Patching pinholes in perovskite films for applications in solar cells

Abstract

Disclosed herein are patched perovskite materials and photoactive devices including photocured polymers to fill voids and improve efficiency and production yield. Methods of producing patched perovskite materials and photoactive devices are provided herein.

Description

PATCHING PINHOLES IN PEROVSKITE FILMS FOR APPLICATIONS IN SOLARCELLSCROSS REFERENCE TO RELATED APPLICATIONSThis application claims the benefit of priority to United States Provisional Application No. 63 / 639,139, filed April 26, 2024, the contents of which are incorporated by reference herein in their entirety for all purposes.STATEMENT OF GOVERNMENT SUPPORT

[0001] This invention was made with government support under Grant Nos. DE-EE0009520 and DE-EE0009529 awarded by Department of Energy. The government has certain rights in the invention.FIELD

[0002] The presently disclosed subject matter relates generally to the use of crosslinking materials to fill voids in perovskite materials for solar cells and other thin film devices.BACKGROUND

[0003] Perovskite materials have been demonstrated or envisioned to provide advantages over other conventional materials in a wide array of applications including photoactive devices such as solar cells and light emitting diodes (LEDs). Certain perovskite materials, such as organic- inorganic perovskite materials, provide for solar cells with higher efficiencies than traditional thin film solar cells and with lower material and manufacturing costs than traditional thin film or silicon solar cells. However, various classes of perovskite materials suffer from poor long-term operational stability and decompose when they react with moisture and oxygen or upon extended exposure to light, heat, and applied voltage. The development of perovskite materials with improved stability and durability is needed for commercial viability.

[0004] A significant challenge for the commercialization of perovskite solar cells is the presence of pinholes in perovskite materials which reduces production yield. Pinholes form channels across perovskite materials causing instability and a significant proportion of devices torapidly lose efficiency and short circuit. Ongoing research to improve the stability and efficiency of perovskite solar cells, such as through surface treatment and composition engineering methods has not adequately addressed the problem of pinholes to provide high production yields.BRIEF SUMMARY

[0005] In one aspect, the presently disclosed subject matter is directed to a perovskite composition, comprising a perovskite material comprising photocured polymer segregated in voids in the perovskite material. The perovskite material comprises a first surface and a second surface that is approximately parallel to the first surface.

[0006] In various embodiments, the voids are defects in the perovskite material.

[0007] In various embodiments, the defects extend through at least the first surface of the perovskite material.

[0008] In various embodiments, the defects comprise holes, pinholes, fractures, or combinations thereof.

[0009] In various embodiments, the defects extend through the first surface of the perovskite material to a second surface of the perovskite material.

[0010] In various embodiments, the first surface and the second surface of the perovskite material are substantially free of the photocured polymer.

[0011] In various embodiments, the photocured polymer comprises a non-conductive material.

[0012] In various embodiments, the photocured polymer is a polymer of one or more monomers or oligomers, wherein the one or more monomers or oligomers comprise an ester group, an epoxy group, a thiol group, or a vinyl group.

[0013] In various embodiments, the vinyl group is a vinyl ether.

[0014] In various embodiments, at least one of the one or more monomers or oligomers is an acrylate.

[0015] In various embodiments, the acrylate is a methacrylate oligomer.

[0016] In various embodiments, the methacrylate oligomer is poly(methyl methacrylate) (PMMA).

[0017] In various embodiments, the photocured polymer is crosslinked.

[0018] In various embodiments, the photocured polymer is crosslinked with a crosslinker comprising two or more acrylate groups.

[0019] In various embodiments, the crosslinker is dipentaerythritol hexaacrylate (DPEHA).

[0020] In various embodiments, the photocured polymer is crosslinked by ultraviolet (UV) or visible light.

[0021] Various embodiments are directed to perovskite materials comprising a photocured and crosslinked polymer of PMMA segregated in voids in the perovskite material, wherein the voids are defects in the perovskite material that extend through at least a first surface of the perovskite material, and wherein the first surface and a second surface of the perovskite material are substantially free of the photocured and crosslinked polymer of PMMA.

[0022] In another aspect, the subject matter described herein is directed to methods of preparing the perovskite compositions described herein, the method comprising: i. contacting at least one of the voids in the perovskite material with a liquid prepolymer solution; ii. curing the liquid prepolymer solution by exposure to UV light or visible light to form photocured polymer segregated in voids in the perovskite material; and iii. optionally washing the first surface of the perovskite material.

[0023] In various embodiments, the liquid prepolymer solution comprises a photoinitiator and one or more monomers or oligomers.

[0024] In various embodiments, the photoinitiator is a cationic photoinitiator or a radical photoinitiator.

[0025] In various embodiments, the photoinitiator is selected from the group consisting of an iodonium salt, a sulfonium salt, an ammonium salt, a phosphonium salt, an ammonium salt, a pyridinium salt, a diazonium salt, an iron complex, a germanium complex, a ruthenium complex, an iridium complex, a titanium complex, a phosphine oxide, a peroxide, an azo compound, and an aromatic ketone.

[0026] In various embodiments, the photoinitiator is a diaryl iodonium salt, a triaryl sulfonium salt, a triaryl phosphonium salt, an aryl diazonium salt, a ferrocenium salt, a germanium ketone salt, a titanocene salt, or an acyl phosphine oxide.

[0027] In various embodiments, the acyl phosphine oxide is diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO).

[0028] In various embodiments, the one or more monomers or oligomers comprise an ester group, an epoxy group, a thiol group, or a vinyl group.

[0029] In various embodiments, the vinyl group is a vinyl ether.

[0030] In various embodiments, at least one of the one or more monomers or oligomers is an acrylate.

[0031] In various embodiments, the acrylate is a methacrylate oligomer.

[0032] In various embodiments, the methacrylate oligomers is poly(methyl methacrylate) (PMMA)

[0033] In various embodiments, the photocured polymer is crosslinked.

[0034] In various embodiments, the photocured polymer is crosslinked with a crosslinker comprising two or more acrylate groups.

[0035] In various embodiments, the crosslinker is dipentaerythritol hexaacrylate (DPEHA).

[0036] In various embodiments, the liquid prepolymer solution further comprises a solvent.

[0037] In various embodiments, the solvent is selected from the group consisting of propylene glycol monomethyl ether acetate (PGMEA), ether acetate (EA), isopropyl alcohol (IP A), toluene, and chlorobenzene.

[0038] In various embodiments, the liquid prepolymer solution comprises diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide (TPO) as the photoinitiator, DPEHA as the crosslinker, PMMA as the oligomer, and PGMEA as the solvent.

[0039] In various embodiments, the contacting comprises coating at least the first surface of the perovskite material with the liquid prepolymer solution by blade coating, spin coating, dip coating, or soaking.

[0040] In various embodiments, the perovskite material masks the UV light or visible light to selectively cure the liquid prepolymer solution in contact with at least one of the voids.

[0041] In various embodiments, at least the first surface of the perovskite material is washed with a washing solvent after curing, optionally wherein the washing solvent is ethyl acetate.

[0042] In another aspect, the subject matter described herein is directed to devices comprising a perovskite material, wherein the perovskite material comprises a photocured polymer segregated in voids in the perovskite material, wherein the perovskite material comprises a first surface and a second surface, and wherein the second surface of the perovskite material is disposed on a first charge transport layer.

[0043] In various embodiments, the first charge transport layer is disposed on a transparent substrate, wherein the transparent substrate comprises glass and / or a transparent conducting oxide (TCO).

[0044] In various embodiments, the TCO is indium tin oxide (ITO).

[0045] In various embodiments, the TCO comprises a first electrode.

[0046] In various embodiments, the first surface of the perovskite material is disposed on a second charge transport layer.

[0047] In various embodiments, a second electrode is disposed on the second charge transport layer. In various embodiments, the device has a greater power conversion efficiency (PCE), a greater open circuit voltage (VOC), a greater short-circuit current density (JSC), and / or a greater fill factor (FF) than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.

[0048] In various embodiments, the device has a lower dark current than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.

[0049] In various embodiments, the device maintains its performance for a longer time than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.

[0050] In another aspect, the subject matter described herein is directed to a method of increasing production yield of a perovskite film, the method comprising: i. contacting at least one void in a perovskite film with a liquid prepolymer solution; and ii. curing the liquid prepolymer solution by exposure to UV light or visible light to form photocured polymer segregated in the at least one void in the perovskite film, wherein the production yield of perovskite film is increased.BRIEF DESCRIPTION OF FIGURES

[0051] Figure 1A-1B shows schematic representations of the use of crosslinked material to fill the pinholes of perovskite solar cells. Figure 1A shows the crosslinking material coated onto the perovskite film. Figure IB shows the crosslinking material coated onto the top charge transport layer (CTL) to cover the perovskite.

