Methods of fabricating compositions containing metal oxide and / or metalloid oxide particles, such as colloidal dispersions and INKS, and related products and systems

Abstract

Methods of fabricating compositions containing metal oxide and / or metalloid oxide particles, such as colloidal dispersions and inks, and related products and systems are generally described.

Description

[0001] METHODS OF FABRICATING COMPOSITIONS CONTAINING METAL OXIDE AND / OR METALLOID OXIDE PARTICLES, SUCH AS COLLOIDAL DISPERSIONS AND INKS, AND RELATED PRODUCTS AND SYSTEMS

[0002] RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 671,890, filed July 16, 2024, and entitled “METHODS OF FABRICATING COMPOSITIONS CONTAINING METAE OXIDE PARTICLES, SUCH AS DISPERSIONS AND INKS, AND RELATED PRODUCTS AND SYSTEMS,” and to U.S. Provisional Patent Application No. 63 / 782,224, filed April 2, 2025, and entitled “METHODS OF FABRICATING COMPOSITIONS CONTAINING METAL OXIDE PARTICLES, SUCH AS DISPERSIONS AND INKS, AND RELATED PRODUCTS AND SYSTEMS,” each of which is incorporated herein by reference in its entirety for all purposes.

[0004] TECHNICAL FIELD

[0005] Methods of fabricating compositions containing metal oxide and / or metalloid oxide particles, such as colloidal dispersions and inks, and related products and systems are generally described.

[0006] SUMMARY

[0007] Methods of fabricating compositions containing metal oxide and / or metalloid oxide particles, such as colloidal dispersions and inks, and related products and systems are generally described. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles.

[0008] Some aspects are related to methods.

[0009] In some embodiments, the method is a method of synthesizing particles. In some embodiments, the method comprises adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the solution to form a suspension; and reacting the solid particles with a reactant capable of undergoing hydrolysis.

[0010] In some embodiments, the method comprises adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations by adding an acid such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the solution to form a suspension; and reacting the solid particles with a base.

[0011] Some aspects are related to colloidal dispersions.

[0012] In some embodiments, the colloidal dispersion comprises solid particles comprising a metal oxide and / or a metalloid oxide in a solvent; wherein the solid particles are stable in the colloidal dispersion such that, after 24 hours at 20 degrees C, less than 1% of the particles by number of the colloidal dispersion are part of an aggregate having a maximum cross-sectional dimension of greater than or equal to 100 nanometers.

[0013] Certain aspects are related to methods of synthesizing particles. In some embodiments, the method comprises adjusting a pH of an aqueous solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the cations precipitate out of the aqueous solution; and reacting the solid particles with a reactant capable of undergoing hydrolysis.

[0014] Some aspects are related to methods of synthesizing colloidal particle dispersions. The method comprises, in some embodiments, adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the cations precipitate out of the solution; and reacting the precipitate with a reactant capable of undergoing hydrolysis, resulting in the precipitate being colloidally dispersed as particles in a solvent.

[0015] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. FIG. 1A is an example method flow diagram, in accordance with some embodiments.

[0018] FIG. IB is an example method flow diagram, in accordance with some embodiments.

[0019] FIG. 1C is a cross-sectional schematic diagram of a substrate on which a layer comprising particles has been coated, according to some embodiments.

[0020] FIG. ID is a cross-sectional schematic diagram of a voltaic device, in accordance with some embodiments.

[0021] FIG. IE is a cross-sectional schematic diagram of an exemplary perovskite solar cell layer sequence, in accordance with some embodiments.

[0022] FIG. IF shows a cross-sectional schematic illustration of a sensor, according to some embodiments.

[0023] FIG. 1G shows a cross-sectional schematic illustration of an electrode with a charge transporting layer for use in a fuel cell, according to some embodiments.

[0024] FIG. 1H shows a cross-sectional schematic illustration of a laser, according to some embodiments.

[0025] FIG. 2 is an optical image of vials containing various metal oxide and / or metalloid oxide inks, according to some embodiments.

[0026] FIG. 3 is a plot of a current- voltage measurement of perovskite solar cells using an electron transport layer as described herein and an electron transport layer formed via chemical bath deposition, in accordance with some embodiments.

[0027] FIG. 4 shows a transmission electron microscope image of SnO2 nanocrystals, according to some embodiments.

[0028] FIG. 5A and 5B show transmission electron microscope image of SnO2 nanocrystals from a basic water-based colloidal SnO2 dispersion, in accordance with some embodiments.

[0029] FIG. 6 shows a transmission electron microscope image of SnO2 nanocrystals from a colloidal SnO2 dispersion in acetic anhydride, in accordance with some embodiments.

[0030] FIG. 7 shows tin oxide particle-containing colloidal dispersions in acetic anhydride mixed with various solvents, including: water, methanol, ethanol, acetonitrile (ACN), tetrahydrofuran (THF), isopropanol (IPA), diethyl ether (Et2O), acetone, or 1-octanol, in accordance with some embodiments.

[0031] FIG. 8 shows a plot of transmittance as a function of particle aggregation in colloidal dispersions, in accordance with some embodiments.

[0032] DETAILED DESCRIPTION Methods of fabricating compositions containing metal oxide and / or metalloid oxide particles, such as colloidal dispersions and inks, and related products and systems are generally described. In certain aspects, colloidal dispersions containing particles are described. The colloidal dispersions are, in accordance with certain embodiments, useful for the fabrication of metal oxide coatings. The colloidal dispersions are, in accordance with certain embodiments, useful for the fabrication of metalloid oxide coatings. In certain embodiments, metal oxidecontaining layers and / or metalloid oxide-containing layers are used, for example, in the fabrication of perovskite solar cells, such as in charge transport layers of such cells.

[0033] It can be desirable to disperse metal oxide or metalloid oxide particles in organic solvents as they can be used to fabricate uniform films via a variety of methods. Metal oxide and metalloid oxide particles, however, are typically not easily dissolved in organic solvents, and they can react undesirably with the organic solvents. Some previous methods for forming colloidal dispersions utilize precursor compounds that are relatively unstable. For instance, some previous methods for making SnCh particle-containing colloidal dispersions begin with a tin tetrachloride precursor, require a 12-hour aging process, and then necessitate a nanoparticle drying step. Some previous methods include reacting the dried SnCh particles with acetic acid to functionalize the particles and stabilize the particles in the colloidal dispersion in the organic solvent (i.e., in the acetic acid).

[0034] Advantageously, certain of the methods described herein utilize low cost precursors, do not require a prolonged aging process, and do not involve a drying process of the nanoparticles prior to the surface functionalization.

[0035] Moreover, certain of the methods described herein include using a reactant capable of undergoing hydrolysis, such as acetic anhydride. Typical methods did not consider using a reactant capable of undergoing hydrolysis, as the reactant does not mix with water is reactive with water. The reactivity with water typically would be considered undesirable, as the decomposition of the reactant into its hydrolysis product is seemingly wasteful. The reactivity with water is unexpectedly desirable, in some embodiments, as reacting the particles with the reactant capable of undergoing hydrolysis may also result in reacting the reactant with any residual water on the particles. Moreover, the reaction with water, in some embodiments, may provide a solution that is substantially free of water or free of water, which may stabilize the particles therein. Substantially free of water or free of water, in this context, means that the water is present in an amount of less than 0.1 wt%, less than 0.01 wt%, or less than 0.001 wt% of the total solution weight, and / or is undetectable by coulometric Karl Fischer titration. This may facilitate subsequent integration of the particles into a device (e.g., as a layer of a device). Improved stability of the particles, in some embodiments, may facilitate a solvent exchange and thus the production of colloidal metal oxide and / or metalloid oxide particles in organic solvents.

[0036] Certain of the methods described herein include reacting the particles with a base, such as potassium hydroxide, in accordance with some embodiments. Advantageously, in some embodiments, reacting the particles with a base electrostatically stabilizes the particles. For instance, in some embodiments, the particles are hydroxyl terminated, and reacting the particles with a base results in a negatively charged oxygen group on the particles, thereby electrostatically stabilizing the particles. Such stabilization, in some embodiments, facilitates storage of the colloidal dispersions containing the particles and / or use of the particles over long times. In contrast, typical methods using a base for synthesizing nanoparticle-based colloidal dispersions start with complex synthetic protocols, e.g., such as flame spray pyrolysis or prolonged reactions starting from tin tetrachloride, leading to high costs and difficulty scaling the synthesis. Furthermore, typical methods include stabilizing ligands comprising nitrogen, which is absent in some embodiments described herein.

[0037] While colloidal dispersions in an aqueous base, in some embodiments, facilitate the use of non-organic solvents with a small carbon footprint, depositing such colloidal dispersions (e.g., in the form of a film) via slot-die coating or other typical methods is challenging and limits the choice of suitable substrates (e.g., due to compatibility with the solvent). Accordingly, some methods described herein include purifying the particles and / or exchanging a solvent of the colloidal dispersions, e.g., to facilitate deposition of the particles, in accordance with some embodiments.

[0038] Certain previous methods of generating particles make use of hot- injection and / or heatup synthesis methods. Hot- injection and heat-up synthesis are reactions where bonds need to be broken and rearranged. Therefore, higher temperatures are typically chosen. Other methods, such as precipitation and co-precipitation, usually change the pH dropwise. Afterward, the particles are separated from the solvent and annealed at higher temperatures (usually for crystallization and calcination). The sol-gel method leads to dispersed nanoparticles, which form a network after some time (e.g., a porous solid built from nanomaterials).

[0039] Certain of the methods described herein synthesize particles (e.g., nanoparticles) by precipitation, but using methods by which the particles are put back into a colloidal dispersion. The formation of a colloidal dispersion can be important for the fabrication of high-quality thin films. Surprisingly, in accordance with certain embodiments, crystalline and rather monodisperse, small nanocrystals were fabricated.

[0040] A dispersion, as used in the context of this disclosure, is a system in which particles of one material are distributed in a continuous medium, and the particles are not soluble in the medium. A suspension, as used in the context of this disclosure, is a specific type of dispersion where solid particles are dispersed in a liquid. The particles and / or particle aggregates in a suspension, in some cases, are large enough for the particles to sediment from the liquid. A colloidal dispersion (also called colloid), as used in the context of this disclosure, is a substantially heterogeneous dispersion and is also a suspension in which the particles are sufficiently small such that they remain suspended and distributed within the continuous phase rather than dissolving or settling out.

