WO2021081380A1

WO2021081380A1 - Perovskite nanocrystal compositions

Info

Publication number: WO2021081380A1
Application number: PCT/US2020/057137
Authority: WO
Inventors: Lutfan SINATRA; Marat LUTFULLIN; Osman Mohammed Bakr
Original assignee: Quantum Advanced Solutions Ltd
Priority date: 2019-10-23
Filing date: 2020-10-23
Publication date: 2021-04-29
Also published as: GB201915382D0

Abstract

Described herein are compositions comprising perovskite quantum dots bonded to one or more ligands, each of the perovskite quantum dots independently having the formula: C_sa(MA)_b(FA)_cRb_dPb_pSn_rBi_sCl_xBr_yI_z, and each of the ligands independently having the formula: R₄P⁺I^-, wherein MA, FA, a, b, c, d, p, r, s, x, y, z and R are as defined herein. Also described are devices comprising such materials, as well as methods of forming such materials.

Description

PEROVSKITE NANOCRYSTAL COMPOSITIONS

BACKGROUND

Technical Field

The present disclosure generally relates to light converting luminescent composite materials. In particular, it relates to perovskite nanocrystals and their applications.

Description of the Related Art

Semiconductor nanocrystals (NCs), including quantum dots (QDs), are emerging as important nanomaterials for applications, such as displays, due to their unique optical properties. The successful exploitation of their excellent luminescent properties, including emission wavelength tunability covering the entire visible spectrum, narrow emission with full width at half maximum (FWHM) of < 30-40 nm, high photoluminescence quantum yield (PLQY) up to 100%, and short photoluminescence (PL) decay time of < 50 nanoseconds (ns), can allow the delivery of true-to-life color display devices.

One way to use quantum dots in display applications is to embed quantum dots in a liquid crystal display (LCD) backlighting unit, wherein quantum dots with green and red emission wavelengths are encapsulated in a polymer film and down-convert blue light from a light source (e.g. light emitting diode (LED)) into highly pure green and red lights. Such display devices benefit from narrow emission from quantum dots, and hence have more realistic color representation covering extended color gamut when compared with display devices with standard backlighting systems based on white LED sources.

Two of the most widely used quantum dots for display devices are InP- and CdSe- based quantum dots. Green InP quantum dot-based display devices with FWHM of 35-45 nm have shown that they can cover > 85% of Rec.2020 standard. The drawback with InP quantum dots is their broad FWHM 35-45 nm that does not allow to reproduce the wider color gamut display. Display devices comprising CdSe quantum dots with FWHM of 25-35 nm can cover a wider color gamut of > 90% of the Rec.2020 standard. One of the downsides of using Cd-based quantum dots, such as CdSe quantum dots, in display devices is the high toxicity of the material. Efficient Cd quantum dot-based display devices typically have polymer films with Cd composition of at least 0.05-0.1 %, by weight. However, Restrictions of Hazardous Substances (RoHS) regulations by the EU limit the Cd composition in a polymer film to a maximum of 0.01 %, by weight. Accordingly, while progress has been made in this field, there remains a need in the art for improved quantum dot materials.

BRIEF SUMMARY

The present disclosure provides compositions comprising: perovskite quantum dots bonded to one or more ligands, each of the perovskite quantum dots independently having the formula:

Csa(MA)b(FA)_cRbdPbpSnrBisClxBr_yIz, and each of the ligands independently having the formula:

R₄P⁺T, wherein:

MA is CH3NH3;

FA is HC(NH₂)₂; a, b, c, and d are each independently a number from 0 to 1, provided that the sum of a, b, c, and d is 1; p, r, and s are each independently a number from 0 to 1, provided that the sum of p, r, and s is 1; x, y, and z are each independently a number from 0 to 3, provided that the sum of x, y, and z is 3; and

R is at each occurrence, independently, an organic substituent.

Additional aspects of the present disclosure comprise perovskite quantum dots, and a monomer, polymer, or both, as well as methods of making the same. Also described herein are devices comprising such a material.

In additional aspects, the present disclosure provides methods for forming a material of the disclosure, the method comprising: mixing (a) the monomer or the polymer, and (b) the perovskite quantum dots.

In still further aspects, provided herein are methods for forming a film comprising spreading a material described herein; and forming the film by curing the material.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the figures, identical reference numbers identify similar elements. The sizes and relative positions of elements in the figures are not necessarily drawn to scale and some of these elements are enlarged and positioned to improve figure legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the figures.

FIG. 1 is a CIE chromaticity diagram of the polymer composite with CsPbBn quantum dots inside the display device.

FIG. 2A is a schematic of the accelerated test of quantum dots in polymer films.

FIG. 2B is a schematic of a high-flux testing method.

FIG. 3 is an experimental plot of the accelerated reliability test of the polymer composite with CsPbBn quantum dots.

FIG. 4. is a graphic representation of oleylamine and oleic acid ligands detachment under heat and light exposure.

FIG. 5 is a PL spectra showing change of emission peak for CsPb(Br/I)3 quantum dots during heat exposure.

FIG. 6A is a plot showing change of normalised emission intensity of the polymer composite with CsPbBn-OLAI quantum dots with OLAI under 85°C, light exposure 450 nm (10 mW/cm²) within 1,000 hours.

FIG. 6B is a plot showing change of emission peak of the polymer composite with CsPbBn-OLAI quantum dots with OLAI under 85°C, light exposure 450 nm (10 mW/cm²) within 1,000 hours.

FIG. 7A is a graphic representation of polymer composites with quantum dots according to embodiments and showing a schematic of its working principle as a light down-conversion layer.

FIG. 7B is a graphic representation of polymer composites with quantum dots according to embodiments and additional red emitting material and a schematic of its working principle as a light down-conversion layer.

FIG. 8A is a schematic of a liquid crystal display (LCD) device.

FIG. 8B is an embodiment of a display device that comprises a film described herein.

FIG. 9 is a PL spectrum of the polymer film with CsPbBn-TMAI quantum dots (0.5%, by weight).

FIG. 10A is a plot showing change of normalised emission intensity of the polymer composite with CsPbBn-TMAI quantum dots under 85°C, light exposure 450 nm (10 mW/cm²) within 1,000 hours. FIG. 10B is a plot showing change of emission peak of the polymer composite with CsPbBn-TMAI quantum dots under 85°C, light exposure 450 nm (10 mW/cm²) within 1,000 hours.

FIG. IOC is a plot showing change of FWHM of the polymer composite with CsPbBn- TMAI quantum dots under 85°C, light exposure 450 nm (10 mW/cm²) within 1,000 hours.

FIG. 11 is a CIE chromaticity diagram of the polymer composite with CsPbBn-TMAI quantum dots inside the display device according to the FIG. 5.

FIG. 12 is an emission spectrum of the polymer composite with CsPbBn-TMAI quantum dots and CdSe/ZnS quantum dots.

FIG. 13 is a schematic of the LCD device.

FIG. 14A is a CIE chromaticity diagram of the polymer composite with CsPbBn-TMAI quantum dots and CdSe/ZnS quantum dots inside the display device.

FIG. 14B is a CIE chromaticity diagram of the polymer composite with CsPbBn-TPPI quantum dots and CdSe/ZnS quantum dots inside the display device.

FIG. 15A is a schematic of the LCD device.

FIG. 15B shows an embodiment of a display device comprising a material described herein.

FIG. 16A is a TEM image of CsPbBn-TMAI quantum dots.

FIG. 16B is an XRD pattern of CsPbBn-TMAI quantum dots.

FIG. 17A is a TEM image of CsPbBn-TMAI quantum dots shelled by TiCh.

FIG. 17B is a TEM image of CsPbBn-TPPI quantum dots shelled by TiCh.

FIG. 18A shows results of temperature-dependent photoluminescence intensity for films comprising quantum dots without additive treatment.

FIG. 18B shows results of temperature-dependent photoluminescence intensity for films comprising quantum dots treated with ammonium iodide.

FIG. 18C shows results of temperature-dependent photoluminescence intensity for films comprising quantum dots treated with phosphonium iodide.

FIG. 18D shows results of temperature-dependent photoluminescence intensity for films comprising quantum dots treated with sulfoxonium iodide.

FIG. 19 shows comparative results of normalized photoluminescence intensity from quantum dot-polymer composite films under accelerated test conditions.

FIG. 20 is an illustration of an embodiment of a lighting device described herein.

FIG. 21 is an illustration of an embodiment of a UV detector described herein. FIG. 22 is an illustration of an embodiment of an x-ray scintillator system described herein.

DETAILED DESCRIPTION

The present disclosure provides perovskite quantum dots treated with ligands ( e.g ., cationic ligands that have the common formula R4P⁺F), as well as materials, emissive films, and display devices (e.g., LCD display devices) comprising the same. Such quantum dots are red- shifted and stabilized, and provide improved color representation and extended color gamut coverage.

Advantageously, the perovskite quantum dots are red-shifted and stabilized by the treatment with the ligands, as described herein. It has been found that the T in the ligands modifies only the surface of the perovskite quantum dots and red-shifts their emission by 10-20 nanometers (nm), depending on the particular type of the ligand, thereby enabling the perovskite quantum dots to have a peak wavelength of > 520 nm, in particular embodiments > 524 nm. It has also been found that this red-shifting of the perovskite quantum dots does not accompany degradation of other emission properties, such as emission intensity. Moreover, it has been found that the cationic ligands described herein also leads to more stable phase and emission properties as compared to the common mix halide perovskite quantum dots such as CsPb(I/Br)3 quantum dots, in which phase segregation and change in the emission peak occurs very quickly when exposed to heat. It is believed that this is because the cationic ligands described herein help to stabilize the perovskite quantum dots.

Prior to setting forth this disclosure in more detail, it may be helpful to an understanding thereof to provide definitions of certain terms to be used herein. Additional definitions are set forth throughout this disclosure.

A “quantum dot” is a nanoscale, luminescent crystal of a semiconductor material. As used herein the term “nanocrystal” refers to a quantum dot.

The term “perovskite” as used herein describes a halide perovskite material with a perovskite crystal structure.

The term "polymer" refers to a material comprising a macromolecule composed of repeated subunits. Each subunit is referred to as a monomer. Polymers may be natural, semi synthetic, or synthetic. As used herein, “polymer” includes polymer resins and oligomers.

A “polymer resin” is an amorphous solid, semi-crystalline solid, or liquid (e.g, highly viscous liquid, medium viscosity liquid, or low viscosity liquid) that has a polymeric or semi polymeric structure. Polymer resins may be thermoplastic resins or thermosetting resins. Thermoplastic resins can be repeatedly molded and melted by cooling and heating, respectively, as no chemical changes generally take place during molding. Thermoset resins undergo chemical reactions ( e.g ., cross-linking) during the molding process.

An “oligomer” is a material comprising less than ten repeating subunits. Oligomers include dimers, trimers, and tetramers, which are oligomers made up of two, three, and four monomers, respectively.

The term "visible light" as used herein refers to light having a wavelength ranging from 380 nanometers (nm) to 750 nm. Violet light has a wavelength ranging from 380 nm to 450 nm. Blue light has a wavelength ranging from 450 nm to 495 nm. Green light has a wavelength ranging from 495 nm to 570 nm. Yellow light has a wavelength ranging from 570 nm to 590 nm. Orange light has a wavelength ranging from 590 nm to 620 nm. Red light has a wavelength ranging from 620 nm to 750 nm.

The term "ultraviolet light" refers to light having a wavelength ranging from 100 nm to 400 nm.