[0052] Figure 2A shows the chemical structure of crosslinking materials polymethyl methacrylate (PMMA) and dipentaerythritol hexacrylate (DPEHA). Figure 2B shows an ultraviolet (UV) light-initiated free radical reaction of initiator 2,4,6-trimethylbenzoyldiphenyl phosphine oxide (TPO). Figure 2C shows a schematic illustration of a UV-initiated crosslinking reaction of PMMA and DPEHA.

[0053] Figure 3A shows the first step of the method involving coating the perovskite film with a crosslinking precursor solution. Figure 3B shows the second step of the method involving the use of light (e.g., UV light) to initiate the crosslinking reaction. Figure 3C shows the third step of the method involving the use of a solvent such as ethyl acetate (EA) to remove residual crosslinking precursors.

[0054] Figure 4A shows the chemical structures of EA) and propylene glycol methyl ether acetate (PGMEA). Figure 4B shows X-ray diffraction analysis (XRD) of a control perovskite film and films soaked in EA or PGMEA for 48h. Figure 4C shows current density-voltage (J-V) characteristics of control perovskite solar cells (PSCs) and PSCs soaked in EA or PGMEA for 60s. Figure 4D shows a scanning electron microscopy (SEM) image of a control perovskite film that was not soaked in solvent. Figure 4E shows a SEM image of a perovskite film soaked in EA for 48 hrs. Figure 4F shows a SEM image of a perovskite film soaked in PGMEA for 48 hrs.

[0055] Figure 5A shows the relationship between crosslinked polymer thickness and the concentration of the crosslinking precursor. Figure 5B shows the relationship between crosslinked polymer thickness and the resistance (for an area of 0.08cm2). Figure 5C shows the top view of an SEM image of a scratched perovskite film treated with crosslinked polymer. Figure 5D shows a cross-section view of an SEM image of a scratched perovskite film treated with crosslinked polymer. Figure 5E shows an enlarged view of the portion of the film that was treated with the crosslinked polymer. Figure 5F shows an enlarged view of the perovskite grain.

[0056] Figure 6A provides a schematic illustration of a PSC scratched and filled with crosslinked polymer. Figure 6B shows an optical image of a PSC scratched below a copper electrode. Figure 6C shows J-V curves of scratched PSCs filled with crosslinked polymer before and after aging under 1 Sun illumination at 85 °C for 48 h. Figure 6D shows the short-circuit current density (Jsc), Figure 6E shows the open circuit voltage (Voc), Figure 6F shows the fill factor (FF), Figure 6G shows the power conversion efficiency (PCE), and Figure 6H shows the dark current at -0.1V of nine scratched devices treated with crosslinked polymer.

[0057] Figure 7A shows J-V curves, Figure 7B shows the efficiency distribution, Figure 7C shows the dark current J-V curve, and Figure 7D shows the distribution of dark current at -0.2V for 1 cm2PSCs with and without crosslinked polymer treatment. Figure 7E shows J-V curves and Figure 7F shows the efficiency distribution of PSCs with different crosslinking precursor coating methods.

[0058] Figure 8A shows an optical image and Figure 8B shows the J-V curve of a scratched PSC minimodule with an aperture area size of 36 mm x 55 mm.DETAILED DESCRIPTION

[0059] During the manufacturing process of perovskite films, it is challenging to prevent the formation of voids, such as pinholes or fractures, which can significantly reduce production yields. The subject matter described herein relates to the utilization of photopolymerization to fill voids (e g., pinholes) in perovskite materials with a polymer by a light-initiated crosslinking reaction. The devices and methods disclosed herein improve the production yield of perovskite materials (e.g., a quantity of good performing devices produced from the perovskite materials) and provide perovskite devices with increased stability and long-term efficiency.

[0060] The presently disclosed subject matter will now be described more fully hereinafter. However, many modifications and other embodiments of the presently disclosed subject matter set forth herein will come to mind to one skilled in the art to which the presently disclosed subject matter pertains having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the presently disclosed subject matter is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. In other words, the subject matter described herein covers all alternatives, modifications, and equivalents. In the event that one or more of the incorporated literature, patents, and similar materials differs from or contradicts this application, including but not limited to defined terms, term usage, described techniques, or the like, this application controls. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in this field. All publications, patent applications, patents and other references mentioned herein are incorporated by reference into their entirety.I. Overview

[0061] Photovoltaic applications benefit from device stability and efficiency, as well as high production yields. One of the most significant challenges for perovskite-based photovoltaic devices, is achieving a high production yield with conventional industry fabrication techniques. For example, a polycrystalline perovskite film may be included in solar cells. While the stability and efficiency of perovskite solar cells may be improved through methods such as surface treatment and composition engineering, it is challenging to prevent the formation of voids in perovskite films. Such voids may provide a low-resistance path for an electrical current to travel through the perovskite material. In other words, voids in the perovskite film can lead to shunting, which may degrade a performance of the solar cell and reduce production yields achievable via conventional fabrication techniques.

[0062] The subject matter described herein is directed to filling (e.g., patching) voids in perovskite films with an insulating photocured polymer. For example, a solar cell may be fabricated by preparing (e.g., layering, coating, depositing) a perovskite film on a substrate that is transparent to ultraviolet (UV) or visible light. Accordingly, the perovskite film may include a first surface (e.g., a top surface) and a second surface (e.g., a bottom surface) in which the second surface may be in contact with the transparent substrate. In various embodiments, the transparent substrate may include a transparent conducting oxide (TCO) and a charge transport later (CTL). The CTL may be in between the TCO and the perovskite film. A liquid prepolymer solution comprising a photo-initiated crosslinking material may be applied to the perovskite film, such that the liquid may fill one or more voids (e.g., any void) in the perovskite film, forming a photocured polymer following light exposure. In various embodiments, the liquid prepolymer solution (e.g., a thin layer of photo-initiated crosslinking material) may be coated directly onto the first surface of the perovskite film. Additionally, or alternatively, the first surface of the perovskite film may be coated with another CTL and the photo-initiated crosslinking material may be coated onto the other CTL. In various embodiments, the photo-initiated crosslinking material may be applied by coating (e.g., blade coating, spin coating, or dip coating) the first surface of the perovskite film with a liquid prepolymer solution (e.g., a crosslinking material precursor ink).

[0063] To initiate the crosslinking process, light (e.g., UV or visible light) may be directed at the perovskite film from the direction of the TCO. In other words, light may be shown through the transparent substrate such that the second (bottom) surface of the perovskite material may beilluminated with the light. The perovskite material in the perovskite film may block at least a portion of the light. For example, the perovskite material may absorb or reflect the light, such that the perovskite film may block the light in areas of the perovskite film that lack voids. In other words, the perovskite film may block light in areas where perovskite material is present, allowing light to penetrate specifically in areas where voids are present. Consequently, only the crosslinking material that is within the voids may undergo the crosslinking process to fill the voids with photocured polymer. In other words, crosslinking material within voids of the perovskite film may be exposed to the light (e.g., due to a lack of perovskite material) and may therefore undergo the crosslinking process. Accordingly, the resulting perovskite material includes a photocured polymer formed from the crosslinking material segregated in voids in the perovskite material.

[0064] The crosslinking material may be nonconductive so that the shunting of device due to the voids may be reduced or eliminated. In various embodiments, residual non-crosslinked material on the first surface of the perovskite film may be removed, for example, by application of one or more solvents to wash off excess liquid prepolymer solution. Although the techniques described herein are primarily described in the context of photovoltaic devices, such techniques may also be applicable to other types of devices that utilize perovskite materials. For example, the techniques described herein may lead to improved production yield or performance for photoresistors, phototransistors, photomultipliers, light emitting diodes, photodetectors, and electrochromic cells, among other examples.II. Definitions

[0065] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the present application and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. The terminology used in the description of the invention herein is for the purpose of describing particular aspects only and is not intended to be limiting of the invention. In case of a conflict in terminology, the present specification is controlling.

[0066] As used herein, the term “and / or” refers to and encompasses any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative (“or”).

[0067] The term “or” refers to any one member of a particular list.

[0068] Unless otherwise apparent from the context, the term “about” when referring to a measurable value such as an amount of a compound or agent of the current subject matter, dose, time, temperature, and the like, is meant to encompass variations of ±20%, ±10%, ±5%, ±1%, ±0.5%, or even ±0.1% of the specified amount.

[0069] As used herein, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and / or steps are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list.

[0070] The singular forms of the articles “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a protein” or “at least one protein” can include a plurality of proteins, including mixtures thereof.

[0071] As used herein, “PSC” refers to perovskite solar cell.

[0072] As used herein, “PCE” refers to power conversion efficiency. The terms “power conversion efficiency,” “PCE,” “photovoltaic efficiency”, and “solar cell efficiency,” may be used interchangeably and refer to the ratio of energy output from the photovoltaic device to the energy input to the photovoltaic device. The energy output is in the form of electrical energy and energy input is in the form of electromagnetic radiation (e.g., sunlight). Unless otherwise indicated, the photovoltaic efficiency refers to terrestrial photovoltaic efficiency, corresponding to AMI.conditions, where AM is Air Mass. PCE may be measured by one or more techniques conventionally known to one of ordinary skill in the art.

