WO2021124220A1

WO2021124220A1 - Passivating vacancy defects in perovskite materials

Info

Publication number: WO2021124220A1
Application number: PCT/IB2020/062140
Authority: WO
Inventors: Osman M. BAKR; Xiaopeng ZHENG
Original assignee: King Abdullah University Of Science And Technology
Priority date: 2019-12-17
Filing date: 2020-12-17
Publication date: 2021-06-24

Abstract

Embodiments include a passivated perovskite material and a method of passivating a perovskite material. A passivated perovskite material may include a perovskite material including a vacancy defect and an under-coordinated atom; and an organic pseudohalogen including an organic cation associated with a pseudohalogen moiety, wherein the pseudohalogen moiety passivates the vacancy defect by bonding to the under-coordinated atom. A method of passivating a perovskite material may include dispersing a perovskite material in a nonpolar solvent, the perovskite material including a vacancy defect and an under-coordinated atom; and mixing the perovskite material with an organic pseudohalogen, the organic pseudohalogen including a pseudohalogen group that passivates the vacancy defect by associating with the under-coordinated atom. Embodiments further include optoelectronic devices including the passivated perovskite material and the passivated perovskite material formed in accordance with the methods disclosed, herein.

Description

PASSIVATING VACANCY DEFECTS IN PEROVSKITE MATERIALS

BACKGROUND

[0001] Perovskite semiconductors have attracted widespread attention as an emerging class of emitters for light-emitting diodes (LEDs), with their facile processing, tunable emission, and high photoluminescence quantum yield (PLQY). While green and red perovskite LEDs have advanced at a rapid pace, achieving quantum efficiencies (EQEs) > 20%, blue perovskite LEDs still lag far behind with EQEs of < 5% for Lemission in the range of 460-480 nm (the wavelength of the Rec. 2020 is 467 nm) and < 11 % for l ώ_dίoh in the range of 480-490 nm, i.e., sky blue. Among the perovskite blue-emitters, mixed halide (Cl/Br) perovskites (MHPs) can afford an easily tunable emission spectra in the blue by adjusting the halide (Cl/Br) ratio. However, despite the facile approach which yields perovskite blue LEDs that emit in the color range relevant to display standards (Rec. 2020), blue MHP LEDs are still a nascent technology, suffering from both poor efficiency and short operational half-life.

[0002] Halogen vacancies are the predominant defect species in inorganic cesium lead halide (CsPbX3, X=C1, Br, I) QDs. However, unlike “defect-tolerant” CsPbL and CsPbBn, chlorine vacancies in MHP CsPb(Br_xCh-_x)3 create deep trap states within the bandgap that irreversibly capture charge carriers and dramatically suppress the radiative recombination channels. Moreover, these defects initiate and catalyze device degradation by facilitating rapid ion migration and making the perovskite more vulnerable to external stimuli under atmospheric and operational conditions. Therefore, the suppression of Cl vacancy is a prerequisite for achieving efficient and stable blue MHP LEDs.

SUMMARY

[0003] According to some aspects, a method of passivating a perovskite material can include dispersing a perovskite material in a nonpolar solvent, the perovskite material including a vacancy defect and an under-coordinated atom; and mixing the perovskite material with an organic pseudohalogen, the organic pseudohalogen including a pseudohalogen that passivates the vacancy defect by associating with the under coordinated atom.

[0004] According to further aspects, an optoelectronic device can include a perovskite material including a vacancy defect and an under-coordinated atom; and an organic pseudohalogen including an organic cation associated with a pseudohalogen, wherein the pseudohalogen passivates the vacancy defect by bonding to the under coordinated atom.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a flowchart of a method of passivating a perovskite material, in accordance with one or more embodiments of the present invention.

[0006] FIG. 2 is a schematic diagram of a passivation strategy to obtain efficient and spectra-stable blue mixed-halide perovskite light-emitting diodes, in accordance with one or more embodiments of the present invention.

[0007] FIG.3 is a photograph of dispersing 50 mg of n-dodecylammonium chloride

(DAC; C₁₂H25NH3CI), n-butylammonium thiocyanate (BAT; C4H₉NH3SCN), and n- dodecylammonium thiocyanate (DAT; C₁₂H25NH3SCN) into 2 ml toluene, in accordance with one or more embodiments of the present invention.

[0008] FIGS. 4A-4F are (A, B) transmission electron microscopy (TEM) images of pristine MHP QDs and DAT treated MHP QDs, respectively; (C, D) high-resolution TEM (HR- TEM) images of pristine MHP QDs and DAT treated MHP QDs, respectively; (E) XRD patterns of pristine MHP QDs and DAT treated MHP QDs; (F) Steady-state optical absorption and PL spectra of pristine MHP QDs and DAT treated MHP QDs, in accordance with one or more embodiments of the present invention.

[0009] FIGS. 5A-5B are graphical views showing size distribution of (A) the pristine MHP QDs and (B) DAT-treated MHP QDs, in accordance with one or more embodiments of the present invention.

[0010] FIGS. 6A-6B are graphical views showing SIMS depth profiles of the drop- casted (left, A) pristine MHP QD films and (right, B) DAT-treated MHP QD films, in accordance with one or more embodiments of the present invention.

[0011] FIGS. 7A-7E are (A) an illustration of halogen vacancy induced Coulomb trap site formation, electron trapping, and self-assembly of organic thiocyanate (RSCN) on the defect sites; (B) calculated defect formation energies of Cl vacancy on CsPbCb (001) surface and Br vacancy on CsPbBo (001) surface at different growth conditions; calculated project density of states (PDOS) and electronic charge densities of valence band maximum (VBM), defect state (DS), and conduction band minimum (CBM) for (C) a CsCl-rich CsPbCb slab, (D) a CsPbCb slab with surface Cl vacancies, and (E) a CsPbCb slab with surface filled SCN groups, in accordance with one or more embodiments of the present invention.

[0012] FIGS. 8A-8F are (A) device structure, (B) normalized EL spectra, (C) luminance-voltage-current density, (D) EQE-current density, (E) operational lifetimes, and (F) peak position at different operation time for pristine device and the DAT treated device at a constant voltage bias of 4.5 V, in accordance with one or more embodiments of the present invention.

[0013] FIG. 9 is a graphical view showing time-resolved photoluminescence (PL) decay of pristine MHP QD films and DAT-treated MHP QD films, in accordance with one or more embodiments of the present invention.

[0014] FIG. 10 is a cross-sectional high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the MHP QD LEDs, in accordance with one or more embodiments of the present invention.

[0015] FIGS. 11A-11B are graphical views showing normalized EL spectra for (A) pristine device and (B) the DAT-treated device in accordance with one or more embodiments of the present invention.

[0016] FIG. 12 is a schematic diagram for a QLED including non-limiting examples of the following: electrode materials, interface layer materials, electron transport layer materials, and hole transport layer materials, according to one or more embodiments of the invention.

DETAILED DESCRIPTION

Definitions

[0017] The term recited below have been defined as described below. All other terms and phrases in this disclosure shall be construed according to their ordinary meaning as understood by one of skill in the art [0018] As used herein, the term “associates” and/or “associating” refers to an interaction between two or more chemical species, such as chemical bonding. The term includes covalent interactions and non-covalent interactions. Examples of associating include, without limitation, covalent bond, electrostatic bond, ligand/metal bond, ionic bond, metallic bond, dipole-dipole interaction, hydrogen bonding, coordinate covalent bond, supramolecular bonds, and any other relevant chemical bonds.

[0019] As used herein, the term “perovskite material” generally refers to materials which have a perovskite structure, such as perovskite quantum dots. The term includes organic perovskites, inorganic perovskites, hybrid organic-inorganic perovskites, halide perovskites, and any combination thereof. Examples include, without limitation, organic halide perovskites, inorganic halide perovskites, hybrid organic-inorganic halide perovskites, and the like. The term can include materials which, in addition to having a perovskite structure, have already been synthesized (e.g., synthesized perovskite materials). The term can further include materials which, in addition to having a perovskite structure and having already been synthesized, have been modified post synthesis (e.g., post-synthesis modified perovskite materials). Perovskite materials can be ID, 2D, and 3D.

[0020] In general, perovskite materials can have the chemical formula:

ABX3 wherein A is at least one cation, B is at least one cation, and X is at least one anion. Examples of A cations include organic cations and inorganic cations, each of which can be monovalent. Examples of B cations include metal cations and metalloid cations, each of which can be multivalent. Examples of X anions include inorganic anions and organic anions. Where the perovskite material includes more than one A cation, the various A cations can be distributed over the A sites in an ordered or disordered way. When the perovskite material includes more than one B cation, the various B cations can be distributed over the B sites in an ordered or disordered way. When the perovskite material includes more than one X anion, the various X anions can be distributed over the X sites in an ordered or disordered way.

[0021] Perovskite materials including at least two A cations can be referred to as a “mixed A cation perovskite” or simply a “mixed cation perovskite.” Mixed cation perovskites in which the at least two A cations include at least two types of organic cations can be referred to as a “mixed organic cation perovskite.” Mixed cation perovskites in which the at least two A cations include at least one type of organic cation and at least one type of inorganic cation can be referred to as a “mixed organic-inorganic cation perovskite.” Mixed cation perovskites in which the at least two A cations include at least two types of inorganic cations can be referred to as a “mixed inorganic cation perovskite.” Perovskite materials including at least two B cations can be referred to as a “mixed B cation perovskite.”

[0022] Perovskite materials including at least two X anions can be referred to as a “mixed anion perovskite.” Perovskite materials in which the at least two X anions include at least two types of inorganic anions can be referred to as a “mixed inorganic anion perovskite.” Perovskite materials in which the at least two X anions include at least one type of inorganic anion and at least one type of organic anion can be referred to as a “mixed inorganic-organic anion perovskite.” Perovskite materials in which the at least two X anions include at least two types of organic anions can be referred to as a “mixed organic anion perovskite.” Perovskite materials in which the at least two X anions include at least two types of halides can be referred to as a “mixed halide perovskite.” Perovskite materials including at least two types of A cations and at least two types of X anions can be referred to as a “mixed-cation mixed-anion perovskite.”

[0023] The perovskite materials can include any combination of at least one A cation, at least one B cation, and at least one X anion. For example, perovskite materials can include at least one of the following perovskite materials: organic cation perovskites, inorganic cation perovskites, mixed cation perovskites, mixed organic cation perovskites, mixed organic-inorganic cation perovskites, and mixed inorganic cation perovskites; and at least one of the following perovskite materials: organic anion perovskites, inorganic anion perovskites, halide perovskites, mixed inorganic anion perovskites, mixed inorganic-organic anion perovskites, mixed organic anion perovskites, and mixed halide perovskites. Examples of perovskite materials include, without limitation, halide perovskites; mixed halide perovskites; mixed-cation halide perovskites, such as mixed- organic cation halide perovskites, mixed organic-inorganic cation halide perovskites, and mixed-inorganic cation halide perovskites; and mixed-cation mixed-halide perovskites, such as mixed-organic cation mixed-halide perovskites, mixed organic-inorganic cation mixed-halide perovskites, and mixed-inorganic cation mixed-halide perovskites.

[0024] In some embodiments, the perovskite materials have the following chemical formula:

A¹(i-x-y)A²xA³yB¹j-zB²zX¹aX²bX³ [0025] wherein A¹ is a first A cation, A² is a second A cation, A³ is a third A cation, B¹ is a first B cation, B² is a second B cation, X¹ is a first X anion, X² is a second X anion, X³ is a third X anion, and where i, j, x, y, z, a, b, and c, are each independently from 0 to 10. For example, in some embodiments, i and j are each 1, and 0 < x < l; 0 < y < l; 0 < z < l; 0 < a < 3; 0 < b < 3; 0 < c < 3; and a + b + c = 3. When the chemical formula does not include a cation and/or anion, the subscript corresponding to that specific cation and/or anion is zero. As one example, for a perovskite material having the following chemical formula: A¹B¹X¹ _aX²b, x is 0, y is 0, z is 0, and c is 0.

