Description:FIELD OF INVENTION
[0001]
The present disclosure relates to the field of optoelectronics, in particular relates to quantum dots, more particularly surface passivated quantum dots. The present disclosure further relates to process of preparation of the surface passivated quantum dots and applications thereof. 5
BACKGROUND OF THE INVENTION
[0002]
Perovskite nanocrystals (PNCs) have attracted considerable attention in the field of optoelectronics due to their exceptional photophysical properties. These include tunable photoluminescence across the visible spectrum, narrow emission linewidths, high photoluminescence quantum yields, and intrinsic defect tolerance. 10
[0003]
Despite their promising attributes, challenges hinder the practical deployment of PNCs in optoelectronic devices. One of the most critical issues is achieving stable blue emission. Blue emission requires a larger bandgap and is often associated with a higher density of surface traps, which promotes nonradiative recombination. Researchers have explored compositional engineering strategies, such as halide 15 substitution to address this challenge. However, these approaches frequently introduce deep-level trap states and phase segregation, which degrade device performance.
[0004]
Surface ligands are pivotal in determining the optical and electronic behavior of perovskite nanocrystals (PNCs). Conventional long-chain alkyl ligands commonly 20 used during synthesis to ensure colloidal stability. However, these ligands are inherently electrically insulating and only loosely attached to the nanocrystal surface. Under conditions of thermal or electrical stress, they tend to desorb, which exposes the nanocrystal surface and leads to the formation of surface trap states. These trap states act as non-radiative recombination centers, significantly diminishing 25 photoluminescence efficiency. As a result, the presence of such ligands limits the performance and long-term stability of PNCs in optoelectronic devices.
[0005]
Additionally, PNCs are highly sensitive to external factors such as moisture, oxygen, heat, and light, which can cause rapid degradation. Protective encapsulation
2
is often employed to mitigate these effects, but it adds complexity and cost to the manufacturing process.
[0006]
To overcome these limitations, ligand exchange strategies have been developed to replace native ligands with alternatives that offer improved electronic coupling, enhanced film quality, and greater environmental resilience. However, 5 identifying an appropriate ligand system remains a challenging task.
[0007]
Therefore, there is a dire need to develop a surface-passivated quantum dot with advanced ligand systems capable of addressing multiple performance parameters including emission tuning, environmental stability, and charge transport.
SUMMARY OF THE INVENTION 10
[0008]
In an aspect of the present disclosure, there is provided a surface passivated quantum dot comprising: a. a perovskite nanocrystal of formula ABX3; and b. a conjugated aromatic ligand of Formula L1,
15
20
Formula L1
wherein A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation, B is selected from Pb, or Sn, X is selected from Br, Cl, or I;
W1, W2, W3, W4, and W5 are independently selected from C, CH, N, NH, O, or S; 25
p is 0 or 1;
Z3 is independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl; 30 3
Z1 and Z2 are independently absent or selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl;
m is independently selected from 0 to 10; 5
Ra is selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rb, and Rc are independently absent or selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, 10 C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rd is selected from H, OH, NH2, or NHNH2;
and
the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal. 15
[0009]
In another aspect of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, the process comprising: a. treating a first precursor solution and a second precursor solution to obtain the perovskite nanocrystal of formula ABX3; and b. treating the perovskite nanocrystal of formula ABX3 with the conjugated aromatic ligand of Formula L1 to 20 obtain the surface passivated quantum dot.
[00010]
In yet another aspect of the present disclosure, there is provided the use of the surface passivated quantum dot as disclosed herein in an optoelectronic device configured to operate under humid conditions
[00011]
These and other features, aspects, and advantages of the present subject 25 matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 30
4
BRIEF DESCRIPTION OF THE DRAWINGS
[00012]
Figure 1 depicts transmission electron microscopy images at varying resolution (a) comparative surface-passivated quantum dot CQD1 (pristine) and (b) surface-passivated quantum dot QD1 (LE), in accordance with an embodiment of the present disclosure. 5
[00013]
Figure 2 depicts X-ray diffraction pattern of surface-passivated quantum dot QD1 (LE), comparative surface-passivated quantum dot CQD1 (pristine), orthorhombic phase, and cubic phase in accordance with an embodiment of the present disclosure.
[00014]
Figure 3 depicts (a) photoluminescence (PL) spectra, and (b) normalized 10 photoluminescence (PL) spectra of the surface-passivated quantum dot QD1 (LE) (DH 1:29), and comparative surface-passivated quantum dots CQD1 (pristine), CQD2 (BH 1:29), CQD3 (TAD 1:29), CQD4 (TDH 1:29), CQD6 (BH 1:290), CQD7 (TAD 1:290), and CQD8 (TDH 1:290), in accordance with an embodiment of the present disclosure. 15
[00015]
Figure 4 depicts (a) absorbance spectra of surface-passivated quantum dot QD1 (LE) (DH 1:29), comparative surface-passivated quantum dot CQD1 (pristine), (b) photoluminescence spectra of surface-passivated quantum dot QD1 (LE) (DH 1:29), comparative surface-passivated quantum dot CQD1 (pristine), (c) absorbance spectra of surface-passivated quantum dot QD1 (LE) (DH (1:29)), and comparative 20 surface-passivated quantum dots CQD1 (pristine), CQD9 (DH 1:1), and CQD10 (DH 1:7), and (d) photoluminescence spectra of surface-passivated quantum dot QD1 (LE) (DH 1:29), and comparative surface-passivated quantum dots CQD1 (pristine), CQD9 (DH 1:1), and CQD10 (DH 1:7), in accordance with an embodiment of the present disclosure. 25
[00016]
Figure 5 depicts X-ray photoelectron spectra of surface-passivated quantum dot QD1 (LE) (DH 1:29), and comparative surface-passivated quantum dot CQD1 (pristine) for (a) N, (b) Br, (c) Pb, (d) Cs, (e) O, and (f) C, in accordance with an embodiment of the present disclosure.
[00017]
Figure 6 depicts photoluminescence (PL) spectra of surface-passivated 30 quantum dot’s QD1 (LE), and comparative surface-passivated quantum dot’s CQD1 5
(pristine) film (a) initially (before (t=0) in water), (b) after 1 hour immersion in water, (c) % retained photoluminescence (PL) intensity of surface-passivated quantum dot QD1 (LE), and comparative surface-passivated quantum dot CQD1 (pristine) film, and (d) comparative surface-passivated quantum dot’s CQD1 (pristine (P)) and surface-passivated quantum dot’s QD1 (LE), under ultra violet (UV) light, after 1 5 hour immersion in water, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[00018]
Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be 10 understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps, features, compositions, and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such steps or features.
Definitions 15
[00019]
For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are delineated here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and 20 completeness, particular terms and their meanings are set forth below.
[00020]
The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.
[00021]
The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be 25 construed as “consists of only”. Throughout this specification, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps. 30 6
[00022]
The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.
[00023]
In the structural formulae given herein and throughout the present disclosure, the following terms have been indicated meaning, unless specifically stated otherwise. 5
[00024]
The term “quantum dot” refers to a semiconductor nanocrystal that exhibits quantum confinement effects and size-dependent optical properties.
[00025]
The term “perovskite nanocrystal” or “pristine quantum dot” refers to a nanoscale crystalline material with the general formula ABX3, where A is a cation, B is a metal ion and X is a halide anion, exhibiting quantum confinement effects and 10 tunable optical properties. For the purpose of present disclosure, A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation, B is selected from Pb, or Sn, and X is selected from Br, Cl, or I.
[00026]
The term “surface passivation” refers to the process of coordinating conjugated aromatic ligand of Formula L1 to the surface atoms of perovskite 15 nanocrystal of formula ABX3, in order to reduce surface defects, trap states, and dangling bonds, thereby improving their optical properties and stability. For the purposes of the present disclosure, the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal.
[00027]
The term “ligand exchange” refers to a post-synthesis process in which 20 surface-bound ligands L2 on perovskite nanocrystal of formula ABX3 are replaced or supplemented with conjugated aromatic ligand of Formula L1 to modify the surface chemistry and properties of the nanocrystals. This ligand exchange (exchange of surface-bound ligands L2 from conjugated aromatic ligand of Formula L1) tunes the emission of perovskite nanocrystals of formula ABX₃ effectively from green to blue, 25 and facilitates the formation of blue-emissive, surface-passivated quantum dots.
[00028]
The term “conjugated aromatic ligand” refers to an organic molecule containing aromatic ring systems with delocalized π-electrons that can coordinate to nanocrystal surfaces and provide electronic coupling between the ligand and nanocrystal. For the purpose of the present disclosure, the conjugated aromatic ligand 30 of Formula L1 is selected from 3,4,5-tris(C6-12aryloxy)benzohydrazide, 3,4,5-tris(C6-
7
12aryloxy)benzoic acid, 3,4,5-tris(C1-6alkyloxy)benzohydrazide, 3,4,5-tris(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)benzohydrazide, 3,5-bis(C6-12aryloxy)benzoic acid, 3,5-bis(C1-6alkyloxy)benzohydrazide, 3,5-bis(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C6-5 12aryloxy)cyclopenta-1,3-dienecarboxylic acid, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, 3-(C6-12aryloxy)benzohydrazide, 3-(C6-12aryloxy)benzoic acid, 3-(C1-6alkyloxy)benzohydrazide, 3-(C1-6alkyloxy)benzoic acid, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C1-6alkyloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarboxylic acid, or 5-(C1-10 6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, preferably 3,4,5-tris(benzyloxy)benzohydrazide, 3,4,5-tris(benzyloxy)benzoic acid, 3,4-bis(benzyloxy)-5-hydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzoic acid, or 3,4-bis(benzyloxy)-5-hydroxybenzoic acid. 15
[00029]
The term “first precursor compound” refers to a compound that serves as a source of A during the synthesis of perovskite nanocrystal with the formula ABX3., wherein A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation. For the purpose of the present disclosure, the first precursor compound is selected from Cs carbonate, Cs chloride, Cs bromide, Cs 20 iodide, methylammonium carbonate, methylammonium chloride, methylammonium bromide, methylammonium iodide, formamidinium carbonate, formamidinium chloride, formamidinium bromide, formamidinium iodide, phenethylammonium carbonate, phenethylammonium chloride, phenethylammonium bromide, or phenethylammonium iodide. 25
[00030]
The term “second precursor compound” refers to a compound that serve as source of B during the synthesis of perovskite nanocrystal with the formula ABX3, wherein B is selected from Pb, or Sn. For the purpose of the presnt disclosure, the second precursor compound is selected from Pb chloride, Pb bromide, Pb iodide, Sn chloride, Sn bromide, or Sn iodide. 30 8
[00031]
The terms “first solvent” refers to a solvent used in the prepration of a solution of the first precursor compound. For the purpose of the presnt disclosure, the first solvent is selected from octadecene, mesitylene, squalane, tetradecane, hexadecane, perfluorodecalin, or combinations thereof.