"Alkyl" refers to a saturated, straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, having from one to twelve carbon atoms (C1-C12 alkyl), one to eight carbon atoms (Ci-Cs alkyl) or one to six carbon atoms (C1-C6 alkyl), and which is attached to the rest of the molecule by a single bond, e.g., methyl, ethyl, «-propyl, 1-methylethyl (Ao-propyl), «-butyl, «-pentyl, 1,1-dimethylethyl (/-butyl), 3-methylhexyl, 2-methylhexyl and the like. Unless stated otherwise specifically in the specification, an alkyl group is optionally substituted.

"Alkenyl" refers to an unsaturated, straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, which contains one or more carbon-carbon double bonds, having from two to twelve carbon atoms (C2-C12 alkenyl), preferably two to eight carbon atoms (C2-C8 alkenyl) or two to six carbon atoms (C2-C6 alkenyl), and which is attached to the rest of the molecule by a single bond, e.g, ethenyl, prop-l-enyl, but-l-enyl, pent-l-enyl, penta-l,4-dienyl, and the like. Unless stated otherwise specifically in the specification, an alkenyl group is optionally substituted.

"Aryl" refers to a carbocyclic ring system radical comprising 6 to 18 carbon atoms and at least one carbocyclic aromatic ring. For purposes of embodiments of this invention, the aryl radical is a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems. Aryl radicals include, but are not limited to, aryl radicals derived from aceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene, benzene, chrysene, fluoranthene, fluorene, awindacene, s-indacene, indane, indene, naphthalene, phenalene, phenanthrene, pleiadene, pyrene, and triphenylene. Unless stated otherwise specifically in the specification, the term "aryl" or the prefix "ar-" is meant to include aryl radicals that are optionally substituted.

"Cycloalkyl" refers to a non-aromatic monocyclic or polycyclic carbocyclic radical consisting solely of carbon and hydrogen atoms, which may include fused or bridged ring systems, having from three to fifteen ring carbon atoms, from three to ten ring carbon atoms, or from three to eight ring carbon atoms and which is saturated or partially unsaturated and attached to the rest of the molecule by a single bond. Monocyclic radicals include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Polycyclic radicals include, for example, adamantyl, norbornyl, decalinyl, 7,7-dimethyl-bicyclo[2.2.1]heptanyl, and the like. Unless otherwise stated specifically in the specification, a cycloalkyl group is optionally substituted.

"Amino" refers to the -Nfh radical.

"Hydroxy" or "hydroxyl" refers to the -OH radical.

"Oxo" refers to the =0 substituent.

"Phosphate" refers to the -OP=0(OH)2 substituent.

"Sulfonic acid" refers to the -S(=0)20H substituent.

"Carboxyl" refers to the -CO2H radical.

The term “substituted” refers to a group as described above wherein at least one hydrogen atom ( e.g ., 1, 2, 3 or all hydrogen atoms) is replaced by a bond to a non-hydrogen atom such as: a halogen atom such as F, Cl, Br, and I; an oxygen atom in groups such as hydroxyl groups, alkoxy groups, and ester groups; a sulfur atom in groups such as thiol groups, thioalkyl groups, sulfone groups, sulfonyl groups, and sulfoxide groups; a nitrogen atom in groups such as amines, amides, alkylamines, dialkylamines, arylamines, alkylarylamines, diarylamines, N-oxides, imides, and enamines; a silicon atom in groups such as trialkylsilyl groups, dialkylarylsilyl groups, alkyldiarylsilyl groups, and triarylsilyl groups; and other heteroatoms in various other groups. “Substituted” also means any of the above groups in which one or more hydrogen atoms are replaced by a higher-order bond (e.g., a double- or triple-bond) to a heteroatom such as oxygen in oxo, carbonyl, carboxyl, and ester groups; and nitrogen in groups such as imines, oximes, hydrazones, and nitriles. “Substituted” further means any of the above groups in which one or more hydrogen atoms are replaced by a bond to an aminyl, cyano, hydroxyl, imino, nitro, oxo, thioxo, halo, alkyl, alkoxy, alkylaminyl, thioalkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, haloalkyl, heterocyclyl, N-heterocyclyl, heterocyclylalkyl, heteroaryl, N-heteroaryl and/or heteroarylalkyl group. In addition, each of the foregoing substituents may also be optionally substituted with one or more of the above substituents.

“Colloidal stability,” as used herein, refers to the long-term integrity of a dispersion and its ability to resist phenomena such as sedimentation or particle aggregation. This is typically defined by the time that dispersed phase particles can remain suspended. Depending on the type of particles and media, different stabilization agents can be used. As explained below, according to embodiments colloidal stability can be achieved using organic substituents having sufficient length to bind with the particle (from one end of the molecule) and interact with media (with another end of the molecule).

The use of the words "optional" or "optionally" means that the subsequently described event or circumstances may or may not occur, and that the description includes instances wherein the event or circumstance occurs and instances in which it does not.

In the present description, any concentration range, percentage range, ratio range, or integer range is to be understood to include the value of any integer within the recited range and, when appropriate, fractions thereof (such as one tenth and one hundredth of an integer), unless otherwise indicated. Also, any number range recited herein relating to any physical feature, such as polymer subunits, size, or thickness, are to be understood to include any integer within the recited range, unless otherwise indicated. As used herein, the term "about" means ± 20%, ± 10%, ± 5% or ± 1% of the indicated range, value, or structure, unless otherwise indicated. It should be understood that the terms "a" and "an" as used herein refer to "one or more" of the enumerated components. The use of the alternative ( e.g ., "or") should be understood to mean either one, both, or any combination thereof of the alternatives.

Unless the context requires otherwise, throughout the present specification and claims, the word "comprise" and variations thereof, such as, "comprises" and "comprising," as well as synonymous terms like "include" and "have" and variants thereof, are to be construed in an open, inclusive sense; that is, as "including, but not limited to," such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the materials, compositions, devices, and methods of this technology. Although the open-ended term "comprising," as a synonym of terms such as including, containing, or having, is used herein to describe and claim the disclosure, the present technology, or embodiments thereof, may alternatively be described using more limiting terms such as "consisting of' or "consisting essentially of the recited ingredients. Unless defined otherwise, all technical and scientific terms herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Similarly, the terms "can" and "may" and their variants are intended to be non-limiting, such that recitation that an embodiment can or may comprise certain elements or features does not exclude other embodiments of the present technology that do not contain those elements or features. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of this disclosure. However, one skilled in the art will understand that the disclosure may be practiced without these details.

As noted above, the present disclosure provides compositions and materials that comprise perovskite quantum dots. As used herein the term “perovskite quantum dot” refers to a perovskite quantum dot of the form ABX3, where A and B are cations and X is, at each occurrence, independently, an anion. In embodiments, A is cesium (Cs), CH3NH3 (MA), HC(NH2)2 (FA), or rubidium (Rb). In embodiments, B is lead (Pb), tin (Sn), or Bismuth (Bi). In particular embodiments, X is bound to both A and B.

In some embodiments, the quantum dots are halide quantum dots having the formula: ABX3, wherein A is a monovalent cation Cs⁺, MA⁺ (CH3NH3⁺), or FA⁺ (HC(NH2)2⁺); wherein B is a divalent cation Pb²⁺, Sn²⁺, or Bi²⁺; and X at each occurrence, independently a CT, Br , or G. In particular embodiments, B is Pb.

In embodiments, X is, at each occurrence, independently, a halogen. Thus, in embodiments, the perovskite quantum dot is a halide perovskite quantum dot having the formula:

Csa(MA)b(FA)cRbdPbpSnrBisClxBr_yIz, wherein:

MA is CH3NH3;

FA is HC(NH₂)₂; a, b, c, and d are each independently a number from 0 to 1, provided that the sum of a, b, c, and d is 1; p, r, and s are each independently a number from 0 to 1, provided that the sum of p, r, and s is 1; and x, y, and z are each independently a number from 0 to 3, provided that the sum of x, y, and z is 3.

In embodiments, each of the perovskite quantum dots independently have the formula: Csa(MA)b(FA)_cRbdPbpSnrBisClxBr_yIz. In embodiments, each of the perovskite quantum dots independently have the formula: Csa(MA)b(FA)_cPbpSnrBisClxBr_yIz.

In some embodiments, each of the perovskite quantum dots independently have the formula: Cs_a(MA)b(FA)_cPbClxBr_yIz.

In particular embodiments, the perovskite quantum dots comprise MAPbF, MAPbBn, FAPbBn, FAPbL, MAPbCb, MAPbBnCl, FAPbCb, CsPbL, CsPbCb, CsPbBn, CsPbCl_xBr_y, CsPbBr_yI_z, or a combination thereof, wherein the sum of x and y is 3 or wherein the sum of y and z is 3.

In particular embodiments, the perovskite quantum dots comprise FASnF, FASnBn, FASnCb, MASnb, MASnBn, MASnCb, CsSnb, CsSnBn, CsSnCb, or a combination thereof. In specific embodiments, the perovskite quantum dots comprise CsPbBn. In particular embodiments, the perovskite quantum dots are CsPbBn.

Perovskite quantum dots have excellent optical properties, such as 100% photoluminescence quantum yield, high color purity, high absorption coefficient, and emission tunability. As is understood, perovskite quantum dots absorb light at a first wavelength (z.e., the excitation wavelength) and emit light at a second wavelength (z.e., the emission wavelength) that is longer than the first wavelength. In various embodiments, the excitation wavelength is blue, UV, red, or a combination thereof. In particular embodiments, the excitation wavelength is blue; UV; blue and red; UV, blue, and red.

Compared to previously developed quantum dots, such as CdSe- and InP -based quantum dots, halide perovskite quantum dots offer additional advantages, including narrower FWHM < 20-25 nm, high PLQY (up to 100%), facile synthesis process, and broader emission wavelength tunability. For example, the visible emission range ( e.g from blue (450 nm) to red (690 nm)) can be selected by varying the composition of the perovskite quantum dot. For example, in CsPbClxBr_yI_z quantum dots, the visible emission range can be selected based on the halide chosen, as described in Protesescu, L., et ak, Nano Lett., 2015. 15: p. 3692-3696, which is incorporated by reference herein with regard to the teachings regarding the same. Additionally, in some embodiments, the band gap of the quantum dots can be altered by controlling the size of the quantum dots.

In embodiments, the disclosed material comprises green emitting perovskite quantum dots, red emitting perovskite quantum dots, or both.

In some embodiments, the perovskite quantum dots are green emitting. In some such embodiments, the perovskite quantum dots have the formula: Csa(MA)b(FA)_cPbBn. Such perovskite quantum dots have a high Photoluminescence Quantum Yield (PLQY; e.g ., up to 100%), a narrow full width to half maximum (FWHM; e.g., less than 20 nm or less than 25 nm). In specific embodiments, the perovskite quantum dots comprise MAPbBn, FAPbBn, or a combination thereof. In particular embodiments, the perovskite quantum dots are MAPbBn. In other embodiments, the perovskite quantum dots are FAPbBn. In various embodiments, such perovskite quantum dots have an emission ranging from 524 nm to 535 nm. In other embodiments, the perovskite quantum dots comprise CsPbBn. In embodiments, such perovskite quantum dots have an emission ranging from 510 nm to 515 nm.

In other embodiments, the perovskite quantum dots are red emitting (e.g, 630 nm). In some embodiments, the perovskite quantum dots have the formula: CsPbBr_yI_z, wherein the sum of y and z is 3.

In further embodiments, the perovskite quantum dots are blue emitting (e.g, 450 nm). In some embodiments, the perovskite quantum dots have the formula: CsPbCl_xBr_y, wherein the sum of x and y is 3.