[0073] As used herein, “photoactive device” refers to (i) a device capable of and configured to convert electromagnetic radiation (e.g., X-ray, infrared, ultraviolet, and / or visible light) to electrical energy and / or converting electrical energy to electromagnetic radiation. A photoactive device may be configured to both convert light to electrical energy (e.g., as a solar cell) and convert electrical energy to light (e.g., via electroluminescence), for example depending on the direction of electrical current in the device (e.g., depending on whether electrical power is withdrawn from or supplied to the device). Exemplary photoactive devices include, but are not limited to, a photovoltaic cell (also referred to as a solar cell), a photodiode, and a light emitting diode (LED). In certain embodiments, a photoactive device can also refer to a device configured to change its optical, physical, and / or electrical properties with change in its exposure to electromagnetic radiation and / or a device configured to change its optical properties in response to a change in input of electrical energy. Exemplary photoactive devices can also include, but are not limited to, a photoresistor, phototransistor, photomultiplier, photoelectric cell, and an electrochromic cell.

[0074] As used herein, “CTL” refers to charge transport layer.

[0075] As used herein, “TCO” refers to transparent conducting oxide.

[0076] As used herein, “ITO” refers to indium-tin-oxide.

[0077] As used herein, “void” refers to a defect that extends (e.g., penetrates) from a surface of a perovskite material through the entire perovskite material or a portion thereof. A defect is an unintended structural irregularity that extends through at least a first surface of a perovskite material. In some examples, a defect may extend through the first surface of the perovskite material to a second surface of the perovskite material. In other words, in some examples, a void may penetrate the entire depth of a perovskite material (e.g., from a top surface of the perovskite material to a bottom surface of the perovskite material). In some other examples, a void may penetrate a portion of the depth of the perovskite material. For example, a void may include a relatively shallow hole or crack in the first surface of the perovskite material. In some examples, liquid prepolymer solution may contact (e.g., fill) the void, and may form photocured polymer segregated in the void upon exposure to UV or visible light and curing. For example, while perovskite material in the remaining portion of the depth of the perovskite material may attenuate the UV or visible light, a thickness of the remaining portion of the depth of the perovskite materialmay be such that the prepolymer solution in contact with the void is exposed to a sufficient quantity of UV or visible light to form the photocured polymer.

[0078] As used herein, the term “segregated in voids” and the like, refers to an amount of cured polymer that is physically isolated within a void and is not contiguous with cured polymer in any other void(s). The cured polymer that is segregated in voids is not dispersed evenly throughout the perovskite material.

[0079] As used herein, “photocured polymer” refers to a solid polymer formed via a light- initiated reaction involving the crosslinking of monomers and / or oligomers.

[0080] As used herein, “polymer” refers to substance that contains large molecules with many repeating units of one or more monomers.

[0081] As used herein, “monomer” refers to a molecule that bonds with other molecules to form a polymer or an oligomer. In various embodiments, a monomer may bond with one or more other monomers to form a polymer. For example, acrylic acid is a monomer which can react with other molecules of acrylic acid to form the polymer poly(acrylic acid).

[0082] As used herein, “oligomer” refers to a molecule that includes at least two repeating units of a monomer. Oligomers can be small polymers which can undergo further crosslinking with a crosslinker to form larger photocured polymers. For example, the monomer methyl methacrylate can be polymerized to form poly(methyl methacrylate), an oligomer composed of repeating units, which can be further polymerized with a crosslinker such as dipentaerythritol hexaacrylate to form a photocured polymer.

[0083] As used herein, “crosslinking” refers to the process of forming of covalent bonds between monomers and / or oligomers during polymerization. In some instances, crosslinking occurs between an oligomer and a crosslinker.

[0084] As used herein, “crosslinker” refers to a molecule that forms two or more bonds between two oligomer or polymer chains. In various embodiments, a crosslinker may be a monomer or an oligomer. A non-limiting example of a crosslinker is dipentaerythritol hexaacrylate, a monomer with six acrylate groups which can form covalent bonds to different oligomer or polymer chains.

[0085] As used herein, “pre-polymer solution” refers to a liquid solution comprising a photoinitiator and monomers and / or oligomers that forms a photocured polymer upon exposure tolight. The pre-polymer solution may also contain a crosslinker and may be dissolved in any appropriate solvent.

[0086] As used herein, “polymer chain” refers to a concatenated sequence of monomers.

[0087] As used herein, “photoinitiator” refers to a molecule that, upon exposure to electromagnetic radiation (e.g., ultraviolet (UV) or visible light), absorbs a photon and forms a reactive species, which can initiate a reaction. The reactive species may include a radical, cation or anion.

[0088] As used herein, “contact” refers to a state or condition of physical touching or mixing.

[0089] As used herein, “cure” refers to a process of toughening or hardening of a material. In various embodiments, a prepolymer solution is cured to form a polymer, which may include light- initiated crosslinking of an oligomer and a crosslinker.

[0090] As used herein, “mask” refers to a process of blocking. In various embodiments, a perovskite material may mask UV light or visible light, for example, by absorbing or reflecting the UV light or visible light.III. Photopolymerization

[0091] In various embodiments, the techniques described herein may include the use of photopolymerization reactions to fill voids in perovskite films with a photocured polymer. For example, in one aspect, the subject matter described herein is directed to devices that include perovskite materials in which voids (e.g., pinholes) in the perovskite materials may be filled with a polymer formed by a light-initiated crosslinking reaction (e.g., a photocured polymer).

[0092] The photopolymerization methods described herein may be used to fill voids for any type of perovskite material. In various embodiments, the perovskite material is a polycrystalline perovskite film with a composition of Formula I, Formula II, or Formula III:ABX3 (I)A2BX4 (II)A2MIMIIIX6 (III) where A is a cation, B is a metal cation, and X is an anion.

[0093] In various embodiments, the perovskite material comprises low dimensional perovskites.

[0094] In various embodiments, A may be selected from a group including: methylammonium (MA), dimethylammonium (DMA), tetramethylammonium (TMA), formamidinium (FA), cesium (Cs), rubidium (Rb), potassium (K), sodium (Na), butylammonium (BAH), phenylethylammonium (PEA), phenyl ammonium (PHA), guanidinium (GU), and a combination thereof.

[0095] In various embodiments, B may include at least one divalent metal.

[0096] In various embodiments, X may include at least one halide (e.g., chlorine, bromine or iodide). For example, the perovskite material may be a metal halide perovskite or an organic metal halide perovskite.

[0097] In various embodiments, M1comprises a monovalent metal and M111comprises a trivalent metal.

[0098] In various embodiments, the photocured polymer is a non-conductive material. The photocured polymer is formed from the polymerization reaction of one or more monomers or oligomers in a liquid pre-polymer solution.

[0099] In various embodiments, the photocured polymer may be formed by curing a liquid prepolymer solution via exposure to UV light or visible light. In such embodiments, the prepolymer solution may include a photoinitiator and the one or more monomers or oligomers.

[0100] In various embodiments, the one or more monomers or oligomers may include an ester group. For example, the one or more monomers or oligomers may include an acrylate, which is characterized by an a,P-unsaturated ester group (e.g., containing a vinyl group adjacent to an ester) as shown in Formula IV.Formula IV

[0101] An acrylate may include various substituents on the vinyl group and the ester group. For example, the acrylate may be a methacrylate, which has a methyl substituent on the vinyl group, wherein R2is CH3 in Formula IV. In some examples, the ester group may have various alkyl substituents shown as R1in Formula IV (e.g., methyl, ethyl, or butyl). In such embodiments, the prepolymer solution which forms the photocured polymer may include methyl methacrylate (MMA), ethyl acrylate, bisphenol A ethoxylate dimethacrylate, polymethyl methacrylate (PMMA), butyl acrylate, 2-hydroxy ethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), or urethane methacrylate, among other examples.

[0102] In various embodiments, the photocured polymer may be crosslinked with a crosslinker. The crosslinker may include a molecule with one or more reactive functional groups. For example, the crosslinker may include two or more acrylate groups. In some examples, the crosslinker is dipentaerythritol hexaacrylate (DPEHA).

[0103] In various embodiments, the one or more monomers or oligomers may include an epoxy group. Epoxy groups include an epoxy ring, a three-membered ring containing two carbon atoms and one oxygen atom (also referred to as an oxirane ring) that may open under UV light exposure and, as such, may facilitate reactions with other epoxy molecules or hardeners to create a crosslinked structure. In such embodiments, the photocured polymer (or prepolymer solution) may include bisphenol A diglycidyl ether (BADGE), Epichlorohydrin, glycidyl methacrylate (GMA), epoxy novolac resins, cycloaliphatic epoxies, tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM), or diglycidyl ether of bisphenol F (DGEBF), among other examples.