[00032]
The term “second solvent” refers to a solvent used in the prepration of a 5 solution of second precursor compound. For the purpose of the presnt disclosure, the second solvent is selected from octadecene, mesitylene, squalane, tetradecane, hexadecane, perfluorodecalin, or combinations thereof.
[00033]
The term “ligand density” refers to the number of ligand molecules coordinated per unit surface area of a nanocrystal, typically expressed as ligands per 10 square nanometer. For the purpose of the present disclosure the surface passivated quantum dot has a ligand density in a range of 1 to 300 ligands/nm2.
[00034]
The term “photoluminescence emission” refers to the release of photons (light) from a quantum dot that has been excited by absorbing light. The emitted light typically has a longer wavelength (lower energy) than the absorbed light due to 15 energy losses during relaxation. For the purpose of the present disclosure the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm after the ligand exchange.
[00035]
The term “colloidal stability” refers to the ability of surface-passivating molecules dispersed in a liquid medium to remain uniformly distributed without 20 aggregation or precipitation.
[00036]
The term “C6-12 aryl” refers to aromatic radicals having 6 to 12 carbon atoms, which may be optionally substituted by one or more substituents. The aryl may be monocyclic, bicyclic or polycyclic and may be fused, bridged or spiral rings. For the purpose of the present disclosure, the C6-12 aryl group includes, but is not 25 limited to phenyl, naphthyl and the like.
[00037]
The term “C3-12 cycloalkyl” refers to a saturated, non-aromatic cyclic hydrocarbon group, having 3 to 12 carbon atoms, which may be optionally substituted by one or more substituents. The cycloalkyl group may be monocyclic or polycyclic depending on the number of carbon atoms and ring complexity. For the 30 9
purpose of the present disclosure, the C3-12 cycloalkyl group includes, but is not limited to cyclopropyl, cyclobutyl, cyclopentyl, and the like.
[00038]
The term “C1-6 alkyl” refers to a saturated hydrocarbon chain containing 1 to 6 carbon atoms. Alkyl groups may be straight-chain or branched and may be optionally substituted. Representative branched alkyl groups can have one, two, or 5 three branches. For the purposes of the present disclosure, the C1-6 alkyl group includes, but is not limited to methyl, ethyl, n-propyl, isopropyl, and similar groups.
[00039]
The term “C1–12 heteroaryl” refers to a heteroaromatic ring system containing 1 to 12 carbon atoms, in which one or more of the ring atoms are heteroatoms such as nitrogen (N), oxygen (O), or sulfur(S). These heteroaryl groups 10 may be monocyclic or fused polycyclic and may be optionally substituted. These may include five-membered and six-membered rings. For the purpose of the present disclosure, the C1–12 heteroaryl group includes but is not limited to pyridyl, furyl, thienyl, imidazolyl, oxazolyl, and quinolyl groups.
[00040]
The term “C1–12 heterocyclyl” refers to a non-aromatic cyclic group 15 containing 1 to 12 carbon atoms, in which one or more of the ring atoms are heteroatoms such as nitrogen (N), oxygen (O), or sulfur (S). These heterocyclic groups may be monocyclic or polycyclic and can include saturated or partially unsaturated rings. They may also be optionally substituted with various functional groups. For the purposes of the present disclosure, the C1–12 heterocyclyl group 20 includes, but is not limited to, morpholinyl, piperidinyl, tetrahydrofuranyl, thiomorpholinyl, and azetidinyl.
[00041]
The term “C1–20 heterocyclylalkyl” refers to an alkyl group attached to a heterocyclic ring, the alkyl group is attached to the carbon atom of the ring or to the heteroatom, preferably to the carbon atom of the ring. The heterocyclic portion may 25 be saturated or partially unsaturated, monocyclic or polycyclic, and includes one or more heteroatoms such as nitrogen (N), oxygen (O), or sulfur (S) within the ring structure. The alkyl chain may be straight or branched and may optionally carry substituents. For the purpose of the present disclosure, C1–20 heterocyclylalkyl group includes but is not limited to morpholinylmethyl, piperidinylethyl, 30 10
tetrahydrofuranylmethyl, and similar structures where a heterocyclic ring is bonded to an alkyl chain.
[00042]
The term “C1–20 heteroarylalkyl” refers to an alkyl group attached to a heteroaromatic ring, the alkyl group is attached to the carbon atom of the ring or to the heteroatom, preferably to the carbon atom of the ring. The heteroaromatic portion 5 may be monocyclic or polycyclic, and includes one or more heteroatoms such as nitrogen (N), oxygen (O), or sulfur (S) within the ring structure. The alkyl chain may be straight or branched and may optionally carry substituents. For the purpose of the present disclosure, C1–20 heteroarylalkyl group includes but is not limited to 2-pyridylmethyl, 2-furylmethyl, 3-thienylpropyl and similar structures where a 10 heteroaromatic ring is bonded to an alkyl chain.
[00043]
The term “C1-6 alkyl amine” refers to an alkyl group containing 1 to 6 carbons, attached to an amine and the amine could be -NH2, primary amine, secondary amine or tertiary amine. The alkyl amine may be optionally further substituted. For the purpose of the present disclosure, C1-6 alkyl amine includes but 15 are not limited to methyl amine, ethyl amine, propyl amine, and the like.
[00044]
The term “C2-6 alkenyl” refers to an aliphatic hydrocarbon group containing a carbon-carbon double bond and which may be straight or branched chain having about 2 to 6 carbon atoms, which may be optionally substituted by one or more substituents. For the purpose of the present disclosure, C2-6 alkenyl includes but is 20 not limited to, ethenyl, 1-propenyl, 2-propenyl, iso-propenyl, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl and the like.
[00045]
The term “C1–6 alkyl–COOH” refers to a carboxylic acid group (–COOH) attached to a saturated alkyl chain containing 1 to 6 carbon atoms. The alkyl group may be straight or branched and can be optionally substituted. For the purposes of 25 the present disclosure, C1–6 alkyl–COOH includes, but is not limited to, formic acid, acetic acid, propionic acid, butyric acid, and the like.
[00046]
The term “C6–12 aryloxy” refers to an aryl group containing 6 to 12 carbon atoms that is bonded to an oxygen atom, forming an ether linkage (–O–Ar). The aryl portion is derived from aromatic hydrocarbons such as phenyl or substituted phenyl 30 rings and may include fused aromatic systems. These groups may be optionally 11
substituted with alkyl, halogen, nitro, or other functional groups. For the purposes of the present disclosure, C6–12 aryloxy includes, but is not limited to, phenoxy, tolyloxy, naphthyloxy, and other substituted aryloxy groups.
[00047]
The term “C1–12 alkyloxy” refers to an alkyl group containing 1 to 12 carbon atoms that is bonded to an oxygen atom, forming an ether linkage (–O–alkyl). The 5 alkyl portion may be straight or branched and may be optionally substituted. These groups are commonly found in organic compounds and are used to modify solubility, reactivity, and lipophilicity. For the purposes of the present disclosure, C1–12 alkyloxy includes, but is not limited to, methoxy, ethoxy, propoxy, butoxy and the like.
[00048]
The term “quantum confinement” refers to the restriction of electron and 10 hole motion in surface passivated quantum dot when their dimensions approach the exciton Bohr radius, resulting in size-dependent optical and electronic properties.
[00049]
The term “excitonic peak” refers to a distinct feature observed in UV-visible absorbance or emission spectra, arising from the bound state of an electron and a hole held by coulombic interactions (exciton formation). This exciton propagates through 15 the material and eventually recombines, resulting in the emission of light.
[00050]
The term “trap states” refers to the energy levels within the bandgap of a semiconductor that can capture charge carriers, leading to non-radiative recombination and reduced luminescence efficiency.
[00051]
The term “non-radiative recombination” refers to the process by which 20 excited charge carriers return to the ground state without emitting photons, typically through trap states or defects.
[00052]
The term “blue shift” refers to the movement of optical absorption or emission spectra toward shorter wavelengths (higher energies), typically occurring when the bandgap of a nanocrystal increases. For the purpose of the present 25 disclosure, the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm after the ligand exchange, exhibiting a blue shift relative to a perovskite nanocrystal of the formula ABX₃.
[00053]
The term “hot-injection technique” or “hot injection synthesis” refers to a solution-based synthesis method where precursor solutions are rapidly mixed 30 through the rapid injection of cold precursor solutions into hot reaction mixtures to
12
initiate nucleation and growth of nanocrystals. For the purpose of the present disclosure, the pristine perovskite nanocrystal ABX₃ is prepared using a modified hot-injection technique.