[0026] The A¹, A², and A³ cations (collectively, the A cations) can include organic cations, inorganic cations, monovalent cations, or combinations thereof. For example, the A cations can include a nitrogen-containing organic compound such as an alkyl ammonium compound. Additional examples for the A cation can include organic cations and/or inorganic cations. Inorganic A cations can include an alkali metal, a transition metal, a lanthanide, and/or an actinide. For example, inorganic A cations can include cesium (Cs), rubidium (Rb), potassium (K), sodium (Na), lithium (Li), copper (Cu I), and/or francium (Fr). Organic A cations can include alkyl ammonium cation, for example, a Ci -20 alkyl ammonium cation, a Ci-6 alkyl ammonium cation, a C2-6 alkyl ammonium cation, a C1-5 alkyl ammonium cation, a C1-4 alkyl ammonium cation, a C1-3 alkyl ammonium cation, a C₁-2 alkyl ammonium cation, and/or a Ci alkyl ammonium cation. Further examples of organic A cations can include methylammonium (CFLNF[³⁺), ethylammonium (CH3CH2NH3 ⁺), propylammonium (CH3CH2 CH2NH3 ⁺), butylammonium (CH3CH2 CFL CH2NH3 ⁺), formamidinium (NFl2CF[=NF[2 ⁺), hydrazinium, acetylammonium, dimethylammonium, imidazolium, guanidinium and/or any other suitable nitrogen-containing or organic compound. In other examples, the A cations can include an alkylamine. Thus, the A cations can include an organic component with one or more amine groups. For example, the A cations can include an alkyl diamine halide such as formamidinium (CH(NH2)2). Thus, the A cations can include an organic constituent in combination with a nitrogen constituent. In some cases, the organic constituent can include an alkyl group such as straight-chain or branched saturated hydrocarbon group having from 1 to 20 carbon atoms. In some embodiments, an alkyl group can have from 1 to 6 carbon atoms. Examples of alkyl groups include methyl (Ci), ethyl (C2), n-propyl (C3), isopropyl (C3), n-butyl (C4), tert-butyl (C4), sec-butyl (C4), iso butyl (C4), n-pentyl (Cs), 3-pentanyl (Cs), amyl (Cs), neopentyl (Cs), 3-methyl-2-butanyl (C5), tertiary amyl (Cs), and n-hexyl (C6). Additional examples of alkyl groups include n- heptyl (C7), n-octyl (Cs) and the like.

[0027] The B¹ and B² cations (collectively, the B cations) can include multivalent elements, such as divalent and/or trivalent metals and/or metalloids. For example, the B cations can include alkaline earth metals, transition metals, post-transition metals, metalloids, lanthanoids, and/or actinoids. More specific examples of B cations include, without limitation, lead (Pb), tin (Sn), germanium (Ge), beryllium (Be), magnesium (Mg), calcium (Ca), cadmium (Cd), strontium (Sr), barium (Ba), iron (Fe II), chromium (Cr II), cobalt (Co II), nickel (Ni II), manganese (Mn II), lead (Pb II), copper (Cu II), palladium (Pd), vanadium (V II), zinc (Zn II), bismuth (Bi), antimony (Sb), indium (In III), iron (Fe), aluminum (Al), europium (Eu), lanthanum (La), and yttrium (Y).

[0028] The X¹, X², and X³ anions (collective, the X anions) can include inorganic anions and/or organic anions. For example, the inorganic anions can include halogens, such as F, Cl, Br, and/or I, an oxalate, a hydroxide, a chlorate, an iodate, a nitrite, a sulfate, a thiosulfate, a phosphate, and/or an antimonite. The organic anions can include, for example, acetate, formate, borate, carborane, and/or phenyl borate. The X or a combination of inorganic anions and organic ions.

[0029] As used herein, the term “vacancy defect” generally refers to a defect in a crystal lattice characterized by the absence of an ion. The defect in the crystal lattice can be localized such that the local crystal structure does not correspond to the crystal structure of the bulk material. Vacancy defects can include, without limitation, anion vacancies and/or cation vacancies. One example of a vacancy defect is an halogen vacancy, where the defect in the crystal lattice includes the absence of a halogen anion. Other types of vacancy defects can be present, including those involving cation vacancies and other anion vacancies.

[0030] As used herein, the term “under-coordinated” refers to an anion or a cation in a crystal structure, the coordination of which is lower than for other ions of the same type in the rest (or bulk) of the crystal. For instance, if cations in the bulk of a crystal are coordinated by 6 nearest neighbor anions a cation in the same crystal structure coordinated by 5 or fewer nearest neighbor anions would be considered under coordinated. Under-coordinated ions can occur at the surface of a crystal due to no further unit cells of the crystal existing beyond the surface to coordinate the ions at the surface, or under-coordinated ions may occur in the bulk of the crystal at sites where there is a vacancy defect (i.e. an absence of an ion, sometimes known as a Schottky defect, particularly when a. pair of ions are absent), as ions adjacent to the vacancy will thus be lacking one nearest neighbor counterion.

[0031] As used herein, the terms “organic pseudohalogen” refers to organic compounds associated with at least one pseudohalogen.

[0032] As used herein, the term “pseudohalogen” refers to a material which is chemically similar to halogens (e.g., but which is not a halogen). For example, the term can include molecules, chemical groups, and moieties (e.g., as attached functional groups, anions, etc.) which can donate electron density and/or bond in a manner similar to halogens. Examples of pseudohalogens include, without limitation, azide, isocyanide, thiocyanide, thiocyanate, isothiocyanate, cyanide, isocyanate, cyanate, cyano, mesyl, tosyl, selenocyanate, methanesulfonate, and the like. The pseudohalogens can associate to other chemical species via any atom of the pseudohalogen. Examples of pseudohalogens include, without limitation, azide ( — N3), isocyanide ( — NºC), thiocyanide ( — S-CºN), isothiocyanate ( — N=C=S), cyanide ( — CºN), isocyanate ( — NºC-0), cyanate ( — 0-CºN), cyano ( — CºN), mesyl ( — SO2CH3), tosyl, selenocyanate ( — Se-Ph), methanesulfonate ( — O — S(=0)2 — CH3), and the like.

[0033] As used herein, the term “alkyl” refers to a linear or branched chain saturated hydrocarbon radical. An alkyl group may be a C_1-18 alkyl group, a Ci-₁₄ alkyl group, a Ci- ₁₀ alkyl group, a Ci-6 alkyl group or a C₁-4 alkyl group. Examples of a Ci-₁₀ alkyl group are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl. Examples of Ci-6 alkyl groups are methyl, ethyl, propyl, butyl, pentyl or hexyl. Examples of C ₁ o alkyl groups are methyl, ethyl, i-propyl, n-propyl, t-butyl, s-butyl or n-butyl. As used herein, the term “cycloalkyl” refers to a saturated or partially unsaturated cyclic hydrocarbon radical. A cycloalkyl group may be a C3-10 cycloalkyl group, a C3-8 cycloalkyl group or a C3-6 cycloalkyl group. Examples of a C3-8 cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclohexenyl, cyclohex-1, 3-dienyl, cycloheptyl and cyclooctyl. Examples of a C3-6 cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0034] As used herein, the term “aryl” refers to a monocyclic, bicyclic or polycyclic aromatic ring which contains from 6 to 14 carbon atoms, typically from 6 to 10 carbon atoms, in the ring portion. Examples include phenyl, naphthyl, indenyl and indanyl groups. The term includes heteroaryl groups. The term "heteroaryl", as used herein, refers to monocyclic or bicyclic heteroaromatic rings which typically contains from six to ten atoms in the ring portion including one or more heteroatoms. A heteroaryl group is generally a 5- or 6-membered ring, containing at least one heteroatom selected from O, S, N, P, Se and Si. It may contain, for example, one, two or three heteroatoms. Examples of heteroaryl groups include pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, furanyl, thienyl, pyrazolidinyl, pyrrolyl, oxazolyl, oxadiazolyl, isoxazolyl, thiadiazolyl, thiazolyl, isothiazolyl, imidazolyl, pyrazolyl, quinolyl and isoquinolyl.

[0035] As used herein, the term “aralkyl” refers to an alkyl group substituted with an aryl group.

[0036] As used herein, the term “alkaryl” refers to an aryl group substituted with an alkyl group.

Discussion

[0037] The present invention relates to the passivation of perovskite materials using organic pseudohalogens. The organic pseudohalogens can be used to passivate vacancy defects in perovskite materials to obtain efficient and stable perovskite materials for use in a wide array of optoelectronic devices. The strategy can be easily and readily integrated with perovskite material processing. For example, the organic pseudohalogens are soluble in nonpolar, nonhalogenated solvents. In addition, the organic pseudohalogens can be used to fill vacancy defects (e.g., halogen vacancies) and remove deep electron traps within the bandgap, without appreciably changing the emission spectrum (e.g., of blue- emitting perovskites) and without altering the crystal structure of the perovskite materials. Organic pseudohalogen-treated perovskite materials exhibited near unity (~ 100%) photoluminescence quantum yields and unprecedented external quantum efficiency. [0038] FIG. 1 is a flowchart of a method of passivating a perovskite material, in accordance with one or more embodiments of the present invention. As shown in FIG. 1 , the method can comprise one or more of the following steps: (a) dispersing a perovskite material in a nonpolar solvent, the perovskite material including a vacancy defect; and (b) mixing the perovskite material with an organic pseudohalogen, the organic pseudohalogen including a pseudohalogen which passivates the vacancy defect. In some embodiments, the method includes a post-treatment method for passivating a perovskite material.

[0039] Step (a) includes dispersing a perovskite material in a nonpolar solvent. In some embodiments, dispersing includes mixing the perovskite material in the nonpolar solvent. In some embodiments, dispersing includes sonicating the perovskite material in the nonpolar solvent. In some embodiments, dispersing includes agitating the perovskite material in the nonpolar solvent. In some embodiments, dispersing includes emulsifying the perovskite material in the nonpolar solvent. In some embodiments, dispersing includes contacting the perovskite material with the nonpolar solvent. In some embodiments, dispersing includes forming a stable dispersion of the perovskite material in the nonpolar solvent. In some embodiments, dispersing includes re-dispersing the perovskite material in the nonpolar solvent. In some embodiments, the perovskite material is dispersed in a nonpolar solvent that is free of halides.

[0040] Materials having a perovskite structure can be utilized herein as the perovskite material. The perovskite material can be selected from synthesized perovskite materials, post-synthesis modified perovskite materials, perovskite material precursors, and combinations thereof. In some embodiments, the perovskite material is selected from mixed cation perovskites, mixed anion perovskites, and mixed-anion mixed-cation perovskites. For example, in some embodiments, the perovskite material includes at least one of the following: organic cation perovskites, inorganic cation perovskites, mixed cation perovskites, mixed organic cation perovskites, mixed organic-inorganic cation perovskites, and mixed inorganic cation perovskites; and at least one of the following perovskite materials: organic anion perovskites, inorganic anion perovskites, halide perovskites, mixed inorganic anion perovskites, mixed inorganic-organic anion perovskites, mixed organic anion perovskites, and mixed halide perovskites. In some embodiments, the perovskite material includes at least one of the following: halide perovskites; mixed halide perovskites; mixed-cation halide perovskites, such as mixed- organic cation halide perovskites, mixed organic-inorganic cation halide perovskites, and mixed-inorganic cation halide perovskites; and mixed-cation mixed-halide perovskites, such as mixed-organic cation mixed-halide perovskites, mixed organic-inorganic cation mixed-halide perovskites, and mixed-inorganic cation mixed-halide perovskites.