[0104] In various embodiments, the one or more monomers or oligomers may include a thiol group. For example, the photocured polymer may be formed from the reaction of a thiol-ene system, which involves a thiol group reacting with an alkene to produce a thioether linkage. In such embodiments, the photocured polymer is formed from a prepolymer solution from a thiol such as pentaerythritol tetra(3-mercaptopropionate) or dithiothreitol (DTT) and an alkene such as trimethylolpropane triacrylate (TMPTA), or other allyl compounds, among other examples.

[0105] In various embodiments, the one or more monomers or oligomers may include a vinyl group. For example, the photocured polymer may be formed from a prepolymer solution including a monomer or oligomer containing a vinyl ether, which has an ether group adjacent to a vinyl group (e.g., CH2=CHO-). Vinyl ethers are highly reactive to cationic polymerization (e.g., under UV light or in the presence of strong acids). In such embodiments, the photocured polymer may be formed from a prepolymer solution including methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, hydroxyethyl vinyl ether, glycidyl vinyl ether, or divinyl ether, among other examples.

[0106] To start the polymerization reaction, the prepolymer solution includes a photoinitiator capable of absorbing UV or visible light and forming a reactive species such as a radical or cation. Any photoinitiator may be used to initiate the photopolymerization reaction. In various embodiments, the photoinitiator may be a cationic photoinitiator or a radical photoinitiator. For example, the photoinitiator may include an iodonium salt, a sulfonium salt, an ammonium salt, aphosphonium salt, an ammonium salt, a pyridinium salt, a diazonium salt, an iron complex, a germanium complex, a ruthenium complex, an iridium complex, a titanium complex, a phosphine oxide, a peroxide, an azo compound, or an aromatic ketone, a diaryl iodonium salt, a triaryl sulfonium salt, a triaryl phosphonium salt, an aryl diazonium salt, a ferrocenium salt, a germanium ketone salt, a titanocene salt, or an acyl phosphine oxide, among other examples photoinitiators capable of absorbing visible or UV light.IV. Methods of Filling Voids

[0107] In one aspect, the subject matter described herein is directed to a method for filling voids in perovskite materials with photocured polymer. The method comprises contacting at least one of the voids in the perovskite material with a liquid prepolymer solution, and curing the liquid prepolymer solution by exposure to UV light or visible light to form photocured polymer segregated in voids in the perovskite material. The liquid prepolymer solution comprises a photoinitiator and one or more monomers or oligomers which form the photocured polymer following exposure to light. The perovskite material may be exposed to light from a source such as a light-emitting diode (LED), a lamp, a laser, or a projector. The light may contain a range of wavelengths or a single wavelength. The light may include visible light, with a wavelength of about 400 nm to about 700 nm, or UV light, with a wavelength of about 300 nm to about 400 nm. The light is selected to include wavelengths capable of exciting the specific photoinitiator included in the liquid prepolymer solution. For example, an LED with a wavelength of 365 nm may be used to cure a prepolymer solution containing TPO as the photoinitiator, which has an absorption peak of about 290 nm to about 380 nm.

[0108] In various embodiments, a void may include a hole. As used herein, a hole may refer to an opening in a surface of a perovskite material that extends through the perovskite material.

[0109] In various embodiments, a void may include a pinhole. As used herein, a pinhole may refer to a relatively small circular hole (e.g., a circular hole with a diameter between about a few micrometers and a hundred micrometers). As used herein, a pinhole may be smaller than a hole.

[0110] In various embodiments, a void may include a fracture. As used herein, a fracture may refer to a break in the perovskite material that extends through at least a first surface of a perovskite material. A fracture may also be referred to herein as a crack or scratch.

[0111] In various embodiments, the method further comprising washing the surface of the perovskite material following the curing process to remove excess liquid prepolymer solution. The washing may be performed with an appropriate solvent such as ethyl acetate (EA) or propylene glycol monomethyl ether acetate (PGMEA).

[0112] For example, devices disclosed herein may include a CTL disposed on top of a TCO (or glass) substrate, and a polycrystalline film of perovskite material disposed on top of the CTL. The perovskite film may include one or more voids (e.g., one or more holes, pinholes, or fractures). A relatively thin layer of photo-initiated crosslinking material is coated onto the perovskite film (e.g., directly, or indirectly). To initiate the cross-linking process, light (UV or visible) is directed onto the perovskite film from the TCO side (e.g., the back or bottom) of the device, such that the perovskite film blocks the light in all areas except where voids are present. Consequently, the cross-linking material within the voids undergoes the crosslinking process and fills the voids. The crosslinking material may include a photocured polymer formed from the crosslinking material may be selected to be a nonconductive material, such that shunting of device due to voids may be reduced. In some examples, a portion of the photo-initiated crosslinking material may coat a top surface of the perovskite film and, due to the perovskite material blocking the light, may not undergo the crosslinking process. The portion of the photo-initiated crosslinking material remaining on the first surface of the perovskite film (e.g., unreacted crosslinking material, uncrosslinked material) may be removed (e.g., from the first surface) by washing, such as with various types of solvents. In various embodiments, the solvent may include EA or PGMEA.V. Devices

[0113] The perovskite materials with filled voids (e.g., filled pinholes) as described herein are useful in a variety of photoactive and photovoltaic applications. For example, the perovskite films may be integrated into, for example, photoluminescent devices, photoelectrochemical devices, thermoelectric devices, and photocatalytic devices. Some non-limiting examples in which the polycrystalline perovskite films may be applied include solar cells, solar panels, solar modules, light-emitting diodes, lasers, photodetectors, x-ray detectors, batteries, hybrid PV batteries, field effect transistors, memristors, or synapses.

[0114] In various embodiments, the perovskite films described herein are useful in solar cells. For example, a solar cell may include one or more photoactive layers of a perovskite material,which may include one or more voids. In accordance with one or more aspects of the present disclosure, the perovskite material may include a photocured polymer segregated in voids in the perovskite material. The photocured polymer may be an example of a photocured polymer as described in the present disclosure. For example, the photocured polymer may be formed from a liquid prepolymer solution. In various embodiments, the prepolymer solution may include poly(Methyl methacrylate) (PMMA), Dipentaerythritol hexa-acrylate (DPEHA), propylene glycol monomethyl ether acetate (PGMEA), methanol, ethyl acetate (EA), and diphenyl(2,4,6- trimethylbenzoyl) phosphine oxide (TPO). For example, a range of concentrations of PMMA, DPEHA, and TPO may be dissolved in PGMEA. In a non-limiting example, the weight ratio of PMMA / DPEHA / TPO may be maintained at 1.0 / 1.0 / 0.2.

[0115] In various embodiments, the perovskite material includes a first surface and a second surface that is approximately parallel to the first surface. The first surface and the second surface refer to the exterior boundaries of the perovskite material (e.g., the outer layers and not the interior of the perovskite material). The first surface may be the top surface and the second surface may be the bottom surface of the perovskite material or the first surface may be the bottom surface and the second surface may be the top surface of the perovskite material. The first surface and the second surface are not perpendicular to each other (e.g., do not intersect at a 90° angle), however the first surface and / or the second surface may be uneven and may not be exactly parallel (e.g., equidistant) in all regions.

[0116] The first surface of the perovskite material and / or the second surface of the perovskite material may be disposed on a charge transport layer (CTL). For example, the second surface (e.g., bottom surface) of the perovskite material may be disposed on a first CTL and the first surface (e.g., top surface) of the perovskite material may be disposed on a second CTL of the perovskite material. The first CTL may be referred to herein as a bottom CTL and the second CTL may be referred to herein as a top CTL.

[0117] In various embodiments, the first (bottom) CTL is disposed on a transparent substrate. The transparent substrate may include glass and / or a transparent conducting oxide (TCO). In various embodiments in which the transparent substrate includes a TCO, the TCO may be a first electrode of the device. Some non-limiting examples of TCOs include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum doped zinc oxide (AZO), and antimony-tin oxide (ATO). In an embodiment, the TCO is an anode. The anode may be referred to herein as a negativeelectrode or bottom electrode. In various embodiments, the anode is a terminal for connection to an external circuit.

[0118] In various embodiments, a second electrode of the device is disposed on the second (top) CTL. In an embodiment, the second electrode is a metal electrode. Some non-limiting examples of metals used in a metal electrode include Al, Au, Cu, Cr, Ca, Mg, Bi, Ag, and Ti. In an embodiment, the metal electrode is a cathode. The cathode may be referred to as a positive electrode or top electrode. In various embodiments, the cathode is a terminal for connection to an external circuit.