[00054]
The term “higher concentration” refers to the dissolution of >1 mmol to 10 mmol of conjugated aromatic ligand of Formula L1 and structurally similar ligand in 5 1mL of chloroform during the preparation process of surface passivated quantum dots. Under standard conditions, 0.1 mmol to 1 mmol of conjugated aromatic ligand of Formula L1 and structurally similar ligand are typically dissolved in 1 mL of chloroform. However, the maximum stable concentration is defined as the dissolution of 1 mmol of conjugated aromatic ligand of Formula L1 and structurally 10 similar ligand in 1mL chloroform, beyond which aggregation begins to occur.
[00055]
The term “dispersion” refers to the distribution of the surface passivated quantum dots (ligand exchanged) throughout a solvent after its preparation. The medium polarity solvent, chloroform can dissolve both perovskite nanocrystal CsPbBr3 (pristine) and conjugated aromatic ligand of Formula L1. After the ligand 15 exchange, the surface passivated quantum dots can also remain dispersed in chloroform, ensuring long-term stability. These quantum dots are soluble in non-polar solvents due to the presence of non-polar long chains of ligand on the surface. The conjugated aromatic ligand of Formula L1, which contains polar groups inside chain such as -NH groups, -COOH groups, requires low polarity solvents. Therefore, 20 pristine quantum dots prefer primary solvents such as chlorobenzene, toluene, hexane, and secondary solvents like chloroform, but are incompatible with highly polar solvents such as dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF). On the other hand, conjugated aromatic ligand of Formula L1 prefers primary solvents like dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) and 25 secondary solvents such as chlorobenzene, and chloroform. Hence, medium polarity solvent, chloroform is selected for the ligand exchange process as it can dissolve both perovskite nanocrystal CsPbBr3 (pristine) and conjugated aromatic ligand of Formula L1 and also maintain the dispersion of the surface passivated quantum dots (ligand exchanged) for long-term stability. 30 13
[00056]
The term “optoelectronic device” refers to an electronic device that sources, detects, or controls light, including light-emitting diodes, photodetectors, and solar cells. For the purpose of the present disclosure, the use of the surface passivated quantum dot as disclosed, in an optoelectronic device configured to operate under humid conditions. 5
[00057]
The term “electronic coupling” refers to the interaction between electronic states of the perovskite nanocrystal of formula ABX3 and the conjugated aromatic ligand of Formula L1 that allows for charge or energy transfer.
[00058]
The term “full width at half maximum (FWHM)” refers to a measure of the spectral width of an emission or absorption peak, defined as the width of the peak at 10 half of its maximum intensity, indicating color purity.
[00059]
The term “bandgap” refers to the energy difference between the valence band and conduction band in a semiconductor, or quantum dot determining the optical and electronic properties.
[00060]
The term “π-π stacking” refers to non-covalent interactions between 15 aromatic rings that can influence molecular packing and electronic properties. For the purpose of the present disclosure, the conjugated aromatic cores of the ligand L1 provides π-π stacking within the nanocrystal structure.
[00061]
The term “ITU Rec. 2020” refers to an international standard that defines color requirements for ultra-high-definition television displays, specifying precise 20 wavelength ranges for red, green, and blue emissions.
[00062]
Unless otherwise substituted, the valency of a carbon atom in the compounds of the present disclosure is understood to satisfy by the presence of hydrogen atoms.
[00063]
The compounds described herein can also be prepared in any solid or liquid 25 physical form, for example the compound can be in a crystalline form, in amorphous form and have any particle size. Furthermore, the compound particles may be micronsized or nanosized, or may be agglomerated, particulate granules, powders, oils, oily suspensions, or any other form of solid or liquid physical forms.
[00064]
Ratios, concentrations, amounts, and other numerical data may be presented 30 herein in a range format. It is to be understood that such range format is used merely 14
for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
[00065]
Unless defined otherwise, all technical and scientific terms used herein have 5 the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described.
[00066]
As discussed in the background, perovskite nanocrystals face significant 10 challenges in optoelectronic applications, particularly in achieving stable blue emission. This difficulty arises due to increased trap states associated with larger bandgaps, poor solubility and the tendency to introduce deep-level defects, which limit their practical use. Environmental instability further complicates their application, as these nanocrystals degrade rapidly when exposed to moisture, oxygen, 15 heat, light, and electric field. Conventional long chain alkyl ligands such as oleic acid and oleylamine, provide colloidal stability, but are electrically insulating, weakly bound, and prone to disruption, leading to surface trap formation and inefficient charge transport. Despite ongoing efforts, developing a highly efficient and environmentally stable blue-emitting quantum dot remains a significant challenge. 20 There is still a need for a surface-passivated quantum dot capable of emitting stable blue light while exhibiting robust environmental stability.
[00067]
To address these challenges, the present disclosure introduces a ligand exchange strategy using conjugated aromatic ligands, specifically designed to tackle targeting multiple issues simultaneously. The present invention discloses a surface-25 passivated quantum dot comprising a perovskite nanocrystal of the formula ABX₃ and a conjugated aromatic ligand of Formula L1. The perovskite nanocrystal and the conjugated aromatic ligand (L1) are used in a mole ratio range of 1:28 to 1:60. The use of a conjugated aromatic ligand, with a perovskite core successfully tunes perovskite nanocrystal emission from green (523 nm) to blue (472 nm), achieving a 30 51 nm blue shift. This is accomplished while maintaining a narrow emission 15
linewidth, ensuring high color purity. These conjugated aromatic ligands offer superior surface passivation through multiple coordination sites, such as hydrazide (-NHNH2) and carboxylic acid (-COOH) functional groups. They exhibit significantly stronger binding affinity than conventional ligands, as demonstrated by a significant increase in surface ligand density. This enhanced passivation effectively suppresses 5 the nonradiative recombination pathways. Additionally, the hydrophobic benzyloxy substituents form protective barriers that improve environmental stability. The surface-passivated quantum dots retain 43% of their photoluminescence intensity after 1 hour of water immersion, whereas pristine dots with conventional ligands show complete quenching under identical conditions. The aromatic rings facilitate 10 electronic coupling and π–π stacking interactions, reducing the insulating nature of long alkyl chains and enhancing intermolecular charge transfer. Conjugated aromatic ligands of Formula L1 allow systematic property tuning via variable substituent patterns, offer additional structural diversity and coordination modes. The methodology involves hot-injection synthesis of perovskite ABX₃ nanocrystals 15 followed by treatment with the conjugated aromatic ligand (Formula L1) to obtain the surface passivated quantum dots via ligand exchange under controlled conditions. Efficient ligand coordination is evidenced by rapid color change within 5 minutes. The conjugated aromatic ligands serve multiple roles: emission tuning via electronic environment modification, stability enhancement through hydrophobic shielding, 20 improved charge transport via aromatic conjugation. The resulting surface passivated quantum dots have particle size in a range of 5 to 15 nm, exhibit a ligand density of 1 to 300 ligands/nm², maintain their morphology with controlled size reduction, and demonstrate enhanced moisture resistance. Notably, the present invention avoids compositional engineering, eliminating the need for complex synthesis 25 modifications. It enables post-synthesis tunability while preserving the cubic perovskite phase and crystal structure.
[00068]
Accordingly, the present disclosure entails the development of a surface passivated quantum dot comprising: a. a perovskite nanocrystal of formula ABX3; and b. a conjugated aromatic ligand of Formula L1, 30 16
5
Formula L1
wherein A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation, B is selected from Pb, or Sn, X is selected from Br, Cl, or I; 10
W1, W2, W3, W4, and W5 are independently selected from C, CH, N, NH, O, or S;
p is 0 or 1;
Z3 is independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 arylCH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-15 12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl;
Z1 and Z2 are independently absent or selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl; 20
m is independently selected from 0 to 10;
Ra is selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rb, and Rc are independently absent or selected from hydrogen, C3-12 cycloalkyl, C1-25 6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rd is selected from H, OH, NH2, or NHNH2,
and 17
the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal. The present disclosure further provides a ligand exchange process of preparing the disclosed surface passivated quantum dot.
[00069] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of 5 exemplification only. Functionally equivalent products, compositions, and methods are clearly within the scope of the disclosure, as described herein.
[00070] In an embodiment of the present disclosure, there is provided a surface passivated quantum dot comprising: a. a perovskite nanocrystal of formula ABX3; and b. a conjugated aromatic ligand of Formula L1, 10
15
Formula L1
wherein A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation, B is selected from Pb, or Sn, X is selected from Br, Cl, or I; 20
W1, W2, W3, W4, and W5 are independently selected from C, CH, N, NH, O, or S;
p is 0 or 1;
Z3 is independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-25 12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl;
Z1 and Z2 are independently absent or selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl; 30
m is independently selected from 0 to 10; 18
Ra is selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rb, and Rc are independently absent or selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, 5 C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rd is selected from H, OH, NH2, or NHNH2;
and the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal.
[00071]
In another embodiment of the present disclosure, A is selected from Cs, 10 methylammonium cation, or formamidinium cation, B is selected from Pb, or Sn, X is selected from Br, or Cl;
W1, W2, W3, W4, and W5 are independently selected from C, CH, N, NH, or O;
p is 0 or 1;
Z3 is independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-15 12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, or C6-12 aryl;
Z1 and Z2 are independently absent or selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-20 12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, or C1-12 heteroaryl;
m is independently selected from 0 to 8;
Ra is selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, or C1-20 heteroarylalkyl; 25
Rb, and Rc are independently absent or selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, or C1-12 heterocyclyl;
Rd is selected from H, OH, or NHNH2;
and 30 19
the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal.