[0041] In some embodiments, the perovskite material includes a blue-emitting perovskite quantum dot, such as a blue-emitting mixed-halide perovskite quantum dot, having a peak emission wavelength of 500 nm or less (e.g., between 460 nm to about 480 nm), or any incremental value or subrange between that range.

[0042] In some embodiments, the perovskite material is represented by the following chemical formula:

A ¹ ( 1 -x-y) A²X A³y B ¹1 -zB ²zX^J aX²bX³c wherein A¹ is a first A cation; A² is a second A cation; A³ is a third A cation; B¹ is a first B cation; B² is a second B cation; X¹ is a first X anion; X² is a second X anion; and X³ is a third X anion. In some embodiments, 0 < x < l, 0 < y < l, and 0 < z < 1. In some embodiments, 0 < a < 3, 0 < b < 3, and 0 < c < 3. In some embodiments, a + b + c = 3. [0043] Each of the cations A¹, A², and A³, if present, can independently include an alkali metal, a transition metal, a lanthanide, an actinide, a nitrogen-containing organic compound such as an alkyl ammonium, or alkylamine, each of which can be monovalent. Examples of alkali metals include, without limitation, cesium (Cs), rubidium (Rb), potassium (K), sodium (Na), lithium (Li), copper (I), and francium (Fr). An example of a transition metal includes, without limitation, Cu (I). Examples of nitrogen-containing organic compounds include, without limitation, alkyl ammonium cations, such as Ci- 20 alkyl ammonium cations, Ci-6 alkyl ammonium cations, C2-6 alkyl ammonium cations, Ci-5 alkyl ammonium cations, C 1 -₄ alkyl ammonium cations, C1-3 alkyl ammonium cations, C1-2 alkyl ammonium cations, and Ci alkyl ammonium cations. Examples of nitrogen-containing organic compounds include, without limitation, methylammonium (CH3NH³⁺), ethylammonium (CH3CH2NH3⁺), propylammonium (CH3CH2CH2NH3⁺), butylammonium (CH3CH2CH2CH2NH3⁺), form ami dinium (FA⁺), hydrazinium, acetylammonium, dimethylammonium, imidazolium, and guanidinium. Examples of alkyl amines include alkyl amines including at least one amine and a linear or branched saturated hydrocarbon having from 1 to 20 carbon atoms, or from 1 to 6 carbon atoms. Additional examples of alkyl amines include those including one or more amine groups and at least one of the following alkyl groups: methyl (Ci), ethyl (C2), n-propyl (C3), isopropyl (C3), n-butyl (C4), tert-butyl (C4), sec-butyl (C4), iso-butyl (C4), n-pentyl (Cs), 3-pentanyl (Cs), amyl (Cs), neopentyl (Cs), 3-methyl-2-butanyl (Cs), tertiary amyl (Cs), n-hexyl (C6), n-heptyl (C7), and n-octyl (Cs). In some embodiments, A¹, A², and A³ are each, if present, independently selected from the group consisting of Cs, methylammonium, and formamidinium. In some embodiments, at least one of A¹, A², and A³ includes Cs. In some embodiments, at least one of A¹, A², and A³ includes methylammonium. In some embodiments, at least one of A¹, A², and A³ includes formamidinium.

[0044] Each of the cations B¹ and B², if present, can independently include an alkaline earth metal, a transition metal, a post-transition metal, a metalloid, a lanthanoid, or an actinoid, each of which can be multivalent, for example, divalent or trivalent. Examples of B¹ and B² cations include, without limitation, lead (Pb), tin (Sn), germanium (Ge), beryllium (Be), magnesium (Mg), calcium (Ca), cadmium (Cd), strontium (Sr), barium (Ba), iron (Fe II), chromium (Cr II), cobalt (Co II), nickel (Ni II), manganese (Mn II), copper (Cu II), palladium (Pd), vanadium (V II), zinc (Zn II), bismuth (Bi), antimony (Sb), indium (In III), iron (Fe), aluminum (Al), europium (Eu), lanthanum (La), and yttrium (Y). In some embodiments, B¹ and B² are each, if present, selected from the group consisting of lead (Pb), tin (Sn), and germanium (Ge). In some embodiments, at least one of B¹ and B² includes lead (Pb). In some embodiments, at least one of B¹ and B² includes tin (Sn). In some embodiments, at least one of B¹ and B² includes germanium (Ge). [0045] Each of the anions X¹ and X², if present, can independently include an inorganic anion or organic anion. Examples of X¹ and X² anions include, without limitation, halogens, such as F, Cl, Br, I, an oxalate, a hydroxide, a chlorate, an iodate, a nitrite, a sulfate, a thiosulfate, a phosphate, an antimonite, an acetate, a formate, a borate, a carborane, and/or a phenyl borate. In some embodiments, X¹ and X² include Br and I. In some embodiments, X¹ and X² include Cl and Br. In some embodiments, X¹ and X² include Cl and I. In some embodiments, X¹ and X² include F and I. In some embodiments, X¹ and X² include Br and F. In some embodiments, X¹ and X² include Cl and F.

[0046] In some embodiments, the perovskite material includes a perovskite of the formula: A'B'X'a, wherein A¹, B¹, and X¹ are as defined above.

[0047] In some embodiments, the perovskite material includes a mixed-anion perovskite of the formula: A¹B¹X¹ _aX²b, wherein A¹, B¹, X¹ and X² are as defined above. [0048] In some embodiments, the perovskite material includes a mixed-anion perovskite of the formula: A¹B¹X¹ _aX²bX³c, wherein A¹, B¹, X¹, X², and X³ are as defined above.

[0049] In some embodiments, the perovskite material includes a mixed cation perovskite of the formula: A¹(i-x)A² _xB¹X¹ _a, wherein A¹, A², B¹, and X¹ are as defined above.

[0050] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹(i-x)A²xB¹X¹ _aX²b, wherein A¹, A², B¹, X¹, and X² are as defined above.

[0051] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹(i-x)A² _xB¹X¹ _aX²bX³c, wherein A¹, A², B¹, X¹, X², and X³ are as defined above. [0052] In some embodiments, the perovskite material includes a mixed-cation perovskite of the formula: A¹(i-x-y)A² _xA³ _yB¹X¹ _a, wherein A¹, A², A³, B¹, and X¹ are as defined above.

[0053] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A'ii-c^A^A^B'C'A^, wherein A¹, A², A³, B¹, X¹, and X² are as defined above.

[0054] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹(i-x-y)A² _xA³ _yB¹X¹ _aX²bX³c, wherein A¹, A², A³, B¹, X¹, X², and X³ are as defined above.

[0055] In some embodiments, the perovskite material includes a mixed cation perovskite of the formula: A¹B¹i-_zB² _zX¹a, wherein A¹, B¹, and X¹.

[0056] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹B¹i-_zB² _zX¹aX²b, wherein A¹, B¹, B², X¹ and X² are as defined above.

[0057] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹B¹i-_zB² _zX¹ _aX²bX³c, wherein A¹, B¹, B², X¹, X², and X³ are as defined above.

[0058] In some embodiments, the perovskite material includes a mixed cation perovskite of the formula: A'fi-^xB'i-Jl^X'a, wherein A¹, A², B¹, B², and X¹ are as defined above.

[0059] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹(i-x)A² _xB¹i-_zB² _zX¹ _aX²b, wherein A¹, A², B¹, B², X¹, and X² are as defined above.

[0060] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹(i-x)A² _xB¹i-_zB² _zX¹ _aX²bX³c, wherein A¹, A², B¹, B², X¹, X², and X³ are as defined above.

[0061] In some embodiments, the perovskite material includes a mixed-cation perovskite of the formula: A -x-yiA^A^B^B^X^, wherein A¹, A², A³, B¹, B², and X¹ are as defined above.

[0062] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹(i-_x-y)A² _xA³ _yB¹i-_zB² _zX¹ _aX²b, wherein A¹, A², A³, B¹, B², X¹, and X² are as defined above. [0063] In some embodiments, the perovskite material includes a mixed-cation mixed-anion perovskite of the formula: A¹(i-x-y)A²xA³ _yB¹i-zB² _zX¹aX²bX³c, wherein A¹, A², A³, B¹, B², X¹, X², and X³ are as defined above.

[0064] In some embodiments, the perovskite material includes a mixed-halide perovskite of the formula A^^X nX²^, where A¹, B¹, X¹, and X² are as defined above and 0 < n < 1.

[0065] Examples of perovskite materials include, without limitation, the following: CsPbL·; CsPbBo; MAPbL·; FAPbL·; FAMA-mixed perovskite, such as MAFAPbL·, FAi- nMAnPb(Bri-xIx)3 (where 0 < x < l, 0 < n < l), and FAi-_nCs_nPb(Ii-xBrx)3 (where 0 < x < 1, 0 < n < 1); CsFAMA-mixed perovskite, such as CsMAFAPb(Br_xIi-_x)3 or Cs_x(FAi-_nMAn)i- xPb(Ii-mBr_m)3 (where 0 < x < l, 0 < n < l, 0 < m < l); mixed-halide perovskites, such as APb(Xi-xYx)3 or APbX3-xYx (where A is MA⁺, Cs⁺, or FA⁺; X and Y are each independently Cl , Br , or G; and x is from 0 to 3), CsFAPb(Br_xIi-_x)3 (where 0 < x < 1), and CsPb(BrxCh-x)3 (where 0 < x < 1). In some embodiments, the perovskite material includes CsPb(Br_xCli-x)3 where 0 < x < 1. In some embodiments, the perovskite material includes at least one of the following: CsPbL·, CsPbBn, MAPbL·, and FAPbh. In some embodiments, the perovskite material includes at least one of the following: CsPb(Br_xCh- x)3 where 0 < x < 1 , FAMA-mixed perovskite, and CsFAMA-mixed perovskite. In some embodiments, the perovskite material includes at least one of the following: FAMA- mixed perovskite and CsFAMA-mixed perovskite. In some embodiments, the perovskite material includes at least one of the following: PEA2(MACS)i.5Pb2.sBr8.5, Cs_xFAi-_xPbBr3, CsPbClo.9Br2.i, PEA2(Rbo.6Cso.4)2Pb3Bno, CsMnyPbi-yBrxCb-x, BA2Cs_n-iPb_n(Br/Cl)3n+i, CsPb(Br_xCll-x)3, PEA2CS(n-i-x)MAxPbnBr3n+I, PEA₂CS(n-i-x)FAxPbnBr3n_+I, PEA2K(n-i- x)MAxPbnBr3n_+i, and the like. In some embodiments, the perovskite material includes a blue emitting perovskite material, such as blue-emitting MAPbBn quantum dots. In some embodiments, a blue emitting perovskite material includes at least RbxCs(i-_x)Pb(Br_yCl(i- y))3 and optionally A2MX4.