[0119] In various embodiments, the first CTL is a hole transport layer (HTL). In various embodiments, the HTL includes at least one of poly(3,4-ethylene di oxi thiophene) (PEDOT - acidic or neutral), poly(3,4-ethylene di oxithiophene) (PEDOT) doped with poly (styrene sulfon icacid) (PSS) [PEDOT:PSS], Spiro-OMeTAD, pm-spiro-OMeTAD, po-spiro-OMeTAD, dopants in spiro-OMeTAD, 4,4'-biskptrichlorosilylpropylphenyl)phenylaminoThiphenyl (TPD-Si2), (2- (3,6-Dimethoxy-9H-carbazol-9-yl)ethyl)phosphonic acid (MeO-2PACz), poly(3-hexyl-2,5- thienylene vinylene) (P3HTV), C60, carbon, carbon nanotube, graphene quantum dot, graphene oxide, copper phthalocyanine (CuPc), Polythiophene, poly(3,4- (Ihydroxymethyl)ethylenedioxythiophene (PHMEDOT), n-dodecylbenzenesulfonic acid / hydrochloric acid doped poly(aniline) nanotubes (a-PANIN)s, poly(styrene sulfonic acid)- graft-poly(aniline) (PSSA-g-PANI), poly(9. 9-dioctylfluorene)-co-N-(4-(l-methylpropyl)phenyl) diphenylamine (PFT), 4,4'-bis(p- trichlorosilylpropylphenyl) phenylaminobiphenyl (TSPP), 5,5'- bis(p-trichlorosilylpropylphenyl) phenylamino-2,20 bithiophene (TSPT), N- propyltriethoxysilane, 3,3,3-trifluo ropropyltrichlorosilane or 3 -aminopropyltri ethoxy silane, Poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA), (Poly[[(2,4-dimethylphenyl)imino]- l,4-phenylene(9,9-dioctyl-9H-fluorene-2,7-diyl)-l,4phenylene], (PF8-TAA)), (Poly [[(2,4- dimethylphenyl)imino]-l,4-phenylene (6,12-dihydro-6,6,12, 12tetraoctylindeno[l,2-b]fluorene- 2,8-diyl)-l,4-phenylene]) (PIF8-TAA), poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[l,2-b:4,5- b]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7), poly[N-90-heptadecanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT), Poly[2,5-bis(2-decyldodecyl)pyrrolo[3,4-c]pyrrole-l,4(2H,5H)-dione-(E)-l,2- di(2, 20-bithi ophen-5 -yl) ethene] (PDPPDBTE), 4,8-dithien-2-yl-benzo[l,2- d ;4,5- d ']bistriazole- alt -benzofl, 2- b :4,5b']dithiophenes (pBBTa-BDTs), pBBTa-BDTl, pBBTa-BDT2 polymers,poly(3-hexylthiophene) (P3HT), poly(4,4’-bis(N-carbazolyl)-l,l ’-biphenyl) (PPN), triarylamine (TAA) and / or thiophene moieties, Paracyclophane, Triptycene, and Bimesitylene, Thiophene and Furan-based hole transport materials, Dendrimer-like and star-type hole transport materials, VO, VOX, MoC, WO, ReO, NiOx, AgOx, CuO, Cu2O, V2O5, Cui, CuS, CuInS2, colloidal quantum dots, lead sulphide (PbS), CuSCN, Cu2ZnSnS4, Au nanoparticles and their derivatives. Thiophene derivatives, Triptycene derivatives, Triazine derivatives, Porphyrin derivatives, Triphenylamine derivatives, Tetrathiafulvalene derivatives, Carbazole derivatives and Phthalocyanine derivatives. As used herein, when a material is referred to a “derivate” or as “derivatives,” such as Triphenylamine derivatives, the material contains Triphenylamine in its backbone structure. In certain embodiments, the HTL is selected from the group consisting of PEDOT, PTAA, Spiro- OMeTAD, PEDOT :PSS, NiO, MoO3, MeO-2PACz, V2O5, Poly-TPD, EH44, P3HT, and a combination thereof. In various embodiments described herein, the HTL may include poly(bis(4- phenyl)(2,4,6-trimethylphenyl)amine) (PTAA).

[0120] In various embodiments, the second CTL is an electron transport layer (ETL). In various embodiments, the ETL includes at least one of LiF, CsP, LiCoO, CsCO, TiOX, TiO, nanorods (NRs), ZnO, ZnO nanorods (NRs), ZnO nanoparticles (NPs), ZnO, ALO, CaO, bathocuproine (BCP), copper phthalocyanine (CuPc), pentacene, pyronin B, pentadecafluorooctyl phenyl-C60-butyrate (F-PCBM), C60, C60 / LiF, ZnO NRS / PCBM, ZnO / cross-linked fullerene derivative (C-PCBSD), single walled carbon nanotubes (SWCNT), poly(ethylene glycol) (PEG), poly(dimethylsi loxane-block-methyl methacrylate) (PDMS-b-PMMA), polar polyfluorene (PF- EP), polyfluorene bearing lateral amino groups (PFN), polyfluorene bearing quaternary ammonium groups in the side chains (WPF-oxy-F), polyfluorene bearing quaternary ammonium groups in the side chains (WPF-6-oxy-F), fluorene alternating and random copolymer bearing cationic groups in the alkyl side chains (PFNBr DBT15), fluorene alternating and random copolymer bearing cationic groups in the alkyl side chains (PFPNBr), poly (ethylene oxide) (PEO), and fullerene derivatives. In certain embodiments, the electron transport layer is selected from the group consisting of C60, BCP, TiO2, SnO2, PCBM, ICBA, ZnO, ZrAcac, LiF, TPBI, PFN, Nb2O5, and a combination thereof.

[0121] Voids in photoactive layers solar cells may lead to shunting, which may reduce the performance of the solar cells. Accordingly, a perovskite solar cell (e.g., a solar cell in which one or more of the photoactive layers is a perovskite material) with photocured polymer segregated invoids of the perovskite material may have improved performance relative to a similar perovskite solar cell that does not include photocured polymer segregated in voids of a perovskite material. For example, a perovskite solar cell with photocured polymer segregated in voids of a perovskite material in the perovskite solar cell may have a greater power conversion efficiency (PCE), a greater open circuit voltage (VOC), a greater short-circuit current density (JSC), and / or a greater fill factor (FF) than a similar perovskite solar cell that does not include photocured polymer segregated in voids of a perovskite material.

[0122] Additionally, or alternatively, a perovskite solar cell with photocured polymer segregated in voids of a perovskite material in the perovskite solar cell may have a lower dark current than a similar perovskite solar cell that does not include photocured polymer segregated in voids of a perovskite material.

[0123] Additionally, or alternatively, a perovskite solar cell with photocured polymer segregated in voids of a perovskite material in the perovskite solar cell may maintain its performance for a longer time than a similar perovskite solar cell that does not comprise photocured polymer segregated in voids of a perovskite material.

[0124] In various embodiments, similar devices, such as similar perovskite solar cells, may include devices with one or more of the same components or one or more different components that provide the same functionality. In a non-limiting example, similar devices may both include a perovskite material, a TCO anode and / or a metal cathode.EMBODIMENTS