[00072]
In yet another embodiment of the present disclosure, A is selected from Cs, or methylammonium cation, B is selected from Pb, or Sn, X is selected from Br, Cl, or I; 5
W1, W2, W3, W4, and W5 are independently selected from C, CH, or N;
p is 0 or 1;
Z3 is independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, or O(C6-12 aryl);
Z1 and Z2 are independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 10 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl);
m is independently selected from 0 to 5;
Ra is selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, or C1-12 heteroaryl; 15
Rb, and Rc are independently absent or selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, or C1-20 heteroarylalkyl;
Rd is selected from OH, or NHNH2; and the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal. 20
[00073]
In one another embodiment of the present disclosure, A is selected as Cs, B is selected as Pb, X is selected as Br;
W1, W2, W3, W4, and W5 are independently selected from C, or CH;
p is 1;
Z3 is independently selected as O; 25
Z1 and Z2 are independently absent or selected as O;
m is independently selected from 0, or 1;
Ra is selected from hydrogen, or C6-12 aryl;
Rb, and Rc are independently absent or selected from hydrogen, or C6-12 aryl;
Rd is selected from OH, or NHNH2, 30 20
and the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal.
[00074]
In an embodiment of the present disclosure, there is provided a surface passivated quantum dot as disclosed herein, wherein the surface passivated quantum dot comprises a ligand (L2) selected from oleic acid, oleylamine, lauric acid, stearic 5 acid, phenethylamine, octanoic acid, octylamine, L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl phosphine oxide, or combinations thereof. In another embodiment of the present disclosure, the surface passivated quantum dot comprises a ligand (L2) selected from oleic acid, oleylamine, lauric acid, stearic acid, 10 phenethylamine, octanoic acid, octylamine, L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, or combinations thereof. In yet another embodiment of the present disclosure, the surface passivated quantum dot comprises a ligand (L2) selected from oleic acid, oleylamine, or combinations thereof. 15
[00075]
In an embodiment of the present disclosure, there is provided a surface passivated quantum dot as disclosed herein, wherein the surface passivated quantum dot has a particle size in a range of 5 to 15 nm. In another embodiment of the present disclosure, the surface passivated quantum dot has a particle size in a range of 6 to 13 nm. In yet another embodiment of the present disclosure, the surface passivated 20 quantum dot has a particle size in a range of 7 to 12 nm.
[00076]
In an embodiment of the present disclosure, there is provided a surface passivated quantum dot as disclosed herein, wherein the perovskite nanocrystal and the conjugated aromatic ligand (L1) are in a mole ratio range of 1:28 to 1:60. In another embodiment of the present disclosure, the perovskite nanocrystal and the 25 conjugated aromatic ligand (L1) are in a mole ratio range of 1:28 to 1:55. In yet another embodiment of the present disclosure, the perovskite nanocrystal and the conjugated aromatic ligand (L1) are in a mole ratio range of 1:28 to 1:45.
[00077]
In an embodiment of the present disclosure, there is provided a surface passivated quantum dot as disclosed herein, wherein the surface passivated quantum 30 dot has a ligand density in a range of 1 to 300 ligands/nm2. In another embodiment
21
of the present disclosure, the surface passivated quantum dot has a ligand density in a range of 20 to 280 ligands/nm2. In yet another embodiment of the present disclosure, the surface passivated quantum dot has a ligand density in a range of 50 to 250 ligands/nm2.
[00078]
In an embodiment of the present disclosure, there is provided a surface 5 passivated quantum dot as disclosed herein, wherein the surface passivated quantum dot comprises a C/Pb atomic ratio in a range of 14 to 1550, a N/Pb atomic ratio in a range of 0.1 to 30, and a O/Pb atomic ratio in a range of 1 to 500. In another embodiment of the present disclosure, the surface passivated quantum dot comprises a C/Pb atomic ratio in a range of 20 to 1548, a N/Pb atomic ratio in a range of 0.5 to 10 29, and a O/Pb atomic ratio in a range of 20 to 490. In yet another embodiment of the present disclosure, the surface passivated quantum dot comprises a C/Pb atomic ratio in a range of 25 to 1547, a N/Pb atomic ratio in a range of 0.8 to 28, and a O/Pb atomic ratio in a range of 30 to 470. In still another embodiment of the present disclosure, the surface passivated quantum dot comprises a C/Pb atomic ratio in a 15 range of 1500 to 1546, a N/Pb atomic ratio in a range of 20 to 28, and a O/Pb atomic ratio in a range of 400 to 460.
[00079]
In an embodiment of the present disclosure, there is provided a surface passivated quantum dot as disclosed herein, wherein the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm. In 20 another embodiment of the present disclosure, the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 452 to 488 nm. In yet another embodiment of the present disclosure, the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 455 to 480 nm. In still another embodiment of the present disclosure, the surface passivated quantum dot 25 exhibits a photoluminescence emission wavelength in the blue region of the visible spectrum after ligand exchange. In one another embodiment of the present disclosure, the surface passivated quantum dot is prepared by exchange of ligands L2 from conjugated aromatic ligand of Formula L1. In another embodiment of the present disclosure, the surface passivated quantum dot is prepared by partial ligand exchange. 30 22
In still another embodiment of the present disclosure, the surface passivated quantum dot is prepared by complete ligand exchange.
[00080]
In an embodiment of the present disclosure, there is provided a surface passivated quantum dot as disclosed herein, wherein the conjugated aromatic ligand of Formula L1 is selected from 3,4,5-tris(C6-12aryloxy)benzohydrazide, 3,4,5-tris(C6-5 12aryloxy)benzoic acid, 3,4,5-tris(C1-6alkyloxy)benzohydrazide, 3,4,5-tris(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)benzohydrazide, 3,5-bis(C6-12aryloxy)benzoic acid, 3,5-bis(C1-6alkyloxy)benzohydrazide, 3,5-bis(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C6-10 12aryloxy)cyclopenta-1,3-dienecarboxylic acid, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, 3-(C6-12aryloxy)benzohydrazide, 3-(C6-12aryloxy)benzoic acid, 3-(C1-6alkyloxy)benzohydrazide, 3-(C1-6alkyloxy)benzoic acid, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C1-6alkyloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarboxylic acid, or 5-(C1-15 6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, preferably 3,4,5-tris(benzyloxy)benzohydrazide, 3,4,5-tris(benzyloxy)benzoic acid, 3,4-bis(benzyloxy)-5-hydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzoic acid, or 3,4-bis(benzyloxy)-5-hydroxybenzoic acid. In another embodiment of the present 20 disclosure, the conjugated aromatic ligand of Formula L1 is selected from 3,4,5-tris(C6-12aryloxy)benzohydrazide, 3,4,5-tris(C6-12aryloxy)benzoic acid, 3,4,5-tris(C1-6alkyloxy)benzohydrazide, 3,4,5-tris(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)benzohydrazide, 3,5-bis(C6-12aryloxy)benzoic acid, 3,5-bis(C1-6alkyloxy)benzohydrazide, 3,5-bis(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-25 12aryloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C6-12aryloxy)cyclopenta-1,3-dienecarboxylic acid, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, 3-(C6-12aryloxy)benzohydrazide, 3-(C6-12aryloxy)benzoic acid, 3-(C1-6alkyloxy)benzohydrazide, 3-(C1-6alkyloxy)benzoic acid, 5-(C6-30 12aryloxy)cyclopenta-1,3-dienecarbohydrazide, or 5-(C1-6alkyloxy)cyclopenta-1,3-
23
dienecarbohydrazide, preferably 3,4,5-tris(benzyloxy)benzohydrazide, 3,4,5-tris(benzyloxy)benzoic acid, 3,4-bis(benzyloxy)-5-hydroxybenzohydrazide, or 3-(benzyloxy)-4,5-dihydroxybenzohydrazide. In yet another embodiment of the present disclosure, the conjugated aromatic ligand of Formula L1 is selected from 3,4,5-tris(C6-12aryloxy)benzohydrazide, 3,4,5-tris(C6-12aryloxy)benzoic acid, 3,4,5-5 tris(C1-6alkyloxy)benzohydrazide, 3,4,5-tris(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)benzohydrazide, 3,5-bis(C6-12aryloxy)benzoic acid, 3,5-bis(C1-6alkyloxy)benzohydrazide, 3,5-bis(C1-6alkyloxy)benzoic acid, 3-(C6-12aryloxy)benzohydrazide, or 3-(C6-12aryloxy)benzoic acid, preferably 3,4,5-tris(benzyloxy)benzohydrazide, 3,4,5-tris(benzyloxy)benzoic acid, or 3,4-10 bis(benzyloxy)-5-hydroxybenzohydrazide. In still another embodiment of the present disclosure, the conjugated aromatic ligand of Formula L1 is selected from 3,4,5-tris(benzyloxy)benzohydrazide, 3,4,5-tris(benzyloxy)benzoic acid, 3,4-bis(benzyloxy)-5-hydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzoic acid, or 3,4-15 bis(benzyloxy)-5-hydroxybenzoic acid.
[00081]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, the process comprising: a. treating a first precursor solution and a second precursor solution to obtain the perovskite nanocrystal of formula ABX3; and b. treating the perovskite 20 nanocrystal of formula ABX3 with the conjugated aromatic ligand of Formula L1 to obtain the surface passivated quantum dot.
[00082]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, wherein the first precursor solution is obtained by mixing a first precursor compound, a first solvent 25 and a first ligand (L2a); and the second precursor solution is obtained by mixing a second precursor compound, a second solvent and a second ligand (L2b).