[0066] Additional examples of perovskite materials include, without limitation, the following: CsPbL·, CsPbBn, MAPbL·, FAPbL·, CsMAFAPb(Br_xIi-_x)3, CsFAPb(Br_xIi-_x)3, MAFAPbL·, -MAPbBr₃, MAPbBnCl, MAPbCL·, FAPbBr₃, FAPbCL·, CsPbCL·, MASnL·, MASnBr3, MASnCL·, FASnL·, FASnBr3, FASnCL·, CsSnL·, CsSnBr3, CsSnCL·, CsSiCL·, CsSiBr₃, CsSiL·, RbSiCL·, RbSiBo, KSiCL·, KSiBr₃, KS1I3, MASiCL·, MASiBn, MASiL·, Cs₂SiCl4, Cs₂SiBr₄, Cs₂Sil4, MA2S1CI4, MA₂SiBr₄, MA2S1I4, Rb₂SiCl4, Rb₂SiBr , Rb₂Sil4, CsSFCls, Cs₂SiCl6, Cs2Si(II)Si(IV)Ck, CsSFBrs, Cs₂SiBr₆, Cs₂Si(II)Si(IV)Br8, CsS b, Cs₂Sil6, Cs2Si(II)Si(IV)l8, RbSbCb, Rb₂SiCb, Rb₂Si(II)Si(IV)Cl₈, RbS Brs, Rb₂SiBre, Rb₂Si(II)Si(IV)Br₈, RbS b, Rb₂SiIe, Rb₂Si(II)Si(IV)I₈, KS Cb, K₂SiC K₂Si(II)Si(IV)Cl₈, KS Brs, K₂SiBre, K₂Si(II)Si(IV)Br₈, KSbb, K₂SiIe, K₂Si(II)Si(IV)I₈, MAS Cb, MA₂SiCle, MA₂Si(II)Si(IV)Cl₈, MASbBrs, MA₂SiBre, MA₂Si(II)Si(IV)Br₈, MAS b, MA₂SiIe, MA₂Si(II)Si(IV)I₈; CsGeCb, CsGeBrs, CsGeb, RbGeCb, RbGeBrs, KGeCb, KGcBi i, KGeb, MAGeCb, MAGeBrs, MAGeb, Cs₂GeCb, Cs₂GeBr , Cs₂GeI , MA₂GeCb, MA₂GeBr₄, MA₂GeI₄, Rb₂GeCb, Rb₂GeBr₄, Rb₂GeI₄, CsGe₂Cb, Cs₂GeCk, Cs₂Ge(II)Ge(IV)Cl₈, CsGe₂Brs, Cs₂GeBre, Cs₂Ge(II)Ge(IV)Br₈, CsGe₂Is,

Cs₂GeIe, Cs2Ge(II)Ge(IV)I₈, RbGe₂Cb, Rb₂GeCb, Rb₂Ge(II)Ge(IV)Cb, RbGe₂Brs, Rb₂GeBre, Rb₂Ge(II)Ge(IV)Br₈, RbGe₂Is, Rb₂GeIe, Rb₂Ge(II)Ge(IV)I₈, KGe₂Cb, K₂GeCb, K₂Ge(II)Ge(I V)C , KGe₂Brs, K₂GeBre, K₂Ge(II)Ge(IV)Br₈, KGe₂Is, K₂GeIe, K₂Ge(II)Ge(IV)I₈, MAGe₂Cb, MA₂GeCb, MA₂Ge(II)Ge(IV)Cl₈, MAGe₂Brs, MA₂GeBre, MA₂Ge(II)Ge(IV)Br₈, MAGe₂Is, MA₂GeIe, MA₂Ge(II)Ge(IV)I₈; CsSnCb, CsSnBr3, CsSnb, RbSnCb, RbSnBr3, KSnCb, KSnBr3, KSnb, MASnCb, MASnBr3, MASnb, Cs₂SnCl₄, Cs₂SnBr₄, Cs₂SnI₄, MA₂SnCl₄, MA₂SnBr₄, MA₂SnI₄, Rb₂SnCl₄, Rb₂SnBr₄, Rb₂SnI₄, CsSmCb, Cs₂SnCk, Cs₂Sn(II)Sn(IV)Cl₈, CsSmBrs, Cs₂SnBr6, Cs₂Sn(II)Sn(IV)Br₈, CsSmb, Cs₂SnI_6, Cs2Sn(II)Sn(IV)I₈, RbSmCb, Rb₂SnCk, Rb₂Sn(II)Sn(IV)Cl₈, RbSmBrs, Rb₂SnBre, Rb₂Sn(II)Sn(IV)Br₈, RbSmb,

Rb₂SnIe, Rb₂Sn(II)Sn(IV)I₈, KSmCb, K₂SnCk, K₂Sn(II)Sn(IV)Cl₈, KSmBrs, K₂SnBre, K₂Sn(II)Sn(IV)Br₈, KSmls, K₂SnIe, K₂Sn(II)Sn(IV)I₈, MASmCb, MA₂SnCb, MA₂Sn(II)Sn(IV)Cl₈, MASmBrs, MA₂SnBre, MA₂Sn(II)Sn(IV)Br₈, MAS b,

MA₂Snl6, MA₂Sn(II)Sn(IV)I₈, Cs3Bi₂Cb, Cs3Bi₂Br9, Cs3Bi₂l9, Cs3Sb₂Cl9, Cs3Sb₂Br9, Cs₃Sb₂l9; CsPbCb, CsPbBo, CsPbb, RbPbCb, RbPbBr₃, KPbCb, KPbBo, KPbb, MAPbCb, MAPbBr₃, MAPbb, Cs₂PbCb, Cs₂PbBr₄, Cs₂PbI₄, MA₂PbCb, MA₂PbBr₄, MA₂PbI , Rb₂PbCl₄, Rb₂PbBr , Rb₂PbI , CsPteCb, Cs₂PbCb, Cs₂Pb(II)Pb(IV)Cl₈, CsPb2Brs, Cs₂PbBre, Cs₂Pb(II)Pb(IV)Br₈, CsPb₂Is, Cs₂PbIe, Cs2Pb(II)Pb(IV)I₈, RbPb₂Cb, Rb₂PbCb, Rb₂Pb(II)Pb(IV)Cb, RbPb₂Brs, Rb₂PbBre, Rb₂Pb(II)Pb(IV)Br₈, RbPb₂Is, Rb₂PbIe, Rb₂Pb(II)Pb(IV)I₈, KPb₂Cb, K₂PbCb, K₂Pb(II)Pb(IV)Cb, KPb₂Brs, K₂PbBre, K₂Pb(II)Pb(IV)Br₈, KPb₂Is, K₂PbIe, K₂Pb(II)Pb(IV)I₈, MAPb₂Cb, MA₂PbCb, MA₂Pb(II)Pb(IV)Cb, MAPb₂Brs, MA₂PbBre, MA₂Pb(II)Pb(IV)Br₈, MAPb₂Is,

MA₂PbIe, MA₂Pb(II)Pb(IV)I₈; Cs₂AgBiCk, Cs₂CuBiCk, Cs₂InAgCl₆, CsdnCuCb, Cs₂AgSbCk, Cs₂CuSbCl6, Cs₂AgBiBr6, Cs₂CuBiBr6, Cs₂InAgBr6, Cs₂InCuBr6, Cs₂AgBil6, Cs₂CuBil6, Cs₂AgSbBr6, Cs₂CuSbBr6, Cs₂AgSbl6, Cs₂CuSbl6, CsdnAgb, CsdnCuL·, Cs3Bi₂Cl9, Cs3Bi₂Br9, Cs3Bi₂l9, Cs3Sb₂Cl9, Cs3Sb₂Br9, Cs3Sb₂l9, Cs3ln₂Cl9, Cs3ln2Br9, CS3I112I9; K2AgBiCl6, foCuBiCk, K2lnAgCl6, K2lnCuCl6, foAgSbCk, K2CuSbCl6, K2AgBiBr6, K2CuBiBr6, K2lnAgBr6, K2lnCuBr6, K2AgBil6, K2CUB1I6, K2AgSbBr6, K2CuSbBr6, K2AgSbl6, K2CuSbl6, K2lnAgl6, K2I11CUI6, K3B12CI9, K3Bi2Br9, K3B12I9, K3Sb₂Cl9, K3Sb2Br9, K3Sb2l9, K3I112CI9, KqIikBb, K3I112I9; Na2AgBiCl6, Na2CuBiCl6, Na2lnAgCl6, Na2lnCuCl6, Na2AgSbCl6, Na2CuSbCl6, Na2AgBiBr6, Na2CuBiBr6, Na2lnAgBr6, Na2lnCuBr6, Na2AgBil6, Na2CuBil6, Na2AgSbBr6, Na2CuSbBr6, Na2AgSbL·, Na2CuSbL·, Na2lnAgL·, Na2lnCul6, Na3Bi2Cl9, Na3Bi2Br9, Na3Bi2l9, NaiSbrCk, Na3Sb2Br9, Na3Sb2l9, Na3ln2Cl9, Na3ln2Br9, Na3ln2l9; LkAgBiCk, LkCuBiCk, LklnAgCk, Li2lnCuCl6, LkAgSbCk, LkCuSbCk, LkAgBiBre, LkCuBiBre, Li2lnAgBr6, LklnCuBre, LFAgBik, LkCuBik, LkAgSbBre, LkCuSbBre, LkAgSbk, LkCuSbk, LklnAgk, LklnCuk, L 13 B i 2C 19 , LkBi2Br9, L 13 B i 219 , Li3Sb2Cl9, Li3Sb2Br9, Li₃Sb₂l9, Li₃In₂Cl9, Li₃In₂Br9, Lhlmh, (BaF)₂PbCl4, (BaF)₂PbBr , (BaF)₂PbI₄, (BaF)2SnCl₄, (BaF)2SnBr₄, (BaF)2SnI₄, and (BaF)2PbCl6, (BaF)2PbBr6, (BaF)2Pbl6, (BaF)2SnCl6, (BaF)2SnBr6, (BaF)2SnL·, and combinations thereof.

[0067] The perovskite materials can include a vacancy defect. For example, the perovskite materials can have at least one vacancy defect which is to be passivated. In some embodiments, the vacancy defect includes at least one anion vacancy. For example, in some embodiments, the vacancy defect includes at least one of an X¹ anion vacancy and an X² anion vacancy. In some embodiments, the vacancy defect includes an organic anion vacancy. In some embodiments, the vacancy defect includes an inorganic anion vacancy. For example, in some embodiments, the vacancy defect includes a halogen vacancy. In some embodiments, the vacancy defect includes a chloride vacancy. In some embodiments, the perovskite material has a bromide vacancy. In some embodiments, the perovskite material has an iodide vacancy. In some embodiments, the perovskite material has a fluoride vacancy. In some embodiments, the perovskite material has at least one of the following: a chloride vacancy, a bromide vacancy, an iodide vacancy, and a fluoride vacancy.

[0068] The perovskite materials can optionally include or further include at least one under-coordinated atom. For example, in some embodiments, the under-coordinated atom includes at least one of an under-coordinated B¹ atom and an under-coordinated B² atom. In some embodiments, the perovskite material includes a vacancy defect and an under-coordinated atom as a result of said vacancy defect. In some embodiments, the perovskite material includes an under-coordinated atom as a result of the halogen vacancy. For example, in some embodiments, the presence of an anion vacancy can lead to a net positive charge being formed on a cation of the perovskite material. In some embodiments, the under-coordinated atom includes an under-coordinated B cation. For example, in some embodiments, the net positive charge is formed on at least one B cation of the perovskite material. In some embodiments, the under-coordinated atom includes an under-coordinated metal atom. For example, in some embodiments, the net positive charge is formed on a metal atom.

[0069] The perovskite material can optionally include or further include at least one additional cation vacancy. In some embodiments, the additional cation vacancy includes an A cation vacancy. For example, in some embodiments, the additional cation vacancy includes an organic cation vacancy. In some embodiments, the additional cation vacancy includes an inorganic cation vacancy. In some embodiments, the additional cation vacancy includes an organic cation vacancy and an inorganic cation vacancy. In some embodiments, the additional cation vacancy includes at least one of an A¹ cation vacancy, an A² cation vacancy, and an A³ cation vacancy.

[0070] The non-polar solvent can include any non-polar solvent suitable for use in the processing and/or fabrication of perovskite materials. In some embodiments, the non polar solvent is free of halides. The absence of halides from the non-polar solvent can prevent or at least reduce the occurrence of unwanted peak shifts that occur during rapid halide exchange in, for example, mixed halide perovskites. For example, the presence of halides in the solvent can shift the bandgap of perovskite materials. The nonpolar solvents are not particularly limited. For example, in some embodiments, the nonpolar solvent includes toluene, n-hexane, pentane, cyclopentane, cyclohexane, benzene, diethylether, dioxane, chloroform, and the like.