[0125] The subject matter described herein includes the following non-limiting embodiments:1. A perovskite composition, comprising: a perovskite material comprising photocured polymer segregated in one or more voids in the perovskite material, wherein the perovskite material comprises a first surface and a second surface that is parallel to the first surface.2. The perovskite composition of embodiment 1, wherein the voids are defects in the perovskite material.3. The perovskite composition of embodiment 2, wherein the defects extend through at least the first surface of the perovskite material.4. The perovskite composition of embodiment 2 or 3, wherein the defects comprise holes, pinholes, fractures, or combinations thereof.5. The perovskite composition of any one of embodiments 2-4, wherein the defects extend through the first surface of the perovskite material to the second surface of the perovskite material.6. The perovskite composition of any one of embodiments 1-5, wherein the first surface and the second surface of the perovskite material are substantially free of the photocured polymer.7. The perovskite composition of any one of embodiments 1-6, wherein the photocured polymer comprises a non-conductive material.8. The perovskite composition of any one of embodiments 1-7, wherein the photocured polymer is a polymer of one or more monomers or oligomers, wherein the one or more monomers or oligomers comprise an ester group, an epoxy group, a thiol group, or a vinyl group.9. The perovskite composition of embodiment 8, wherein the vinyl group is a vinyl ether.10. The perovskite composition of embodiment 8, wherein at least one of the one or more monomers or oligomers is an acrylate.11. The perovskite composition of embodiment 10, wherein the acrylate is a methacrylate oligomer.12. The perovskite composition of embodiment 11, wherein the methacrylate oligomer is poly(methyl methacrylate) (PMMA).13. The perovskite composition of any one of embodiments 1-12, wherein the photocured polymer is crosslinked.14. The perovskite composition of embodiment 13, wherein the photocured polymer is crosslinked with a crosslinker comprising two or more acrylate groups.15. The perovskite composition of embodiment 14, wherein the crosslinker is dipentaerythritol hexaacrylate (DPEHA).16. The perovskite composition of any one of embodiments 13-15, wherein the photocured polymer is crosslinked by ultraviolet (UV) or visible light.17. The perovskite composition of any one of embodiments 1-16, comprising a perovskite material comprising a photocured and crosslinked polymer of PMMA segregated in voids in the perovskite material, wherein the voids are defects in the perovskite material that extend through at least the first surface of the perovskite material, and wherein the first surface and the second surface of the perovskite material are substantially free of the photocured and crosslinked polymer of PMMA.18. A method of preparing the perovskite composition of any one of embodiments 1-17, comprising: contacting at least one of the voids in the perovskite material with a liquid prepolymer solution; curing the liquid prepolymer solution by exposure to UV light or visible light to form photocured polymer segregated in at least one void in the perovskite material; and optionally washing the first surface of the perovskite material.19. The method of embodiment 18, wherein the liquid prepolymer solution comprises a photoinitiator and one or more monomers or oligomers.20. The method of embodiment 19, wherein the photoinitiator is a cationic photoinitiator or a radical photoinitiator.21. The method of embodiment 20, wherein the photoinitiator is selected from the group consisting of an iodonium salt, a sulfonium salt, an ammonium salt, a phosphonium salt, an ammonium salt, a pyridinium salt, a diazonium salt, an iron complex, a germanium complex, a ruthenium complex, an iridium complex, a titanium complex, a phosphine oxide, a peroxide, an azo compound, and an aromatic ketone.22. The method of embodiment 21, wherein the photoinitiator is a diaryl iodonium salt, a triaryl sulfonium salt, a triaryl phosphonium salt, an aryl diazonium salt, a ferrocenium salt, a germanium ketone salt, a titanocene salt, or an acyl phosphine oxide.23. The method of embodiment 22, wherein the acyl phosphine oxide is diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO).24. The method of any one of embodiments 18-23, wherein the one or more monomers or oligomers comprise an ester group, an epoxy group, a thiol group, or a vinyl group.25. The method of embodiment 24, wherein the vinyl group is a vinyl ether.26. The method of embodiment 24, wherein at least one of the one or more monomers or oligomers is an acrylate.27. The method of embodiment 26, wherein the acrylate is a methacrylate oligomer.28. The method of embodiment 27, wherein the methacrylate oligomers is poly(methyl methacrylate) (PMMA).29. The method of any one of embodiments 18-28, wherein the photocured polymer is crosslinked.30. The method of embodiment 29, wherein the photocured polymer is crosslinked with a crosslinker comprising two or more acrylate groups.31. The method of embodiment 30, wherein the crosslinker is dipentaerythritol hexaacrylate (DPEHA).32. The method of any one of embodiments 18-31, wherein the liquid prepolymer solution further comprises a solvent.33. The method of embodiment 32, wherein the solvent is selected from the group consisting of propylene glycol monomethyl ether acetate (PGMEA), ether acetate (EA), isopropyl alcohol (IP A), toluene, and chlorobenzene.34. The method of embodiment 33, wherein the liquid prepolymer solution comprises diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as the photoinitiator, DPEHA as the crosslinker, PMMA as the oligomer, and PGMEA as the solvent.35. The method of any one of embodiments 18-34, wherein the contacting comprises coating at least the first surface of the perovskite material with the liquid prepolymer solution by blade coating, spin coating, dip coating, or soaking.36. The method of any one of embodiments 18-35, wherein the perovskite material masks the UV light or visible light to selectively cure the liquid prepolymer solution in contact with at least one of the voids.37. The method of any one of embodiments 18-36, wherein at least the first surface of the perovskite material is washed with a washing solvent after curing, optionally wherein the washing solvent is ethyl acetate.38. A device comprising a perovskite material, wherein the perovskite material comprises a photocured polymer segregated in one or more voids in the perovskite material, wherein the perovskite material comprises a first surface and a second surface that is parallel to the first surface, and wherein the second surface of the perovskite material is disposed on a first charge transport layer.39. The device of embodiment 38, wherein the first charge transport layer is disposed on a transparent substrate, wherein the transparent substrate comprises glass and / or a transparent conducting oxide (TCO).40. The device of embodiment 39, wherein the TCO is indium tin oxide (ITO).41. The device of embodiment 39 or 40, wherein the TCO comprises a first electrode.42. The device of any one of embodiments 38-41, wherein the first surface of the perovskite material is disposed on a second charge transport layer.43. The device of embodiment 42, wherein a second electrode is disposed on the second charge transport layer.44. The device of embodiment 43, wherein the device has a greater power conversion efficiency (PCE), a greater open circuit voltage (VOC), a greater short-circuit current density (JSC), and / or a greater fill factor (FF) than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.45. The device of embodiment 43 or 44, wherein the device has a lower dark current than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.46. The device of any one of embodiments 43-45, wherein the device maintains its performance for a longer time than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.47. A method of increasing production yield of a perovskite film, the method comprising: contacting at least one void in a perovskite film with a liquid prepolymer solution; and curing the liquid prepolymer solution by exposure to UV light or visible light to form photocured polymer segregated in the at least one void in the perovskite film, wherein the production yield of perovskite film is increased.EXAMPLESMaterials and Methods

[0126] Poly(methyl methacrylate) (PMMA), dipentaerythritol hexaacrylate (DPEHA), propylene glycol monomethyl ether acetate (PGMEA), diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA; number- averaged molecular mass, Mn=7, 000-10,000), bathocuproine (BCP), lead(ii) iodide (99.999% trace metals), lead(ii) bromide (99.999% trace metals basis), cesium iodide, N,N- dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 2-methoxyethanol (2-ME), toluene, chlorobenzene, methanol, ethanol, isopropyl alcohol (IP A), and ethyl acetate (EA) were purchased from Sigma Aldrich and used without further purification. Formamidine iodide was purchased from Great Cell Solar.

[0127] A range of PMMA / DPEHA / TPO crosslinking precursor concentrations (1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt% and 5.0 wt%) was dissolved in PGMEA. The weight ratio of PMMA / DPEHA / TPO was maintained at 1.0 / 1.1 / 0.2. To prevent exposure to light, the precursor was carefully packaged with aluminum foil.Device Fabrication

[0128] Patterned indium tin oxide (ITO) glass substrates were cleaned by acetone then UV- ozone treated for about 15 minutes before use. All perovskite solar devices were fabricated by blade coating at room temperature inside a fume hood with a relative humidity level of 30 ± 5%.

[0129] To create a charge transport layer (e.g., a hole transport layer), a solution of poly[bis(4- phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) with a concentration of 2.2 mg / mL was prepared in toluene and applied to the ITO glass substrate by blade coating. A 1.1 M FAo.9Cso.1Pbh perovskite precursor was formulated by directly mixing FAPbh in 2-ME, CsPbl.i in DMSO, and other additives in 2-ME. This solution was further diluted with 2-ME solvent prior to the blade coating process. Specifically, 0.23% v / v FAH2PO3, 2.3 mg / mL formamidinium chloride (FAQ), and 0.57 mg / mL cesium iodide (CsI) additives were introduced into the perovskite precursor solutions.

[0130] The precursor solution was then evenly blade-coated onto the substrates, with a constant movement speed of about 20 mm / s, following previously established procedures. Subsequently, the resulting film was annealed at 150 °C for a duration of 2.5-3 minutes in air to achieve a desired perovskite phase. In some examples, the desired perovskite phase may depend on the composition of the perovskite material.

[0131] Photovoltaic solar cells (PSCs) may be created by thermally evaporating about a 30 nm layer of carbon 60 fullerene (Ceo), about a 6 nm layer of bathocuproine (BCP), and about a 100 nm layer of copper. A fabrication process used for photovoltaic minimodules (also referred to as PSC minimodules) may closely followed that of a small cell. In various embodiments, laser scribing may be performed multiple times (e.g., twice). For example, laser scribing may be performed after the deposition of BCP and after the deposition of copper.Application process

[0132] Various coating methods may be used to deposit the crosslinking polymer onto perovskite films, including blade coating, spin coating, and dip coating. For the blade coating method, the precursor solution may be evenly spread onto the perovskite film with about a 300 pm gap, using a coating speed of about 20 mm / s. In the case of spin coating, the precursor solution may be applied to the perovskite film by spinning it at about 3000 rpm for 30 seconds. For dip coating, the perovskite film may be immersed in the precursor at room temperature for about 30seconds, followed by drying with an inert gas (e.g., nitrogen gas, argon gas). To initiate crosslinking of the polymer within voids of the perovskite material, a 365 nm 50 W UV LED may be applied for about 10 seconds from the ITO side. Remaining non-crosslinked polymer may be removed by immersing the films in EA (or PGMEA) for about 30 seconds, and then drying with nitrogen gas (or another inert gas, such has argon gas). In various embodiments, a post-curing step may be performed at 100°C for 10 minutes.Device characterization

[0133] Experiments to analyze the I-V characteristics of solar cells and minimodules utilized a solar simulator based on a xenon lamp (Oriel Sol3A, Class AAA Solar Simulator), with the simulated light intensity calibrated to 100 mW / cm2using a silicon reference cell (Newport 91150V-KG5).