[0041] In some embodiments, the method comprises adjusting a pH of an aqueous solution comprising solubilized metal cations and / or metalloid cations by adding an acid such that solid particles containing at least some of the cations precipitate out of the aqueous solution; and reacting the solid particles with a base. For instance, FIG. IB shows method 101 which is similar to method 100 in FIG. 1A, but includes adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations by adding an acid such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the solution 103.

[0042] In some embodiments, the method includes forming a solution comprising solubilized metal cations and / or metalloid cations. In some embodiments, the solution comprises water. In some embodiments, a metal and / or metalloid cation containing precursor compound is added to the solution. In some embodiments, the precursor compound is soluble in the solution (e.g., at least 1 gram of the compound is dissolvable in 5 mL of the solution).

[0043] Desirably, in accordance with some embodiments, the metal oxide and / or metalloid oxide precursor is relatively non-toxic, for instance, compared to typical precursors used to synthesize metal oxide and / or metalloid oxide particles. In some embodiments, the precursor comprises a metal oxide, a metal hydroxide, a metalloid oxide, and / or a metalloid hydroxide. In some embodiments, the precursor comprises a metal halide and / or a metalloid halide. Nonlimiting examples of precursors that may be added to a solution include Na2SnO3, Na2SiO3, Na2WO4, manganese(II) chloride, nickel(II) acetate tetrahydrate, calcium iodide, copper(II) acetate monohydrate, and indium(III) chloride. Other precursors are also possible.

[0044] The disclosed synthesis can be useful for various metal oxide and / or metalloid oxide nanoparticles and inks. The method works, in accordance with certain embodiments, with alkaline earth, lanthanoids, actinoids, transition metals, post-transition metals, and metalloids forming the corresponding oxides / hydroxides.

[0045] Metal ions generally have a high affinity to oxygen and corresponding metal oxide and / or metalloid oxide nanoparticles have surfaces terminated with surface hydroxyl groups, in accordance with certain embodiments. In some embodiments, some or all of the metal ions in the solution include a hydroxyl functional group due to the affinity with oxygen. The particle surfaces in water-based suspensions are generally difficult to functionalize. The particle surfaces in water-based suspensions are also generally difficult to stabilize.

[0046] Here, in accordance with some embodiments, a method for preparing colloidal dispersions and nanoparticle inks for metal oxide and / or metalloid oxide coatings is disclosed. Metal oxides and / or metalloid oxides cannot generally be easily dissolved in (organic) solvents as they either are not soluble, or react with the solvent forming metal-organic materials. Colloidally dispersed materials in organic solvents are highly desired for the fabrication of uniform metal oxide and / or metalloid oxide films by, e.g., printing, blade coating, slot-die coating, and / or spin coating.

[0047] Certain aspects are related to methods of synthesizing particles. In some embodiments, the method comprises adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the aqueous solution to form a suspension; and reacting the solid particles with a reactant capable of undergoing hydrolysis. In some embodiments, the method further includes reacting the solid particles with an acid. In some embodiments, the method comprises adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations by adding an acid such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the aqueous solution to form a suspension; and reacting the solid particles with a base. In some embodiments, the method includes reacting the solid particles with an acid and / or a reactant capable of undergoing hydrolysis. In some embodiments, the solution of the method is an aqueous solution.

[0048] Some aspects are related to methods of synthesizing particles and forming colloidal particle dispersions. The method comprises, in some embodiments, adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the cations precipitate out of the solution to form a suspension; and reacting the precipitate with a reactant capable of undergoing hydrolysis and / or with an acid, resulting in the precipitate being colloidally dispersed as particles in a solvent. In certain embodiments, the solution comprising the solubilized metal cations and / or metalloid cations is an aqueous solution.

[0049] FIG. 1A shows an example method flow diagram showing example method 100. In some embodiments, the method includes adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the aqueous solution to form a suspension 102. In some embodiments, adjusting a pH comprises modifying a pH of the solution until solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the aqueous solution to form a suspension. In some embodiments, adjusting the pH comprises adding an acid and / or a base to the solution. In some instances, adjusting the pH comprises adding an acid to the solution such that the pH is lowered. In some instances, adjusting the pH comprises adding a base to the solution such that the pH is raised.

[0050] Any of a variety of acids and bases are suitable for adjusting the pH of the solution, in accordance with some embodiments. In some embodiments, adding an acid and / or a base may alter a solubility of the metal and / or metalloid cation. In some embodiments, adding an acid may protonate a solubilized hydrated metal ion and / or reduce the metal and / or metalloid cation complex in solution. In some embodiments, adding a base may oxidize and / or form an oxide and / or hydroxide of the hydrated metal and / or metalloid cation complex. In some embodiments, the acid is a Bronsted-Lowry acid. In some embodiments, the acid comprises hydrochloric acid. In some embodiments, the acid is an organic acid. In some embodiments, the acid comprises acetic acid. In some embodiments, the base comprises a Bronsted-Lowry base. In some embodiments, the base comprises a hydroxide. In some embodiments, the base comprises an alkali metal hydroxide, for instance, LiOH, NaOH, KOH, RbOH, and / or CsOH. In some instances, the base comprises ammonium hydroxide. In some embodiments, the base is an organic base, for instance, an alkoxide, an amide, and / or an amine.

[0051] In some embodiments, the change in the pH of the solution may be at least 1, at least 2, at least 3, at least 4, at least 5, and / or up to 6, up to 7, up to 8, or up to 9 pH units. As a nonlimiting example, in some embodiments, an initial pH of the solution is approximately 11, and the pH of the solution is adjusted to approximately 2.5 by adding acetic acid.

[0052] In some embodiments, adjusting the pH of the solution alters the solubility of the solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the cations precipitate out of the solution to form a suspension. In some embodiments, precipitating out of the solution to form a suspension comprises forming a solid phase (e.g., solid particles) from the solubilized metal cations and / or metalloid cations. In some embodiments, the solid phase comprises the metal cations and / or metalloid cations, e.g., in the form of a salt (e.g., a metal oxide, a metal halide, a metalloid oxide, a metalloid halide, etc.). In some embodiments, the solid phase comprises the metal and / or metalloid from the cations, e.g., in a reduced form such as a metallic phase. In some embodiments, the particles comprise SnxOy(e.g., SnCh), MoxOy (e.g., MoOa), CuxOy (e.g., CuO), MnxOy(e.g., MnO), NixOy(e.g., NiO), InxOy(e.g., I112O3), W Oy (e.g., WO3), and / or SixOy(e.g., SiCh). In some embodiments, the solid particles comprise SnxOy(e.g., SnCh), MoxOy(e.g., MoOs), CuxOy(e.g., CuO), MnxOy(e.g., MnO), NixOy(e.g., NiO), InxOy (e.g., h Os), WxOy(e.g., WO3), and / or SixOy(e.g., SK ). In some embodiments, the particles comprise SnxOy, MoxOy, CuxOy, MnxOy, NixOy, InxOy, WxOy, and / or SixOy, wherein x is 1 or 2 and y is 1, 2, or 3. In some embodiments, the particles comprise SnxOy(e.g., SnO2). In some embodiments, the particles comprise MoxOy(e.g., MoOs). In some embodiments, the particles comprise CuxOy(e.g., CuO). In some embodiments, the particles comprise MnxOy(e.g., MnO). In some embodiments, the particles comprise NixOy(e.g., NiO). In some embodiments, the particles comprise InxOy(e.g., I112O3). In some embodiments, the particles comprise WxOy(e.g., WO3). In some embodiments, the particles comprise SixOy(e.g., SiO2). It will be understood that, in some embodiments, the metal oxide and / or metalloid oxide particles may include a surface that is terminated with one or more hydroxyl functional groups due to the affinity of the metal and / or metalloid with water and / or hydroxide ions in solution.

[0053] In some embodiments, the particles are nanoparticles (e.g., having maximum cross- sectional dimensions of less than or equal to 1 micron, less than or equal to 100 nanometers, less than or equal to 50 nanometers, or less than or equal to 10 nanometers (and / or as little as 5 nanometers, as little as 2 nanometers, or as little as 1 nanometer).

[0054] In some embodiments, the plurality of particles has an average maximum cross-sectional dimension of less than or equal to 1 micron, less than or equal to 100 nanometers, less than or equal to 50 nanometers, less than or equal to 10 nanometers, less than or equal to 5 nanometers, less than or equal to 2 nanometers, or less than or equal to 1 nanometer. In some embodiments, the plurality of particles has an average maximum cross-sectional dimension of greater than or equal to 0.5 nanometers, greater than or equal to 1 nanometer, greater than or equal to 2 nanometers, greater than or equal to 5 nanometers, greater than or equal to 10 nanometers, greater than or equal to 50 nanometers, greater than or equal to 100 nanometers, or greater than or equal to 500 nanometers. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 0.5 nanometers and less than or equal to 1 micron). Other ranges are also possible. The “average maximum cross-sectional dimension” of a plurality of particles is the number average of the individual maximum cross-sectional dimensions of those particles.

[0055] In some embodiments, at least 80%, at least 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%, or all of the total volume of the particles is made up of particles having a maximum cross-sectional dimension of less than or equal to 1 micron, less than or equal to 100 nanometers, less than or equal to 50 nanometers, less than or equal to 10 nanometers, less than or equal to 5 nanometers, less than or equal to 2 nanometers, or less than or equal to 1 nanometer. In some embodiments, at least 80%, at least 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%, or all of the total volume of the particles is made up of particles having a maximum cross-sectional dimension of greater than or equal to 0.5 nanometers, greater than or equal to 1 nanometer, greater than or equal to 2 nanometers, greater than or equal to 5 nanometers, greater than or equal to 10 nanometers, greater than or equal to 50 nanometers, greater than or equal to 100 nanometers, or greater than or equal to 500 nanometers. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 0.5 nanometers and less than or equal to 1 micron). Other ranges are also possible.

[0056] In some embodiments, the particles are monodisperse. For instance, in some embodiments, for at least 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%, or all of the particles, the maximum cross-sectional dimension of the particle deviates by no more than 100%, no more than 75%, no more than 50%, no more than 25%, no more than 10%, or no more than 5% from the average maximum cross-section dimension of the plurality of particles.

[0057] The particles synthesized using the processes described herein can be crystalline, in some embodiments. For example, in some embodiments, the particles comprise polycrystalline particles. In certain embodiments, the particles comprise single crystalline particles. In some embodiments, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%, at least 99.999%, at least 99.9999%, at least 99.99999%, at least 99.999999%, or all of the particles are polycrystalline or single crystalline. In some embodiments, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%, at least 99.999%, at least 99.9999%, at least 99.99999%, at least 99.999999%, or all of the particles are single crystalline.

[0058] The particles synthesized using the processes described herein can be amorphous, in some embodiments.