In embodiments, the perovskite quantum dots have an average diameter ranging from 2 nm to 100 nm. In further embodiments, the perovskite quantum dots have an average diameter ranging from 5 nm to 100 nm. Imaging and the size measurements for the perovskite quantum dots may be performed, for example, using transmission electron microscopy (TEM). An advantage of selecting these sizes of quantum dots is that it provides a means of tuning the wavelength(s) of the quantum dots. This is because of the quantum confinement effect, which becomes prominent when at least one of the dimensions of a material is comparable in length to the de Broglie wavelength. In quantum-confined materials, such as quantum dots, the bandgap is inversely proportional to the sizes of the particles, which in other words means that the wavelength(s) of the perovskite quantum dots can be increased/decreased by increasing/decreasing the sizes of the particles.

The perovskite quantum dots of the present disclosure may comprise a shell. In embodiments, the shell comprises an oxide (e.g, S1O2, AI2O3, T1O2, ZrCk, ZnO, or a combination thereof), a sulphide ( e.g ZnS, InS, CdS, PbS, or a combination thereof), or a halide ( e.g CsX, NaX, KX, LiX, RbX, MgX₂, CaX₂, ZnX₂, T1X, PbX₂, CuX, CuX₂, or a combination thereof, wherein X is, at each occurrence, independently Cl, Br, or I). The shell may enhance the thermal stability of perovskite quantum dots especially at high humidity, prevent the interaction of perovskite quantum dots with moisture, or both.

Perovskite quantum dots may be prepared using any suitable methods. For example, perovskite quantum dots having the formula: CsPbClxBr_yI_z may be formed in accordance with the procedures described in Protesescu, L., et ah, Nano Lett., 2015. 15: p. 3692-3696, which is incorporated by reference in its entirety for its teachings regarding the same. In particular embodiments, the perovskite quantum dots have low defects (i.e., halide vacancies), as evidenced by a PLQY near to unity.

A perovskite quantum dot as described herein is bound to a ligand comprising two or more quaternary or ternary centers. In some embodiments, the ligand has the formula RANCT, R₃S⁺T, R4PN , or a combination thereof, wherein each R is, independently, an optionally substituted organic substituent. Thus, in some embodiments, the ligand comprises more than one of R4N⁺, R₃S⁺, and R4P⁺. In some such embodiments, the ligand has the formula R4N⁺T or R4P⁺L. In particular embodiments, the ligand has the formula R4P⁺.

The bonding between cationic centres and the surfaces of quantum dots, which prevents detachment of the ligands from the surface of the quantum dots under heat, has been found to be strongest when quaternary R4 is used with P. Without being bound to theory, this is believed to be the case because the surface of the perovskite quantum dots is positively or negatively charged depending on the atoms available on the surface. For example, in CsPbBn quantum dots, the halide-terminated surface (i.e. the portions where the Br are located at the edges/surface of the quantum dots) has negative charge, whereas the cation-terminated surface (i.e. the Cs⁺-terminated surface) has positive charge. The positively charged organic part of the cationic ligands (R4P⁺) can bind strongly to the negatively charged surface of the perovskite quantum dots. On the other hand, anionic ligands, such as carboxylic acids, sulfonates or phosphonate, can be used to passivate the positively charged surface. Strong binding of either cationic or anionic ligands improves perovskite quantum dot stability. The more binding energy, the higher the stability of the perovskite quantum dots under heat and light exposure.

Ligands comprising materials other than R4P⁺ are prone to deprotonate when exposed to heat. Ligands that are non-quaternary (when used with P) include ligands with primary or secondary cation centres such as R.3HN⁺, R.2H2N⁺, RH3N⁺, R.3HP⁺, R.2H2P⁺, RH3P⁺. Examples of the deprotonation processes of such ligands are as follows:

R₃HN⁺ = R3N⁰ + H⁺

R₂H₂N⁺ = R2HN⁰ + H⁺

RH₃N⁺ = RH2N⁰ + H⁺

R₃HP⁺ = R₃P° + H⁺

R₂H₂P⁺ = R2HP⁰ + H⁺

RH₃P⁺ = RH₂P° + H⁺

After the deprotonation, these cationic ligands become non-ionic. Non-ionic ligands are not charged and, therefore, are not able to form a strong bond to the surface of the perovskite quantum dots and can be easily detached from the surface. On the other hand, ligands comprising R4N⁺, or R4P⁺, cannot be deprotonated, keeping them positively charged and bonded strongly to the negatively charged perovskite quantum dots surface even at high temperature.

Each instance of R is independently any suitable optionally substituted organic substituent. In other words, the organic substituent cannot be H. In embodiments, the organic substituent is alkyl, alkenyl, or aryl. In embodiments, the organic substituent is cyclic. In some embodiments, the organic substituent is cycloalkyl. In embodiments, each occurrence of R is the same. In other embodiments, at least one occurrence of R is different from at least one other occurrence of R.

In some embodiments, at least one of the organic substituents comprises at least six carbons ( e.g ., dodecyl-, hexadecyl-, n-octyl-, hexyl-, and phenyl-). In particular embodiments, each of the organic substituents comprises at least six carbons. In some embodiments, having at least one of the organic substituents comprise at least six carbons increases colloidal stability of the perovskite quantum dots and prevents the aggregation of the perovskite quantum dots. In some embodiments, at least one of the organic substituents comprises no more than eight carbons (e.g., methyl-, octyl-, hexyl- and phenyl-). In some embodiments, each of the organic substituents comprises no more than eight carbons. In some embodiments, having at least one of the organic substituents comprise no more than eight carbons increases the binding strength between the ligand’s cation and the negatively charged surface of the perovskite quantum dots. This is due to steric reasons: P+ ions should not be located too far away from the negatively charged surface of the quantum dots. In some embodiments, the organic substituent is optionally substituted with hydroxyl, oxo, carboxyl, amino, phosphate, sulfonic acid, or a combination thereof. In some embodiments, R is a polymer. In a specific embodiment, R is [CEECEI[N(CE[3)3]- {CH2CH(N(CH3)3]}n-CH2CH2N(CH3)3]⁽ⁿ⁺²⁾⁺x(n+2)I , where n is an integer that is at least 1. In another embodiment, R is [CH3CH[P(CH3)3]-{CH2CH(P(CH3)3]}n-

CH2CH2P(CH3)3]^(n+2)+x(n+2)P, where n is an integer that is at least 1.

In embodiments, the ligand comprises R4N⁺ or R4P⁺, wherein at least one occurrence of R has no more than eight carbon atoms. In embodiments, the ligand comprises R4P⁺, wherein at least one occurrence of R has no more than eight carbon atoms. In some embodiments, the ligand comprises R4P⁺, wherein at least one occurrence of R has no more than eight carbon atoms and at least one occurrence of R has at least six carbon atoms.

In certain embodiments, the ligand comprises tridodecylmethylammonium iodide, Hexadecyltrimethylammonium Iodide, tetra-n-octylammonium iodide, tetrahexylammonium iodide, methyltriphenylphosphonium iodide, tetraphenylphosphonium iodide, trioctylsulfonium iodide, ethyldimethylphenethylammonium iodide, alkyl(C8-Ci8)dimethylbenzylammonium iodide, dialkyl(C8-Ci8)dimethylammonium iodide, trimethylhexadecylammonium iodide, or a combination thereof. In other embodiments, the ligand comprises 2 -Butene- 1,4-bis (triphenylphosphonium Iodide).

In particular embodiments, the ligand comprises tetraethylphosphonium iodide, tetraphenylphosphonium iodide, methyltriphenylphosphonium iodide,

Ethyltriphenylphosphonium iodide, Isopropyltriphenylphosphonium iodide,

(Iodomethyl)triphenylphosphonium iodide, didodecyltriphenylphosphonium iodide, Methyltriphenylphosphonium iodide-polymer-bound, tetrabutylphosphonium iodide, [2- (methylidynesilyl)ethyl](triphenyl)phosphonium iodide, (l-iodoethyl)(triphenyl)phosphonium iodide, or a combination thereof.

In embodiments, the ligands comprise more than one cation center of any of R4P⁺ in any one ligand. For example, 2-Butene- 1,4-bis (triphenylphosphonium Iodide).

The I- of the ligands modify the surface of the perovskite quantum dots to shift the emission(s) of the perovskite quantum dots to one or more higher wavelength(s). In other words, the G in the ligands leads to a red-shifting of the one or more emission wavelength(s) of the perovskite quantum dots. The shift of the emission toward one or more higher wavelength(s) is achieved without influencing other emission properties of the perovskite quantum dots, such as the emission intensity. Depending on the types of the ligands used, the emission wavelength(s) of the perovskite quantum dots can be red-shifted by 10-20 nm and be tuned to the desired wavelength(s), e.g ., ITU-R Recommendation BT.2020-2 10/2015 (referred to as Rec. 2020) standard for green emission (524-535 nm). The Rec. 2020 standard requires the green emission to have a color coordinate (CIE 1931 x, y) of (0.17, 0.797), which corresponds to an emission wavelength range of 524-535 nm with FWHM < 20-25 nm.

For example, it has been demonstrated that MAPbBn and FAPbBn perovskite quantum dots meet the requirements for green emission at this concentration and thickness (see, for example, U.S. Patent Publication Nos. US2017/369776, US2018/273841, US2018/179440, and US2019/153313). However, MAPbBn- and FAPbBn-based devices generally suffer from low stability when exposed to heat due to the organic nature of their cations (MA⁺ or FA⁺). In addition, although CsPbBn quantum dots are more stable against heat when compared to perovskite quantum dots with organic cations, the optical properties still show significant degradations when exposed to high internal temperatures such as those encountered within display devices.

Green emission from a polymer film with 0.3% to 0.5%, by weight CsPbBn quantum dots has a wavelength ranging from 510 to 515 nm, which is outside the desirable range of 524 to 535 nm. Although it is possible to increase the emission wavelength to approximately 524 nm by increasing the concentration of CsPbBn quantum dots in the film up to 100%, by weight, this is non-compliant with the RoHS regulations limiting the maximum Pb concentration in a polymer film to 0.1%, by weight, which corresponds to 0.3% to 0.5%, by weight, for CsPbBn quantum dots with ligands. This means that even with the maximum RoHS-compliant concentration, a polymer film with CsPbBn quantum dots can only emit at a maximum wavelength of 510 to 515 nm, and therefore, are not able to provide color gamut coverage of < 90% Rec 2020 required for the display industry (see, FIG. 1).

Another way to red-shift the emission of CsPbBn quantum dots to > 524 nm is to make a mix halide perovskite CsPb(Br/I)3 quantum dots. This is a feasible way to shift emission in any range 510-680 nm by varying the ratio of bromide to iodide. However, because of the mixed nature of the cations, the perovskite phases CsPbBn and CsPbF segregate and the emission peak shifts considerably. The change of emission peak for CsPb(Br/I)3 quantum dots may be from 532 nm to 529 nm within a couple of minutes of exposure to heat at 95°C (see, FIG. 5, for example). Such an emission shift is generally not acceptable for use in displays.

For example, CsPbBn-Oleylamine iodide (OLAI) quantum dots in composite have the initial emission peak centered at 528 nm with FWHM 20 nm and film PLQY > 80%. During the accelerated test under heat 85°C and light (450 nm, 10 mW/cm²), the emission blue-shifts from 528 to 513 nm after 1,000 hours of the test (see, FIG. 6A). Moreover, emission intensity retains just 20% of original PL after 1,000 hours (see, FIG. 6B). The reason for this process is that OLAI can be easily detached from the surface by the process of de-protonation of the ammonium centre resulting in the ligand detachment: C18H35NH3I = C18H35NH2 + HI. The detached HI results in blue-shifting of the emission peak and the detached OLA results in the degradation of the CsPbBn quantum dots.