[0071] Step (b) includes mixing the perovskite material with an organic pseudohalogen. In some embodiments, mixing includes contacting the perovskite material and the organic pseudohalide. In some embodiments, mixing includes mechanically mixing the perovskite material and organic pseudohalide. In some embodiments, mixing includes stirring the perovskite material and organic pseudohalide. In some embodiments, mixing includes agitating the perovskite material and organic pseudohalide. In some embodiments, mixing includes combining the perovskite material and organic pseudohalide. In some embodiments, upon mixing the organic pseudohalogen and perovskite material, the organic pseudohalogen dissolves or solubilities. [0072] The organic pseudohalogen can include a pseudohalogen associated with an organic compound. In some embodiments, the organic pseudohalogen has at least one of the following characteristics: (1) the organic pseudohalogen is sufficiently soluble in nonpolar solvents used in the fabrication and/or processing of perovskite materials; (2) the pseudohalogen of the organic pseudohalogen can remove deep electron trap states within the bandgap of perovskite materials; (3) the pseudohalogen group of the organic pseudohalogen can donate electron density and/or bond to the under-coordinated atom of the perovskite material; (4) the organic pseudohalogen can be halogen free, meaning it does not include any halogens; (5) the organic pseudohalogen does not undergo halide exchange with the perovskite materials (which can cause undesirable peak shifts) or otherwise alter the structure of the perovskite material; and (6) the organic pseudohalogen does not cause any appreciable shift in the bandgap of the perovskite material.

[0073] In accordance with one or more embodiments, passivating agents for blue- emitting mixed-halide perovskites are provided. The passivating agents should be compatible with mixed-halide perovskites and not cause unwanted peak shifts during their fast halide exchange mixed-halide perovskites. The passivating agents should also fill in halogen vacancies without appreciably changing the emission spectrum. Since low solubility in non-polar solvents can be a major hurdle facing most perovskite passivating agents (e.g., as polar solvents decompose the highly ionic perovskites), the passivating agent for vacancy defects (e.g., Cl vacancies in mixed-halide perovskite quantum dots) should be soluble in nonpolar solvents, including those which are compatible with mixed- halide perovskite quantum dot processing. In addition to being nonpolar, solvents for passivation processing of mixed-halide perovskite emitters should also be halogen free as halogen-containing solvents, such as chloroform among others, carry halide ions that may halide exchange and cause a shift in the bandgap of mixed-halide perovskite quantum dots. Passivating agents soluble in nonpolar solvents can include organic pseudohalides, such as organic thiocyanates (RSCN), with sufficient hydrophobic groups to dissolve in nonpolar, non-halogenated solvents.

[0074] The organic pseudohalogens can include an organic cation and a pseudohalogen. For example, in some embodiments, the organic pseudohalogen includes a compound of the formula: R — P_s and/or [R⁺,P_S ] , wherein R is an organic cation and P_s is a pseudohalogen. The organic cation can include ammonium ions and/or substituted ammonium ions, such as R — NH3⁺, R2 — NH2⁺, R3 — NH⁺, and R4 — N⁺. In some embodiments, each R is independently an alkyl, an aryl, an aralkyl, an alkaryl, or a cycloalkyl. In some embodiments, the alkyl includes a C₁-C20 alkyl, C₁-C20 aryl, C₁-C30 aralkyl, C₁-C30 alkaryl, or C₁-C30 cycloalkyl. In some embodiments the alkyl includes an alkyl having 5 or more carbon atoms. In some embodiments, the alkyl includes a C4-C8 alkyl, a C6-C20 alkyl, a C8-C20 alkyl, a C10-C20 alkyl, a C12-C20 alkyl, a C10-C18 alkyl, a C10-C14 alkyl, a Cs-Ci4 alkyl, a C14-C20 alkyl, and a C10-C16 alkyl, among others. The solubility of the organic pseudohalogen in nonpolar solvents can be modulated by selecting organic pseudohalogens with R groups having varying degrees of hydrophobicity. The pseudohalogen can include an isocyanate, a thiocyanate, an isothiocyanate, a cyanide, an azide, a cyanate, a cyano, a mesyl, a tosyl, a selenocyanate, a methanesulfonate, and the like. In some embodiments, the pseudohalogen includes at least one of the following: an isocyanate, a thiocyanate, an isothiocyante, and a cyanide. [0075] Examples of organic pseudohalogens include, without limitation, n- dodecylammonium thiocyanate (DAT), n-dodecylammonum chloride (DAC), n- butylammonium thiocyanate (BAT), benzylammonium thiocyanate, ethylammonium thiocyanate, form ami dinium thiocyanate, methylammonium thiocyanate, i- pentylammonium thiocyanate, neo-pentylammonium thiocyanate, phenethylammonium thiocyanate, cyclohexylammonium thiocyanate, n-hexylammonium thiocyanate, n- octylammonium thiocyanate, tert-octylammonum thiocyanate, phenylammonium thiocyanate, pyrrolidnium thiocyanate, methylammonium cyanate, benzylammonium isocyanate, n-butylammonium isocyanate, cyclohexylammonium isocyanate, n- dodecylammonium isocyanate, ethylammonium isocyanate, formamidinium isocyanate, n-hexylammonium isocyanate, methylammonium isocyanate, n-octylammonium isocyanate, tert-octylammonium isocyanate, iso-pentylammonium isocyanate, neo- pentylammonium isocyanate, phenethylammonium isocyanate, phenylammonium isocyanate, pyrrolidinium isocyanate, benzylammonium isothiocyante, n- butylammonium isothiocyante, cyclohexylammonium isothiocyante, n- dodecylammonium isothiocyante, ethylammonium isothiocyante, formamidinium isothiocyante, n-hexylammonium isothiocyante, methylammonium isothiocyante, n- octylammonium isothiocyante, tert-octylammonium isothiocyante, iso-pentylammonium isothiocyante, neo-pentylammonium isothiocyante, phenethylammonium isothiocyante, phenylammonium isothiocyante, pyrrolidinium isothiocyante, and the like.

[0076] The concentration of the organic pseudohalogen in the dispersion of the perovskite material can range from about 0.01 wt.% to about 20 wt.%, or any incremental value or subrange between that range, wherein the weight percent is based on the total weight of the dispersion. In some embodiments, the concentration of the organic pseudohalogen is about 1 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.9 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.8 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.7 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.6 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.5 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.4 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.3 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.2 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.1 wt.% or less. In some embodiments, the concentration of the organic pseudohalogen is about 0.01 wt.%.

[0077] The solubility of the organic pseudohalogen in the nonpolar solvent can be at least about 100 mg/ml. In some embodiments, for example, the solubility of the organic pseudohalogen can be greater than about 100 mg/ml. Organic pseudohalogen groups having solubilities of about 100 mg/ml or less are permitted and thus can be utilized herein. In general, the solubility of the organic pseudohalogen group in the nonpolar solvent (e.g., the nonpolar solvent of interest) can be at least about 10 mg/ml, preferably at least about 50 mg/ml, more preferably about 100 mg/ml, or greater.

[0078] Through the mixing the organic pseudohalogen can passivate at least one vacancy defect of the perovskite material. In some embodiments, the pseudohalogen group passivates the vacancy defect by bonding (e.g., chemically bonding) to the under coordinated atom. In some embodiments, the at least one vacancy defect includes an X anion vacancy defect. For example, in some embodiments, the pseudohalogen group of the organic pseudohalogen passivates the anion vacancy defect. In some embodiments, the pseudohalogen group passivates the anion vacancy defect by filling the vacancy. In some embodiments, the pseudohalogen group passivates the anion vacancy by bonding to the under-coordinated atom of the perovskite material. The organic pseudohalogen group can optionally passivate a second vacancy defect. For example, in some embodiments, the second vacancy defect includes a B cation vacancy defect. In some embodiments, the organic cation of the organic pseudohalogen passivates the cation vacancy defect by filling the vacancy. [0079] Embodiments of the present disclosure also provide passivated perovskite materials. The passivated perovskite materials may include passivated perovskite materials formed in accordance with the methods disclosed herein (e.g., in FIG. 1). In some embodiments, a passivated perovskite material includes a perovskite material including a vacancy defect and an under-coordinated atom and an organic pseudohalogen including an organic cation associated with a pseudohalogen moiety, wherein the pseudohalogen moiety passivates the vacancy defect by bonding to the under-coordinated atom. Any of the features of the present disclosure, including those features disclosed above in connection with FIG. 1 , may be included or applied here.

[0080] Embodiments further include optoelectronic devices comprising any of the passivated perovskite materials formed in accordance with the methods disclosed herein. For example, in some embodiments, an optoelectronic device comprises a perovskite material including a vacancy defect and an under-coordinated atom and an organic pseudohalogen including an organic cation associated with a pseudohalogen moiety, wherein the pseudohalogen moiety passivates the vacancy defect by bonding to the under coordinated atom. Examples of optoelectronic devices include, without limitation, light- emitting diodes of any color; solar cells (e.g., ultrathin organic photovoltaics OIPVs), photodetectors, paraelectric devices, field-effect transistors, photodiodes, phototransistors, photomultipliers, optoisolators, integrated optical circuits, photoresistors, photoconductive tubes, charge-coupled devices, injection laser diodes, quantum cascade lasers, photoemissive tubes, and the like. In some embodiments, a blue- emitting perovskite light-emitting diode comprising a passivated perovskite material according to any of the methods disclosed herein is provided.

[0081] In accordance with one or more embodiments, efficient Cl vacancy passivating agents can be used for blue-emitting mixed-halide perovskites (MHP). Organic halides which are usually useful as passivating agents for halogen vacancies in CsPbBn and CsPbF can be incompatible with MHPs because of unwanted peak shifts that occur during their fast halide exchange with MHPs. Pseudohalogens, such as thiocyanate (SCN ), can fill in the halogen vacancies without appreciably changing the emission spectrum. However, low solubility in non-polar solvents can be a major hurdle facing most perovskite passivation agents, including pseudohalogens, as polar solvents can decompose the highly ionic perovskites. Nonpolar solvents that can be used for passivation processing of MHP emitters can be halogen-free, as halogen containing solvents, such as chloroform, carry halide ions that may halide-exchange and shift the bandgap of MHP QDs. Accordingly, pseudohalogen passivators disclosed herein for halogen vacancies in MHP QDs can by soluble in at least one non-polar solvent that is compatible with MHP processing.

[0082] In accordance with one or more embodiments, blue-emitting perovskites are easily attainable by precisely tuning the halide ratio of mixed halide (Br/Cl) perovskites (MHPs). However, the adjustable halide ratio also hinders the passivation of Cl vacancies - the main source of deep trap states leading to inferior performance blue MHP light- emitting diodes (LEDs). In certain embodiments, a strategy to passivate Cl vacancies in MHP quantum dots (QDs) using non-polar-solvent-soluble organic pseudohalide (n- dodecylammonium thiocyanate (DAT)) is provided, enabling blue MHP LEDs with enhanced efficiency. (FIG. 2) Density-function-theory calculations reveal that the thiocyanate (SCN ) groups fill in the Cl vacancies and remove deep electron traps within the bandgap. DAT-treated CsPb(Br_xCli-_x)3 QDs exhibit near unity (-100%) photoluminescence quantum yields; and their blue (-470 nm) LEDs are spectrally stable with an external quantum efficiency (EQE) of 6.3% - a record for perovskite LEDs emitting at the 460-480 nm range relevant to Rec. 2020 display standards.