[0059] In some embodiments, the particles synthesized using the methods described herein can be relatively small and relatively monodisperse. For example, in some embodiments, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%, at least 99.999%, at least 99.9999%, at least 99.99999%, at least 99.999999%, or all of the particles have a maximum cross-sectional dimensions of less than or equal to 100 nanometers, less than or equal to 50 nanometers, less than or equal to 10 nanometers, or less than or equal to 5 nanometers (and / or as little as 3 nanometers, as little as 2 nanometers, or as little as 1 nanometer).

[0060] Referring again to method 100 in FIG. 1A, in some embodiments, the method further includes allowing the solid particles to settle out of the suspension 104. In some embodiments, the particles settle out of the suspension when the suspension is left unattended (e.g., crash out of the suspension). In some embodiments, the method includes actively removing the particles from the suspension. In some embodiments, the method includes actively removing excess solvent from the particle suspension by centrifugation or filtering. In some embodiments, removing the particles comprises centrifuging the suspension comprising the solid particles. It will be understood that the suspension and the solid particles are contained within a container, e.g., a vial, a flask, and / or a beaker, in some embodiments. Allowing the solid particles to settle out of suspension and / or removing the particles from suspension may provide an accumulated solid (e.g., settled solid, such as sediment) comprising the solid particles separate from a supernatant containing most of the solvent within the container, in accordance with some embodiments.

[0061] In some instances, the method 100 shown in FIG. 1A includes decanting excess solution (e.g., solvent, the supernatant) from solid particles 106. In some instances, the method includes decanting excess solution (e.g., solvent, the supernatant) from the accumulated solid containing the solid particles.

[0062] In some embodiments, the method includes washing the particles. In some embodiments, the particles are washed with water (e.g., deionized water). In some embodiments, washing the particles before any further reacting steps (e.g., before reacting with a reactant capable of undergoing hydrolysis) may advantageously improve the purity of the final colloidal dispersion. Without wishing to be bound by any particular theory, it is believed that washing the particles (e.g., with deionized water) returns the solution to a near-neutral pH, which prevents or reduces the amount of byproducts and / or unreacted educts in solution, thereby resulting in stable colloidal nanoparticle dispersions and films made therefrom.

[0063] Washing may proceed subsequent to decanting the solution, in some embodiments, by adding a washing solution. In some embodiments, the washing solution comprises water (e.g., deionized water). Other washing solutions are also possible, for example, sequentially and / or following other steps described herein (e.g., after one or more reacting steps, after exchanging a solvent, etc.). In some embodiments, after adding the washing solution, the settled particles may be suspended within the washing solution, e.g., by shaking, vortexing, stirring, or any other suitable method. In some embodiments, mixing the settled particles with the washing solution will form a suspension, which may again be allowed to settle and the excess washing solution may then be decanted off. In some embodiments, the washing steps may be performed a single time, or may be repeated any suitable number of times (e.g., at least twice, at least 3 times, or at least 5 times and / or no more than 10 times). Similarly to the initial decanting, the last washing step may be decanting any excess washing solution (e.g., from a supernatant) from settled particles to provide an accumulated solid (e.g., settled solid, such as sediment) comprising the particles, in some embodiments. Decanting in such a manner may decrease the amount of water present before adding the reactant capable of undergoing hydrolysis, in accordance with some embodiments.

[0064] In some embodiments, the method comprises adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the cations precipitate out of the solution to form a suspension; and reacting the precipitate with a base, resulting in the precipitate being colloidally dispersed as particles in a solvent. In some embodiments, the method comprises reacting the precipitate with a base. Referring again to FIG. IB, the method 101 includes, in some embodiments, reacting the precipitate with a base as shown in step 107. In some embodiments, the reacting forms a colloidal dispersion of the particles of the precipitate in solution.

[0065] A variety of bases can be used in embodiments that employ base as a reactant. For example, in some embodiments, the base comprises a hydroxide (e.g., sodium hydroxide, potassium hydroxide, or another alkali metal hydroxide). In some embodiments, the method includes adding a base to the suspension containing the particles. In some embodiments, the method further includes adding a base to the solution. In some embodiments, the base is a compound that, when added to a pH neutral solution (i.e., pH 7), the solution containing the base has a pH greater than 7. In some embodiments, the base reacts with hydroxyl functional groups of the particles, resulting in negatively charged oxygen that electrostatically stabilizes the particles and thus forms a colloidal dispersion. For instance, in certain embodiments, the particles comprise a metal oxide and / or metalloid oxide domain that is electrostatically charged. In some embodiments, the base comprises a Bronsted-Lowry base. In some embodiments, the base comprises a hydroxide. In some embodiments, the base comprises an alkali metal hydroxide, for instance, LiOH, NaOH, KOH, RbOH, and / or CsOH. In some instances, the base comprises ammonium hydroxide. In some embodiments, the base is an organic base, for instance, an alkoxide, an amide, and / or an amine. In some embodiments, due to the electrostatic stabilization of the particles, is it unnecessary to add any additional stabilizing compounds to the colloidal dispersion to maintain the particles in solution. Accordingly, in some embodiments, the colloidal dispersions described herein are substantially free of stabilizing compounds or free of stabilizing compounds, e.g., nitrogen-containing stabilizing compounds. Substantially free of stabilizing compounds or free of stabilizing compounds means, in this context, that stabilizing compounds are present in an amount of less than 5 wt%, less than 0.5 wt%, or less than 0.05 wt% of the total colloidal dispersion weight, and / or are undetectable by nuclear magnetic resonance (NMR).

[0066] In some embodiments, the method further includes adding the reactant capable of undergoing hydrolysis to the suspension. In some embodiments, the reactant capable of undergoing hydrolysis is configured to undergo hydrolysis under ambient conditions (e.g., at 20 degrees C and 1 atm of pressure) when exposed to water. In some embodiments, the reactant capable of undergoing hydrolysis is configured to react under ambient conditions (e.g., at 20 degrees C and 1 atm of pressure) when exposed hydroxyl functional groups (e.g., of particle surfaces as described herein). Any of a variety of reactants capable of undergoing hydrolysis are suitable for adding to the suspension, in accordance with some embodiments. Referring again to the method 100 in FIG. 1A, the method includes reacting the solid particles with the reactant capable of undergoing hydrolysis 108, in accordance with some embodiments. In some embodiments, the method includes reacting water and / or hydroxyl functional groups of the solid particles with the reactant capable of undergoing hydrolysis. In some embodiments, the reactant capable of undergoing hydrolysis is added in excess of the total amount of hydroxyl functional groups (-OH) of the solid particles and / or water present in the suspension. In some embodiments, the method includes adding the reactant capable of undergoing hydrolysis in excess of the total amount of hydroxyl functional groups (-OH) of the solid particles and / or water present in the suspension. In some embodiments, adding the reactant capable of undergoing hydrolysis in such an excess consumes the residual water and may make the formed colloidal dispersion suitable for application and / or use with water-sensitive materials. For instance, consumption of water by the reactant capable of undergoing hydrolysis facilitates using the resulting colloidal dispersion with a water- sensitive active layer in a solar cell, such as a lead halide perovskite. Similarly, in some embodiments, the particles may be dispersed in an additional solvent (e.g., alternative to water). In some embodiments, the additional solvent does not react with a desirable substrate on which the particles may be deposited, e.g., a lead halide perovskite.

[0067] In some embodiments, adding the reactant capable of undergoing hydrolysis to the suspension occurs after centrifuging the suspension and decanting excess solution (e.g., decanting solvent from an accumulated solid comprising the solid particles). In some embodiments, it may be desirable to centrifuge and decant excess solvent from the suspension prior to adding the reactant capable of undergoing hydrolysis, as the reactant may react with any remaining water from the suspension. For instance, decanting excess solvent from the container (e.g., excess water) may allow the reactant undergoing hydrolysis to be added in excess while using less of the reactant, thereby requiring less of the reactant and producing less waste.

[0068] In some embodiments, adding the reactant capable of undergoing hydrolysis leads to the reaction between the reactant and hydroxyl functional groups (-OH) of the solid particles and / or water present in the solution. For instance, below is an exemplary sketch of an anhydride (i.e., acetic anhydride in this case) reacting with water:

[0069] Similarly, below is an exemplary sketch of an anhydride (i.e., acetic anhydride in this case) reacting with surface hydroxyl groups on nanoparticles:

[0070] While the above examples are depicted with acetic anhydride, it will be understood that other reactants capable of undergoing hydrolysis are also possible. Examples of chemicals capable of undergoing hydrolysis include, but are not limited to, anhydrides, esters, amides, imides, imines, carboxylic anhydrides (e.g., acetic anhydride), propylphosphonic anhydride, sulfur trioxide, and methanesulfonic anhydride. In some embodiments, the reactant capable undergoing hydrolysis comprises an anhydride. In some embodiments, the reactant capable undergoing hydrolysis comprises acetic anhydride. Further, in accordance with certain embodiments, the surface of the particles can be engineered with functional groups (e.g., with phosphonate, sulfate, and / or other groups) by using a suitable reactant instead of using a carboxylic acid anhydride. In certain embodiments, the particles comprise a metal oxide and / or metalloid oxide domain that is functionalized with a functional group that originates from the reactant. For instance, as shown in the depicted example above with acetic anhydride, the reaction between the hydroxyl functionalized nanoparticle and the reactant resulted in a particle comprising a metal oxide and / or metalloid oxide domain that is functionalized with a carboxylate (e.g., an acetate) functional group. In some embodiments, due to the ligand stabilization of the particles, is it unnecessary to add any additional stabilizers to the colloidal dispersion to maintain the particles in solution. Accordingly, in some embodiments, the colloidal dispersions described herein are substantially free of or free of stabilizing compounds other than the ligands on the particles. Substantially free of or free of stabilizing compounds other than the ligands on the particles means, in this context, that stabilizing compounds other than the ligands on the particles are present in an amount of less than 5 wt%, less than 0.5 wt%, or less than 0.05 wt% of the total colloidal dispersion weight, and / or are undetectable by nuclear magnetic resonance. In some embodiments, the colloidal dispersions described herein are substantially free of nitrogen-containing stabilizing compounds or are free of nitrogen-containing stabilizing compounds. Substantially free of nitrogen-containing stabilizing compounds or free of nitrogencontaining stabilizing compounds means, in this context, that nitrogen-containing stabilizing compounds are present in an amount of less than 5 wt%, less than 0.5 wt%, or less than 0.05 wt% of the total colloidal dispersion weight, and / or are undetectable by nuclear magnetic resonance.