By treating the perovskite quantum dots with ligands as described herein, it is possible not only to red-shift the emission wavelength, but also to passivate the perovskite quantum dots. At the same time, the strong bond(s) between the perovskite quantum dots and the ligands, particularly the ion center(s) of the IPR⁺ portions of the ligands, reduces the probability of detachment of the ligands from the perovskite quantum dots by thermal deprotonation. Thus, the heat resistance properties of the composition is also improved. The improved resistance to heat of the perovskite quantum dots decreases the temperature dependence of the optical properties, including the emission intensity, emission wavelength and FWHM. This allows the green emission of the perovskite quantum dots to retain a low FWHM of less than 20-25 nm even at high temperatures, which is also required by the Rec. 2020 standard for a green emission, in addition to emitting the correct wavelength range (524-535 nm).

In embodiments, the emission wavelength(s) of the perovskite quantum dots described herein is at least 520 nm. In some embodiments, the emission wavelength(s) of the perovskite quantum dots described herein is at least 524 nm.

As compared to other quantum dots ( e.g ., CdSe, InP, etc.), perovskite quantum dots provide several advantages, including narrower FWHM, higher PLQY, facile synthesis process, and broader emission control. In some embodiments, the perovskite quantum dots have a FWHM of less than 25 nm. In further embodiments, the perovskite quantum dots have a FWHM of less than 20 nm. In various embodiments, the perovskite quantum dots have a PLQY of at least 70%. In some embodiments, the perovskite quantum dots have a PLQY of at least 80%. In further embodiments, the perovskite quantum dots have a PLQY of at least 90%. In particular embodiments, the perovskite quantum dots have a PLQY of at least 95%.

The perovskite quantum dots may be treated with additional agents, for example, to improve stability further, to shift the emission range, or both. Examples of such treatments are described, for example, in Sinatra, L., et ak, SID Symposium Digest of Technical Papers, 2019. 50(1): p. 1712-1715, which is incorporated by reference herein for its teachings regarding the same.

In certain embodiments, the perovskite quantum dots compositions described herein are interspersed in a monomer or a polymer. Suitable monomers for use in the materials described herein include urethanes, vinyl chloride, vinyl monomers, esters, acrylates, amides, olefins, thermoplastic elastomers, styrene block monomers, ether block amides, or a combination thereof. Suitable polymers for use in the materials of the present disclosure include polyurethanes, rubbers, polyvinylchloride (PVC), vinyl polymers, polyesters, polyacrylates, polyamides, biopolymers, polyolefins, thermoplastic elastomers, styrene block copolymers, polyether block amides, or a combination thereof. In some embodiments, the rubber is a silicon rubber, a latex rubber, or a combination thereof. In embodiments, the polymer is a polymer resin.

In various embodiments, the monomer or polymer is non-polar. In some embodiments, the monomer or polymer is ultra-violet (UV) curable. In some embodiments, the polymer comprises a mixture of acrylate and styrene-based polymers. In certain embodiments, the polymer does not comprise -epoxy, hydroxyl (-OH), amine (-NH2), and/or carboxyl (-COOH) group(s).

A concentration of perovskite quantum dots in a material may be selected based on the application and may also vary based on factors including the operational conditions. In embodiments, the material comprises the perovskite quantum dots in a concentration ranging from 0.01% to 75%, by weight. In some embodiments, the material comprises the perovskite quantum dots in a concentration ranging from 0.05% to 75%, by weight. In some embodiments, the material comprises perovskite quantum dots in a concentration ranging from 0.1% to 60%, by weight. In some embodiments, the material comprises perovskite quantum dots in a concentration ranging from 10% to 70%, by weight. In some embodiments, the material comprises perovskite quantum dots in a concentration ranging from 20% to 60%, by weight. For example, for LCD color filter applications, the material generally comprises perovskite quantum dots in a concentration ranging from 20% to 60%, by weight. In other embodiments, the material comprises perovskite quantum dots in a concentration ranging from 0.1% to 0.5%, by weight. For example, for LCD backlighting applications, the material generally comprises perovskite quantum dots in a concentration ranging from 0.1% to 0.5%, by weight. In further embodiments, the material comprises perovskite quantum dots in a concentration ranging from 0.01% to 0.75%, by weight. In additional embodiments, the material comprises perovskite quantum dots in a concentration ranging from 0.05% to 0.75%, by weight. In particular embodiments, the material comprises perovskite quantum dots in a concentration ranging from 0.3% to 0.5%, by weight. For example, in display backlighting applications the concentration of quantum dots generally ranges from 0.3% to 0.5%, by weight. In specific embodiments, the material comprises perovskite quantum dots in a concentration of about 0.5%, by weight. In various embodiments, the composite comprises additive(s). For example, in embodiments, the composite comprises a photoinitiator, an adhesive, a viscosity modifier, a light scattering agent, or a combination thereof. In particular embodiments, the viscosity modifier comprises S1O2 nanoparticles. In specific embodiments, the photoinitiator comprises 2,2-Dimethoxy-2-phenylacetophenone, Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-Hydroxy-2-methylpropiophenone, or a combination thereof. In particular embodiments, the adhesive comprises Loctite 3195. In some embodiments, the light scattering agent comprises TiCh, S1O2, AI2O3, or a combination thereof.

The mixture of the perovskite quantum dots, additive(s), and monomer or polymer is referred to as a material. In some embodiments, the material is a liquid.

In other embodiments, the material is solid. In some embodiments, the material is formed as a film. In embodiments where the materialis in the form of a layer ( e.g ., a film), the total thickness of the material ranges from 1 micrometer (pm) to 1,000 pm. In some such embodiments, the film further comprises barrier layer(s) arranged on one or both sides of the material. In particular embodiments, barrier layers are arranged on both sides of the material. Such barrier layers protect provide additional protection for the composite from the environment (e.g., air and moisture).

Barrier layers may comprise any suitable transparent material. For example, suitable barrier layers comprise a polymer film, glass, or both. In some embodiments, the barrier layer(s) comprise a polymer film. In certain embodiments, the barrier layer(s) comprise a multilayer polymer film. In some such embodiments, the multilayer polymer film comprises an inorganic layer. In specific embodiments, the inorganic layer comprises AI2O3, S1O2, or both. In particular embodiments, the barrier layer(s) comprise glass. In various embodiments, the barrier layer has a water vapor transmission rate (WVTR) of about < 0.001 g/m²-day at 20°C. In various embodiments, the barrier layer has a WVTR of about < 0.1 g/m²-day at 20°C.

In some embodiments, the barrier layer has a thickness ranging from 1 pm to 100 pm. In further embodiments, the barrier layer has a thickness ranging from 25 pm to 100 pm. In particular embodiments, the barrier layer has a thickness of about 50 pm.

In various embodiments, a film of the present disclosure has a thickness ranging from 1 pm to 1000 pm. In some embodiments, the film has a thickness ranging from 100 pm to 500 pm. In particular embodiments, the film has a thickness of about 200 pm.

In embodiments, a film of the present disclosure (also referred to as an “emissive layer”), absorbs a first one or more range(s) of wavelength(s) of light and emits a second one or more range(s) of wavelength(s) of light with one or more peak wavelength(s) higher than 520 nm and FWHM lower than 25 nm. In particular embodiments, the one or more peak wavelength(s) may optionally be higher than 524 nm. In embodiments, a material of the present disclosure further comprises emissive particles. In some embodiments, the emissive particles are red emissive particles. In some embodiments, the emissive particles comprise narrow band phosphors, narrow band quantum dots, or both. In particular embodiments, the narrow band phosphor comprises a rare-earth phosphors ( e.g ., KSF:Mn). In certain embodiments, the narrow band quantum dots comprise CdSe, CdSe/ZnS, CdSe/ZnSe, CdSe/CdS, InP, InP/ZnS, InP/ZnSe, CuInS2, or a combination thereof. In other embodiments, the narrow band quantum dots comprise CsPb(Br/I)3, CsPbU, or a combination thereof. Such a combination of the perovskite quantum dots described herein and red emissive particles allow for green emission from the perovskite quantum dots and red emission from the red emissive materials, hence enabling multiple down-conversions (e.g. blue to green, blue to red, and green to red) without using a plurality of films with different emission wavelengths.

The materials of the present disclosure can be made using any suitable methods. Methods of forming the materials of the present disclosure comprise mixing perovskite quantum dots bonded to the ligands with a monomer or a polymer (e.g, a polymer resin). In some embodiments, the method comprises mixing an additive (e.g, a light scattering agent, an adhesive, etc.) into the material comprising the perovskite quantum dot(s) and the monomer or polymer.

Once mixed, the material can be shaped, e.g, to form a film, using any suitable method. For example, the material may be blade coated, drop casted, printed, or the like. Accordingly, described herein are methods for forming a film comprising a material of the disclosure, the method comprising: spreading a material described herein; and forming the film by curing the material. In some embodiments, the material is spread by blade coating. In other embodiments, the material is spread by drop casting. In further embodiments, the material is spread by printing. In some embodiments, the material is spread onto a barrier layer. In some embodiments, curing the material comprises exposing the material to UV light (e.g, at an intensity of about 800 mW/cm²). In some embodiments, the methods for forming the film comprise forming a composite by mixing the monomer or the polymer and the perovskite quantum dots; spreading the composite; and forming the film by curing the composite.

An exemplary process of forming a film of the disclosure comprises missing perovskite quantum dots with a polymer resin and a photoinitiator. A light scattering agent is then added to the resulting mixture. The composition is then blade coated onto barrier layers to provide a layered structure in which the composition is arranged between two barrier layers. Finally, the layered structure is UV irradiated to cure the polymer resin. Traditional materials comprising perovskite quantum dots may be unstable when operating outside of optimal conditions. Due to the ionic structure, perovskite quantum dots may be susceptible to degradation when exposed to conditions ( e.g ., moisture, heat, light irradiation, etc.) outside of optimal ranges. Under such conditions, the perovskite quantum dots may lose their optical properties, such as a decrease in PLQY and broadening of the FWHM. Advantageously, the materials described herein provide improved stability of the perovskite quantum dots when exposed to conditions outside of the optimal ranges. For example, the materials of the present disclosure sustain their photoluminescence emission under high temperature conditions (e.g, up to 100°C), high humidity (e.g, up to 90% relative humidity (RH)), and high light exposure. Thus, the disclosed materials are suitable for use in various devices.

Materials of the present disclosure can be used in various devices, for example, a display device, a lighting device, an ultraviolet detector, an x-ray scintillator, or a gamma-ray scintillator. Accordingly, provided herein are devices comprising a material (e.g., as an emissive layer) described herein.

In various embodiments, a material described herein is used in a display device. In some such embodiments, a display device comprises a material as described herein and a light source that emits first wavelength(s) of light. In some embodiments, the first wavelength(s) of light are blue, UV, blue with red, or UV with blue and red. Advantageously, a display device of the present disclosure provides improved color representation and extended color gamut coverage.

In embodiments, a material of the present disclosure is used in liquid crystal display (LCD) backlighting, LCD color filters, or light emitting diode (LED) color filters (e.g. organic LED (OLED) or microLED color filters). In embodiments, the device comprises an LED. In some such embodiments, the material is a film arranged on the LED. In particular embodiments, the device comprises an OLED. In some such embodiments, the material is a film arranged on the OLED. In some embodiments, the device comprises a microLED. In some such embodiments, the material is a film arranged on the microLED.

In embodiments, the device comprises an LCD. In some embodiments, a material of the present disclosure is used as color converters in an LCD device. In some embodiments, the materials are used to down-convert the color (e.g, from blue light to green light, from blue light to red light, or both) in an LCD device.

Schematics of exemplary down conversion layers and the related working principles are provided in FIG. 7A and FIG. 7B. FIG. 7A shows a graphic representation of green emissive quantum dots 402 embedded in a polymer 403 with barrier layers 401 on both sides. The film is exposed to one wavelength of light 404 ( e.g ., blue light) that excites the quantum dots and second wavelengths of light 405 (e.g., green and blue light) are emitted. In a particular example of such a down conversion layer, CsPbBn quantum dots are encapsulated in the polymer resin, and further encapsulated by barrier layers. Such a polymer composite, when used as a down-conversion material, absorbs a first one or more ranges of wavelengths of blue light and emits a second one or more ranges of wavelengths of blue and green light with one or more peak wavelengths higher than 520 nm, or 524 nm, and FWHM lower than 25 nm, wherein the first wavelength is shorter than the second wavelength.