[00083]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, wherein the first precursor compound is selected from cesium carbonate, cesium chloride, cesium 30 bromide, cesium iodide, methylammonium carbonate, methylammonium chloride, 24
methylammonium bromide, methylammonium iodide, formamidinium carbonate, formamidinium chloride, formamidinium bromide, formamidinium iodide, phenethylammonium carbonate, phenethylammonium chloride, phenethylammonium bromide, or phenethylammonium iodide; and the second precursor compound is selected from lead chloride, lead bromide, lead iodide, tin 5 chloride, tin bromide, or tin iodide. In another embodiment of the present disclosure, the first precursor compound is selected from cesium carbonate, cesium chloride, cesium bromide, cesium iodide, methylammonium carbonate, methylammonium chloride, methylammonium bromide, methylammonium iodide, formamidinium carbonate, formamidinium chloride, formamidinium bromide, or formamidinium 10 iodide; and the second precursor compound is selected from lead chloride, lead bromide, lead iodide, tin chloride, or tin bromide. In yet another embodiment of the present disclosure, the first precursor compound is selected from cesium carbonate, cesium chloride, cesium bromide, or cesium iodide and the second precursor compound is selected from lead chloride, lead bromide, or lead iodide. 15
[00084]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, wherein the first solvent and the second solvent are independently selected from octadecene, mesitylene, squalane, tetradecane, hexadecane, perfluorodecalin, or combinations thereof. In another embodiment of the present disclosure, the first solvent and the 20 second solvent are independently selected from octadecene, mesitylene, squalane, tetradecane, or combinations thereof. In yet another embodiment of the present disclosure, the first solvent and the second solvent are independently selected from octadecene, mesitylene, squalane, or combinations thereof.
[00085]
In an embodiment of the present disclosure, there is provided a process of 25 preparing the surface passivated quantum dot as disclosed herein, wherein the first ligand (L2a) and the second ligand (L2b) are independently selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl phosphine oxide, 30 or combinations thereof. In another embodiment of the present disclosure, the first 25
ligand (L2a) and the second ligand (L2b) are independently selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, or combinations thereof. In yet another embodiment of the present disclosure, the first ligand (L2a) and the second ligand (L2b) are independently 5 selected from oleic acid, oleylamine, or combinations thereof.
[00086]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, wherein the first precursor solution is dried under nitrogen at a temperature in a range of 100 to 130℃, followed by heating to a temperature in a range of 140 to 160℃, prior to treating 10 with the second precursor solution. In another embodiment of the present disclosure, the first precursor solution is dried under nitrogen at a temperature in a range of 103 to 128℃, followed by heating to a temperature in a range of 143 to 158℃, prior to treating with the second precursor solution. In yet another embodiment of the present disclosure, the first precursor solution is dried under nitrogen at a temperature in a 15 range of 110 to 125℃, followed by heating to a temperature in a range of 145 to 155℃, prior to treating with the second precursor solution.
[00087]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, wherein the second precursor solution is heated to a temperature in a range of 180 to 220℃, prior to 20 treating with the first precursor solution. In another embodiment of the present disclosure, the second precursor solution is heated to a temperature in a range of 185 to 215℃, prior to treating with the first precursor solution. In yet another embodiment of the present disclosure, the second precursor solution is heated to a temperature in a range of 190 to 210℃, prior to treating with the first precursor 25 solution.
[00088]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, wherein the perovskite nanocrystal of formula ABX3 and the conjugated aromatic ligand of Formula L1 are taken in a mole ratio range of 1:28 to 1:60. In another embodiment 30 of the present disclosure, the perovskite nanocrystal of formula ABX3 and the
26
conjugated aromatic ligand of Formula L1 are taken in a mole ratio range of 1:28 to 1:55. In yet another embodiment of the present disclosure, the perovskite nanocrystal of formula ABX3 and the conjugated aromatic ligand of Formula L1 are taken in a mole ratio range of 1:28 to 1:45.
[00089]
In an embodiment of the present disclosure, there is provided a process of 5 preparing the surface passivated quantum dot as disclosed herein, wherein the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm. In another embodiment of the present disclosure, the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 458 to 488 nm. In yet embodiment of the present disclosure, the surface passivated 10 quantum dot exhibits photoluminescence emission wavelength in a range of 455 to 485 nm.
[00090]
In an embodiment of the present disclosure, there is provided a process of preparing the surface passivated quantum dot as disclosed herein, wherein the first precursor solution is obtained by mixing a first precursor compound, wherein the first 15 precursor compound is selected from cesium carbonate, cesium chloride, cesium bromide, cesium iodide, methylammonium carbonate, methylammonium chloride, methylammonium bromide, methylammonium iodide, formamidinium carbonate, formamidinium chloride, formamidinium bromide, formamidinium iodide, phenethylammonium carbonate, phenethylammonium chloride, 20 phenethylammonium bromide, or phenethylammonium iodide; a first solvent, wherein the first solvent is selected from octadecene, mesitylene, squalane, tetradecane, hexadecane, perfluorodecalin, or combinations thereof; and a first ligand (L2a), wherein the first ligand (L2a) is selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, L-cysteine, 25 octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl phosphine oxide, or combinations thereof; and the second precursor solution is obtained by mixing a second precursor compound, wherein the second precursor compound is selected from lead chloride, lead bromide, lead iodide, lead chloride, lead bromide, or lead 30 iodide; a second solvent, wherein the second solvent is selected from octadecene, 27
mesitylene, squalane, tetradecane, hexadecane, perfluorodecalin, or combinations thereof; and a second ligand (L2b), wherein the second ligand (L2b) is selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl 5 phosphine oxide, or combinations thereof. In another embodiment of the present disclosure, the first precursor solution is obtained by mixing a first precursor compound, wherein the first precursor compound is selected from cesium carbonate, cesium chloride, cesium bromide, or cesium iodide; a first solvent, wherein the first solvent is selected from octadecene, mesitylene, squalane, or combinations thereof; 10 and a first ligand (L2a), wherein the first ligand (L2a) is selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, or combinations thereof; and the second precursor solution is obtained by mixing a second precursor compound, wherein the second precursor compound is selected from lead chloride, lead bromide, or lead iodide; a second solvent, wherein the 15 second solvent is selected from octadecene, mesitylene, squalane, or combinations thereof; and a second ligand (L2b), wherein the second ligand (L2b) is selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, or combinations thereof.
[00091]
In an embodiment of the present disclosure, there is provided the use of the 20 surface passivated quantum dot as disclosed herein, in an optoelectronic device configured to operate under humid conditions.
[00092]
In an embodiment of the present disclosure, there is provided an optoelectronic device as disclosed herein, wherein the device is a light-emitting diode, display, or sensor. 25
[00093]
Although the subject matter has been described in considerable detail with reference to certain examples and implementations thereof, other implementations are possible.
EXAMPLES 30 28
[00094] The disclosure will now be illustrated with the following examples, which are intended to illustrate the working of disclosure and not intended to restrictively imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure 5 belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply. The present invention will be 10 described in a more detailed manner by way of examples. However, these examples should not be construed as limiting the scope of the present invention. Materials and methods
[00095]
For the purpose of the present disclosure, cesium carbonate (Cs2CO3, 99.9%) was purchased from BLD Pharmaceuticals. Lead bromide (PbBr2, 99.9%) 15 and octadecence (ODE) were purchased from Sigma. Oleic acid (OA), and oleylamine (OAm) were purchased from SRL. All these reagents were used without further purification.
[00096]
Transmission electron microscopy was performed on TEM; Jeol JEM-2100F, at an accelerating voltage of 200 kV. X-ray diffraction was obtained using 20 the Xpert PRO PAN analytical instrument with a Cu Kα source (λ 1.541 Å). UV-visible absorbance spectrum was measured using a Jasco V-730 spectrophotometer, and the photoluminescence spectrum were obtained using a Hitachi F-7100 fluorescence spectrophotometer. X-ray photoelectron spectroscopy (XPS) was performed on a Thermo Fisher Scientific spectrometer using a monochromatic Al Kα 25 (hυ = 1486.6 eV) as an X-ray source.
EXAMPLE 1
Preparation of surface passivated quantum dot
[00097]
The preparation of surface-passivated quantum dots comprises: (a) treating 30 a first precursor solution and a second precursor solution to obtain the perovskite
29
nanocrystal of formula ABX3; and (b) treating the perovskite nanocrystal of formula ABX3 with a conjugated aromatic ligand of Formula L1 to obtain surface-passivated quantum dots by ligand exchange.
Step a-Preparation of perovskite nanocrystal CsPbBr3 (pristine)
[00098]
The perovskite nanocrystal CsPbBr₃ was prepared using a modified hot-5 injection technique. The Cs-oleate solution (first precursor solution) was prepared by mixing Cs₂CO₃ (0.61 mmol, first precursor) with octadecene (ODE) (15 mL, first solvent) and oleic acid (OA) (1.5 mL, first ligand L2a) in a 100 mL two-neck round-bottom flask. The resulting solution was dried under nitrogen at 120°C for 90 minutes, followed by heating to 150°C to ensure complete dissolution of Cs₂CO₃, 10 thereby yielding the Cs-oleate solution (first precursor solution).
[00099]
The PbBr3 solution (second precursor solution) was prepared by mixing PbBr2 (0.38 mmol, second precursor) with octadecene (ODE) (20 mL, first solvent) and oleylamine (OAm) (4 mmol, second ligand L2b) and heating the mixture to 200°C for complete dissolution of PbBr₂, thereby yielding the PbBr3 solution (second 15 precursor solution).
[000100]
Subsequently, the hot Cs-oleate solution (1.0 mL, first precursor solution) was treated by injecting it into the PbBr₃ solution (second precursor solution). The reaction mixture was immediately quenched in an ice-water bath after 10 seconds. To purify the prepared perovskite nanocrystals CsPbBr₃, ethyl acetate was added to 20 the crude solution at a volume ratio of 2:1, followed by centrifugation at 9000 rpm for 10 minutes. The resulting precipitate was collected and redispersed in toluene, yielding perovskite nanocrystal CsPbBr₃ (pristine, perovskite nanocrystal of formula ABX3). The prepared CsPbBr₃ perovskite nanocrystals showed green emission.