[0071] In some embodiments, the method further comprises adding an acid and / or reacting the solid particles with an acid. In some embodiments, the acid comprises acetic acid. Adding an acid and / or reacting the solid particles with an acid may also functionalize the solid particles. For instance, an anion of the acid may react with a functional group of the solid particles (e.g., a hydroxyl functional group).

[0072] In some embodiments, the reacting (e.g., the reacting with the reactant capable of undergoing hydrolysis and / or the acid) results in the precipitate being colloidally dispersed as particles in a solvent. In some embodiments, the solid particles comprising a metal oxide and / or a metalloid oxide are suspended in the solvent, thereby forming a colloidal dispersion. In some embodiments, the method includes filtering the colloidal dispersion of particles. In some embodiments, a filter having a pore size of less than or equal to 250 nanometers, less than or equal to 220 nanometers, or less than or equal to 200 nanometers is used to filter the colloidal dispersion. In some embodiments, the filtering of the colloidal dispersion results in the particles of the colloidal dispersion having an average maximum cross-sectional dimension less than or equal to the pore size of the filter. In some embodiments, the filtering of the colloidal dispersion results in the particles of the colloidal dispersion having an average maximum cross- sectional dimension and / or a distribution of maximum cross-sectional dimensions that corresponds to any of the foregoing ranges described elsewhere herein regarding the cross- sectional dimensions of the particles.

[0073] In some embodiments, the reacting functionalizes the solid particles, thereby making a stable colloidal dispersion. In some embodiments, the solid particles in the colloidal dispersion are stable such that, after 24 hours at 20 degrees C, less than 1% of the particles by number of the colloidal dispersion are part of an aggregate having a maximum cross-sectional dimension of greater than or equal to 100 nanometers. In some embodiments, the solid particles in the colloidal dispersion are stable such that a small amount of the particles settle out of the colloidal dispersion as an accumulated solid. In some embodiments, less than 20 wt%, less than 10 wt%, less than 5 wt%, less than 1%, or less of the particles in solution settle out of colloidal dispersion when the colloidal dispersion is allowed to sit at 20 degrees C and 1 atm of pressure over a period of time of at least 12 hours (or over a period of time of at least 1 day, at least 2 days, at least 3 days, at least 5 days, at least 1 week, at least 2 weeks, at least 3 weeks, at least 1 month, at least 3 months, or at least 6 months and / or less than or equal to 3 years, less than or equal to 2 years, less than or equal to 1 year, less than or equal to 6 months, less than or equal to 3 months, less than or equal to 1 month, less than or equal to 3 weeks, less than or equal to 2 weeks, or less than or equal to 1 week). The number and sizes of aggregates may be determined by utilizing transmittance measurements using light having a wavelength corresponding to energy that is smaller than the bandgap of the material of the particles. In some embodiments, the transmittance of a colloidal dispersion using light having a suitable wavelength is greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 90%, greater than or equal to 95%, or greater than or equal to 97%. As a non-limiting example, transmittance measurements of a colloidal dispersion comprising SnCh particles may be performed using light having a wavelength of 500 nanometers. In some embodiments, once the particles (e.g., nanoparticles) have been synthesized, the particles are directly transferred into a dispersible medium. In other embodiments, after the particles (e.g., nanoparticles) have been synthesized, the particles are subjected to one or more particle purification steps before being transferred into a dispersible medium. In some embodiments, once the particles (e.g., nanoparticles) have been synthesized and / or reacted with a base, a reactant capable of undergoing hydrolysis, and / or an acid, the particles are directly transferred into a dispersible medium. In other embodiments, after the particles (e.g., nanoparticles) have been synthesized and / or reacted with a reactant capable of undergoing hydrolysis and / or an acid, the particles are subjected to one or more particle purification steps (i.e., one or more washing steps) before being transferred into a dispersible medium.

[0074] Certain embodiments comprise purifying the particles prior to incorporating the particles into a final colloidal dispersion. For example, in some embodiments, the particles are purified (e.g., by one or more washing steps) prior to being incorporated within a final colloidal dispersion. In some embodiments, purifying the particles comprising exchanging a solvent as described in more detail elsewhere herein. It will be understood that purifying the particles may occur before and / or after reacting the particles with reactant capable of undergoing hydrolysis and / or an acid.

[0075] In certain embodiments, the particles are purified by precipitation with an antisolvent, followed by redispersion. In certain embodiments, the particles are purified by precipitation with an antisolvent to form accumulated solid (e.g., a pellet) comprising the particles and a supernatant comprising the antisolvent. It will be understood that following use of an antisolvent, in some embodiments, some or all of the antisolvent may be removed from the particles, e.g., by decanting. Redispersion of the particles in a solvent may proceed by adding one or more additional solvents to the particles, in accordance with some embodiments.

[0076] Certain embodiments comprise reacting the particles with a compound, thus dispersing them in a solvent. In some embodiments, the compound comprises a base, a reactant capable or undergoing hydrolysis, and / or an acid, as described elsewhere herein in more detail.

[0077] The reactions can be performed at room temperature, but can also be performed at higher temperatures or lower temperatures. In some embodiments, it may be desirable to perform the reactions at room temperature (e.g., 20 degrees C) and at standard atmospheric pressure (e.g., 1 atm) to decrease energy input into the reaction. In some embodiments, it may be desirable to perform the reaction at a temperature above room temperature (e.g., at least 25 degrees C, at least 30 degrees C, at least 40 degrees C, at least 50 degrees C, or at least 60 degrees C and / or no more than 70 degrees C, no more than 80 degrees C, no more than 90 degrees C, or no more than 100 degrees C) to accelerate the reaction. In some embodiments, the reacting is performed at a temperature of greater than 0 °C, greater than or equal to 5 °C, greater than or equal to 10 °C, greater than or equal to 15 °C, greater than or equal to 20 °C, and / or less than or equal to 100 °C, less than or equal to 90 °C, less than or equal to 80 °C, less than or equal to 70 °C, less than or equal to 60 °C, less than or equal to 50 °C, less than or equal to 40 °C, less than or equal to 30 °C, or less than or equal to 25 °C. In some embodiments, the reacting occurs under turbulent conditions (e.g., active convection via shaking and / or a stir bar). In some embodiments, the reacting occurs under static conditions without active mixing.

[0078] The method 100 in FIG 1A further includes, in certain embodiments, mixing the colloidal particle dispersion with an additional solvent 110. In some embodiments, mixing the colloidal particle dispersion with an additional solvent yields a colloidal dispersion comprising a cosolvent (e.g., comprising the initial solvent of the solution and the additional solvent). In some embodiments, the initial solvent and the additional solvent are present in a ratio of initial solvent to additional solvent, by volume, of at least 1:1, at least 2:1, at least 3:1, at least 4:1, or at least 5:1 and / or no more than 6:1, no more than 7:1, no more than 8:1, no more than 9:1, or no more than 10:1. In some embodiments, the additional solvent and the initial solvent are present in a ratio of additional solvent to initial solvent, by volume, of at least 1:1, at least 2:1, at least 3:1, at least 4:1, or at least 5:1 and / or no more than 6:1, no more than 7:1, no more than 8:1, no more than 9:1, or no more than 10:1. Other cosolvent combinations are also possible, e.g., the inclusion of a third solvent, a fourth solvent, and so forth, in various ratios. In some embodiments, additional solvents that may be added to the colloidal dispersion include organic solvents. In some embodiments, additional solvents that may be added to the colloidal dispersion include an alcohol. In some embodiments, the additional solvent comprises ethanol, isopropanol, butanol (e.g., 1-butanol), pentanol, hexanol, heptanol, and / or octanol. In some embodiments, the solvent comprises acetonitrile (ACN), tetrahydrofuran (THF), 2-methyl tetrahydrofuran, diethyl ether (Et2O), and / or acetone. In some embodiments, it may be desirable to add one or more additional solvents comprising an organic solvent, as the organic solvent may have a high vapor pressure (e.g., compared to water) and may facilitate deposition of particles therefrom.

[0079] In some embodiments, mixing the particles with an additional solvent comprises exchanging a solvent. For example, in some embodiments, the suspension in which the metal cations and / or metalloid cations that has its pH adjusted is a suspension comprising a first solvent, and one or more additional solvents may be exchanged with the first solvent of the suspension. As noted above, in some embodiments, the first solvent may be water. Accordingly, in some such embodiments, the water of the suspension may be exchanged with one or more additional solvents. Solvent exchange, in accordance with some embodiments, may proceed by allowing the particles to settle and / or centrifuging the suspension to form an accumulated solid (e.g., settled solid, such as sediment) and supernatant, decanting the supernatant, adding the one or more additional solvents to the accumulated solid and dispersing the particles from the accumulated solid in the solvent. In some embodiments, the settling, decanting, and adding of the one or more additional solvent steps may be repeated a suitable number of times to exchange most or all of the initial solvent with the one or more additional solvents.

[0080] In some embodiments, the one or more additional solvents may be suitable for dispersing solid particles contained therein. For instance, in some embodiments, the one or more additional solvents do not react with a substrate on which the colloidal dispersion may be deposited (e.g., as described below and elsewhere herein), whereas the initial solvent (e.g., water) does react with the substrate. In some embodiments, the one or more additional solvents may desirably be more volatile than the initial solvent (e.g., having a higher vapor pressure at 20 degrees C and 1 atm of pressure), which may facilitate removal of the one or more additional solvents when deposited on a substrate. In some embodiments, the solid particles may be more stable in the one or more additional solvents than in the initial solvent.

[0081] In some embodiments, a colloidal dispersion can be further diluted with one or more solvents (e.g., one or more organic solvents). Examples of solvents include but are not limited to methanol, ethanol, acetonitrile, tetrahydrofuran, isopropanol, acetone, diethyl ether, butanol, and 1 -octanol. In some embodiments, the colloidal dispersion may be diluted with one or more solvents already contained in the colloidal dispersion, or diluted with a separate solvent. For example, in some embodiments, a colloidal dispersion of particles contained in 1 -butanol may be diluted with additional 1 -butanol. In some embodiments, a colloidal dispersion of particles contained in 1 -octanol may be diluted with additional 1 -butanol.

[0082] Mixed solvent colloidal nanoparticle dispersions can, in accordance with some embodiments, have beneficial properties desired for slot-die coating and / or blade coating. As a non-limiting example, 1 -octanol can be particularly useful for such applications. As another nonlimiting example, 1 -butanol can be particularly useful for such applications.

[0083] Referring again to method 100 in FIG. 1A, some embodiments further comprise coating a substrate surface with the particles to form a layer comprising the particles 112. FIG. 1C is a cross-sectional schematic diagram of a substrate 120 on which a layer 124 comprising particles has been coated, according to some embodiments.