[0083] In accordance with one or more embodiments, organic pseuohalogens, such as organic thiocyanate (RSCN) with sufficient hydrophobic groups to dissolve in nonpolar nonhalogenated solvents can be used. In some embodiments, the organic pseudohalides can include at least one of the following: n-dodecylammonium thiocyanate (DAT; C12H25NH3SCN); n-dodecylammonium chloride (DAC; C12H25NH3CI); and n- butylammonium thiocyanate (BAT; C4H9NH3SCN). DAT had a high solubility of >100 mg/ml in toluene - a non-polar solvent that is used during MHP QD synthesis and storage, whereas n-dodecylammonium chloride (DAC; C12H25NH3Q) and shorter alkyl chain oil- like n-butylammonium thiocyanate (BAT; C4H9NH3SCN) cannot dissolve in toluene (FIG. 3). Accordingly, in some embodiments, DAC and BAT are used in nonpolar solvents other than toluene. In some embodiments, MHP QDs are subjected to a post treatment of DAT by mixing them together in toluene. In some embodiments, MHP QDs include CsPb(Br_xCh-_x)3 QDs are used, wherein the MHP QDs are synthesized according to known methods.

[0084] In accordance with one or more embodiments, the influence of the DAT post-treatment on the structural properties of MHP QDs, was investigated by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The pristine MHP QDs and DAT treated MHP QDs were found to have a cuboid shape with average size of 8.7 nm and 9.2 nm, respectively (FIGS. 4A-4B and 5A-5B). Both pristine MHP QDs and DAT treated MHP QDs had a lattice constant (d) of 0.58 nm, corresponding to the (001) crystal plane of the cubic phase perovskite, indicating that the DAT post treatment did not alter the MHP QD’s crystal structure (FIGS.4C-4D). The XRD patterns show that both pristine MHP QDs and DAT treated MHP QDs have a cubic phase (FIG. 4E). To verify the presence of DAT in the MHP QD films with high sensitivity, secondary ion mass spectrometry (SIMS) with a detection limit of as low as parts per billion (ppb) was collected. See FIGS. 6A-6B.

[0085] In accordance with one or more embodiments, a notable enhancement of the PL intensity and PLQY of these MHP QDs with DAT post-treatment was observed. The pristine MHP QDs exhibited an emission peak at 468.4 nm, with a full width at half maximum (FWHM) of -15 nm and a PLQY of 83%. The DAT treated MHP QDs exhibit an emission peak at 468.8 nm, and the DAT treatment increased the PLQY of MHP QDs to near unity (-100%) (FIG. 4F). The slight shift of emission peaks can be attributed to the minor change in the NC’s size caused by DAT treatment.

[0086] In accordance with one or more embodiments, to further elucidate the mechanism underpinning the PLQY enhancements, the effect of DAT post-treatment on the electronic properties of CsPbCb was investigated by using DFT calculations. Three slab models were considered as given in FIGS. 7C-7E, which are i) the ideal CsPbCb slab, (ii) the CsPbCb slab with removed surface Cl atoms, and (iii) the CsPbCb slab treated with the SCN on the surface. Here the Cl vacancy was the dominating defect on the CsPbCb surface as the formation energy of surface Cl vacancy was even lower than Br vacancy in CsPbBo which represented the major defect species in CsPbBo (FIG. 7B). In the ideal CsPbCb slab, both hole and electron wavefunction were delocalized in the bulk. The Cl vacancy led to the formation of a trap state that was -0.2 eV below the conduction band with a localized charge density on the surface layer (FIG.7D), acting as an electron-trapping center for the nonradiative recombination. Once the Cl vacancy on the surface was filled by SCN , it removes the midgap states and enriches the top of the valence band density through contributions from SCN (FIG. 7E).

[0087] According to one or more embodiments, the plausible mechanisms behind the PLQY enhancement is summarized in FIG. 7A. Halogen vacancy formation led to a net positive charge residing on the Pb atom which is also known as an under-coordinated Pb atom. The injected electrons can be electrostatically attracted into this Coulomb trap site (halogen vacancies); and this picosecond electron trapping is the dominant channel impairing the PLQYs of CsPbCb NCs. SCN can fill in these halogen vacancies, and donate electron density to under-coordinated Pb atom of MHP QDs.

[0088] In accordance with one or more embodiments, encouraged by the improved PLQYs, LEDs were fabricated using these MHP QD inks combined with DAT for passivation. LEDs were structured as follows: indium tin oxide (ITO) glass substrate/Poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB)/nafion perfluorinated resin (PFI)/MHP QDs/tris(2,4,6-triMethyl-3-(pyridin-3- yl)phenyl)borane (3TPYMB)/Liq/Al, as shown in FIG. 8A. The MHP LEDs exhibited electroluminescence (EL) with an emission peak of 471 nm and a narrow FWHM of ~17 nm (FIG. 8B).

[0089] FIG. 8C shows luminance and current density characteristics as a function of applied voltage for pristine device and the DAT treated device. The maximum luminance for DAT treated device reached 465 cd/cm², which was over two times higher than the pristine device (210 cd/cm²). The maximum EQE for DAT treated device was 6.3% (FIG. 8D), a record for perovskite LEDs with emission between 460-480 nm. The EQE was nearly two times higher than pristine MHP QD LEDs (3.5%), attributing to the reduced Cl vacancy density and promoted radiative-recombination. The DAT treated device exhibited a half-lifetime close to 100s, much higher than pristine MHP QD LEDs (15s) (FIGS. 8E-8F). The improved device stability was ascribed to the suppressed Cl vacancy density, which suppressed ion migration by reducing the hoping sites. FIG. 9 is a graphical view showing time-resolved photoluminescence (PL) decay of pristine MHP QD films and DAT-treated MHP QD films, in accordance with one or more embodiments of the present invention. FIG. 10 is a cross-sectional high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the MHP QD LEDs, in accordance with one or more embodiments of the present invention. FIGS. 11A- 11B are graphical views showing normalized EL spectra for (A) pristine device and (B) the DAT-treated device, in accordance with one or more embodiments of the present invention.

[0090] In accordance with one or more embodiments, a strategy to passivate Cl vacancy was demonstrated, enhancing efficiency and stability of MHP QD LEDs through the use of an organic pseudohalide that dissolved in a non-polar solvent. As a result of Cl vacancy passivation, MHP QDs post- treated with DAT had their PLQYs enhanced to near unity (-100%). The Cl- vacancy passivation enabled the fabrication of efficient blue (-470 nm, i.e. in the Rec 2020 range relevant display standards) MHP QD LEDs with an EQE of 6.3% (vs. 3.5% for pristine devices) and half-lifetime of -100 s (vs. -15 s for the pristine devices). Cl vacancy passivation can be useful for enhancing the efficiency and stability of MHP QD LEDs; and provides an avenue for significantly improving blue perovskite LEDs relevant to display applications.

[0091] In accordance with one or more embodiments, LED characterization can involve current-voltage characteristics which are measured with a computer controlled Keithley 2400 source meter. Electroluminescence spectra was collected by using a photonic multichannel analyzer PMA-12 (Hamamatsu 00027-01). The external quantum efficiency of the devices (calculated in the range of 300-980 nm) was obtained by measuring the light intensity in the forward direction by using an integrating sphere (Hamamatsu A10094). All the measurements were carried out in ambient air.

[0092] In accordance with one or more embodiments, DFT calculations can be carried out using a projector augmented wave (PAW) method as implemented in the Vienna ab initio Simulation Package (VASP). The PerdewBurke-Ernzerhof (PBE) formulation of the generalized gradient functional (GGA) for exchange-correlation energy was used. The energy cutoff for the wave function expanded in the plane-wave basis was 500 eV. Monkhorst-Pack-type k-meshes of 6x6x6 and 6x6x1 were used for the cubic-phase bulk CsPbCb, and the 2x2 slabs are exposing the (001) surface, respectively. Three slab models of (/) the ideal CsPbCb slab, (77) with the removed Cl on the surface, and (iii) with the surface filled SCN- were considered. All the slabs were separated by both top and bottom vacuum layers (~10 A) to prevent spurious inter-slab interactions. Each structure was optimized until the forces on every single atom were smaller than 0.01 eV/A. The molecular graphics viewer VESTA was used to plot crystal structures and charge densities.

[0093] FIG. 12 is a schematic diagram of a QLED, according to one or more embodiments of the invention. As shown in FIG. 12, the QLED may include a perovskite. On one side of the perovskite, an electron transport layer, an interface layer, and an electrode may be provided as shown in FIG. 12. On an opposing side of the perovskite, a hole transport layer, an indium tin oxide layer, and glass or PET may be provided as shown in FIG. 12. In some embodiments, the electrode includes one or more of Al, Ag, Au, and Cu. In some embodiments, the interface layer includes one or more of LiF, Liq, Ca, Ba, and CsF. In some embodiments, the electron transport layer includes one or more of TPBi, Mg:ZnO, ZnO, 3TPYMB, and TmPyPB. In some embodiments, the hole transport layer includes one or more of PEDOT:PSS, PVK, PTAA, PolyTPD, NiOx, M0O3, and TFB:PFI. These shall not be limiting as other materials for each layer may be used herein and/or the arrangement and order of each layer may vary.

[0094] The following Examples are intended to illustrate the above invention and should not be construed as to narrow its scope. One skilled in the art will readily recognize that the Examiners suggest many other ways in which the invention could be practiced. It should be understood that numerous variations and modifications may be made while remaining within the scope of the invention.

Example 1

Synthesis and Post-Treatment

[0095] All chemicals were used as received without further purification: cesium carbonate (Cs2C03, 99.995%, Sigma-Aldrich), PbO (98%, Sigma- Aldrich), oleic acid (OA, technical grade 90%, Alfa Aesar), n-oleylamine (OAm, 70%, Sigma-Aldrich), 1- octadecene (ODE, technical grade 90%, Sigma-Aldrich), toluene (Honeywell Burdick & Jackson), OAmCl (>99.5%, Xi’an Polymer Light Technology Corp.), and OAmBr (>99.5%, Xi’an Polymer Light Technology Corp.).

[0096] CsPb(Br_xCli-x)3 QDs were synthesized according to a well-established synthesis protocol. For a typical procedure, CS2CO3 (0.2 mmol), PbO (0.4 mmol), ODE 20 ml, OA 4 ml, and OAm 2 ml were added into a 250 mL flask. The solution was heated to 120 °C and kept for 1 hour in order to dissolve the chemicals and get rid of oxygen and moisture. It was then purged 3 times with inert gas and heated to 200 °C. The CsPb(Br_xCli- _x)3 QDs were formed after the injection of a mixture of OAmBr (1.19 mmol) and OAmCl (0.835 mmol) in 2 ml OAm. The crude solution was centrifuged at 8000 rpm for 5 minutes. Then, the supernatant was removed, and the precipitate was collected and re dispersed in 10 mL toluene. One more centrifugation was required to purify the final QDs, with 8000 rpm for 1 minute in order to remove larger QDs. CsPb(Br_xCli-_x)3 QDs were subjected to a post-treatment of DAT by mixing them together in toluene.

Example 2

Passivated CsPb(Br_xCli-_x)3 QDs [0097] A perovskite material CsPb(Br_xCli-_x)3 quantum dots (QDs) was synthesized according to known methods. The crude CsPb(Br_xCli-_x)3 quantum dots were collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which included removing larger QDs. The QDs were dispersed in n-hexane, the concentration of the QDs being about 12 mg/ml. About 0.1 mg/ml of n-dodecylammonium thiocyanate (DAT) was added to and mixed with the QDs dispersion to passivate the QDs.