[0134] All measurements were performed using a Keithley 2400 source meter without a temperature controller, with a scan rate of approximately 0.1 V / s for small cells and 0.5 V / s for minimodules. EQE spectra were obtained using a Newport QE measurement kit, focusing a monochromatic beam of light onto the devices. SEM images were captured using a Hitachi S-4700 cold cathode field emission scanning electron microscope. Transmittance and reflectance were measured using a LAMBDA 1050 UV / Vis / NIR spectrophotometer.Results and Discussion

[0135] During the manufacturing process of perovskite films, various types of voids (e.g., pinholes, cracks, fractures, scratches) may form and significantly reduce production yields. To reduce the impact of such voids and improve practical production efficiency, the techniques described herein may be used to fill the voids with an insulating material. For example, in accordance with the techniques described herein, a photo-initiated crosslinking polymer may be used to effectively fill (e.g., patches) voids in the perovskite film to prevent contact between the top and bottom electrodes, as shown in Figures 1A-1B.

[0136] In various embodiments, the crosslinking precursor may be prepared by dissolving polymethyl methacrylate (PMMA), diethylene glycol phenyl ether acrylate (DPEHA) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) in the solvent propylene glycol monomethyl ether acetate (PGMEA). TPO may be used as the initiator for the free radicalcrosslinking process. For example, when exposed to UV light, TPO generates free radicals (Figure 2B) to initiate the crosslinking of PMMA and DPEHA (Figures 2A and 2C). PMMA may be used as the crosslinking polymer, for example, because it has been shown to be effective as a passivation material for PSCs.

[0137] The process used to fill (e.g., patch) perovskite films may include three steps, as shown in Figures 3A-3C. First, the crosslinking precursor is applied to the perovskite film with a coating method such as blade coating, spin coating, or dip coating. Consequently, one surface of the perovskite film is in contact with a charge transport layer, which is in contact with a transparent conductive oxide / glass substrate. Next, light (e.g., UV light) is applied on the surface of the transparent conductive oxide / glass (e.g., indium tin oxide (ITO)). The transparent conductive oxide / glass substrate may be transparent to the light and, as such, the surface of the perovskite material in contact with the conductive oxide / glass substrate may be exposed to the light. The perovskite material may block (e.g., absorb or reflect) the light. Consequently, the light may only penetrate the perovskite film in areas of the perovskite film with voids (e.g., pinholes or cracks). Such voids may also be filled with the crosslinking precursor. In the areas that the light penetrates the perovskite film (e.g., in the voids filled with the crossing precursor) the light may initiate crosslinking to form an insulating polymer in those areas. In some examples, residual precursors that have not been crosslinked (e.g., unreacted crosslinking precursor, uncrosslinked material) may be removed using a solvent, such as EA or PGMEA.

[0138] Solvents used in the process may not damage the perovskite films. To determine the influence of solvents, the perovskite films were soaking in EA and PGMEA for 48 hr. The chemical structures of solvents EA and PGMEA are shown in Figure 4A. X-ray diffraction analysis (XRD) and scanning electron microscope (SEM) measurements were conducted on the treated perovskite films. From the XRD measurement shown in Figure 4B, both films soaked in EA and PGMEA maintained the same crystallinity and grain structures as the control films. The inset image represents the perovskite films after soaking process. The SEM images shown in Figures 4D-4F demonstrate that the perovskite films soaked in EA and PGMEA maintained the same grain size as the control film. Then, PSCs were fabricated with the PSCs with films which were soaked with EA or PGMEA for 60 seconds. Figure 4C shows the J-V curves of PSCs soaked in EA and PGMEA overlapped with that of the control film, confirming that EA and PGMEA donot damage perovskite films. For the crosslinking protocol, EA and PGMEA may be safely used as washing or process solvents, respectively.

[0139] The relationship between the precursor concentration and the resulting thickness of the crosslinking polymer is shown in Figure 5A. The film thickness exhibits a roughly linear relationship with the precursor concentration. In some examples, a 2.5 wt% precursor concentration was selected, resulting in a crosslinking polymer thickness of 550-650 nm, which is close to the thickness of the perovskite layer (approximately 700 nm). Figure 5B shows the relationship between the thickness of the crosslinked polymer and resistance, which increased exponentially. The resistance was measured for a simple structure of ITO / crosslinked polymer / Cu with an area of 0.08 cm2. For the 550 nm thick crosslinked PMMA by this method, the resistance is over 20k ohm. The increased resistance may be due to the thicker films providing better coverage.

[0140] Top view and cross-section view SEM images were collected of scratched perovskite films treated with crosslinking polymer (Figures 5C-F). The top view SEM (Figure 5C) exhibited clear perovskite grains with a grain size of approximately 1 um. Compared to the SEM image of a control film, the treated film exhibited a similar morphology. As shown in Figure 5D, no residual polymer was observed on the perovskite surface, indicating the EA washing process effectively removed any residual material from the perovskite film surface. The edge area of the scratched perovskite film showed a clear demarcation between the perovskite grain and the crosslinking polymer, indicating the crosslinking process only occurred under pinholes or scratched areas where UV light passed through. The strong adherence of the crosslinking polymer to the perovskite grain edges indicates better coverage over the broken area and demonstrates that the crosslinked polymer effectively serves the function of pinhole filling. Figure 5E shows a magnified view of the crosslinked polymer, revealing its compact and uniform nature with a film thickness of approximately 550nm (at the 2.5% wt. concentration). Finally, Figure 5F underscores the cleanliness of the perovskite grain, attributable to the thorough removal of residual non-crosslinked polymer during the ethyl acetate washing process. These comprehensive findings provide valuable insights into the effectiveness of the UV-initiated crosslinking method when applied to the perovskite film with induced needle scratches.

[0141] The UV-initiated crosslinking filling method has been developed to address the occurrence of voids (e g., pinholes or cracks) in perovskite films that typically arise during realindustrial production processes. To deliberately create such defects on the films, scratches were intentionally introduced using a needle, and the UV-initiated crosslinking fdling method was performed to treat the film as a part of the fabrication of the device. Figure 6A shows a schematic representation of the perovskite solar cells featuring needle-induced scratches. The copper electrode is indicated in the microscopic image under transmission mode as shown in Figure 6B and the center region represents the space between the two electrodes. Notably, the bright needle scratches are clearly visible in the film because of the much-reduced light absorption in the scratched region.

[0142] To showcase the effectiveness of the UV-initiated crosslinking filling method on PSCs, scratched devices (0.08 cm2) were measured after crosslinking polymer treatment. The resulting J-V characteristics of the PSCs are shown in Figure 6C and summarized in Table 1. The lower short-circuit current density (Jsc) of 23.0 mA / cm2for device 1 and 22.6 mA / cm2for device 2 is due to the mechanical damage of perovskite film which reduced the active area. The statistical distribution of nine devices is shown in Figures 6D-6G. All the devices exhibited a Voc over 1.07 and none of devices shorted. This indicates the crosslinking polymer could well fill the scratched gap. The dark current at -0.1 V of the devices was between 10’7and 10’8A as shown in Figure 6H. The low dark current indicates a good coverage of crosslinked polymer over the scratched area. Using these devices, the impact of the crosslinking material on the long-term stability of the perovskite solar cells may be evaluated. The unencapsulated devices were tested under LED light with 1 Sun light intensity at 85 °C in a glovebox filled with N2 for 48 h to simulate aging. The open-circuit voltage (Voc) of scratched and patched PSCs increased and the fill factor (FF) and Jsc were maintained, indicating that the crosslinking polymer did not reduce the stability of PSCs.

[0143] Table 1. Photovoltaic parameters of scratched solar cells treated with UV-initiated crosslinking method.

[0144] To evaluate the effect of pinhole patching in real devices, relatively large area PSCs (1 cm2) were fabricated with and without crosslinked polymer. As shown in Figure 7A, a typical bad control solar cell without UV-initiated crosslinked polymer showed a Voc of 1.05 V, a Jsc of 24.7mA / cm2, a FF of 59.2% and a PCE of 15.3% under air mass (AM) 1.5 global (G) one-sun illumination. With the crosslinked polymer patching, the resulting PCE was improved to 21.7%, along with an enhanced Voc of 1.14 V, a maintained Jsc of 25.0 mA / cm2and an improved FF of 76%. The efficiency statistics are shown in Figure 7B. The treatment not only increased the device performance, but also improved the yield of good devices. In other words, the treatment may lead to an improved yield of functional devices produced (e.g., in increase in the quantity of devices produced via the techniques described herein) and / or an improved photoproduction yield of the functional devices (e.g., an increased PCE).