[0084] In some embodiments, coating the substrate surface (e.g., as shown in FIG. 1C) comprises coating the substrate surface with a colloidal particle dispersion to form a layer comprising the particles after solvent removal. In some embodiments, it is desirable for the colloidal particle dispersion to comprise a solvent that does not react with the substrate such that the particles may be deposited on the surface as desired. In some embodiments, the solvent may be chosen such that it does not react with the desired substrate (e.g., a solvent comprising 1- butanol and a perovskite substrate). In some embodiments, the colloidal dispersion may comprise the desired solvent by mixing the desired solvent as the additional solvent as described in more detail elsewhere herein. In some embodiments, coating the substrate surface may proceed via any of a variety of suitable methods, non-limiting examples of which include printing, blade coating, slot-die coating, and spin coating. In some embodiments, a layer may be formed by coating the substrate surface once via any suitable method. In some embodiments, coating the surface via any suitable method may occur more than once to form a layer (e.g., twice, thrice, and so forth) to obtain a more complete layer and / or a thicker layer. For instance, coating the surface once may yield a partially coated substrate (e.g., an incomplete layer on the substrate surface, a layer having cracks, etc.), in some embodiments, and thus it may be desirable to coat the substrate surface a second time to form a more complete layer.

[0085] In some embodiments, simultaneous to coating the substrate, the substrate may be heated. In accordance with some embodiments, the method includes heating the substrate when coating the substrate surface with the colloidal dispersion containing the particles. In some embodiments, the substrate may be heated to at least 25 degrees C, at least 30 degrees C, at least 40 degrees C, at least 50 degrees C, or at least 60 degrees C and / or no more than 70 degrees C, no more than 80 degrees C, no more than 90 degrees C, or no more than 100 degrees C. Heating the substrate, in some embodiments, may facilitate evaporation of the solvent and formation of a layer comprising the solid particles from the colloidal dispersion. In some embodiments, heating may be performed in any of a variety of suitable methods, non-limiting examples of which include placing the substrate on a hot plate, in an oven, directing heated air at the substrate, exposure to a flame, and / or exposure to radiation from an infrared lamp.

[0086] A layer, as used in the context of this disclosure, has a thickness in a first direction, a width in a second direction perpendicular to the first direction, and a length in a third direction perpendicular to both the first and second directions, where both the width and the length of the layer are each at least 10 times the thickness of the layer. In some embodiments, both the width and the length of the layer are each at least 100 times, at least 1,000 times, at least 10,000 times, or at least 100,000 times the thickness of the layer. In some embodiments, an average thickness of the layer is at least 3 nanometers, at least 4 nanometers, at least 5 nanometers, at least 6 nanometers, at least 7 nanometers, at least 8 nanometers, at least 9 nanometers, at least 10 nanometers, at least 100 nanometers, at least 500 nanometers, or at least 1 micron. In some embodiments, the average thickness of the layer is less than or equal to 1 millimeter, less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, less than or equal to 1 micrometer, less than or equal to 500 nanometers, less than or equal to 100 nanometers, less than or equal to 10 nanometers, less than or equal to 9 nanometers, less than or equal to 8 nanometers, less than or equal to 7 nanometers, less than or equal to 6 nanometers, less than or equal to 5 nanometers, less than or equal to 4 nanometers, or less than or equal to 3 nanometers. Combinations of the foregoing ranges are possible (e.g., at least 3 nanometers and less than or equal to 10 nanometers or at least 3 nanometers and less than or equal to 100 micrometers). Other ranges are also possible.

[0087] In some embodiments, the layer is uniform. For instance, in some embodiments, across at least 80%, at least 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%, or all of the facial surface are of the layer, the thickness of the layer deviates by no more than 100%, no more than 75%, no more than 50%, no more than 25%, no more than 10%, or no more than 5% from the average thickness of the layer. In some embodiments, the layer is conformal. In some embodiments, the thickness and uniformity of the layer are determined based on the solvent used during deposition, the number of times the colloidal dispersion is coated on the substrate surface to form the layer, and / or the concentration of particles present in the colloidal dispersion coated on the substrate surface.

[0088] Certain embodiments further comprise integrating the particles (and / or the layer) into an electronic device. Some embodiments further comprise integrating the particles (and / or the layer) into an optoelectronic device.

[0089] In certain embodiments, the particles described herein can be used in the formation of voltaic devices (e.g., photovoltaic devices). For example, FIG. ID shows a schematic diagram of an example voltaic device 150 including an electrode layer 152 (e.g., an Au electrode), a hole transport layer 154, a perovskite layer 156 (e.g., a 3D / 2D perovskite layer), a layer 158 comprising metal oxide and / or metalloid oxide particles (e.g., SnCF particles), and a substrate 160 (e.g., a glass / FTO substrate, glass / ITO substrate, plastic / ITO substrate). Layer 158 can be, for example, a layer formed using the methods described herein (e.g., layer 124 in FIG. 1C). FIG. IE shows an embodiment of a photovoltaic device similar to that shown in FIG. ID, where the electrode layer is a Au electrode, the perovskite layer is a 3D / 2D perovskite layer, the layer comprising metal oxide and / or metalloid oxide particles contains SnO2 particles and was formed using the methods described herein, and the substrate was FTO on glass.

[0090] Some embodiments further comprise integrating the particles (and / or the layer) into a light emitting diode, a laser, a photodetector, a solar cell, a fuel cell, or a sensor. In some embodiments, the particles form all or part of an insulation layer within the device. In certain embodiments, the particles form all or part of a charge transport layer within the device. In certain embodiments, the particles form all or part of an electron transport layer within the device.

[0091] In some embodiments, the colloidal dispersion containing the particles is coated onto an electrode for use in a solar cell. In some embodiments, the colloidal dispersion containing the particles is coated onto a substrate for use in a solar cell. The term “solar cell,” as used herein, is interchangeable with the term “photovoltaic cell.” Solar cells can be used to generate electricity from energy produced by the sun or other sources of energy. In some embodiments, the solar cell is part of a system that uses the sun as a source of energy that generates electricity from the solar cell. The solar cell could also be used in a system that employs other sources of energy to generate electricity from the solar cell. In some embodiments, the solar cell comprises one or more layers as described in more detail elsewhere herein. For example, in some embodiments, the colloidal dispersion containing the particles is coated onto a photoactive layer for use in a solar cell. In some embodiments, a photoactive layer comprises a perovskite. In some embodiments, a photoactive layer comprises an organic semiconductor. In some embodiments, a photoactive layer comprises a quantum dot film. In some embodiments, a quantum dot film comprises PbS and / or HgTe quantum dots.

[0092] In some embodiments, the device is a solar cell. In some embodiments, the solar cell including one or more metal oxide and / or metalloid oxide layers as described herein and a single active layer (i.e., not a tandem solar cell) has a suitable efficiency. In some embodiments, the efficiency of the solar cell is at least 12%, at least 15%, at least 18%, at least 20%, or at least 22%. In some embodiments, the efficiency of the solar cell is up to 23%, up to 24%, up to 25%, up to 26%, or more. Combinations of the foregoing ranges are possible (e.g., at least 15% and up to 26%). Other ranges are also possible. In some embodiments, the device is a tandem solar cell. In some instances, referring again to FIG. ID the electrode layer 152 comprises silicon (e.g., and in some cases consists essentially of silicon), thereby forming a tandem solar cell. Other constructions are also possible. In some embodiments, the tandem solar cell includes one or more metal oxide and / or metalloid oxide layers as described herein. In some embodiments, the efficiency of the tandem solar cell is at least 28%, at least 29%, at least 30%, at least 31%, or at least 32%. In some embodiments, the efficiency of the tandem solar cell is up to 32% up to 33%, up to 34%, or more. Combinations of these ranges are possible. Other ranges are also possible.

[0093] In addition to voltaic devices (e.g., photovoltaic devices), in some embodiments, the devices described herein comprise a light emitting diode, a photodetector, a fuel cell, and / or a sensor. A structure of a light emitting diode and / or a photodetector may be similar to the voltaic devices described in FIGS. ID- IE. In some embodiments, in place of the perovskite layer 156, an active layer may be present and may comprise a material that is the same or different from those used for the light absorbing layer. For instance, in some embodiments, an active layer may comprise a film comprising HgTe quantum dots and / or PbS quantum dots. In some embodiments, when the device is a light emitting diode, the potential (i.e., an electric potential) may be biased in the opposite direction when compared to a photovoltaic device, e.g., to input energy rather than to extract energy. In some embodiments, energy input into the quantum dots of the active layer may be converted and released as light. In some embodiments, the material of the active layer may function as a light absorbing layer, but may absorb light of various wavelengths, and those of ordinary skill in the art would be able to select an appropriate active layer based on the desired application. In some embodiments, HgTe quantum dots may be used as a light absorbing layer within a photodetector to detect light having wavelengths greater than 800 nanometers (e.g., infrared light). As a non-limiting example, an infrared photodetector may comprise a glass / FTO substrate, upon which a charge transporting layer comprising SnO2 (e.g., which may be fabricated using the methods described herein), a layer comprising an HgTe quantum dot film, a hole transporting layer comprising spiro-MeOTAD, and a gold electrode are disposed, in that order. As another non-limiting example, an light emitting diode may comprise a glass / FTO substrate, upon which a charge transporting layer comprising SnO2 (e.g., which may be fabricated using the methods described herein), a layer comprising an HgTe quantum dot film, a hole transporting layer comprising spiro-MeOTAD, and a gold electrode are disposed, in that order. FIG. IF shows a schematic diagram of a sensor 170 including a substrate 172, electrodes 176, and a charge transporting layer 174 positioned between electrodes 176. The charge transporting layer of the sensor, in some embodiments, may comprise SnCh, (e.g., which may be fabricated using the methods described herein), the substrate may comprise alumina, and the electrodes may comprise gold. In some embodiments, the sensor may be configured in an electrical circuit such that, when a reducing atmosphere is present (e.g., an atmosphere comprising a combustible gas), less oxygen may be adsorbed on the surface of the charge transporting layer and charge may flow freely through the circuit. FIG. 1G shows a schematic diagram of an article 180 comprising a charge transporting layer 184 present on an electrode 182, which may be integrated into a fuel cell. For instance, in some embodiments, a cathode of a fuel cell may include article 180 where the charge transporting layer comprises a metal oxide and / or a metalloid oxide film that supports a catalyst (e.g., a nanoparticle catalyst) thereon.