Step b: Preparation of surface-passivated quantum dot QD1 (LE) 25
[000101]
To prepare surface-passivated quantum dots by ligand exchange, CsPbBr₃ (perovskite nanocrystal with the formula ABX₃), prepared in step (a), was treated with 3,4,5-tris(benzyloxy)benzohydrazide (conjugated aromatic ligand of Formula L1). CsPbBr₃ and 3,4,5-tris(benzyloxy)benzohydrazide were used in a molar ratio of 1:29. Upon addition of 3,4,5-tris(benzyloxy)benzohydrazide to 30 CsPbBr₃, followed by dispersion in 2 mL of chloroform, a change in emission from 30
green to blue was observed within 5 minutes, which indicated the ligand exchange. To ensure ligand exchange, the mixture was stirred for 2 hours. After the exchange, the solution was centrifuged at 9000 rpm for 10 minutes to remove unreacted 3,4,5-tris(benzyloxy)benzohydrazide. The supernatant containing the unreacted 3,4,5-tris(benzyloxy)benzohydrazide was discarded, and the precipitate was redispersed in 5 chlorobenzene. This dispersed solution was then centrifuged at 5000 rpm for 5 minutes to eliminate larger, undissolved particles. The precipitate was discarded, and the supernatant was collected to obtain surface-passivated quantum dot QD1 (LE), (Table 1).
[000102]
Similarly, surface-passivated quantum dot QD2, was prepared by treating 10 CsPbBr₃ (perovskite nanocrystal with the formula ABX₃), with 3,4,5-tris(benzyloxy)benzoic acid (conjugated aromatic ligand of Formula L1) as mentioned in Table 1.
[000103]
Similarly, for comparative purposes, comparative surface-passivated quantum dots CQD1 to CQD10 were prepared as mentioned in Table 1. 15
Table 1
S.No.
Surface-passivated quantum dots
Perovskite nanocrystal of formula ABX3
Conjugated aromatic ligand of Formula L1
Mole ratio
Perovskite nanocrystal of formula ABX3: Conjugated aromatic ligand of Formula L1
1
QD1(LE)
(DH 1:29)
CsPbBr3
3,4,5-Tris(benzyloxy)benzohydrazide
1:29
2
QD2 (LE)
(DH 1:29)
CsPbBr3
3,4,5-Tris(benzyloxy)benzoic acid
1:29
3
CQD1 (pristine)
CsPbBr3
-
1:0
4
CQD2
(BH 1:29)
CsPbBr3
Benzohydrazide
1:29
5
CQD3 (TAD 1:29)
CsPbBr3
Terephthalic aldehyde
1:29
6
CQD4 (TDH 1:29)
CsPbBr3
Terephthalic dihydrazide
1:29 31
7
CQD5 (DH 1:290)
CsPbBr3
3,4,5-Tris(benzyloxy)benzohydrazide
1:290
8
CQD6 (BH 1:290)
CsPbBr3
Benzohydrazide
1:290
9
CQD7 (TAD 1:290)
CsPbBr3
Terephthalic aldehyde
1:290
10
CQD8 (TDH 1:290)
CsPbBr3
Terephthalic dihydrazide
1:290
11
CQD9
(DH 1:1)
CsPbBr3
3,4,5-Tris(benzyloxy)benzohydrazide
1:1
12
CQD10 (DH 1:7)
CsPbBr3
3,4,5-Tris(benzyloxy)benzohydrazide
1:7
EXAMPLE 2
Morphological studies
Transmission electron microscopy (TEM) studies
[000104]
Transmission Electron Microscopy (TEM) was employed to examine the 5 morphology and particle size of quantum dots (prepared in Example 1). Both, surface-passivated quantum dot QD1(LE) and comparative surface-passivated quantum dot CQD1 (pristine) exhibited cubic morphologies, as shown in Figures 1(a) and 1(b), at varying resolutions (i) 100 nm, (ii) 50 nm, (iii) 20 nm, and (iv) 10 nm, respectively. Ligand exchange and passivation resulted in a significant reduction in 10 particle size from approximately 20 nm in CQD1 (pristine) to around 8 nm in QD1 (LE). This downsizing influenced quantum confinement effects, potentially enhanced the optical properties and enabled improved charge transport characteristics, and factors that were advantageous for optoelectronic device performance. 15
X-ray diffraction studies
[000105]
As shown in Figure 2, the X-ray diffraction (XRD) pattern of both surface-passivated quantum dot QD1 (LE) and comparative surface-passivated quantum dot CQD1 (pristine) confirmed the presence of the cubic phase. This indicated that the crystal structure of the CsPbBr₃ perovskite nanocrystal was retained following ligand 20 exchange with 3,4,5-tris(benzyloxy)benzohydrazide. A comparison of the XRD peak
32
positions and corresponding crystallographic planes for QD1 (LE) and CQD1 (pristine) presented in Table 2, further validated the preservation of the cubic phase.
Table 2
S. No.
Peak position (2θ) QD1 (LE) Peak position (2θ)
CQD1 (pristine)
Corresponding planes
1
15.70
14.80
100
2
22.1
21.16
110
3
31.29
30.14
200
4
35.12
34.05
210
5
38.53
37.33
211
6
44.78
43.53
220
Photoluminescence studies 5
[000106]
The photoluminescence (PL) spectra (Figure 3(a)) and normalized PL spectra (Figure 3(b)) of the surface-passivated quantum dot QD1 (LE) (DH 1:29), and comparative surface-passivated quantum dots CQD1 (pristine), CQD2 (BH 1:29), CQD3 (TAD 1:29), CQD4 (TDH 1:29), CQD6 (BH 1:290), CQD7 (TAD 1:290), and CQD8 (TDH 1:290), (prepared in Example 1) were recorded and 10 analyzed.
[000107]
As illustrated in Figures 3 (a) and 3 (b), and summarized in Table 3, the comparative surface-passivated quantum dot CQD1 (pristine) exhibited a characteristic green emission. In contrast, the comparative quantum dots CQD2 (BH 1:29), CQD3 (TAD 1:29), and CQD4 (TDH 1:29), were prepared using small organic 15 molecules bearing functional groups analogous to those in the conjugated aromatic ligand of Formula L1 and employed at the same molar ratio as in QD1, did not show any blue shift in their photoluminescence profiles.
[000108]
Furthermore, in the comparative quantum dots CQD6 (BH 1:290), CQD7 (TAD 1:290), and CQD8 (TDH 1:290), even upon increasing the molar concentration 20 of these similar (structurally) ligands, the emission characteristic remained unchanged. This observation indicated that the spectral shift was not a generic consequence of the functional groups alone. Additionally, at higher concentrations,
33
these ligands exhibited poor solubility in the chloroform solvent, which further hindered their effectiveness in modifying the optical properties of the ABX3 type perovskite nanocrystals.
[000109]
For, complete solubilization of 3,4,5-tris(benzyloxy)benzohydrazide or 3,4,5-tris(benzyloxy)benzoic acid (conjugated aromatic ligand of Formula L1), the 5 molar ratio of perovskite nanocrystal CsPbBr3 (pristine), to 3,4,5-tris(benzyloxy)benzohydrazide or 3,4,5-tris(benzyloxy)benzoic acid (conjugated aromatic ligand of Formula L1), was in the range of 1:29 (claimed range 1:28 to 1:60). At higher concentrations of 3,4,5-tris(benzyloxy)benzohydrazide or 3,4,5-tris(benzyloxy)benzoic acid (conjugated aromatic ligand of Formula L1), where the 10 molar ratio of perovskite nanocrystal CsPbBr3 (pristine), to 3,4,5-tris(benzyloxy)benzohydrazide or 3,4,5-tris(benzyloxy)benzoic acid (conjugated aromatic ligand of Formula L1), exceeded 1:60, component, became completely insoluble. For instance, 3,4,5-tris(benzyloxy)benzohydrazide or 3,4,5-tris(benzyloxy)benzoic acid (conjugated aromatic ligand of Formula L1), at a molar 15 ratio1:290 were completely insoluble, as shown in Table 3.
[000110]
These results revealed that in surface-passivated quantum dots QD1 (LE), and QD2 (LE) the 3,4,5-tris(benzyloxy)benzo hydrazide ligand, and 3,4,5-tris(benzyloxy)benzoic acid, played a unique and pivotal role in inducing a photoluminescence shift from green to blue. The conjugated aromatic scaffold of 20 3,4,5-tris(benzyloxy)benzo hydrazide ligand as well as 3,4,5-tris(benzyloxy)benzoic acid not only tailored the optical properties of CsPbBr₃ perovskite nanocrystals but also enhanced their colloidal and structural stability through improved surface passivation and ligand nanocrystal interactions.
Table 3 25
S. No.
Surface-passivated quantum dots
PL λmax (nm)
Observation
Solubility of ligand
1
QD1 (LE)
(DH 1:29)
472
Blue shift
Soluble
2
QD2(LE)
(DH 1:29)
482
Blue shift
Soluble
3
CQD1 (Pristine)
523
-
-
4
CQD2
(BH 1:29)
523
No shift
Soluble 34
5
CQD3 (TAD 1:29)
522
No shift
Soluble
6
CQD4 (TDH 1:29)
522
No shift
Soluble
7
CQD5 (DH 1:290)
-
-
Not Soluble
8
CQD6 (BH 1:290)
534
Red shift
Soluble
9
CQD7 (TAD 1:290)
510
Emission completely quenched
Soluble
10
CQD8 (TDH 1:290)
513
-
Not Soluble
[000111]
As illustrated in Figure 4(a), the absorbance spectrum of the comparative surface-passivated quantum dot CQD1 (pristine) displayed a first excitonic peak at 521 nm. After ligand exchange, this peak underwent a notable blue shift to 467 nm in the surface-passivated quantum dot QD1 (LE) (DH 1:29). These results indicated 5 a significant alteration in the electronic structure due to surface passivation by ligand exchange.