FIG. 7B shows a graphic representation of green emissive quantum dots 407 and red emissive materials (e.g, quantum dots) 408 embedded in a polymer 409 with barrier layers 406 on both sides. The film is exposed to exciting light 410 (e.g, blue light) and emits light 411 (e.g, red, green, and blue light). In a particular example of such a down conversion layer, CsPbBr3 quantum dots are included in a mixture with additional red emissive particles. Such a layer can be used as a polymer film for display applications, such as LCD applications. The CsPbBn quantum dots and red emissive particles are encapsulated in a polymer resin, which is encapsulated by barrier layers. The material absorbs a first wavelength of light and emits light with a second wavelength > 524 nm and FWHM < 25 nm and a third wavelength, wherein the first wavelength is shorter than the second and third wavelengths.

In further embodiments, the materials can be used in other color filter applications. In certain embodiments, the material is used in display backlighting and comprises perovskite quantum dots in a concentration ranging from 0.3% to 0.5%, by weight, and a thickness ranging from 100 pm to 500 pm.

In various embodiments, a material of the present disclosure is formed as a film, which is arranged between a light source and an LCD matrix. In alternate embodiments, a material of the present disclosure is formed as pixel sized composites on an LCD matrix.

A particular embodiment of a display device comprising a film of the present disclosure is illustrated in FIG. 8 A. The film 504 comprises composite with quantum dots (e.g, CsPbBn) is arranged between a light source 501 and an LCD matrix 506. The light source 501 is a pink LED, which emits red (630 nm) and blue (450 nm) light 503, as shown in the spectrum 502. The material 504 down converts a portion of the blue light from the light source 501 that has an emission center greater than 524 nm and a FWHM less than 25 nm. In other words, the light of the first wavelength (e.g. the blue light) is converted into light of a second wavelength, longer than the first (e.g. green light with an emission center > 520 nm, or greater than 524 nm and FWHM < 25 nm). The red emissions would pass through the film. The red, green, and blue emissions 505 then pass through the LCD matrix 506 and color filters 507, giving the image 508. In embodiments, this configuration allows for greater than 90% of Rec.2020 coverage. In some embodiments, this configuration allows for greater than 95% of Rec.2020 coverage.

A further embodiment of a display device comprising a film of the present disclosure is illustrated in FIG. 8B. The film 12 comprises composite with CsPbBn quantum dots is arranged between a light source and an LCD matrix. The light source comprises red LED 10 and blue LED 9, which emits red (630 nm) and blue (450 nm) light 11. The material 12 down converts a portion of the blue light from the light source and the red emissions pass through the film. The resulting red, green, and blue emissions 13 then pass through the LCD matrix 14 and color filters 15, giving the image 16.

Another embodiment of a display device comprising a film of the present disclosure is illustrated in FIG. 13. The film 1403 comprises a composite with a mixture of CsPbBn quantum dots and red emissive particles ( e.g ., CdSe quantum dots) arranged between a blue LED light source 1401 and an LCD matrix. The film 1403 down converts a portion of the blue light 1402 and emits red light and green light with an emission center greater than 524 nm and FWHM less than 25 nm. The resulting red, green, and blue light 1404 then passes through the LCD matrix 1405 and color filters 1406, resulting in the image 1407. In embodiments, this configuration allows for greater than 90% of Rec.2020 coverage. A similar configuration could be used with a blue organic LED (OLED) or microLED.

A further embodiment of a display device of the present disclosure is illustrated in FIG. 15 A. An LED light source 1601 emits blue light 1602, which first passes through the LCD matrix 1603 and then a material of the present disclosure. Such materials are arranged as a plurality of pixel sized films comprising CsPbBn quantum dots 1604. The pixel sized films 1604 convert blue light into green light with emission greater than 524 nm and FWHM less than 25 nm. Additional composites comprising red emissive particles are arranged in pixel sized films 1605. A portion of the light passes through the pixel sized films 1604, a portion of the light passes through the pixel sized films 1605, and a portion passes without any color filter 1606. Thus, red, green, and blue light forms the image 1607. Depending on the red emissive particles type, it is possible to achieve greater than 90% or 95% of Rec.2020 coverage. A similar configuration could be used with a blue OLED or microLED.

A further embodiment of a display device of the present disclosure is illustrated in FIG. 15B. An OLED or microLED light source emits blue light, which passes through a color filter, a first material of the present disclosure, or a second material of the present disclosure. The first material converts blue light into green light and the second material converts blue light into red light. Thus, red, green, and blue light forms the resulting image.

In alternate embodiments, the materials of the present disclosure are used in lighting devices ( e.g ., LED based lamps). For example, a material of the present disclosure could be incorporated into existing lighting technology in order to facilitate a more energy efficient lighting source with a tunable emission spectrum. A material of the present disclosure could be used to convert a portion of blue light emitted from a light source into red and/or green light using red and/or green emissive perovskite quantum dots, respectively. In particular combinations, blue light passed through a material of the present disclosure provides a combination of red, green, and blue light that provides a white color spectrum. An embodiment of such a lighting device of the present disclosure is illustrated in FIG. 20. In embodiments, the materials of the present disclosure may alternatively be used in quantum dot-on chip or remote technologies.

In further embodiments, the materials of the present disclosure are used in UV detectors. Commercially available photodiodes are generally based on silicon and indium gallium arsenide, which is typically only sensitive to light in the visible or near infrared range. In other words, such photodiodes have low responsivity for wavelengths of light below 400 nm. Advantageously, a material of the present disclosure may be used to convert UV light to visible light, which can then be detected by a photodiode with better responsivity. An embodiment of a UV detector of the present disclosure is illustrated in FIG. 21.

In further embodiments, the materials of the present disclosure are used in x-ray scintillators (e.g., for medical, security, or commercial diagnostics). Perovskite quantum dots are sensitive to x-rays and can convert x-rays to visible light. Thus, materials of the present disclosure can be used in x-ray scintillator systems. An embodiment of an x-ray scintillator of the present disclosure is illustrated in FIG. 22. Advantageously, the materials of the present disclosure are solution processable and have tunable emissions.

In order to confirm that a material is suitable for use in such devices, accelerated testing may be performed. For example, high -temperature accelerated testing may be conducted using the following procedure. First, the film is heated to a temperature of 85°C at 60% of RH and irradiated with blue light (450 nm) at a power of 10 mW/cm². During the accelerated testing, the emission intensity of the film is monitored periodically.

A schematic of such a testing setup 100 is shown in FIG. 2A. The film 106, comprising a composite that includes a polymer resin 103, perovskite quantum dots 102, and barrier layers 101, is arranged adjacent to a heat source 105 while irradiated by a light source 104 ( e.g ., emitting blue light). In embodiments, the quantum dots are present in a concentration ranging from 0.3 to 0.5%, by weight excluding the barrier layer(s), and the film has a thickness of lOOpm to 500pm. The blue light has a wavelength, for example, of 450 nm, and an intensity, for example, of 10 mW/cm². The heat source 105 heats the film (e.g. 85°C), to which the film is exposed for a period of time, for example 1000 hours.

For example, when a polymer film comprising standard CsPbBn quantum dots with oleic acid and oleylamine as ligands encapsulated in a polymer resin is exposed to such conditions, the photoluminescence (PL) intensity of the emission from the quantum dots decreases by about 100% in the first 96 hours of the test, as shown in the experimental data of FIG. 3. The explanation for such abrupt degradation, as shown in FIG. 4, is that the bonds between the CsPbBn quantum dots 301 and oleic acid 302; and CsPbBn quantum dots and oleylamine 303 are broken under the heat exposure 304. This detachment of the ligands results in the creation of surface defects, aggregation of the quantum dots and PL light intensity deterioration.

Further, high-flux accelerated testing may be conducted using the following procedure. First, the film is heated to a temperature of 60°C at 60% of RH and irradiated with blue light (450 nm) at a power of 100 mW/cm². During the accelerated testing, the emission intensity of the film is monitored periodically.

A schematic of such testing is shown in FIG. 2B. The film, comprising a composite that includes a polymer resin 3, perovskite quantum dots 2, and barrier layers 1, is arranged adjacent to a heat source 5 while irradiated by a light source 4.

In embodiments, the materials of the present disclosure retain at least about 70% of the initial emission intensity after 1000 hours of exposure. In some embodiments, the materials of the present disclosure retain at least about 80% of the initial emission intensity after 1000 hours of exposure.

Various embodiments of the disclosure are described herein. It will be recognized that features specified in each embodiment may be combined with other specified features to provide further embodiments of the present disclosure. The following embodiments are included within the scope of the disclosure:

Embodiment 1. A composition comprising: perovskite quantum dots bonded to one or more ligands, each of the perovskite quantum dots independently having the formula:

Csa(MA)b(FA)cRbdPbpSnrBisClxBr_yIz, and each of the ligands independently having the formula:

R₄P⁺F, wherein:

MA is CH3NH3;

FA is HC(NH₂)₂; a, b, c, and d are each independently a number from 0 to 1, provided that the sum of a, b, c, and d is 1; p, r, and s are each independently a number from 0 to 1, provided that the sum of p, r, and s is 1; and x, y, and z are each independently a number from 0 to 3, provided that the sum of x, y, and z is 3; and

R is at each occurrence, independently, an organic substituent.

Embodiment 2. The composition of embodiment 1, wherein the perovskite quantum dots independently have the formula: Csa(MA)b(FA)_cPbpSnrBisClxBr_yIz.

Embodiment 3. The composition of embodiment 1 or 2, wherein the perovskite quantum dots have the formula: Csa(MA)b(FA)_cPbClxBr_yIz.

Embodiment 4. The composition of any one of embodiments 1-3, wherein the perovskite quantum dots comprise MAPbE, MAPbBn, FAPbBn, FAPbE, MAPbCb, MAPbBnCl, FAPbCb, CsPbb, CsPbCb, CsPbBn, CsPbCl_xBr_y, CsPbBr_yI_z, or a combination thereof, wherein the sum of x and y is 3 or wherein the sum of y and z is 3.

Embodiment 5. The composition of any one of embodiments 1-4, wherein the perovskite quantum dots comprise CsPbBn.

Embodiment 6. The composition of embodiment 1 or 2, wherein the perovskite quantum dots comprise FASnb, FASnBn, FASnCb, MASnb, MASnBn, and MASnCb, CsSnb, CsSnBn, CsSnCb, or a combination thereof.

Embodiment 7. The composition of any one of embodiments 1-5, wherein the perovskite quantum dots comprise CsPbCl_xBr_y, wherein the sum of x and y is 3.

Embodiment 8. The composition of any one of embodiments 1-5, wherein the perovskite quantum dots comprise CsPbBr_yI_z, wherein the sum of y and z is 3.

Embodiment 9. The composition of any one of embodiments 1-8, wherein the perovskite quantum dots further comprise a shell comprising one or more oxides, one or more sulphides, one or more halides, or a combination thereof. Embodiment 10. The composition of embodiment 9, wherein the one or more oxides comprise SiCk, AI2O3, T1O2, ZrCk, ZnO, or a combination thereof, the one or more sulphides comprise ZnS, CdS, PbS, NiS, ImS3, or a combination thereof, or the one or more halides comprise CsX, NaX, KX, LiX, RbX, MgX₂, CaX₂, ZnX₂, T1X, PbX₂, CuX, CuX₂, or a combination thereof, where X is Cl, Br or I.