[0094] In some embodiments, the metal oxide and / or metalloid oxide film may comprise SnO2 (e.g., which may be fabricated using the methods described herein). FIG. 1H shows a schematic diagram of laser 190. The laser 190 includes a charge transporting layer 196, an active layer 198, and a hole transporting layer 200. The laser 190 further includes an optional substrate 192 creating an optical cavity (e.g., a semi-transparent mirror, or a bragg grating), an optically transparent electrode 194 (e.g., FTO), and a metal electrode 202 (e.g., aluminum). In this example embodiment, the charge transporting layer 196, the active layer 198, and the hole transporting layer 200 are included within an optical cavity forming in between metal electrode 202 and substrate 192 to facilitate lasing behavior. In accordance with some embodiments, the substrate comprises a glass / FTO substrate, the charge transporting layer comprises SnO2, the active layer comprises quantum dots, the hole transporting layer comprises Spiro-MeOTAD and / or TCTA.

[0095] In some embodiments, a colloidal dispersion containing the solid particles is diluted. Accordingly, in some embodiments, the method includes diluting the colloidal dispersion containing the solid particles. In some instances, the solvent of the colloidal dispersion may be diluted with more of the same solvent or a different solvent, depending on the desired characteristics of the final solvent or cosolvent. In some embodiments, the method may include coating the diluted colloidal dispersion on a substrate to form an antireflective coating. In some embodiments, an antireflective coating formed using a diluted colloidal dispersion may be desired on a transparent substrate, for instance, a substrate for a window (e.g., an electrochromic window). In some embodiments, following coating of the colloidal dispersion on a substrate and forming of a layer thereby, it may be advantageous to heat the substrate. In some embodiments, the method comprises heating the substrate. Heating the substrate, in some embodiments, may anneal the layer. In some embodiments, annealing the layer forms a transparent conductive oxide. For instance, the colloidal dispersion may contain SnCF and ImOa particles or indium- doped tin oxide (ITO) particles, and a layer formed thereof may be annealed to form a transparent conductive oxide (e.g., ITO).

[0096] In some embodiments, methods of making metal oxide and / or metalloid oxide colloidal dispersions and / or inks are described. In some embodiments, methods of making metalloid oxide colloidal dispersions and / or inks are described.

[0097] In certain embodiments, methods described herein can be used to make thin films of metal oxides. In certain embodiments, methods described herein can be used to make thin films of metalloid oxides. Thin films of metal oxides and / or metalloid oxides are used for example as electrical insulation layers, protection layers, and / or charge transport layers.

[0098] The articles described herein can be used in any of the following applications: heterogenous catalysts, optoelectronic devices, light emitting diodes, lasers, photodetectors, solar cells, fuel cells, electrochromic windows, sensors, antireflective coatings, transparent conductive oxides, and / or moisture and / or oxygen diffusion barrier films.

[0099] The material deposition by inks can be advantageous as it allows the fast deposition on any substrate including soft substrates such as polymer films.

[0100] Nanoparticle inks (e.g., SnCF nanoparticle inks) can be commercially purchased and are widely used for perovskite solar cell development. Typical inks formed using hot-injection methods, heat-up synthesis methods, and / or flame spray pyrolysis methods require elevated temperatures for at least tens of minutes and often hours, and are thus energy intensive. However, the synthesis route described herein results in higher yields and lower cost. For instance, certain of the methods described herein are performed at room temperature (e.g., at approximately 20 degrees C). Moreover, removing heating steps improves the safety of certain methods described herein compared to typical methods that include heating steps, and also circumvents challenges associated with upscaling of certain methods, e.g., for industrial usage.

[0101] Additionally, in accordance with some embodiments, the methods described herein have a high yield. In this context, “yield” is calculated as the percentage of the theoretical maximum number of metal oxide and / or metalloid oxide nanoparticles that could be produced based on the concentration of metal and / or metalloid ions initially included in solution. In some embodiments, the yield of the methods described herein is at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, and / or up to 100%. In some embodiments, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, and / or up to 100% of the nanoparticles that are produced have the size and / or size distribution characteristics described elsewhere herein.

[0102] According to certain aspects of this disclosure, nanoparticle synthesis is conducted at room temperature (e.g., at 20 degrees C). The synthesis can result in nearly 100% yield from low-cost precursors. In addition, this synthesis is economically favorable. For instance, typical syntheses require heating steps to facilitate reactions. These costs associated with typical methods make the methods described herein economically favorable in comparison.

[0103] In accordance with certain embodiments, water soluble metal salts (and / or metalloid salts) are used, where the corresponding metal oxide or metal hydroxide (or metalloid oxide or metalloid hydroxide) has a lower solubility at a certain pH range. In some embodiments, once the salt is dissolved in water, a base or an acid is added to the salt solution, the solubility changes and the metal oxide and / or metal hydroxide (and / or metalloid oxide and / or metalloid hydroxide) precipitates quickly. Next, in certain embodiments, the metal oxide and / or metal hydroxide (and / or metalloid oxide and / or metalloid hydroxide) is separated from the excess water (e.g., by centrifugation, filtration). A reactant is added, in accordance with certain embodiments, which undergoes hydrolysis when in contact with water and also undergoes hydrolysis when in contact with hydroxy-terminated metal-oxide surfaces (removing water by reaction and reacting with surface hydroxyl groups).

[0104] In one set of embodiments, the synthesis steps are as follows:

[0105] 1. A suitable metal salt is dissolved in water.

[0106] 2. The metal oxide and / or hydroxide is rapidly precipitated by changing the pH value into a range, where the metal oxide and / or hydroxide has a limited solubility in water (e.g., by potassium hydroxide solution or acetic acid).

[0107] 3. The particles are separated from the excess of water by centrifugation and the supernatant is discarded.

[0108] 4. A suitable reactant (in combination with a solvent) is added to the remaining particles and residual water. The reactant undergoes hydrolysis, removing excess water by reaction. Further it also reacts with surface hydroxyl groups, functionalizing the particle surface. Often the reactant and solvent can be the same material such as acetic anhydride. After some time (e.g. 24 hours), the particles are colloidally dispersed in the solvent. 5. Optionally, the colloidal dispersion can be filtered with e.g. 0.22 pm PTFE syringe filter. The ink can be mixed with additional solvents for improved ink deposition properties.

[0109] In some embodiments, the synthesis steps are as follows:

[0110] 1. A suitable metal salt or metalloid salt is dissolved in water.

[0111] 2. The metal oxide and / or hydroxide is rapidly precipitated by changing the pH value into a range, where the metal oxide and / or hydroxide has a limited solubility in water (e.g., by potassium hydroxide solution or acetic acid solution).

[0112] 3. The particles are separated from the excess of water by centrifugation and the supernatant is discarded.

[0113] 4. A suitable reactant (in combination with a solvent) is added to the remaining particles and residual water. The reactant undergoes hydrolysis, removing excess water by reaction. Further it also reacts with surface hydroxyl groups, functionalizing the particle surface. Often the reactant and solvent can be the same material such as acetic anhydride. After some time (e.g. 24 hours), the particles are colloidally dispersed in the solvent.

[0114] 5. Optionally, the colloidal dispersion can be filtered with e.g. 0.22 pm PTFE syringe filter. In some embodiments, the synthesis steps are as follows:

[0115] 1. A suitable metal salt or metalloid salt is dissolved in water.

[0116] 2. The metal oxide and / or hydroxide is rapidly precipitated by changing the pH value into a range, where the metal oxide and / or hydroxide has a limited solubility in water (e.g., by potassium hydroxide solution or acetic acid solution).

[0117] 3. The particles are separated from the excess of water by centrifugation and the supernatant is discarded.

[0118] 4. A suitable reactant (in combination with a solvent) is added to the remaining particles and residual water. The reactant (e.g., potassium hydroxide, or potassium hydroxide solutions) deprotonates hydroxyl functional groups on the particles, rendering them electrostatically charged and thereby stabilized within the solvent. After some time (e.g., 24 hours), the particles are colloidally dispersed in the solvent.

[0119] 5. Optionally, the colloidal dispersion can be filtered with e.g. 0.22 pm PVDF syringe filter.

[0120] The ink can be mixed with additional solvents for improved ink deposition properties.

[0121] In some embodiments, estimation of the amount of material colloidally dispersed in the solvent can be determined by the following: The solvent of an aliquot can be removed and the remaining material can be weighed. Another approach is by measuring the density of the ink and comparison to the pristine solvent.

[0122] Various of the methods, devices, and materials described herein can exhibit one or more advantages and / or improvements over existing methods, devices or materials. Previously, SnCh nanoparticle inks were synthesized in an organic solvent at higher temperature with specialized precursors (expensive), followed by a purification step removing unwanted side products. The method disclosed herein is, in accordance with certain embodiments, extremely simple, at room temperature, with a very high yield, and uses low-cost materials.

[0123] The results from the fabricated solar cells described herein demonstrate that the material disclosed herein is as good as other methods for fabrication of such layers.

[0124] Methods, devices, and materials described herein can be used in a variety of commercial applications. Metal oxide nanoparticle inks are commercially available (e.g., from Avantama AG). The devices and materials described herein can be used, for example, for solar cell development, and potentially for LEDs, light detectors, sensors, electrochromic windows, and transistors as well as catalytic applications. Due to a lower film density, certain of the devices and materials described herein may also be used for the production of antireflective coatings. The deposition of certain mixtures of colloidal dispersions (e.g., SnCL and I112O3 particles), or the deposition of ITO (h OaiSn) particles followed up with thermal annealing may be used to produce transparent conductive oxides. It may further have applications in the fabrication of moisture and / or oxygen diffusion barrier films.

[0125] The synthesis described herein will, in some embodiments, be of lower cost in comparison to previously available products (e.g., from Avantama AG). In some embodiments, the methods described herein start with low-cost precursors, have a very high yield, and / or are fabricated at room temperature.

[0126] The methods described herein are not limited to SnO2 nanoparticle inks, but can be used for various metal oxide, metal hydroxide, metalloid oxide, and / or metalloid hydroxide (nanoparticle) inks. The methods described herein can be used, for example, with alkaline earth, lanthanoids, actinoids, transition metals, post-transition metals, and metalloids forming the corresponding oxides / hydroxides.

[0127] In some embodiments, the solvent can comprise acetic acid (e.g., instead of acetic anhydride). Other acids might also be used.

[0128] In some embodiments, the method comprises precipitating a metal oxide and / or metalloid oxide first, at which point, a stable colloidal nanoparticle dispersion is not formed (and a gel is also not formed). In some such embodiments, after precipitation, the particles are transferred into a colloidal dispersion. In this way, the method can comprise a precipitate-sol synthesis. In some embodiments, a colloidal dispersion (sol) is formed, which allows easy processing steps using the metal oxide and / or metalloid oxide containing material, such as printing and slot-die coating.

