encapsulated devices retained more than 90% (T90) of the initial PCE after 27 days, 85% (T85) of the initial PCE after 58 days; and 80% (T80) of initial PCE were found after 86 days, as shown in Figure 2B.

[0179] Example 5: Device Stability

[0180] The stability of the perovskite layer underneath the encapsulation layer (TA-Ti4+coating) was probed by photoluminescence (PL) and trim resolved photoluminescence (TrPL). Photoluminescence characterisations were performed using a pulsed OPO laser at 328 nm with a glacier XTE-cooled CCD spectrometer having a detection range of 200 - 1050 nm. Encapsulated and control devices showed similar characteristics on Day 1. With time, control devices exhibited lower peak intensity and shorter carrier lifetime than the encapsulated devices. After 135 days, the control devices showed much lower PL intensities compared to freshly prepared devices while the encapsulated samples had almost similar PL and TrPL response over time, as shown in Figure 3 A and Figure 3B.

[0181] Crystal characteristics of the perovskite materials was analysed by XRD. X-ray diffraction (XRD) with CuKa radiation was performed by step-scanning with a step size of 0.01 degree. The XRD spectra of the control and encapsulated devices for Day 1, Day 20, and Day 135 are shown in Figure 3C and Figure 3D. Devices were kept in a dark environment at ambient temperature and humidity. The characteristic XRD peaks at 14.1 (100), 28.3 (200), and 31.7 (210) degrees for perovskite crystals remained almost unaltered after 135 days for the encapsulated devices. These peaks of the control device disappeared for the Day 20, and Day 135 samples, leaving the substrate peaks only. The retention of the perovskite peaks after 135 days relative to the control device further confirmed the protection of perovskite layer against moisture when encapsulated by the TA-Ti4+coating.

[0182] Control and encapsulated PSCs were immersed in 50 mL of water and Pb leaching into the water was monitored over time via inductively coupled plasma mass spectrometry (ICP-MS). The average initial Pb2+leaching rate in 50 mL water was 43 ppb / min for control samples and 9.6 ppb / min for encapsulated samples. After 300 minutes, encapsulated samples reduced Pb2+leaching to 0.14 ppb / min whereas the control samples continued leaching at a rate of 1.0 ppb / min. The TA-Ti4+coating was able to capture more than 90% of the leaching Pb2+ions after 300 minutes. Overall, the encapsulated PSC was able to capture more than 75% of the Pb2+ions compared to the control samples, see Figure 4.

[0183] It will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS1. A coating composition comprising:• a polyphenol comprising a plurality of catechol and / or gallol groups and• at least one transition metal.

2. A coating composition formulated for a solar cell, the coating comprising:• a polyphenol comprising a plurality of catechol and / or gallol groups and• at least one transition metal.

3. A coating composition when used on a solar cell, the composition comprising:• a polyphenol comprising a plurality of catechol and / or gallol groups and• at least one transition metal.

4. The coating composition according to any one of the preceding claims, wherein the polyphenol comprises a plurality of catechol and gallol groups and / or optionally one or more functional groups selected from: a,P-unsaturated carbonyl, acid, acyl halide, acylazide, haloimide, alcohol, aldehyde, alkene, alkyne, amide, amine, azide, aziridine, carbocyclic acid, disulfide, epoxide, ester, activated ester (optionally N- hydroxysuccinimide ester, pentynoic acid STP ester), halide, heteroaryl group, heterocyclic or heteroaryl group, hydrazide, hydrazine, hydrazone, hydroxide, imidoester, imine, isocyanate, isothiocyanate, ketone, maleimide, nitrile, nitrone, oxime, phosphine, sulfhydryl, sulfinic acid, sulfonic acid, sulfonyl halide, tetrazine, tetrazole, thioester, triazolyl, and mixtures thereof.

5. The coating composition according to any one of the preceding claims, wherein the polyphenol comprises at least one of: catechin, epicatechin, gallocatechin, catechin gallate, gallocatechin gallate, epicatechin gallate, epigallocatechin gallate, epigallocatechin, tannic acid, gallotannin, ellagitannin, and mixtures thereof.

6. The coating composition according to any one of the preceding claims, wherein the polyphenol comprises tannic acid.

7. The coating composition according to any one of the preceding claims, wherein the at least one transition metal is a group III or a group IV transition metal.

8. The coating composition according to any one of the preceding claims, wherein the at least one transition metal is a group IV transition metal, optionally selected from titanium and zirconium.

9. The coating composition according to any one of the preceding claims, wherein the at least one transition metal comprises titanium.

10. The coating composition according to any one of the preceding claims, wherein the at least one transition metal comprises Ti4+ions.

11. The coating composition according to any one of the preceding claims, wherein the molar ratio between the polyphenol and the at least one transition metal is in a range of about 1: 1 to about 1:5, optionally about 1: 1 to about 1:3.

12. The coating composition according to any one of the preceding claims, wherein the molar ratio between the polyphenol and the at least one transition metal is in a range of about 1: 1 to about 1: 1.5, optionally in a range of about 1: 1.4 or about 1: 1.