[0145] For the treated devices, 85% of devices had over 15% PCE, while only 10% of control devices had over 15% PCE. The corresponding dark J-V is shown in Figure 7C and the statistical distribution of dark current at -0.2 V is shown in Figure 7D. The corresponding dark currents at - 0.2 V were 2.6 x IO'3A and 2x10'7A. The dark current of devices with crosslinked polymer were 100 times lower than the control devices. From the statistical distribution, the dark current of treated PSCs was between the range of 10’6and 10‘7A, while majority of control devices had dark currents between 10'2and 10'3A, which indicates a relatively serious current leakage.

[0146] As illustrated in Figures 7E and 7F, various coating methods may be used to deposit the UV-initiated crosslinking precursor, including blade coating, spin coating and dip coating. The corresponding photovoltaic performance parameters are summarized in Table 2. The UV-initiated crosslinking method demonstrated good performance with all three coating methods. Of the PSCs fabricated with crosslinked polymer, 91% of those applied via blade coating crosslinking precursor, 83% via spin coating crosslinking precursor, and another 83% via dip coating crosslinking precursor exhibited efficiencies over 21%, respectively.

[0147] Table 2. Photovoltaic parameters of solar cells (e.g., champion solar cells) with UV- initiated crosslinking material made from different coating methods.

[0148] To evaluate the scalability of this method, perovskite mini modules were fabricated with the same UV-initiated crosslinking method. Figure 7A shows the scratched module with an aperture area of 36 mm x 55 mm (19.8 cm2) and 6 sub-cells. The aperture PCE of the controlmodule was 13.3% with a Voc of 6.4V (1.07 V for each sub-cell), a short-circuit current (Isc) of 62.8 mA (photocurrent density as 19.0mA / cm2) and an FF of 65.4%. The reduced PCE is due to the reduction of aperture area and FF.

[0149] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which the inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMSWhat is claimed is:

1. A perovskite composition, comprising: a perovskite material comprising photocured polymer segregated in one or more voids in the perovskite material, wherein the perovskite material comprises a first surface and a second surface that is parallel to the first surface.

2. The perovskite composition of claim 1, wherein the voids are defects in the perovskite material.

3. The perovskite composition of claim 2, wherein the defects extend through at least the first surface of the perovskite material.

4. The perovskite composition of claim 2, wherein the defects comprise holes, pinholes, fractures, or combinations thereof.

5. The perovskite composition of claim 2, wherein the defects extend through the first surface of the perovskite material to the second surface of the perovskite material.

6. The perovskite composition of any one of claims 1-5, wherein the first surface and the second surface of the perovskite material are substantially free of the photocured polymer.

7. The perovskite composition of claim 1, wherein the photocured polymer comprises a non-conductive material.

8. The perovskite composition of claim 1, wherein the photocured polymer is a polymer of one or more monomers or oligomers, wherein the one or more monomers or oligomers comprise an ester group, an epoxy group, a thiol group, or a vinyl group.

9. The perovskite composition of claim 8, wherein the vinyl group is a vinyl ether.

10. The perovskite composition of claim 8, wherein at least one of the one or more monomers or oligomers is an acrylate.

11. The perovskite composition of claim 10, wherein the acrylate is a methacrylate oligomer.

12. The perovskite composition of claim 11, wherein the methacrylate oligomer is poly(methyl methacrylate) (PMMA).

13. The perovskite composition of claim 1, wherein the photocured polymer is crosslinked.

14. The perovskite composition of claim 13, wherein the photocured polymer is crosslinked with a crosslinker comprising two or more acrylate groups.

15. The perovskite composition of claim 14, wherein the crosslinker is dipentaerythritol hexaacrylate (DPEHA).

16. The perovskite composition of claim 13, wherein the photocured polymer is crosslinked by ultraviolet (UV) or visible light.

17. The perovskite composition of any one of claims 1-16, comprising a perovskite material comprising a photocured and crosslinked polymer of PMMA segregated in voids in the perovskite material, wherein the voids are defects in the perovskite material that extend through at least the first surface of the perovskite material, and wherein the first surface and the second surface of the perovskite material are substantially free of the photocured and crosslinked polymer of PMMA.

18. A method of preparing the perovskite composition of claim 1, comprising: contacting at least one of the voids in the perovskite material with a liquid prepolymer solution;curing the liquid prepolymer solution by exposure to UV light or visible light to form photocured polymer segregated in at least one void in the perovskite material; and optionally washing the first surface of the perovskite material.

19. The method of claim 18, wherein the liquid prepolymer solution comprises a photoinitiator and one or more monomers or oligomers.

20. The method of claim 19, wherein the photoinitiator is a cationic photoinitiator or a radical photoinitiator.

21. The method of claim 20, wherein the photoinitiator is selected from the group consisting of an iodonium salt, a sulfonium salt, an ammonium salt, a phosphonium salt, an ammonium salt, a pyridinium salt, a diazonium salt, an iron complex, a germanium complex, a ruthenium complex, an iridium complex, a titanium complex, a phosphine oxide, a peroxide, an azo compound, and an aromatic ketone.

22. The method of claim 21, wherein the photoinitiator is a diaryl iodonium salt, a triaryl sulfonium salt, a triaryl phosphonium salt, an aryl diazonium salt, a ferrocenium salt, a germanium ketone salt, a titanocene salt, or an acyl phosphine oxide.

23. The method of claim 22, wherein the acyl phosphine oxide is diphenyl(2,4,6- trimethylbenzoyl) phosphine oxide (TPO).

24. The method of any one of claims 18-23, wherein the one or more monomers or oligomers comprise an ester group, an epoxy group, a thiol group, or a vinyl group.

25. The method of claim 24, wherein the vinyl group is a vinyl ether.

26. The method of claim 24, wherein at least one of the one or more monomers or oligomers is an acrylate.

27. The method of claim 26, wherein the acrylate is a methacrylate oligomer.

28. The method of claim 27, wherein the methacrylate oligomers is poly(methyl methacrylate) (PMMA).

29. The method of any one of claims 18-28, wherein the photocured polymer is crosslinked.

30. The method of claim 29, wherein the photocured polymer is crosslinked with a crosslinker comprising two or more acrylate groups.

31. The method of claim 30, wherein the crosslinker is dipentaerythritol hexaacrylate (DPEHA).

32. The method of any one of claims 18-31, wherein the liquid prepolymer solution further comprises a solvent.

33. The method of claim 32, wherein the solvent is selected from the group consisting of propylene glycol monomethyl ether acetate (PGMEA), ether acetate (EA), isopropyl alcohol (IP A), toluene, and chlorobenzene.

34. The method of claim 33, wherein the liquid prepolymer solution comprises diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as the photoinitiator, DPEHA as the crosslinker, PMMA as the oligomer, and PGMEA as the solvent.

35. The method of any one of claims 18-34, wherein the contacting comprises coating at least the first surface of the perovskite material with the liquid prepolymer solution by blade coating, spin coating, dip coating, or soaking.

36. The method of any one of claims 18-35, wherein the perovskite material masks the UV light or visible light to selectively cure the liquid prepolymer solution in contact with at least one of the voids.

37. The method of any one of claims 18-36, wherein at least the first surface of the perovskite material is washed with a washing solvent after curing, optionally wherein the washing solvent is ethyl acetate.

38. A device comprising a perovskite material, wherein the perovskite material comprises a photocured polymer segregated in one or more voids in the perovskite material, wherein the perovskite material comprises a first surface and a second surface that is parallel to the first surface, and wherein the second surface of the perovskite material is disposed on a first charge transport layer.

39. The device of claim 38, wherein the first charge transport layer is disposed on a transparent substrate, wherein the transparent substrate comprises glass and / or a transparent conducting oxide (TCO).

40. The device of claim 39, wherein the TCO is indium tin oxide (ITO).

41. The device of claim 39 or 40, wherein the TCO comprises a first electrode.

42. The device of any one of claims 38-41, wherein the first surface of the perovskite material is disposed on a second charge transport layer.

43. The device of claim 42, wherein a second electrode is disposed on the second charge transport layer.

44. The device of claim 43, wherein the device has a greater power conversion efficiency (PCE), a greater open circuit voltage (VOC), a greater short-circuit current density (Jsc), and / or a greater fill factor (FF) than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.

45. The device of claim 43 or 44, wherein the device has a lower dark current than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.

46. The device of any one of claims 43-45, wherein the device maintains its performance for a longer time than a similar device that does not comprise photocured polymer segregated in voids of a perovskite material.

47. A method of increasing production yield of a perovskite film, the method comprising: contacting at least one void in a perovskite film with a liquid prepolymer solution; and curing the liquid prepolymer solution by exposure to UV light or visible light to form photocured polymer segregated in the at least one void in the perovskite film, wherein the production yield of perovskite film is increased.

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