Embodiment 11. The composition of any one of embodiments 1-10, wherein R is, at each occurrence, independently, alkyl, alkenyl, or aryl.

Embodiment 12. The composition of any one of embodiments 1-11, wherein R is, at each occurrence, independently, optionally substituted with hydroxyl, oxo, carboxyl, amino, phosphate, sulfonic acid, or a combination thereof.

Embodiment 13. The composition of any one of embodiments 1-12, wherein at least one occurrence of R is a polymer.

Embodiment 14. The composition of any one of embodiments 1-13, wherein at least one occurrence of R comprises at least six carbons.

Embodiment 15. The composition of any one of embodiments 1-14, wherein R, at each occurrence, independently, comprises at least six carbons.

Embodiment 16. The composition of any one of embodiments 1-15, wherein at least one occurrence of R comprises no more than eight carbons.

Embodiment 17. The composition of any one of embodiments 1-16, wherein R, at each occurrence, independently, comprises no more than eight carbons.

Embodiment 18. The composition of any one of embodiments 1-17, wherein the one or more ligands comprise tetraethylphosphonium iodide, tetraphenylphosphonium iodide, methyltriphenylphosphonium iodide, ethyltriphenylphosphonium iodide, isopropyltriphenylphosphonium iodide, (iodomethyl)triphenylphosphonium iodide, didodecyltriphenylphosphonium iodide, methyltriphenylphosphonium iodide-polymer-bound, tetrabutylphosphonium iodide, [2-(methylidynesilyl)ethyl](triphenyl)phosphonium iodide, (1- iodoethyl)(triphenyl)phosphonium iodide, or a combination thereof.

Embodiment 19. A material comprising the composition of any one of embodiments 1- 18 and a monomer, a polymer, or both.

Embodiment 20. The material of embodiment 19, wherein the polymer comprises a polyurethane, a rubber, polyvinylchloride (PVC), a vinyl polymer, a polyester, a polyacrylate, a polyamide, a biopolymer, a polyolefin, a thermoplastic elastomer, a styrene block copolymer, a polyether block amid, or a combination thereof. Embodiment 21. The material of embodiment 19 or 20, wherein the rubber is a silicon rubber, a latex rubber, or a combination thereof.

Embodiment 22. The material of any one of embodiments 19-21, wherein the polymer comprises a mixture of acrylate and styrene-based polymers.

Embodiment 23. The material of any one of embodiments 19-22, wherein the polymer is ultra-violet (UV) curable.

Embodiment 24. The material of any one of embodiments 19-23, wherein the perovskite quantum dots are in a concentration ranging from 0.01% to 75%, by weight.

Embodiment 25. The material of embodiment 24, wherein the concentration ranges from 0.1% to 60%, by weight.

Embodiment 26. The material of embodiment 24, wherein the concentration ranges from 0.01% to 0.75%, by weight.

Embodiment 27. The material of embodiment 24, wherein the concentration ranges from 0.1% to 0.5%, by weight.

Embodiment 28. The material of embodiment 24, wherein the concentration ranges from 10% to 70%, by weight.

Embodiment 29. The material of embodiment 24, wherein the concentration ranges from 20% to 60%, by weight.

Embodiment 30. The material of embodiment 24, wherein the concentration is about 0.5%, by weight.

Embodiment 31. The composition of any one of embodiments 1-18 or material of any one of embodiments 19-30, wherein the perovskite quantum dots have an emission wavelength of at least 520 nm.

Embodiment 32. The composition of any one of embodiments 1-18 or material of any one of embodiments 19-31, wherein the full width at half maximum (FWHM) of the emission of the perovskite quantum dots is lower than 25 nm.

Embodiment 33. The material of any one of embodiments 19-32, further comprising emissive particles.

Embodiment 34. The material of embodiment 33, wherein the emissive particles comprise narrow band phosphors, narrow band quantum dots, or both.

Embodiment 35. The material of embodiment 34, wherein the narrow band phosphors comprise a rare-earth phosphor. Embodiment 36. The material of embodiment 35, wherein the rare-earth phosphor comprise KSF:Mn

Embodiment 37. The material of any one of embodiments 34-36, wherein the narrow band quantum dots comprise CdSe, CdSe/ZnS, CdSe/ZnSe, CdSe/CdS, InP, InP/ZnS, InP/ZnSe, CuInS2, or a combination thereof.

Embodiment 38. The material of any one of embodiments 19-37, further comprising a photoinitiator.

Embodiment 39. The material of any one of embodiments 19-37, further comprising a light scattering agent.

Embodiment 40. The material of any one of embodiments 19-39, further comprising a viscosity modifier.

Embodiment 41. The material of embodiment 40, wherein the viscosity modifier comprises S1O2 nanoparticles.

Embodiment 42. The material of any one of embodiments 19-41, wherein the material is solid.

Embodiment 43. The material of any one of embodiments 19-42, wherein the material is a film.

Embodiment 44. The material of embodiment 43, wherein the film comprises a barrier layer arranged on at least one side.

Embodiment 45. The material of embodiment 44, wherein the film comprises a barrier layer arranged on each side.

Embodiment 46. The material of embodiment 44 or 45, wherein the barrier layer comprises a polymer film.

Embodiment 47. The material of any one of embodiments 44-46, wherein the barrier layer comprises a multilayer film.

Embodiment 48. The material of embodiment 47, wherein the multilayer film comprises an inorganic layer.

Embodiment 49. The material of embodiment 48, wherein the inorganic layer comprises AI2O3, S1O2, or a combination thereof.

Embodiment 50. The material of any one of embodiments 44-49, wherein the barrier layer comprises glass.

Embodiment 51. The material of any one of embodiments 44-50, wherein the barrier layer has a thickness ranging from 1 micrometers (pm) to 100 pm. Embodiment 52. The material of embodiment 51, wherein the thickness is about 50 mih.

Embodiment 53. The material of any one of embodiments 44-52, wherein the barrier layer has a water vapor transmission rate (WVTR) of about < 0.001 g/m²-day at 20°C.

Embodiment 54. The material of any one of embodiments 44-52, wherein the barrier layer has a WVTR of about < 0.1 g/m²-day at 20°C.

Embodiment 55. The material of any one of embodiments 43-54, wherein the film has a thickness ranging from 1 pm to 1000 pm.

Embodiment 56. The material of any one of embodiments 43-55, wherein the film has a thickness ranging from 100 pm to 500 pm.

Embodiment 57. The material of embodiment 56, wherein the thickness is about 200 pm.

Embodiment 58. The material of any one of embodiments 19-41, wherein the material is liquid.

Embodiment 59. The composition of any one of embodiments 1-18 or the material of any one of embodiments 19-58, wherein the perovskite quantum dots have an average diameter ranging from 2 nanometers (nm) to 100 nm.

Embodiment 60. The composition of any one of embodiments 1-18 or the material of any one of embodiments 19-59, wherein the perovskite quantum dots have an average diameter ranging from 5 nm to 100 nm.

Embodiment 61. A device comprising the composition of any one of embodiments 1-18 or the material of any one of embodiments 19-57, 59, or 60.

Embodiment 62. The device of embodiment 61, further comprising a light source.

Embodiment 63. The device of embodiment 62, wherein the light source emits blue light, ultraviolet (UV) light, blue and red light, or UV light with blue and red light.

Embodiment 64. The device of any one of embodiments 61-63, wherein the device comprises a liquid crystal display (LCD), wherein the material is a film in the LCD.

Embodiment 65. The device of any one of embodiments 61-63, wherein the device comprises a light emitting diode (LED), wherein the material is a film arranged on the LED.

Embodiment 66. The device of any one of embodiments 61-63, wherein the device comprises an organic LED (OLED), wherein the material is a film arranged on the OLED.

Embodiment 67. The device of any one of embodiments 61-63, wherein the device comprises a microLED, wherein the material is a film on the microLED.

Embodiment 68. The device of any one of embodiments 61-63, wherein the device is a UV detector. Embodiment 69. The device of any one of embodiments 61-63, wherein the device is an x-ray scintillator.

Embodiment 70. A method for forming a material of any one of embodiments 19-60, the method comprising: mixing (a) the monomer or the polymer, and (b) the perovskite quantum dots.

Embodiment 71. The method of embodiment 70, wherein the mixing (a) and (b) produces a composite, and wherein the method further comprises an additive into the composite.

Embodiment 72. The method of embodiment 71, wherein the additive comprises a light scattering agent.

Embodiment 73. The method of any one of embodiments 70-72, wherein the polymer comprises a combination of acrylate and styrene-based polymer resins.

Embodiment 74. A method for forming a film, the method comprising: spreading the material of any one of embodiments 19-41 or 58-60; and forming the film by curing the material.

Embodiment 75. The method of embodiment 74, wherein the film is the film as recited in any one of embodiments 42-57, 59, or 60.

Embodiment 76. The method of embodiment 74, wherein the material is spread onto a barrier layer.

Embodiment 77. The method of any one of embodiments 74-76, wherein curing the material comprises exposing the material to ultraviolet (UV) light.

Embodiment 78. The method of embodiment 77, wherein the UV light has an intensity of about 800 mW/cm².

Embodiment 79. A composition comprising perovskite nanocrystals (NCs); wherein the perovskite NCs are of the form ABX3, where A and B are cations and X is an anion; wherein the perovskite NCs have bonded thereto one or more ligands having the formula RdNkT, R.3S⁺T, and/or R.4P⁺I , where R is an organic chain.

Embodiment 80. The composition of embodiment 79 wherein B is lead (Pb) and/or wherein X is a halogen.

Embodiment 81. The composition of embodiment 79 or 80, wherein the cations of ABX3 perovskite NCs, A, are selected from Cs⁺, Rb⁺, CEENEE^ and HC(NH2)2⁺.

Embodiment 82. The composition of any one of embodiments 79-81, wherein X is C1-, Br- or I- or a mixture of any two or more thereof. Embodiment 83. The composition of any one of embodiments 79-82, wherein the composition of NCs is CsPbBn.

Embodiment 84. The composition of any one of embodiments 79-83 wherein at least one of the organic chains of each of the ligands comprises at least 6 carbon atoms.

Embodiment 85. The composition of embodiment 84 wherein at least some of the ligands comprise a quaternary centre R.4N⁺ or R.4P⁺ having at least one carbon chain R, having 8 or fewer carbon atoms.

Embodiment 86. The composition of any of embodiments 83 to 85, wherein the organic chain, R, of the ligands includes at least one of alkyl, alkenyl, and aryl chains.

Embodiment 87. The composition of any one of embodiments 79-86, wherein the organic part, R, of the ligands comprises at least one of the functional groups hydroxyl, carbonyl, carboxylic, amino, phosphate, and sulphate.

Embodiment 88. The composition of any one of embodiments 79-87, wherein the organic part, R, of at least one of the one or more ligands is in a polymeric form.

Embodiment 89. The composition of any of embodiments 79 to 87, wherein the ligands are at least one of tridodecylmethylammonium iodide, Hexadecyltrimethylammonium iodide, tetra-n-octylammonium iodide, tetrabutylammonium iodide, methyltriphenylphosphonium iodide, trimethyl sulfoxonium iodide, tetrahexylammonium iodide, ethyldimethylphenethylammonium iodide, alkyl(C8-C18)dimethylbenzylammonium iodide, dialkyl(C8-18)dimethylammonium iodide, trioctylsulfonium iodide, and/or trimethy lhexadecy 1 ammonium i odi de .

Embodiment 90. The composition of any one of embodiments 79-89, wherein the average diameter of the perovskite NCs is 5-100 nm.

Embodiment 91. The composition of any one of embodiments 79-90, wherein the perovskite NCs are quantum dots (QDs).