[0129] Some aspects are related to colloidal dispersions.

[0130] In some embodiments, the colloidal dispersion comprises solid particles suspended in solvent. Any of a variety of solvents are suitable for dissolution of colloidal dispersion, in accordance with some embodiments. Suitable solvents include those disposed elsewhere herein, for example, water and 1 -butanol. Other solvents are also possible for the colloidal dispersion.

[0131] In some embodiments, the solid particles of the colloidal dispersion comprise a metal oxide and / or a metalloid oxide. In some embodiments, the metal oxide and / or metalloid oxide comprise the size distribution and materials described elsewhere herein in more detail. For instance, in some embodiments, an average maximum cross-sectional dimension of the solid particles of greater or equal to 0.5 nanometers and less than or equal to 1 micron. Other ranges for the average maximum cross-sectional dimension of the solid particles as described elsewhere in herein in more detail are also possible for the solid particles in the colloidal dispersion. In some embodiments, the solid particles comprise SnxOy(e.g., SnO2), MoxOy(e.g., MoOa), CuxOy(e.g., CuO), MnxOy(e.g., MnO), NixOy(e.g., NiO), InxOy(e.g., h CF), WxOy(e.g., WO3), and / or SixOy(e.g., SiO2). In some embodiments, the solid particles comprise SnxOy, MoxOy, CuxOy, MnxOy, NixOy, InxOy, WxOy, and / or SixOy, wherein x is 1 or 2 and y is 1, 2, or 3. In some embodiments, the solid particles comprise SnxOy(e.g., SnCh), MoxOy(e.g., MoOs), CuxOy(e.g., CuO), MnxOy(e.g., MnO), NixOy(e.g., NiO), InxOy(e.g., h CF), WxOy(e.g., WO3), and / or SixOy(e.g., SiO2). In some embodiments, the solid particles comprise SnxOy, MoxOy, CuxOy, MnxOy, NixOy, InxOy, WxOy, and / or SixOy, where x is greater than 0 and less than or equal to 2 and y greater than 0 and less than or equal to 3.

[0132] In some embodiments, the colloidal dispersions described herein are stable. In some embodiments, a stable colloidal dispersion includes particles that are resistant to settling out of colloidal dispersion as an accumulated solid. In some embodiments, the solid particles of the colloidal dispersion are stable such that, after 24 hours at 20 degrees C, less than 1% of the particles by number of the colloidal dispersion are part of an aggregate having a maximum cross-sectional dimension of greater than or equal to 100 nanometers, greater than or equal to 300 nanometers, or greater than or equal to 500 nanometers and / or less than or equal to 750 nanometers or less than or equal to 1 micron. In some embodiments, the colloidal dispersion is stable such that a small amount of the particles settle out of solution as an accumulated solid. In some embodiments, less than 20 wt%, less than 10 wt%, less than 5 wt%, less than 1%, or less of the particles in the colloidal dispersion aggregate and fall out of the colloidal dispersion when the colloidal dispersion is allowed to sit at 20 degrees C and 1 atm of pressure over a period of time of at least 12 hours (or over a period of time of at least 1 day, at least 2 days, at least 3 days, at least 5 days, at least 1 week, at least 2 weeks, at least 3 weeks, at least 1 month, at least 3 months, or at least 6 months and / or less than or equal to 3 years, less than or equal to 2 years, less than or equal to 1 year, less than or equal to 6 months, less than or equal to 3 months, less than or equal to 1 month, less than or equal to 3 weeks, less than or equal to 2 weeks, or less than or equal to 1 week). The number and sizes of aggregates may be determined by utilizing transmittance measurements using light having a wavelength corresponding to energy that is smaller than the bandgap of the material of the particles. In some embodiments, the transmittance of a colloidal dispersion using light having a suitable wavelength is greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to, 90%, greater than or equal to 95%, or greater than or equal to 97%. As a non-limiting example, transmittance measurements of a colloidal dispersion comprising SnCh particles may be performed using light having a wavelength of 500 nanometers.

[0133] The following examples are intended to illustrate certain embodiments of the present invention, but do not exemplify the full scope of the invention.

[0134] EXAMPLE 1

[0135] Tin oxide solutions / inks were synthesized using the methods described herein and as outlined above. A perovskite solar cell using this ink was fabricated with efficiencies as good as a reference device.

[0136] EXAMPLE 2

[0137] This example describes the preparation of various solutions containing different metal oxide or metalloid oxide solid particles.

[0138] The following are examples in which precipitation is happening by addition of acids: Ink formulation for SnCh, SiCh, WOX(the solution of SiCh particles is shown in FIG. 2):

[0139] • SnO2 inks: 1 g Na2SnO3-3H2O was dissolved in 5mL deionized water. Addition of 2mL acetic acid. Centrifuged at 6000rpm for 2 minutes. Supernatant was discarded, and 2mL acetic anhydride were added to the precipitate (which looks like a slurry). Within 24 hours, the particles got colloidally dispersed in the solvent. Filtered through 0.2 pm PTFE filter. The colloidal dispersion was mixed 1:1 with butanol.

[0140] • SiO2 inks: Na2SiOa dissolved in H2O, followed by the addition of acetic acid. A slurry forms, centrifuged, and acetic anhydride is added to the precipitate. Filtered through 0.2 pm PTFE filter.

[0141] • WOXinks: Na2WO4-2 H2O dissolved in H2O followed by the addition of acetic acid. A slurry forms, centrifuged, and acetic anhydride is added to the precipitate, after 4 days, the colloidal dispersion is completely clear. Filtered through 0.2 pm PTFE filter.

[0142] The following are examples where precipitation is happening by addition of bases: Ink formulation for CaO, MnOx, NiOx, CuOx, h CF (some of the solutions of which are shown in FIG. 2):

[0143] • Manganese(II)chloride dissolved in water. Addition of potassium hydroxide solution (precipitate appears). Centrifugated (6000rpm, 3minutes). Acetic anhydride was added to the precipitated. After a few hours, the precipitate colloidally dispersed in the solvent. Filtered through 0.22 pm PTFE syringe filter.

[0144] • Nickel(II)acetate tetrahydrate dissolved in water. Addition of potassium hydroxide solution (precipitate appears). Centrifugated (6000rpm, 3minutes). Acetic anhydride was added to the precipitated. After a few hours, the precipitate colloidally dispersed in the solvent. Filtered through 0.22 pm PTFE syringe filter.

[0145] • Calcium iodide dissolved in water. Addition of potassium hydroxide solution (precipitate appears). Centrifugated (6000rpm, 3minutes). Acetic anhydride was added to the precipitated. After a few hours, the precipitate colloidally dispersed partially in the solvent. Filtered through 0.22 pm PTFE syringe filter.

[0146] • Copper(II) acetate monohydrate dissolved in water. Addition of potassium hydroxide solution (precipitate appears). Centrifugated (6000rpm, 3minutes). Acetic anhydride was added to the precipitated. After a few hours, the precipitate colloidally dispersed in the solvent. Filtered through 0.22 pm PTFE syringe filter.

[0147] • Indium(III)chloride dissolved in water. Addition of potassium hydroxide solution (precipitate appears). Centrifugated (6000rpm, 3minutes). Acetic anhydride was added to the precipitated. After a few hours, the precipitate colloidally dispersed in the solvent. Filtered through 0.22 pm PTFE syringe filter. FIG. 2 shows an optical image of vials containing various metal oxide and / or metalloid oxide inks. The color of each ink shown in FIG. 2 varied with the material therein. For instance, the SiO2 containing ink is colorless, the MnOxcontaining ink is orange-brown, the CuOxcontaining film is blue, the NiOxcontaining ink is green, and the ImOa containing ink is colorless.

[0148] In general, the metal oxide or metalloid oxide precipitated quickly. In some cases, for some precursor materials, mostly amorphous particles were formed. In other cases, mostly crystalline particles were formed.

[0149] EXAMPLE 3

[0150] Device fabrication using SnO2-ink:

[0151] Substrate cleaning: Prior to the nanoparticle deposition, the substrates (fluorine-doped tin oxide; FTO) were cleaned 10 minutes in an ultrasonic bath for 10 minutes at room temperature in a mixture of 1:50 Hellmanex Ill / dcionizcd water mixture, followed by cleaning in an ultrasonic bath at 50 °C following a sequence of deionized water, fresh deionized water, acetone, and isopropanol where each cleaning step was performed for a duration of 10 minutes, finally the substrates were dried with a nitrogen gas gun.

[0152] Nanoparticle deposition:

[0153] The FTO substrates were cleaned with oxygen plasma cleaner for 5 minutes at a reduced pressure. Following this step, the colloidal nanoparticle dispersion as described above was spincoated (2000rpm / 2000ramp / 30s) in air on fluorine-doped tin oxide substrates, and annealed at a temperature of 170 °C for 3 minutes.

[0154] Reference device, has a chemical bath deposited tin oxide layer:

[0155] The substrates are placed in a Hellendahl staining dish and 45 mL deionized water is added. The solution is heated in a water bath to a temperature of 85° C. A solution of 1.6 g Na2SnO3-3H2O in 5 mL deionized water was rapidly added to the vessel. After 6 minutes the transparent solution turns slightly turbid. The reaction is quenched by removing the substrates from the growth solution. The substrates were cleaned in an ultrasonic bath at 50 °C following a sequence of deionized water, fresh deionized water, acetone, and isopropanol where each cleaning step was performed for a duration of 10 minutes. Finally, the substrates were dried using an air-drying gun. Solar cell preparation:

[0156] The SnO2 coated substrate (e.g., glass / FTO / SnC ) was oxygen plasma cleaned for 10 minutes at reduced pressure. A potassium chloride solution was deposited by spin coating (10 mM KC1 in deionized water; spin coater setting: 3000 rpm(max) for 30 seconds). Following this step, the substrate was transferred into a dry air deposition chamber with a relative humidity below 1 %. A perovskite solution consisting of 704 mg lead iodide (Pbb), 240 mg formamidinium iodide (FAI), 9 mg methylammonium lead bromide (MAPbBn), 25 mg methylammonium chloride (MAC1), 890 pL N,N-dimethylformamide, and 110 pL dimethyl sulfoxide was deposited at 5000 rpm(max) for 30 seconds by spin coating. During this spin coating process, 600 pL diethyl ether were deposited dynamically to initiate the perovskite crystallization process. The perovskite film was annealed at 100 °C for 1 hour followed by 150 °C for 5 minutes. Subsequently, a 2D perovskite passivation layer was fabricated by spin coating (4000 rpm(max) for 30 s) a 15 mM n-hexylammonium bromide solution in chloroform, followed by annealing at 100 °C for 10 minutes.