13. The coating composition according to any one of the preceding claims, wherein the molar ratio between the polyphenol and the at least one transition metal is in a range of about 1: 1 to about 5: 1.

14. The coating composition according to any one of the preceding claims, further comprising at least one other excipient or additive.

15. The coating composition according to any one of the preceding claims, when used or applied to at least a portion of an article.

16. The coating composition according to claim 15, wherein the article is a solar cell.

17. The coating composition according to claim 15 or claim 16, wherein the article is a perovskite solar cell.

18. The coating composition according to any one of claims 15 to 17, wherein the article is a lead halide perovskite solar cell.

19. The coating composition according to claim 17 or claim 18, wherein the perovskite has a mixed cation and mixed halide structure.

20. The coating composition according to any one of claims 17 to 19, wherein the perovskite has a formula of Cs0.06Rb0.04FA0.77M Ao.13PbI2.55Bro.45, wherein FA is formamidinium and MA is methylammonium.

21. Use of:• a polyphenol comprising a plurality of catechol and / or gallol groups; and / or• at least one transition metal, in the formation of the coating composition according to any one of the preceding claims.

22. A method of forming a coating composition according to any one of claims 1 to 20, the method comprising a step of:• combining the polyphenol with at least one transition metal containing compound.

23. The method according to claim 22, wherein the combined polyphenol and the at least one transition metal containing compound is diluted in a solvent.

24. The method according to claim 23, wherein the solvent is an alcohol, optionally selected from: methanol, ethanol, isopropanol and mixtures thereof.

25. The method according to any one of claims 22 to 24, wherein the coating composition is formulated as a sol prior to application to at least a portion of an article.

26. A coating composition obtained by the method according to any one of claims 22 to 25.

27. A method of coating at least a portion of an article, the method comprising introducing the coating composition according to any one of claims 1 to 20, or 26, to at least the portion of the article.

28. A method of encapsulating at least a portion of an article, the method comprising introducing the coating composition according to any one of claims 1 to 20, or 26, to at least the portion of the article.

29. The method according to claim 27 or claim 28, wherein the article is a solar cell.

30. A method of sequestering at least one metal or metal ion released from an article, the method comprising introducing the coating composition according to any one of claims 1 to 20, or 26, to at least a portion of the article.

31. A method of sequestering at least one metal or metal ion from a solar cell, the method comprising introducing the coating composition according to any one of claims 1 to 20, or 26, to at least a portion of the solar cell.

32. The method of claim 30 or claim 31, wherein the at least one metal or metal ion comprises lead.

33. The method according to any one of claims 27 to 32, wherein the article or solar cell is a lead halide perovskite solar cell.

34. The method according to any one of claims 27 to 33, wherein the coating composition is formulated as a sol prior to application to at least a portion of an article.

35. The method according to any one of claims 27 to 34, wherein the coating composition is applied to at least a portion of the article or the solar cell via a method selected from: spray coating, dip coating, spin coating, or mixtures thereof.

36. The method according to any one of claims 27 to 35, wherein the coating composition is annealed following application to at least a portion of the article or the solar cell, optionally at a temperature range of about 100 °C to about 150 °C, and optionally for a period of about 2 minutes to about 5 minutes.

37. The method according to any one of claims 27 to 36, wherein the efficiency of the solar cell is reduced by no more than about 75, 80, 85 or 90% of the initial power conversion efficiency measured prior to application of the coating, optionally for up toabout 650 hours (27 days), about 1400 hours (58 days), about 2050 hours (86 days), or about 3600 hours (150 days), respectively.

38. Use of the coating composition according to any one of claims 1 to 20 or 26, on at least a portion of an article.

39. The use according to claim 38, wherein the article is a solar cell.

40. The use according to claim 38 or claim 39, wherein the article is a lead halide perovskite solar cell.

41. An article comprising a coating composition according to any one of claims 1 to 20 or 26.

42. The article according to claim 41, wherein the article is a solar cell.

43. The article according to claim 40 or claim 41, wherein the article is a lead halide perovskite solar cell.

44. A solar cell comprising a coating composition according to any one of claims 1 to 20 or 26.

45. The solar cell according to claim 44, wherein the solar cell is a lead halide perovskite solar cell.

46. The solar cell according to claim 44 or claim 45, wherein the solar cell retains at least 75, 80, 85 or 90% of the initial power conversion efficiency measured prior to application of the coating, optionally for up to about 650 hours (27 days), about 1400 hours (58 days), about 2050 hours (86 days), or about 3600 hours (150 days), respectively.

47. The article or solar cell according to any one of claims 41 to 46, wherein about, or at least about: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, of the article or solar cell is covered with one or more layers of the coating composition.

48. The article or solar cell according to any one of claims 41 to 47, wherein all or essentially all of the article or solar cell is covered with one or more layers of the coating composition.

49. An array comprising a plurality of the article or solar cell according to any one of claims 41 to 48.

Images