Embodiment 92. The composition of any one of embodiments 79-91, wherein the perovskite NCs further comprise a shell comprising one or more oxides such as S1O2, AI2O3, T1O2, ZrCk, ZnO, one or more sulphides such as ZnS, CdS, PbS, and/or one or more halides such as CsX, NaX, KX, LiX, RbX, MgX₂, CaX₂, ZnX₂, T1X, PbX₂, CuX, CuX₂ etc., where X is Cl, Br or I.

Embodiment 93. The composition of any one of embodiments 79-92, wherein the one or more red-shifted emission wavelength(s) of the perovskite NCs is higher than 520 nm

Embodiment 94. The composition of any one of embodiments 79-93, wherein the full width at half maximum (FWHM) of the perovskite NCs’ emission is lower than 25 nm. Embodiment 95. A light emitting device having an emissive layer comprising the composition of any one of embodiments 79-94.

Embodiment 96. The light emitting device of embodiment 95 further comprising a layer comprising one or more red emissive materials.

Embodiment 97. The light emitting device of embodiment 95 or 96 comprising a polymer film, having a polymer resin encapsulating the composition of any of embodiments 79 to 94.

Embodiment 98. The light emitting device of any of embodiments 96 or 97, wherein the red emissive material(s) is/are selected from rare-earth phosphor KSF:Mn and narrow-band QDs including CdSe, CdSe/ZnS, CdSe/ZnSe, CdSe/CdS, InP, InP/ZnS, InP/ZnSe, and CuInS2 QDs.

Embodiment 99. The light emitting device of any of embodiments 95 to 98, wherein the emissive layer comprising the composition of any of embodiments 1 to 14 absorbs a first one or more range(s) of wavelength(s) of light and emits a second one or more range(s) of wavelength(s) of light with one or more peak wavelength(s) higher than 520 nm and FWHM lower than 25 nm.

Embodiment 100. The light emitting device of any of embodiments 95 to 99 further comprising one or more barrier layers encapsulating the composition of any of embodiments 79 to 94, wherein the barrier layer comprises one or more of polymer films, multilayer polymer films with inorganic layers including AI2O3 or S1O2, glass, and other transparent materials.

Embodiment 101. The light emitting device of any of embodiments 95 to 100, wherein the composite thickness varies from 1 pm to 1000 pm.

Embodiment 102. A display device comprising the light emitting device of any of embodiments 95 to 101 and a light source, wherein the light source emits a first one or more ranges of wavelengths of light.

Embodiment 103. The display device of embodiment 102, wherein the light source is blue, UV, blue with red, or UV with blue and red.

Embodiment 104. The display device of embodiments 102 or 103, wherein at least one of the light emitting devices of embodiments 17 to 23 is used in at least one of LCD backlighting, LCD colour filters, OLED colour filters, and microLED colour filters of the display device.

Embodiment 105. A polymer comprising the composition of any of embodiments 79 to 94.

Embodiment 106. The polymer of embodiment 105 wherein the polymer is a polymer matrix having embedded therein the perovskite nanocrystals of any of embodiments 79 to 94. EXAMPLES

TEM AND XRD ANALYSIS

As referenced below, Transmission Electron Microscopy (TEM) was carried out on the Titan G2 80-300, FEI Co., operating at 300 kV. Samples were diluted in toluene and a drop of the solution was poured onto a carbon coated 300 mesh copper TEM grid for analysis. X-ray diffraction (XRD) spectrums were obtained from Powder XRD Bruker D8 Advance using Cu Ka radiation (l = 1.5409 A) from 20 = 10-50°.

EXAMPLE 1 LIGAND COMPARISON

CsPbBn quantum dots were synthesized by a modified hot-injection procedure as described in Protesescu, L., et al., Nano Lett., 2015. 15: p. 3692-3696. In summary, PbBn in 1- octadecene (ODE) was loaded in a flask and dried under vacuum at 120°C. Then, oleic acid and oleylamine were injected. After the precursors were in solution, the temperature was raised to 150-200°C, and quantum dots were formed by the quick addition of Cs oleate solution. After five seconds, powder Tridodecylmethylammonium iodide (TMAI) was added to the reaction mixture and the reaction was cooled by an ice-water bath. The crude solution was centrifuged, washed by toluene, and the quantum dots were kept in paste form.

According to Transmission Electron Microscopy (TEM) images, as exemplified in FIG. 16 A, the resulting quantum dots have a cubic structure with a = b = c = 10 nm. X-ray diffraction (XRD) analysis, as shown in FIG. 16B showed that characteristic diffraction peaks correspond for the cubic phase of CsPbBn quantum dots (Joint Committee on Powder Diffraction Standards (JCPDS) or International Centre for Diffraction Data (ICDD) No 18-0364). It shows that no CsPb(Br/I)3 formed.

To make a polymer composite material from the CsPbBn-TMAI quantum dots in paste form were dissolved in Isobornyl acrylate monomer (IBOA). Optionally one or more of a photoinitiator, adhesives, T1O2 nanoparticles (as a light scattering agent), and/or S1O2 nanoparticles (as a viscosity modifier) were added to the resin and mixed well. The concentration of quantum dots was kept at 0.5%, by weight. The mixture was blade casted on a substrate and cured under UV light 800 mW/cm² light intensity for 1 minute. The formed film had a thickness 200 pm. Additionally, polymer films were laminated with a barrier polymer film 3M™ FTB3-50 (50pm thickness and VWTR < 0.001 g/m²-day@20°C). The resulting polymer composite had an emission peak centered at 525 nm with FWHM 20 nm and film PLQY > 80% (FIG. 9).

The obtained polymer composite was exposed to heat of 85°C and 450 nm light of intensity 10 mW/cm² according to the test explained in relation to FIG. 2 A. The composite’s light intensity retained 70-80% of its original intensity after 1000 hours of exposure as shown in FIG. 10A. The emission peak retains almost the same 525 nm centering and FWHM less than 22 nm, as shown in the results of FIG.10B and FIG. IOC. As can be seen, these CsPbBn-TMAI quantum dots are very stable under the accelerated tests and compliant with industrial requirements for displays. This is due to the combination of the T ion that redshifts the emission to > 524 nm and the quaternary ammonium ion TMA ion that stabilizes the quantum dots at high temperatures.

The resulting polymer composite can be used for display backlighting applications of the sort described in relation to FIG. 7 A or FIG. 7B. For example, the polymer composite may be excited by a pink light source such as an LED containing KSF phosphor. The rec 2020 coverage area has been found to be > 95% as illustrated in FIG. 11 (simulated based on individual color coordinates).

CsPbBn quantum dots were treated with similar ligands in the same manner described above with regard to TMAI with the results in Table 1.

Table 1

EXAMPLE 2

LIGAND COMPARISON

CsPbBn quantum dots were synthesized by a modified hot-injection procedure as described in Protesescu, L., et ah, Nano Lett., 2015. 15: p. 3692-3696. PbBn in 1-octadecene (ODE) was loaded in a flask and dried under vacuum at 120°C. Then, oleic acid and oleylamine were inj ected. After the precursors were in solution, the temperature was raised to 150-200°C, and quantum dots were formed by the quick addition of Cs oleate solution. After five seconds, the reaction was cooled down with an ice-water bath. The crude solution was centrifuged, and the precipitate was redispersed in toluene for further study. For treatment with an additive, a different organic halide source was added to the quantum dots in toluene as a post-treatment synthesis step. The effect of the post-treatment step to the stability of quantum dots at elevated temperature was compared.

In this example, the effect of different post-treatment on the CsPbBn quantum dots stability under high temperature was compared. The synthesized quantum dots were treated with different ligands. For this measurement, the quantum dots solutions are drop casted on toluene and allowed to dry in ambient conditions before performing the measurement. Under temperature dependent photoluminescence measurement, the quantum dots films samples were subjected to the increase/decrease of temperature from room temperature to 100°C. The results are shown in FIG. 18A - FIG. 18D. As shown in FIG. 18 A, at 100°C, quantum dots without additive treatment maintain only 25% of their initial photoluminescence intensity. By repeating the cycle of heating and cooling the quantum dots films, it is also clear that the quantum dots films are not stable, as the photoluminescence intensity at 20°C has dropped as compared to the initial intensity after 3 cycles of heating/cooling.

The sample with tetraphenylphosphonium iodide (TPPI) ligand had better stability under temperature cycle (FIG. 18C) compared to the sample with tridodecylmethylammonium iodide (TMAI) ligand (FIG. 18B) and the sample without treatment. Under heating and cooling cycle, sample with TPPI ligand showed lower temperature quenching at high temperature and maintain >80% of the initial intensity at RT. Similarly, the sample treated with trimethyl sulfoxonium iodide shows better stability at high temperature as compared to the quantum dots without treatment (FIG. 18D). This sample maintained 50% of its initial intensity at 100°C but the photoluminescence at 20°C dropped directly after only 1 cycle of heating.

From this comparison, phosphonium iodide treatment showed the best performance in term of passivating the quantum dots and improving the stability of the quantum dots under high temperature condition for long-term use.

The stability of films comprising quantum dots having undergone treatment with TMAI and TPPI under high temperature test was also compared. The samples were mixed with IBOA and polymer films are formed as described in Example 1. The perovskite-polymer films obtained were then subjected to accelerated test condition at 85°C temperature and blue light exposure (450 nm wavelength) with intensity around 10 mW/cm². Comparison between these films show that the sample with TPPI ligands has better stability under accelerated test condition. The films with CsPbBn-TMAI retained about 70% of original the intensity and the films with CsPbBn-TPPI retained about 90% of the initial intensity after 1000 hours of exposure as shown in FIG. 19. The phosphonium ligand clearly provided better stability as compared to the ammonium ligand. EXAMPLE 3

CSPBBR3 QUANTUM DOTS + CDSE/ZNS QUANTUM DOTS

CsPbBn-TMAI quantum dots were mixed with CdSe/ZnS quantum dots, the mixture was encapsulated together in a polymer film. To make a polymer composite material from the mixture, CsPbBn-TMAI quantum dots in paste form were dissolved in IBOA. A photoinitiator, adhesive, TiCk nanoparticles (as alight scattering agent), and/or SiCk nanoparticles (as a viscosity modifier) were added to the resin and mixed well. The concentration of CsPbBn-TMAI quantum dots was 0.5%, by weight, and the concentration of CdSe/ZnS quantum dots was 0.1%, by weight. The mixture was blade casted on a substrate and cured under UV light 800 mW/cm² light intensity for 1 minute. The formed film had a thickness 200 pm. Additionally, the polymer films were laminated with barrier polymer film 3M™ FTB3-50 (50 pm thickness and VWTR < 0.001 g/m²- day@20 °C). The resulting polymer composite had an emission peak centered at 525 nm with FWHM 20 nm, and an emission peak at 620 nm with FWHM < 35 nm, as illustrated in the results of FIG. 12. Film PLQY was > 70%. The rec 2020 coverage area was found to be > 90%, as shown in the results of FIG. 14 A.

It is possible to increase the color coverage, for example, by adjusting the properties of the CdSe quantum dots. For example, it is possible to make CdSe quantum dots with an emission peak at 630 nm.

Similarly, CsPbBn-TPPI quantum polymer composite film had an emission peak centered at 525 nm with FWHM 20 nm. The film PLQY was > 85% and the rec 2020 coverage area was measured to be > 90%. (FIG. 14B)

EXAMPLE 4 CSPBBR.3 COLOR FILTER

CsPbBn-TMAI quantum dots were tested in color filter applications according to the display device illustrated in FIG. 15 A. CsPbBn-TMAI quantum dots were mixed with IBOA and, optionally, a photoinitiator. The concentration of quantum dots was 45%, by weight. The mixture was drop casted on the top of the glass substrate and cured under UV light 800 mW/cm² light intensity for one minute. The film formed had a thickness 10 pm. The resulting polymer composite has the emission peak centered at 530 nm with FWHM 20 nm and film PLQY > 70%.