[0157] The hole transporting layer (HTL) consisting of a mixture of spiro-MeOTAD with about 10 mol% 2,2’,7,7’-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9’-spirobifluorene bis(trifluoromethanesulfonyl)imide ([Spiro-MeOTAD] 1[TFSI] 1) in chlorobenzene (ca 70 mg / mL) was spin coated at 3000 rpm(max) for 20 seconds.

[0158] A 100 nm thick gold electrode was evaporated with a thermal evaporator with a deposition speed of about 0.1 nm / s.

[0159] Results:

[0160] FIG. IE shows a schematic of a perovskite solar cell that was fabricated as outlined above. FIG. 3 shows the current voltage measurement of the perovskite solar cell with tin oxide nanoparticles as electron transport layer, as compared to a reference device (with a chemical bath deposition grown tin oxide layer). The efficiency of both solar cells are identical within measurement uncertainty. This result shows that the layers resulting from the colloidal dispersions described herein function similarly to typically formed layers. Accordingly, the advantages described elsewhere herein in more detail of the methods are obtained without detracting from device performance.

[0161] EXAMPLE 4 This example describes particle synthesis and suspension in water. A solution was prepared by mixing 1 g sodium stannate trihydrate with 10 mL deionized water. Once the salt was dissolved in water, 1 mL acetic acid was added (e.g., adjusting the pH). Nanoparticles were formed. The material was centrifuged at 5000 rpm for 1 minute. The particles were added to water forming a suspension. FIG. 4 shows a transmission electron microscope image of the nanoparticles.

[0162] EXAMPLE 5

[0163] This example describes particle synthesis and colloidal dispersion into a watercontaining basic solution. A solution was prepared by mixing 1 g sodium stannate trihydrate with 10 mL deionized water. Once the salt was dissolved in water, 1 mL acetic acid was added. Nanoparticles were formed. The material was centrifuged at 5000 rpm for 1 minute. The supernatant was discarded, and the precipitate was mixed with 10 mL of a 1 molar water-based potassium hydroxide solution. A colloidal dispersion was formed after some time. FIGS. 5 A and 5B show two transmission electron microscope images of the nanoparticles.

[0164] EXAMPLE 6

[0165] Tin oxide solutions / inks were synthesized using the methods described in Example 5 and as outlined above. A perovskite solar cell using this ink was fabricated with efficiencies as good as a reference device.

[0166] EXAMPLE 7

[0167] This example describes particle synthesis in which purification steps are performed prior to transferring nanoparticles into a dispersible medium A solution was prepared by mixing 1 g sodium stannate trihydrate with 10 mL deionized water. Once the salt was dissolved in water, 1 mL acetic acid was added. Nanoparticles were formed. The material was centrifuged at 5000 rpm for 1 minute. The supernatant was discarded, 20 mL of deionized water was added to the nanoparticles, and the material was well mixed, resulting in a suspension. The suspension was centrifuged again at 5000 rpm for 1 minute; the supernatant was discarded, and 10 mL acetic anhydride was added to the nanoparticles, forming a colloidal dispersion. FIG. 6 shows a transmission electron microscopy image of the nanocrystals.

[0168] This colloidal dispersion containing the nanoparticles can be further diluted, as shown in FIG. 7, with organic solvents such as methanol, ethanol, acetonitrile, tetrahydrofuran, isopropanol, acetone, diethyl ether, butanol (not shown in the figure), and 1 -octanol forming colloidal dispersions stable for at least 24 hours. Some of those mixed solvent colloidal dispersions have beneficial properties desired for slot-die coating and blade coating for example with 1-octanol. After 24 hours, FIG. 7 shows mixing the tin oxide particle-containing colloidal dispersions with various solvents results in stable colloidal dispersions.

[0169] EXAMPLE 8

[0170] This example describes measuring the aggregation of particles via transmittance measurements.

[0171] Three colloidal dispersions of SnCL particles were synthesized and the transmittance was measured thereof. FIG. 8 shows the transmittance measurements for the three samples, and how to determine whether aggregation of the particles in solution has occurred. In the plot, the low transmittance around 325 nm can be assigned to the bandgap absorption of SnO2. High transmittance can be observed between 400 nm and 600 nm when basically no aggregates are present in the colloidal dispersion. Light scattering on nanoparticle aggregates reduces the transmission in that wavelength range, as shown in the plot.

[0172] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0173] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0174] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0175] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0176] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0177] As used herein, “wt%” is an abbreviation of weight percentage. As used herein, “at%” is an abbreviation of atomic percentage.

[0178] Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and / or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

[0179] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0180] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMSWhat is claimed is:

1. A method of synthesizing particles, comprising: adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the solution to form a suspension; and reacting the solid particles with a reactant capable of undergoing hydrolysis.

2. The method of claim 1, wherein the reactant capable of undergoing hydrolysis is acetic anhydride.

3. The method of any one of claims 1-2, further comprising adding the reactant capable of undergoing hydrolysis to the suspension.

4. The method of any one of claims 1-3, wherein the reactant capable of undergoing hydrolysis is added in excess of the total amount of -OH groups of the solid particles and / or water present in the suspension.

5. The method of any one of claims 1-4, wherein the particles comprise a metal oxide and / or metalloid oxide domain that is functionalized with a functional group that originates from the reactant.

6. A method of synthesizing particles, comprising: adjusting a pH of a solution comprising solubilized metal cations and / or metalloid cations by adding an acid such that solid particles containing at least some of the metal and / or metalloid of the cations precipitate out of the solution to form a suspension; and reacting the solid particles with a base.

7. The method of any one of claims 1-6, wherein the reacting results in the solid particles being colloidally dispersed as particles in a solvent.

8. The method of any one of claims 1-7, wherein the solution is an aqueous solution.

9. The method of any one of claims 1-8, further comprising centrifuging the suspension comprising the solid particles.

10. The method of claim 9, further comprising decanting excess solvent from solid particles.

11. The method of any one of claims 1-10, further comprising purifying the solid particles.

12. The method of any one of claims 1-11, further comprising reacting the solid particles with an acid.

13. The method of any one of claims 1-12, wherein the reacting results in the precipitate being colloidally dispersed as particles in a solvent.

14. The method of claim 13, wherein the solid particles are stable in the colloidal dispersion such that, after 24 hours at 20 degrees C, less than 1% of the particles by number of the colloidal dispersion are part of an aggregate having a maximum cross- sectional dimension of greater than or equal to 100 nanometers.

15. The method of any one of claims 1-14, wherein the particles are nanoparticles.

16. The method of any one of claims 1-15, further comprising mixing the particles with an additional solvent.

17. The method of claim 16, wherein the additional solvent is an organic solvent.

18. The method of claim 16, wherein the additional solvent is an alcohol.

19. The method of claim 16, wherein the additional solvent is 1-butanol.

20. The method of any one of claims 1-19, further comprising coating a substrate surface with the particles to form a layer comprising the particles.

21. The method of claim 20, wherein coating the substrate surface comprises coating the substrate surface with a colloidal particle dispersion to form a layer comprising the particles after solvent removal.

22. The method of any one of claims 1-21, further comprising integrating the particles into an electronic device.

23. The method of any one of claims 1-22, further comprising integrating the particles into an optoelectronic device.

24. The method of any one of claims 1-23, further comprising integrating the particles into a light emitting diode, a laser, a photodetector, a solar cell, a fuel cell, or a sensor.

25. The method of any one of claims 22-24, wherein the particles form all or part of an insulation layer within the device.

26. The method of any one of claims 22-25, wherein the particles form all or part of a charge transport layer within the device.

27. The method of any one of claims 1-26, wherein the particles comprise SnxOy, MoxOy, CuxOy, MnxOy, NixOy, InxOy, W Oy, and / or SixOy, wherein x is 1 or 2 and y is 1, 2, or 3.

28. The method of any one of claims 1-27, wherein the particles comprise SnC .

29. The method of any one of claims 1-28, wherein the particles are purified by precipitation with an antisolvent, followed by redispersion.

30. The method of any one of claims 1-29, wherein the particles are purified (e.g., by one or more washing steps) prior to being incorporated within a final colloidal dispersion.

31. The method of any one of claims 1-30, further comprising reacting the particles with a compound and dispersing them in a solvent.

32. The method of any one of claims 1-31, wherein the particles are crystalline.

33. The method of claim 32, wherein the particles comprise polycrystalline particles.

34. The method of any one of claims 30-33, wherein the particles comprise single crystalline particles.

35. The method of any one of claims 1-34, wherein the particles comprise amorphous particles.

36. The method of any one of claims 1-35, wherein at least 75% of all of the particles have a maximum cross-sectional dimension of less than or equal to 100 nanometers.

37. The method of any one of claims 1-36, further comprising adding an organic solvent to the colloidal dispersion.

38. The method of claim 37, wherein the organic solvent comprises 1-octanol.

39. The method of claim 37, wherein the organic solvent comprises 1-butanol.

40. The method of any one of claims 1-39, wherein the colloidal dispersion is stable for at least 24 hours.

41. A colloidal dispersion, comprising: solid particles comprising a metal oxide and / or a metalloid oxide suspended in a solvent; wherein the solid particles are stable in the colloidal dispersion such that, after 24 hours at 20 degrees C, less than 1% of the particles by number of the colloidal dispersion are part of an aggregate having a maximum cross-sectional dimension of greater than or equal to 100 nanometers.

42. The colloidal dispersion of claim 41, wherein the solid particles comprise SnxOy, MoxOy, CuxOy, MnxOy, NixOy, InxOy, W Oy, and / or SixOy, wherein x is 1 or 2 and y is 1, 2, or 3.

43. The colloidal dispersion of any one of claims 41-42, wherein an average maximum cross-sectional dimension of the solid particles of greater or equal to 0.5 nanometers and less than or equal to 1 micron.

44. The colloidal dispersion of any one of claims 41-43, wherein the solid particles of the colloidal dispersion are stable such that, after 24 hours at 20 degrees C, less than 1% of the particles by number of the colloidal dispersion are part of an aggregate having a maximum cross-sectional dimension of greater than or equal to 100 nanometers.

45. The colloidal dispersion of any one of claims 41-44, wherein the solvent comprises water.

46. The colloidal dispersion of any one of claims 41-45, wherein the solvent comprises 1 -butanol.

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