Example 3

Passivated CsPb(Br_xCh-_x)3 QDs

[0098] A perovskite material CsPb(Br_xCh-_x)3 quantum dots (QDs) was synthesized according to known methods. The crude CsPb(Br_xCli-_x)3 quantum dots were collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which included removing larger QDs. The QDs were dispersed in toluene, the concentration of the QDs being about 12 mg/ml. About 0.1 mg/ml of n-dodecylammonium thiocyanate (DAT) was added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 4 Passivated FAMAPbE QDs

[0099] A perovskite material of FAMAPbh QDs is synthesized according to known methods. The crude FAMAPbE QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 5 Passivated FAMAPbE QDs

[00100] A perovskite material of FAMAPbb QDs is synthesized according to known methods. The crude FAMAPbE QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 6 Passivated FAi-nMAnPb(Bri-_xI_x)3 QDs

[00101] A perovskite material of FAi-nMAnPb(Bri-_xI_x)3 (where 0 < x < l, 0 < n < l) QDs is synthesized according to known methods. The crude FAi-nMAnPb(Bri-_xI_x)3 QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 7 Passivated FAi-_nMAnPb(Bri-xI_x)3 QDs

A perovskite material of FAi-nMAnPb(Bri-_xIx)3 (where 0 < x < l, 0 < n < l) QDs is synthesized according to known methods. The crude FAi-nMAnPb(Bri-_xI_x)3 QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 8 Passivated FAi-nCsnPb(Ii-_xBr_x)3 QDs

[00102] A perovskite material of FAi-nCsnPb(Ii-_xBr_x)3 (where 0 < x < l, 0 < n < l) (where 0 < x < l, 0 < n < l) QDs is synthesized according to known methods. The crude FAi-nCsnPb(Ii-_xBr_x)3 QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 9 Passivated FAi-_nCs_nPb(Ii-xBrx)3 QDs

[00103] A perovskite material of FAi-nCsnPb(Ii-xBr_x)3 (where 0 < x < l, 0 < n < l) (where 0 < x < l, 0 < n < l) QDs is synthesized according to known methods. The crude FAi-nCsnPb(Ii-xBr_x)3 QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 10 Passivated Csx(FAi-nMAn)i-xPb(Ii-mBr_m)3 QDs

[00104] A perovskite material of Cs_x(FAi-nMAn)i-xPb(Ii-mBr_m)3 (where 0 < x < 1, 0 < n < l, 0 < m < l) QDs is synthesized according to known methods. The crude Cs_x(FAi- _nMAn)i-xPb(Ii-mBr_m)3 QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 11 Passivated Csx(FAi-_nMAn)i-xPb(Ii-mBr_m)3 QDs

[00105] A perovskite material of Csx(FAi-nMAn)i-xPb(Ii-_mBr_m)3 (where 0 < x < 1, 0 < n < l, 0 < m < l) QDs is synthesized according to known methods. The crude Cs_x(FAi- _nMAn)i-xPb(Ii-mBr_m)3 QDs is collected, re-dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in toluene, the concentration of the QDs being between about 10 mg/ml and about 20 mg/ml. About 0.05 to about 0.15 mg/ml of n-dodecylammonium thiocyanate (DAT) is added to and mixed with the QDs dispersion to passivate the QDs.

Constructive Example 12 Passivated CsPb(Br_xCli-_x)3 QDs

[00106] A perovskite material CsPb(Br_xQi-x)3 quantum dots (QDs) is synthesized according to known methods. The crude CsPb(Br_xCh-_x)3 quantum dots is collected, re dispersed in toluene, and centrifuged to further purify the QDs, which includes removing larger QDs. The QDs are dispersed in n-hexane, the concentration of the QDs being about 10 mg/ml and about 20 mg/ml. About 0.01 to about 0.20 mg/ml of a nonpolar solvent- soluble alkylammonium thiocyanate is added to and mixed with the QDs dispersion to passivate the QDs.

Example 13 LED Fabrication

[00107] The patterned ITO/glass substrates were sequentially cleaned with soap, deionized water, acetone, and isopropanol under ultrasonication. The ITO/glass substrates were then dried with N2 and treated with ultraviolet (UV) ozone for 15 min. PoIy(9,9- dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB) was dissolved in chlorobenzene at 5 mg/ml and spin-coated on treated ITO substrates at 6000 rpm, followed by annealing at 120 °C for 15 min. Then a thin film of nafion perfluorinated resin (PFI) (0.05 wt% in isopropanol) was deposited at 6000 rpm and dried at 120 °C for 15 min. QDs were dispersed in n-hexane with concentration about 12 mg/ml and spin- coated on the top of substrates. For DAT treated device, DAT with concentration of -0.1 mg/ml was added into QDs dispersion. Finally, films were transferred to evaporation chamber, where 40 nm tris(2,4,6-triMethyI-3-(pyridin-3-yl)phenyI)borane (3TPYMB), 1.6 nm Liq, and 100 nm A1 were deposited. Before measurement, all devices were encapsulated. (FIG. 8A)

Claims

WHAT IS CLAIMED IS:

1. A method of passivating a perovskite material, comprising:

(a) dispersing a perovskite material in a nonpolar solvent, the perovskite material including a vacancy defect and an under-coordinated atom; and

(b) mixing the perovskite material with an organic pseudohalogen, the organic pseudohalogen including a pseudohalogen moiety that passivates the vacancy defect by associating with the under-coordinated atom.

2. The method according to claim 1, wherein the perovskite material includes a mixed-halide perovskite quantum dot.

3. The method according to claims 1-2, wherein the perovskite material includes a synthesized perovskite material having the following chemical formula:

A ¹ _{( 1} -x-y) A² A³y B ¹zB²l-zX¹aX²bX³c wherein:

A¹, A², and A³ are each independently an alkali metal, a transition metal, a lanthanide, an actinide, a C1-C20 alkyl ammonium, or a C1-C20 alkylamine;

B¹ and B² are each independently an alkaline earth metal, a transition metal, a post-transition metal, a metalloid, a lanthanoid, or an actinoid;

X¹, X², and X³ are each independently a halogen, an oxalate, a hydroxide, a chlorate, an iodate, a nitrite, a sulfate, a thiosulfate, a phosphate, an antimonite, an acetate, a formate, a borate, a carborane, or a phenyl borate; and

0 < x < l; 0 < y < l; 0 < z < l; 0 < a < 3; 0 < b < 3; 0 £ c < 3.

4. The method according to claim 3, wherein A¹, A², and A³ are each independently cesium, rubidium, potassium, sodium, lithium, francium, copper, methylammonium, ethylammonium, propylammonium, butylammonium, formamidinium, hydrazinium, acetylammonium, dimethylammonium, imidazolium, or guanidinium.

5. The method according to claims 3-4, wherein B¹ and B² are each independently lead (Pb), tin (Sn), germanium (Ge), beryllium (Be), magnesium (Mg), calcium (Ca), cadmium (Cd), strontium (Sr), barium (Ba), iron (Fe II), chromium (Cr II), cobalt (Co II), nickel (Ni II), manganese (Mn II), copper (Cu II), palladium (Pd), vanadium (V II), zinc (Zn II), bismuth (Bi), antimony (Sb), indium (In III), iron (Fe), aluminum (Al), europium (Eu), lanthanum (La), or yttrium (Y).

6. The method according to claims 3-5, wherein X¹, X², and X³ are each independently F, Cl, Br, or I.

7. The method according to claims 1-6, wherein the perovskite material includes at least one of the following: CsPbL; CsPbBn; MAPbL; FAPbL; MAFAPbL; FAi- _nMAnPb(Bri-xIx)3 where 0 < x < 1 and 0 < n < 1 ; FAi-_nCs_nPb(Ii-xBrx)3 where 0 < x < 1 and 0 < n < 1; CsMAFAPb(Br_xIi-x)3; Csx(FAi-_nMAn)i-xPb(Ii-mBr_m)3 where 0 < x < l, 0 < n < 1, and 0 < m < 1; APb(Xi-_xY_x)3 or APbX3-xYx where A is MA⁺, Cs⁺, or FA⁺, X and Y are each independently CP, Br , or T, and x is from 0 to 3; CsFAPb(Br_xIi-_x)3 where 0 < x < 1; CsPb(Br_xCli x)3 where 0 < x < 1; PEA2(MACS)i.5Pb2.sBr8.5; Cs_xFAi-_xPbBr3; CsPbClo.9Br2.i; PEA2(Rbo.6Cso.4)2Pb3Bno; CsMn_yPbi-yBrxCb-x; BA2Csn-iPbn(Br/Cl)3n+i; CsPb(BrxCll-x)3; PEA2CS(n-i-x)MAxPbnBr3n+P PEA2CS(n-i-x)FAxPbnBr3n+P PEA2K(n-i- x)MAxPb_nBr3n_+i; and RbxCs(i-_x)Pb(Br_yCl(i-_y))3 and optionally A2MX4.

8. The method according to claims 1-7, wherein the perovskite material includes at least one of the following: CsPbL, CsPbBo, MAPbb, FAPbL, CsMAFAPb(Br_xIi-_x)3, CsFAPb(Br_xIi-x)3, MAF APbL ,-M APbBr₃ , MAPbBr₂Cl, MAPbCL, FAPbBr₃, FAPbCL, CsPbCL, MASnL, MASnBn, MASnCL, FASnL, FASnBr3, FASnCL, CsSnL, CsSnBr3, CsSnCL, CsSiCL, CsSiBr₃, CsSiL, RbSiCL, RbSiBr₃, KSiCL, KSiBr₃, KSiL, MASiCL, MASiBr₃, MASiL, Cs₂SiCl₄, Cs₂SiBr , Cs₂SiI₄, MA2S1CI4, MA₂SiBr₄, MA2S1I4, Rb₂SiCl4, Rb₂SiBr₄, Rb₂Sil4, CsSLCL, Cs2SiCk, Cs₂Si(II)Si(IV)Cl8, CsSLBrs, Cs₂SiBr₆, Cs₂Si(II)Si(IV)Br8, CsSLL, Cs₂SiI_6, Cs2Si(II)Si(IV)L, RbSLCL, Rb₂SiCl6, Rb₂Si(II)Si(IV)Cl8, RbSLBrs, Rb₂SiBr₆, Rb₂Si(II)Si(IV)Br8, RbSLL,

Rb₂Sil6, Rb₂Si(II)Si(IV)l8, KS12CI5, K₂SiCl₆, K₂Si(II)Si(IV)Cl8, KSLBrs, K₂SiBr₆, K₂Si(II)Si(IV)Br8, KS12I5, K₂SiI_6, K₂Si(II)Si(IV)l8, MASLCls, MA₂SiCl₆, MA₂Si(II)Si(IV)Cl8, MASLBrs, MA₂SiBre, MA₂Si(II)Si(IV)Br8, MAS12I5,

MA2S1I6, MA₂Si(II)Si(I V) ; CsGeCL, CsGeBr₃, CsGeL, RbGeCL, RbGeBr₃, KGeCL, KGeBo, KGeL, MAGeCL, MAGeBr₃, MAGeL, Cs₂GeCl4, Cs₂GeBr , Cs₂GeI , MA₂GeCl4, MA₂GeBr₄, MA₂GeI₄, Rb₂GeCl4, Rb₂GeBr4, Rb₂Gel4, CsGe₂CL, Cs₂GeCl6, Cs₂Ge(II)Ge(IV)Cl8, CsGe₂Br₅, Cs₂GeBr₆, Cs₂Ge(II)Ge(IV)Br8, CsGe₂L,