[000112]
In the photoluminescence (PL) spectra (Figure 4b), CQD1 (pristine) exhibited a PL maximum at 523 nm. Following ligand exchange, QD1 (LE) (DH (1:29)) showed a pronounced blue shift in its PL maximum to 472 nm, further 10 confirmed, the impact of the ligand on the optical properties of the quantum dots.
[000113]
Figures 4(c) and 4(d) illustrated the absorbance and PL spectra of comparative surface-passivated quantum dots CQD9 (DH 1:1) and CQD10 (DH 1:7), respectively. As shown in Table 4, these samples exhibited only minor blue shifts relative to surface-passivated quantum dot QD1 (LE) (DH 1:29), which indicated that 15 the 3,4,5-tris(benzyloxy)benzohydrazide ligand (a conjugated aromatic ligand of Formula 1) and the molar ratio between CsPbBr₃ and 3,4,5-tris(benzyloxy)benzohydrazide used in the preparation of QD1 (LE) played a key role in tuning the optical characteristics of the quantum dots. Additionally, QD1 (LE) showed a full width at half maximum (FWHM) of 15.40 nm, which reflected the 20 spectral purity and size distribution of the quantum dots. A narrower FWHM indicated more uniform particle size and better color purity in the surface-passivated quantum dot QD1 and hence made the quantum dots more suitable for optoelectronic applications such as display technologies and LEDs. 35
Table 4
S. No.
Surface-passivated quantum dots
Absorbance λmax
Photoluminescence (PL) λmax (nm)
FWHM (nm)
1
QD1 (LE) (DH 1:29)
467
472
15.40
2
CQD1 (pristine)
521
523
20.54
3
CQD9 (DH 1:1)
498
500
20.45
4
CQD10 (DH 1:7)
494
495
20.54
[000114]
Hence, QD1(LE) prepared using the process described in the present invention exhibited the most substantial blue shift in both absorbance and PL spectra, reaching 472 nm. This highlighted the superior efficacy of the ligand exchange 5 strategy employed in QD1 for enhancing quantum dot performance.
X-ray photoelectron spectroscopy (XPS) studies
[000115]
The surface composition of the prepared quantum dots (QDs) was investigated using X-ray photoelectron spectroscopy (XPS). These studies confirmed the presence of nitrogen (N), cesium (Cs), lead (Pb), bromine (Br), oxygen (O), and 10 carbon (C) in the surface-passivated quantum dot QD1 (LE) and the comparative surface-passivated quantum dot CQD1 (pristine) (Figures 5(a)–(f)). High-resolution spectra of nitrogen (N) 1s and bromine (Br) 3d (Figures 5(a) and 5(b)) provided deeper insights into the chemical environments of these elements.
[000116]
Ligand density: XPS analysis verified the presence of ligands on the 15 surface of surface-passivated quantum dot QD1 (LE). Following ligand exchange, the atomic ratio of nitrogen (N) to lead (Pb) N/Pb, increased drastically from 0.144 to 27.40 represented an approximately 190-fold enhancement compared to the CQD1 (pristine). Similarly, carbon (C) to lead (Pb), C/Pb ratio rose from 14.93 to 1543.00, and another carbon (C) to lead (Pb), C/Pb ratio increased from 43.71 to 65.04, 20 reflected a 103-fold increase. The oxygen (O) to lead (Pb), O/Pb ratio surged from 1.336 to 423.8, marked a 317-fold increase. The substantial increase in the atomic ratios of N, C, and O relative to Pb indicated a significantly higher ligand density on the surface of QD1 (LE) after ligand exchange. Further quantification of ligand density, based on the atomic percentages of N and Pb derived from XPS data, 25 36
revealed a dramatic increase from 1.22 ligands/nm² to 232.9 ligands/nm² on the surface of the ligand exchanged nanocrystals.
[000117]
In the nitrogen (N) 1s spectra (Figure 5(a)), the ammonium cation (NH₃⁺) peak shifted toward higher binding energy, suggested changes in the chemical environment due to ligand binding. In contrast, the bromine (Br) 3d (Figure 5(b)) and 5 lead (Pb) 4f (Figure 5(c)) peaks shifted toward lower binding energies after ligand exchange in QD1 (LE). This shift was attributed to the electron-donating nature of the amine (-NH₂) group in the ligand, which bound to Pb²⁺ ions and increased the electron density around Pb²⁺ and Br⁻, thereby reducing their binding energies.
[000118]
Minor satellite peaks were observed in the cesium (Cs), 3d spectra (Figure 10 5(d)) of the CsPbBr₃ (pristine) nanocrystals disappeared after ligand exchange. The peaks indicated the elimination of undercoordinated or surface-disordered Cs⁺ ions. This disappearance suggested improved surface coordination and defect passivation due to ligand binding.
[000119]
The narrowing of the oxygen (O) 1s peak (Figure 5(e)) post-ligand 15 exchange reflected a more chemically uniform oxygen environment on the surface of QD1 (LE). This was likely due to the replacement of disordered and physisorbed oxygen species with uniformly coordinated carboxylate ligands. Hence, further enhanced the surface passivation and reduced contamination.
[000120]
The carbon (C) 1s spectra (Figure 5(f)) for both the surface-passivated 20 quantum dot QD1 (LE) and the comparative surface-passivated quantum dot CQD1 (pristine) showed a dominant peak at approximately 284.8 eV after charge correction. Minor peaks between ~282–289 eV were attributed to C–C, C–O, and carboxylic groups. The C–C peak shifted from 283.5 eV to 284 eV. This indicated stronger ligand-surface interactions and the incorporation of electron-withdrawing aromatic 25 benzene rings in place of non-polar alkyl chains. Hence, confirmed the binding of 3,4,5-tris(benzyloxy)benzohydrazide (conjugated aromatic ligand of Formula L1) to the CsPbBr₃ (formula ABX3) perovskite nanocrystal.
[000121]
The C–N peak shifted from 285.8 eV to 286 eV. This further confirmed strong binding of the -NH₂ groups to the CsPbBr₃ surface. The peak at 286.7 eV, 30 attributed to the C–O–C group, shifted to 286.8 eV and increased in intensity, 37
indicated its presence in the ligand. Similarly, the carboxylic peak shifted from 287.8 eV to 288 eV. The peak at 287.8 was due to the carboxylic group (-C=O) of the 3,4,5-tris(benzyloxy)benzohydrazide. Hence confirmed strong ligand binding through carboxylic group in QD1.
Stability studies 5
[000122]
The water stability of the prepared quantum dots (QDs) was evaluated by forming films on quartz substrates and immersing them in water. The photoluminescence (PL) spectra of comparative surface-passivated quantum dot CQD1 (pristine (P)) and surface-passivated quantum dot QD1 (LE) were recorded initially (before (t=0) in water) and after 1 hour of immersion in water (Figures 6(a) 10 and 6(b)). The PL intensity of comparative surface-passivated quantum dot CQD1 (pristine (P)) was completely quenched after 1 hour. This indicated poor water stability. In contrast, surface-passivated quantum dot QD1(LE) retained 43% of its initial PL intensity after the same duration, demonstrated significantly enhanced water stability due to ligand exchanged surface passivation of CsPbBr₃ (Figure 6(c)). 15 As shown in Figure 6(d), the photographs of the surface-passivated quantum dot CQD1 (pristine (P)) showed no emission under ultraviolet (UV) light after 1 hour of immersion in water, whereas the surface-passivated quantum dot QD1(LE) films exhibited blue emission under UV light after the same duration.
[000123]
Hence, the emission of CsPbBr3 (perovskite nanocrystal of formula ABX3) 20 was tuned from green to blue using the 3,4,5-tris(benzyloxy)benzohydrazide (conjugated aromatic ligand of Formula L1), which resulted in blue emissive surface passivated quantum dot QD1 (LE), without chloride or anion exchange. These surface-passivated quantum dot QD1 (LE) also showed better water stability in comparison to comparative surface-passivated quantum dot CQD1 (pristine). 25
[000124]
Therefore, the emission of perovskite nanocrystals of formula ABX₃ was effectively tuned from green to blue through ligand exchange using a conjugated aromatic ligand (Formula 1). This ligand facilitated the formation of blue-emissive, surface-passivated quantum dots. Furthermore, the ligand exchange, surface-passivated quantum dot also exhibited superior water stability. Therefore, the 30 38
conjugated ligand of Formula L1 demonstrated effectiveness in enhancing both the optical and environmental stability of the perovskite nanocrystal of formula ABX3.
ADVANTAGES OF THE PRESENT DISCLOSURE
[000125]
The present disclosure provides a surface passivated quantum dot 5 comprising: a. a perovskite nanocrystal of formula ABX3; and b. a conjugated aromatic ligand of Formula L1, wherein A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation, B is selected from Pb, or Sn, X is selected from Br, Cl, or I, and the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal. The surface passivated quantum 10 dot comprises a ligand (L2). The conjugated aromatic ligand of Formula L1 along with the other ligand (L2) enables precise tuning of optical properties of the perovskite nanocrystal of formula ABX3 and exhibit photoluminescence emission wavelength in the range of 450 to 490 nm. The ligand exchange also significantly enhances the moisture stability of ABX3 nanocrystals, addressing a major limitation 15 in pervoskite materials. Moreover, the conjugated aromatic cores of the ligand L1 improves charge transport within the nanocrystal structure. The surface passivated quantum dot exhibits a ligand density in a range of 1 to 300 ligands/nm2, ensuring optimal surface coverage and functional performance. Collectively, this invention marks a significant advancement in perovskite nanocrystal technology by 20 introducing a unified approach that simultaneously enables emission tuning, enhances environmental stability, and improves charge transport. This is achieved through innovative ligand design and precise surface modification. To meet the stringent color standards for high-definition displays as defined by the International Telecommunication Union (ITU Rec.2020) Ultra High-Definition Television 25 specification, it is essential to achieve pure blue (460–470 nm), emissions along with pure green (525–535 nm), and pure red (620–650 nm) emissions from perovskite nanocrystals. This breakthrough opens the door to the practical integration of perovskite nanocrystals into commercial optoelectronic applications, including LEDs, display technologies, and sensors. 30 39
I/We Claim:
1.