Similarly, CsPbBn-TPPI quantum dots were tested in color filter applications. The film formed had a thickness about 10 pm. The resulting polymer composite has the emission peak centered at 532 nm with FWHM 21 nm and film PLQY > 85%. EXAMPLE 5

CSPBBR3 WITH T1O2 SHELL

CsPbBn-TMAI quantum dots from Example 1 were additionally shelled by a TiCE shell. For this purpose, 2 g of CsPbBn-TMAI quantum dots were dispersed in 100 mL of octadecene (ODE). 2 mL of titanium-diisopropoxide-bis-acetylacetonate was added dropwise to the mixture under rigorous stirring. The mixture was stirred for 10 minutes and then 10 mL of Isopropanol/Ethanol (volume 1:1) was added to initiate titanium precursor hydrolysis. The final mixture was stirred for 30 minutes and then isolated from ODE by centrifugation.

According to TEM analysis (FIG. 17A), the synthesized particles represent the plurality of perovskite quantum dots covered by TiCE shell. The protective shell was found to increase the thermal stability of perovskite quantum dots at high humidity and the composite material similar to that shown in FIG. 7A incorporating these shelled quantum dots was found to retain > 80% of original intensity during the test according to FIG. 2A at 85°C and relative humidity >95%.

Using similar approach, CsPbBn-TPPI quantum dots were also shelled by a TiCE. As shown from TEM image, it confirmed that the CsPbBn quantum dots are protected by TiCE shell (FIG. 17B). The protective shell was found to increase the thermal stability of perovskite quantum dots at high humidity and it was found to retain > 85% of original intensity during the test at 85°C and relative humidity > 95%.

The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including but not limited to United Kingdom Patent Application No. GB1915382.4, filed on October 23, 2019 and U.S. Provisional Patent Application No. 63/072,861 filed on August 31, 2020, are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

1. A composition comprising: perovskite quantum dots bonded to one or more ligands, each of the perovskite quantum dots independently having the formula:

R₄P⁺F, wherein:

MA is CH3NH3;

R is at each occurrence, independently, an organic substituent.

2. The composition of claim 1, wherein the perovskite quantum dots independently have the formula: Csa(MA)b(FA)_cPbpSnrBisClxBr_yIz.

3. The composition of claim 1 or 2, wherein the perovskite quantum dots have the formula: Cs_a(MA)b(FA)_cPbClxBr_yIz.

4. The composition of any one of claims 1-3, wherein the perovskite quantum dots comprise MAPbb, MAPbBn, FAPbBn, FAPbb, MAPbCb, MAPbBnCl, FAPbCb, CsPbb, CsPbCb, CsPbBn, CsPbCl_xBr_y, CsPbBr_yI_z, or a combination thereof, wherein the sum of x and y is 3 or wherein the sum of y and z is 3.

5. The composition of any one of claims 1-4, wherein the perovskite quantum dots comprise CsPbBn.

6. The composition of claim 1 or 2, wherein the perovskite quantum dots comprise FASnb, FASnBn, FASnCb, MASnb, MASnBn, and MASnCb, CsSnb, CsSnBn, CsSnCb, or a combination thereof.

7. The composition of any one of claims 1-5, wherein the perovskite quantum dots comprise CsPbClxBr_y, wherein the sum of x and y is 3.

8. The composition of any one of claims 1-5, wherein the perovskite quantum dots comprise CsPbBr_yI_z, wherein the sum of y and z is 3.

9. The composition of any one of claims 1-8, wherein the perovskite quantum dots further comprise a shell comprising one or more oxides, one or more sulphides, one or more halides, or a combination thereof.

10. The composition of claim 9, wherein the one or more oxides comprise S1O2, AI2O3, T1O2, ZrCb, ZnO, or a combination thereof, the one or more sulphides comprise ZnS, CdS, PbS, NiS, ImS3, or a combination thereof, or the one or more halides comprise CsX, NaX, KX, LiX, RbX, MgX2, CaX2, ZnX2, T1X, PbX2, CuX, CuX2, or a combination thereof, where X is Cl, Br or I.

11. The composition of any one of claims 1-10, wherein R is, at each occurrence, independently, alkyl, alkenyl, or aryl.

12. The composition of any one of claims 1-11, wherein R is, at each occurrence, independently, optionally substituted with hydroxyl, oxo, carboxyl, amino, phosphate, sulfonic acid, or a combination thereof.

13. The composition of any one of claims 1-12, wherein at least one occurrence of R is a polymer.

14. The composition of any one of claims 1-13, wherein at least one occurrence of R comprises at least six carbons.

15. The composition of any one of claims 1-14, wherein R, at each occurrence, independently, comprises at least six carbons.

16. The composition of any one of claims 1-15, wherein at least one occurrence of R comprises no more than eight carbons.

17. The composition of any one of claims 1-16, wherein R, at each occurrence, independently, comprises no more than eight carbons.

18. The composition of any one of claims 1-17, wherein the one or more ligands comprise tetraethylphosphonium iodide, tetraphenylphosphonium iodide, methyltriphenylphosphonium iodide, ethyltriphenylphosphonium iodide, isopropyltriphenylphosphonium iodide, (iodomethyl)triphenylphosphonium iodide, didodecyltriphenylphosphonium iodide, methyltriphenylphosphonium iodide-polymer-bound, tetrabutylphosphonium iodide, [2-(methylidynesilyl)ethyl](triphenyl)phosphonium iodide, (1- iodoethyl)(triphenyl)phosphonium iodide, or a combination thereof.

19. A material comprising the composition of any one of claims 1-18 and a monomer, a polymer, or both.

20. The material of claim 19, wherein the polymer comprises a polyurethane, a rubber, polyvinylchloride (PVC), a vinyl polymer, a polyester, a polyacrylate, a polyamide, a biopolymer, a polyolefin, a thermoplastic elastomer, a styrene block copolymer, a polyether block amid, or a combination thereof.

21. The material of claim 19 or 20, wherein the rubber is a silicon rubber, a latex rubber, or a combination thereof.

22. The material of any one of claims 19-21, wherein the polymer comprises a mixture of acrylate and styrene-based polymers.

23. The material of any one of claims 19-22, wherein the polymer is ultra-violet (UV) curable.

24. The material of any one of claims 19-23, wherein the perovskite quantum dots are in a concentration ranging from 0.01% to 75%, by weight.

25. The material of claim 24, wherein the concentration ranges from 0.1% to 60%, by weight.

26. The material of claim 24, wherein the concentration ranges from 0.01% to 0.75%, by weight.

27. The material of claim 24, wherein the concentration ranges from 0.1% to 0.5%, by weight.

28. The material of claim 24, wherein the concentration ranges from 10% to 70%, by weight.

29. The material of claim 24, wherein the concentration ranges from 20% to 60%, by weight.

30. The material of claim 24, wherein the concentration is about 0.5%, by weight.

31. The composition of any one of claims 1-18 or material of any one of claims 19-30, wherein the perovskite quantum dots have an emission wavelength of at least 520 nm.

32. The composition of any one of claims 1-18 or material of any one of claims 19-31, wherein the full width at half maximum (FWHM) of the emission of the perovskite quantum dots is lower than 25 nm.

33. The material of any one of claims 19-32, further comprising emissive particles.

34. The material of claim 33, wherein the emissive particles comprise narrow band phosphors, narrow band quantum dots, or both.

35. The material of claim 34, wherein the narrow band phosphors comprise a rare-earth phosphor.

36. The material of claim 35, wherein the rare-earth phosphor comprise KSF :Mn

37. The material of any one of claims 34-36, wherein the narrow band quantum dots comprise CdSe, CdSe/ZnS, CdSe/ZnSe, CdSe/CdS, InP, InP/ZnS, InP/ZnSe, CuInS2, or a combination thereof.

38. The material of any one of claims 19-37, further comprising a photoinitiator.

39. The material of any one of claims 19-37, further comprising a light scattering agent.

40. The material of any one of claims 19-39, further comprising a viscosity modifier.

41. The material of claim 40, wherein the viscosity modifier comprises S1O2 nanoparticles.

42. The material of any one of claims 19-41, wherein the material is solid.

43. The material of any one of claims 19-42, wherein the material is a film.

44. The material of claim 43, wherein the film comprises a barrier layer arranged on at least one side.

45. The material of claim 44, wherein the film comprises a barrier layer arranged on each side.

46. The material of claim 44 or 45, wherein the barrier layer comprises a polymer film.

47. The material of any one of claims 44-46, wherein the barrier layer comprises a multilayer film.

48. The material of claim 47, wherein the multilayer film comprises an inorganic layer.

49. The material of claim 48, wherein the inorganic layer comprises AI2O3, S1O2, or a combination thereof.

50. The material of any one of claims 44-49, wherein the barrier layer comprises glass.

51. The material of any one of claims 44-50, wherein the barrier layer has a thickness ranging from 1 micrometers (pm) to 100 pm.

52. The material of claim 51, wherein the thickness is about 50 pm.

53. The material of any one of claims 44-52, wherein the barrier layer has a water vapor transmission rate (WVTR) of about < 0.001 g/m²-day at 20°C.

54. The material of any one of claims 44-52, wherein the barrier layer has a WVTR of about < 0.1 g/m²-day at 20°C.

55. The material of any one of claims 43-54, wherein the film has a thickness ranging from 1 pm to 1000 pm.

56. The material of any one of claims 43-55, wherein the film has a thickness ranging from 100 pm to 500 pm.

57. The material of claim 56, wherein the thickness is about 200 pm.

58. The material of any one of claims 19-41, wherein the material is liquid.

59. The composition of any one of claims 1-18 or material of any one of claims 19-58, wherein the perovskite quantum dots have an average diameter ranging from 2 nanometers (nm) to 100 nm.

60. The composition of any one of claims 1-18 or material of any one of claims 19-59, wherein the perovskite quantum dots have an average diameter ranging from 5 nm to 100 nm.

61. A device comprising the composition of any one of claims 1-18 or the material of any one of claims 19-57, 59, or 60.

62. The device of claim 61, further comprising a light source.

63. The device of claim 62, wherein the light source emits blue light, ultraviolet (UV) light, blue and red light, or UV light with blue and red light.

64. The device of any one of claims 61-63, wherein the device comprises a liquid crystal display (LCD), wherein the material is a film in the LCD.

65. The device of any one of claims 61-63, wherein the device comprises a light emitting diode (LED), wherein the material is a film arranged on the LED.

66. The device of any one of claims 61-63, wherein the device comprises an organic LED (OLED), wherein the material is a film arranged on the OLED.

67. The device of any one of claims 61-63, wherein the device comprises a microLED, wherein the material is a film on the microLED.

68. The device of any one of claims 61-63, wherein the device is a UV detector.

69. The device of any one of claims 61-63, wherein the device is an x-ray scintillator.

70. A method for forming a material of any one of claims 19-60, the method comprising: mixing (a) the monomer or the polymer, and (b) the perovskite quantum dots.

71. The method of claim 70, wherein the mixing (a) and (b) produces a composite, and wherein the method further comprises an additive into the composite.

72. The method of claim 71, wherein the additive comprises a light scattering agent.

73. The method of any one of claims 70-72, wherein the polymer comprises a combination of acrylate and styrene-based polymer resins.

74. A method for forming a film, the method comprising: spreading the material of any one of claims 19-41 or 58-60; and forming the film by curing the material.

75. The method of claim 74, wherein the film is the film as recited in any one of claims 42-57, 59, or 60.

76. The method of claim 74, wherein the material is spread onto a barrier layer.

77. The method of any one of claims 74-76, wherein curing the material comprises exposing the material to ultraviolet (UV) light.

78. The method of claim 77, wherein the UV light has an intensity of about 800 mW/cm².