Cs₂Gel6, Cs2Ge(II)Ge(IV)l8, RbGe₂CL, Rb₂GeCl6, Rb₂Ge(II)Ge(IV)Cl8, RbGe₂Br₅, Rb₂GeBre, Rb₂Ge(II)Ge(IV)Br₈, RbGe₂Is, Rb₂GeIe, Rb₂Ge(II)Ge(IV)I₈, KGe₂Cb, K₂GeCle, K₂Ge(II)Ge(I V)C1₈ , KGe₂Brs, K₂GeBre, K₂Ge(II)Ge(IV)Br₈, KGe₂Is, K₂GeIe, K₂Ge(II)Ge(IV)I₈, MAGe₂Cb, MA₂GeCb, MA₂Ge(II)Ge(IV)Cl₈, MAGe₂Brs, MA₂GeBre, MA₂Ge(II)Ge(IV)Br₈, MAGe₂Is, MA₂GeIe, MA₂Ge(II)Ge(IV)I₈; CsSnCb, CsSnBr3, CsSnb, RbSnCb, RbSnBr3, KSnCb, KSnBr3, KSnb, MASnCb, MASnBr3, MASnb, Cs₂SnCb, Cs₂SnBr4, Cs₂Snl4, MA₂SnCb, MA₂SnBr4, MA₂Snl4, Rb₂SnCb, Rb₂SnBr4, Rb₂Snl4, CsSmCb, Cs₂SnCk, Cs₂Sn(II)Sn(IV)Cl₈, CsSmBrs, Cs₂SnBr6, Cs₂Sn(II)Sn(IV)Br₈, CsSmb, Cs₂SnI_6, Cs2Sn(II)Sn(IV)I₈, RbSmCb, Rb₂SnCk, Rb₂Sn(II)Sn(IV)Cl₈, RbSmBrs, Rb₂SnBre, Rb₂Sn(II)Sn(IV)Br₈, RbSmb,

Rb₂SnIe, Rb₂Sn(II)Sn(IV)I₈, KSmCb, K₂SnCk, K₂Sn(II)Sn(IV)Cb, KSmBrs, K₂SnBre, K₂Sn(II)Sn(IV)Br₈, KSmls, K₂SnIe, K₂Sn(II)Sn(IV)I₈, MASmCb, MA₂SnCb, MA₂Sn(II)Sn(IV)Cb, MASmBrs, MA₂SnBre, MA₂Sn(II)Sn(IV)Br₈, MAS b,

MA₂Snl6, MA₂Sn(II)Sn(IV)I₈, Cs3Bi₂Cb, Cs3Bi₂Br9, Cs3Bi₂l9, Cs3Sb₂Cl9, Cs3Sb₂Br9, Cs3Sb₂I₉; CsPbCb, CsPbBn, CsPbb, RbPbCb, RbPbBr₃, KPbCb, KPbBn, KPbb, MAPbCb, MAPbBr₃, MAPbb, Cs₂PbCb, Cs₂PbBr , Cs₂PbI , MA₂PbCb, MA₂PbBr₄, MA₂PbI , Rb₂PbCb, Rb₂PbBr , Rb₂PbI , CsPteCb, Cs₂PbC Cs₂Pb(II)Pb(IV)Cb, CsPb2Brs, Cs₂PbBre, Cs₂Pb(II)Pb(IV)Br₈, CsPb₂Is, Cs₂PbIe, Cs2Pb(II)Pb(IV)Is, RbPb₂Cb, Rb₂PbCb, Rb₂Pb(II)Pb(IV)Cb, RbPb₂Brs, Rb₂PbBre, Rb₂Pb(II)Pb(IV)Br₈, RbPb₂Is, Rb₂PbIe, Rb₂Pb(II)Pb(IV)I₈, KPb₂Cb, K₂PbCb, K₂Pb(II)Pb(IV)Cb, KPb₂Brs, K₂PbBre, K₂Pb(II)Pb(IV)Br₈, KPb₂Is, K₂PbIe, K₂Pb(II)Pb(IV)I₈, MAPb₂Cb, MA₂PbCb, MA₂Pb(II)Pb(IV)Cb, MAPb₂Brs, MA₂PbBre, MA₂Pb(II)Pb(IV)Br₈, MAPb₂Is,

MA₂PbIe, MA₂Pb(II)Pb(IV)I₈; Cs₂AgBiCk, Cs₂CuBiCk, Cs₂InAgCl₆, CsdnCuCb, Cs₂AgSbCk, Cs₂CuSbCl6, Cs₂AgBiBr6, Cs₂CuBiBr6, Cs₂InAgBr6, Cs₂InCuBr6, Cs₂AgBil6, Cs₂CuBil6, Cs₂AgSbBr6, Cs₂CuSbBr6, Cs₂AgSbL·, Cs₂CuSbl6, CsdnAgL·, Cs₂InCul6, Cs3Bi₂Cl9, Cs3Bi₂Br9, Cs3Bi₂l9, Cs3Sb₂Cb, Cs3Sb₂Br9, Cs3Sb₂l9, Cs3ln₂Cl9, Cs3ln₂Br9, Cs3ln₂l9; K₂AgBiCb, K₂CuBiCb, K₂InAgCb, K₂InCuCk, K₂AgSbCk, K₂CuSbCk, K₂AgBiBr6, K₂CuBiBr6, K₂InAgBr6, K₂InCuBr6, K₂AgBil6, K₂CuBil6, K₂AgSbBr6, K₂CuSbBr6, K₂AgSbl6, K₂CuSbl6, K₂InAgl6, K₂InCul6, K3Bi₂Cb, K3Bi₂Br9, K3Bi₂l9, K3Sb₂Cb, K3Sb₂Br9, K3Sb₂l9, KjlmCb, K3ln₂Br9, K3ln₂l9; Na₂AgBiCb, Na₂CuBiCb, Na₂InAgCb, NadnCuCb, Na₂AgSbCk, Na₂CuSbCb, Na₂AgBiBr6, Na₂CuBiBr6, Na₂InAgBr6, Na₂InCuBr6, Na₂AgBil6, Na₂CuBil6, Na₂AgSbBr6, Na₂CuSbBr6, Na₂AgSbl6, Na₂CuSbl6, NadnAgb, Na₂InCul6, Na3Bi₂Cb, Na3Bi₂Br9, Na3Bi₂l9, Na3Sb₂Cb, Na3Sb₂Br9, Na3Sb₂l9, Na3ln₂Cl9, Na3ln₂Br9, Na3ln₂l9; L AgBiCk, Li₂CuBiCl6, L lnAgCk, Li₂InCuCl6, Li₂AgSbCl6, LbCuSbCb, Li₂AgBiBr6, Li₂CuBiBr6, Li2lnAgBr6, LFInCuBiY,, LFAgBih, LhCuBih, LFAgSbBiY,. LFCuSbBiY,, LkAgSbh, LFCuSbh, LFInAgh, LklnCuIe, L i¾ B i 2C 1 y , LuBirBn;, L i¾ B i 21 y , Li3Sb2Cl9, Li3Sb2Br9, Li₃Sb₂l9, Li₃In₂Cl9, Li₃In₂Br9, Li₃In₂l9, (BaF)₂PbCl4, (BaF)₂PbBr , (BaF)₂PbI₄, (BaF)₂SnCl₄, (BaF)₂SnBr₄, (BaF)₂SnI₄, (BaF)₂PbCl6, (BaF)₂PbBr₆, (BaF)₂PbI₆, (BaF)2SnCl6, (BaF)2SnBr6, and (BaF)2Snl6.

9. The method according to claims 1-8, wherein the nonpolar solvent is nonhalogenated.

10. The method according to claims 1-9, wherein the nonpolar solvent includes at least one of the following: toluene, n-hexane, pentane, cyclopentane, cyclohexane, benzene, diethylether, and dioxane.

11. The method according to claims 1-10, wherein the nonpolar solvent includes toluene.

12. The method according to claims 1-11, wherein the vacancy defect includes a halogen vacancy.

13. The method according to claims 1-12, wherein the vacancy defect includes a Cl vacancy and/or wherein the under-coordinated atom includes Pb.

14. The method according to claims 1-13, wherein the organic pseudohalogen is soluble in the nonpolar solvent.

15. The method according to claims 1-14, wherein the organic pseudohalide includes an organic ammonium cation and a pseudohalogen, wherein the organic ammonium cation includes an alkyl, an aryl, an aralkyl, an alkaryl, or a cycloalkyl, and wherein the pseudohalogen includes an azide, an isocyanide, a thiocyanide, a thiocyanate, an isothiocyanate, a cyanide, an isocyanate, a cyanate, a cyano, a mesyl, a tosyl, a selenocyanate, or a methanesulfonate.

16. The method according to clai s 1-15, wherein the organic pseudohalogen includes n-dodecylammonium thiocyanate (DAT).

17. The method according to claims 1-16, wherein the organic pseudohalogen includes at least one of the following: n-dodecylammonium thiocyanate (DAT), n- dodecylammonum chloride (DAC), n-butylammonium thiocyanate (BAT), benzylammonium thiocyanate, ethylammonium thiocyanate, formamidinium thiocyanate, methylammonium thiocyanate, i-pentylammonium thiocyanate, neo- pentylammonium thiocyanate, phenethylammonium thiocyanate, cyclohexylammonium thiocyanate, n-hexylammonium thiocyanate, n-octylammonium thiocyanate, tert- octylammonum thiocyanate, phenylammonium thiocyanate, pyrrolidnium thiocyanate, methylammonium cyanate, benzylammonium isocyanate, n-butylammonium isocyanate, cyclohexylammonium isocyanate, n-dodecylammonium isocyanate, ethylammonium isocyanate, formamidinium isocyanate, n-hexylammonium isocyanate, methylammonium isocyanate, n-octylammonium isocyanate, tert-octylammonium isocyanate, iso-pentylammonium isocyanate, neo-pentylammonium isocyanate, phenethylammonium isocyanate, phenylammonium isocyanate, pyrrolidinium isocyanate, benzylammonium isothiocyante, n-butylammonium isothiocyante, cyclohexylammonium isothiocyante, n-dodecylammonium isothiocyante, ethylammonium isothiocyante, formamidinium isothiocyante, n-hexylammonium isothiocyante, methylammonium isothiocyante, n-octylammonium isothiocyante, tert- octylammonium isothiocyante, iso-pentylammonium isothiocyante, neo- pentylammonium isothiocyante, phenethylammonium isothiocyante, phenylammonium isothiocyante, and pyrrolidinium isothiocyante.

18. An optoelectronic device comprising a passivated perovskite material according to claims 1-17.

19. A blue-emitting perovskite light-emitting diode comprising a passivated perovskite material according to claims 1-17.

20. A quantum dots light-emitting device (QLED) comprising: an anode, a cathode, an electron transport layer, a hole transport layer, and a quantum dot light emitting layer, wherein the quantum dot light emitting layer of the QLED includes the passivated perovskite material according to any one of claims 1-17.

21. A passivated perovskite material comprising: a perovskite material including a vacancy defect and an under-coordinated atom; and an organic pseudohalogen including an organic cation associated with a pseudohalogen moiety, wherein the pseudohalogen moiety passivates the vacancy defect by bonding to the under-coordinated atom.

22. The passivated perovskite material according to claim 21, wherein the organic pseudohalide includes an organic ammonium cation and a pseudohalogen, wherein the organic ammonium cation includes an alkyl, an aryl, an aralkyl, an alkaryl, or a cycloalkyl, and wherein the pseudohalogen includes an azide, an isocyanide, a thiocyanide, a thiocyanate, an isothiocyanate, a cyanide, an isocyanate, a cyanate, a cyano, a mesyl, a tosyl, a selenocyanate, or a methanesulfonate.

23. The passivated perovskite material according to claim 21, wherein the organic pseudohalogen includes an organic ammonium cation and wherein the organic ammonium cation includes at least one of an alkyl, an aryl, an aralkyl, an alkaryl, and a cycloalkyl.

24. The passivated perovskite material according to claim 21, wherein the organic pseudohalogen includes an alkyl ammonium cation and at least one of the following pseudohalogens: an azide, an isocyanide, a thiocyanide, a thiocyanate, an isothiocyanate, a cyanide, an isocyanate, a cyanate, a cyano, a mesyl, a tosyl, a selenocyanate, and a methanesulfonate.

25. The passivated perovskite material according to claim 24, wherein the alkyl ammonium cation includes a C4-C20 alkyl.

26. The passivated perovskite material according to claim 24, wherein the alkyl ammonium cation includes a C8-C20 alkyl.