A surface passivated quantum dot comprising:
a.
a perovskite nanocrystal of formula ABX3; and
b.
a conjugated aromatic ligand of Formula L1, 5
10
Formula L1
wherein A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation, B is selected from Pb, or Sn, X is selected from 15 Br, Cl, or I;
W1, W2, W3, W4, and W5 are independently selected from C, CH, N, NH, O, or S;
p is 0 or 1;
Z3 is independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, 20 CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl;
Z1 and Z2 are independently absent or selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), 25 P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl;
m is independently selected from 0 to 10;
Ra is selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, 30 C1-12 heterocyclyl, or C1-20 heterocyclylalkyl; 40
Rb, and Rc are independently absent or selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rd is selected from H, OH, NH2, or NHNH2;
and 5
the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal.
2.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot comprises a ligand (L2) selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, 10 L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl phosphine oxide, or combinations thereof.
3.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot has a particle size in a range of 5 to 15 nm. 15
4.
The surface passivated quantum dot as claimed in claim 1, wherein the perovskite nanocrystal and the conjugated aromatic ligand of Formula L1 are in a mole ratio range of 1:28 to 1:60.
5.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot has a ligand density in a range of 1 to 300 ligands/nm2. 20
6.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot comprises a C/Pb atomic ratio in a range of 14 to 1550, a N/Pb atomic ratio in a range of 0.1 to 30, and a O/Pb atomic ratio in a range of 1 to 500.
7.
The surface passivated quantum dot as claimed in claim 1, wherein the surface 25 passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm.
8.
The surface passivated quantum dot as claimed in claim 1, wherein the conjugated aromatic ligand of Formula L1 is selected from 3,4,5-tris(C6-12aryloxy)benzohydrazide, 3,4,5-tris(C6-12aryloxy)benzoic acid, 3,4,5-tris(C1-30 6alkyloxy)benzohydrazide, 3,4,5-tris(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-
41
12aryloxy)benzohydrazide, 3,5-bis(C6-12aryloxy)benzoic acid, 3,5-bis(C1-6alkyloxy)benzohydrazide, 3,5-bis(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C6-12aryloxy)cyclopenta-1,3-dienecarboxylic acid, 3,5-bis(C1-5 6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, 3-(C6-12aryloxy)benzohydrazide, 3-(C6-12aryloxy)benzoic acid, 3-(C1-6alkyloxy)benzohydrazide, 3-(C1-6alkyloxy)benzoic acid, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C1-6alkyloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarboxylic acid, or 10 5-(C1-6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, preferably 3,4,5-tris(benzyloxy)benzohydrazide, 3,4,5-tris(benzyloxy)benzoic acid, 3,4-bis(benzyloxy)-5-hydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzoic acid, or 3,4-bis(benzyloxy)-5-hydroxybenzoic acid. 15
9.
A process of preparing the surface passivated quantum dot as claimed in claim 1, the process comprising:
a. treating a first precursor solution and a second precursor solution to obtain a perovskite nanocrystal of formula ABX3; and
b. treating the perovskite nanocrystal of formula ABX3 with the conjugated 20 aromatic ligand of Formula L1 to obtain the surface passivated quantum dot.
10.
The process as claimed in claim 9, wherein the first precursor solution is obtained by mixing a first precursor compound, a first solvent and a first ligand (L2a); and the second precursor solution is obtained by mixing a second precursor compound, a second solvent and a second ligand (L2b). 25
11.
The process as claimed in claim 10, wherein the first precursor compound is selected from cesium carbonate, cesium chloride, cesium bromide, cesium iodide, methylammonium carbonate, methylammonium chloride, methylammonium bromide, methylammonium iodide, formamidinium carbonate, formamidinium chloride, formamidinium bromide, formamidinium 30 iodide, phenethylammonium carbonate, phenethylammonium chloride,
42
phenethylammonium bromide, or phenethylammonium iodide; and the second precursor compound is selected from lead chloride, lead bromide, lead iodide, tin chloride, tin bromide, or tin iodide.
12.
The process as claimed in claim 10, wherein the first solvent and the second solvent are independently selected from octadecene, mesitylene, squalane, 5 tetradecane, hexadecane, perfluorodecalin, or combinations thereof.
13.
The process as claimed in claim 10, wherein the first ligand (L2a) and the second ligand (L2b) are independently selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl 10 phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl phosphine oxide, or combinations thereof.
14.
The process as claimed in claim 9, wherein the first precursor solution is dried under nitrogen at a temperature in a range of 100 to 130℃, followed by heating to a temperature in a range of 140 to 160℃, prior to treating with the second 15 precursor solution.
15.
The process as claimed in claim 9, wherein the second precursor solution is heated to a temperature in a range of 180 to 220℃, prior to treating with the first precursor solution.
16.
The process as claimed in claim 9, wherein the perovskite nanocrystal of formula 20 ABX3 and the conjugated aromatic ligand of Formula L1 are taken in a mole ratio range of 1:28 to 1:60.
17.
The process as claimed in claim 9, wherein the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm.
18.
Use of the surface passivated quantum dot as claimed in claim 1 in an 25 optoelectronic device configured to operate under humid conditions.
19.
The use as claimed in claim 18, wherein the device is a light-emitting diode, display, or sensor.
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43
ABSTRACT
A SURFACE PASSIVATED QUANTUM DOT USING AROMATIC LIGAND AND PROCESS THEREOF
The present disclosure provides a surface passivated quantum dot comprising a. a perovskite nanocrystal of formula ABX3; and b. a conjugated aromatic ligand of 5 Formula L1, and the conjugated aromatic ligand of Formula L1 passivates surface of the perovskite nanocrystal. The present disclosure further provides a process of preparing the surface passivated quantum dot and use thereof.
10
44 , Claims:I/We Claim:
1.
A surface passivated quantum dot comprising:
a.
a perovskite nanocrystal of formula ABX3; and
b.
a conjugated aromatic ligand of Formula L1, 5
10
Formula L1
wherein A is selected from Cs, methylammonium cation, formamidinium cation, or phenethylammonium cation, B is selected from Pb, or Sn, X is selected from 15 Br, Cl, or I;
W1, W2, W3, W4, and W5 are independently selected from C, CH, N, NH, O, or S;
p is 0 or 1;
Z3 is independently selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, 20 CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl;
Z1 and Z2 are independently absent or selected from O, C, NH, S, Se, -PH, -PH2, CH2-C6-12 aryl, CH(C6-12 aryl)2, NH(C6-12 aryl), N(C6-12 aryl)2, PH(C6-12 aryl), 25 P(C6-12 aryl)3, O(C6-12 aryl), S(C6-12 aryl), Se(C6-12 aryl), C(C6-12 aryl)3, C6-12 aryl C3-12 cycloalkyl, C1-6 alkyl, C6-12 aryl, C1-12 heteroaryl, or C1-12 heterocyclyl;
m is independently selected from 0 to 10;
Ra is selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, 30 C1-12 heterocyclyl, or C1-20 heterocyclylalkyl; 40
Rb, and Rc are independently absent or selected from hydrogen, C3-12 cycloalkyl, C1-6 alkyl, C2-6 alkenyl, C1-6 alkylamine, C1-6 alkyl-COOH, C6-12 aryl, C1-12 heteroaryl, C1-20 heteroarylalkyl, C1-12 heterocyclyl, or C1-20 heterocyclylalkyl;
Rd is selected from H, OH, NH2, or NHNH2;
and 5
the conjugated aromatic ligand of Formula L1 passivates surface of the pervoskite nanocrystal.
2.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot comprises a ligand (L2) selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, 10 L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl phosphine oxide, or combinations thereof.
3.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot has a particle size in a range of 5 to 15 nm. 15
4.
The surface passivated quantum dot as claimed in claim 1, wherein the perovskite nanocrystal and the conjugated aromatic ligand of Formula L1 are in a mole ratio range of 1:28 to 1:60.
5.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot has a ligand density in a range of 1 to 300 ligands/nm2. 20
6.
The surface passivated quantum dot as claimed in claim 1, wherein the surface passivated quantum dot comprises a C/Pb atomic ratio in a range of 14 to 1550, a N/Pb atomic ratio in a range of 0.1 to 30, and a O/Pb atomic ratio in a range of 1 to 500.
7.
The surface passivated quantum dot as claimed in claim 1, wherein the surface 25 passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm.
8.
The surface passivated quantum dot as claimed in claim 1, wherein the conjugated aromatic ligand of Formula L1 is selected from 3,4,5-tris(C6-12aryloxy)benzohydrazide, 3,4,5-tris(C6-12aryloxy)benzoic acid, 3,4,5-tris(C1-30 6alkyloxy)benzohydrazide, 3,4,5-tris(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-
41
12aryloxy)benzohydrazide, 3,5-bis(C6-12aryloxy)benzoic acid, 3,5-bis(C1-6alkyloxy)benzohydrazide, 3,5-bis(C1-6alkyloxy)benzoic acid, 3,5-bis(C6-12aryloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C1-6alkyloxy)cyclopenta-1,3-diene carbohydrazide, 3,5-bis(C6-12aryloxy)cyclopenta-1,3-dienecarboxylic acid, 3,5-bis(C1-5 6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, 3-(C6-12aryloxy)benzohydrazide, 3-(C6-12aryloxy)benzoic acid, 3-(C1-6alkyloxy)benzohydrazide, 3-(C1-6alkyloxy)benzoic acid, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C1-6alkyloxy)cyclopenta-1,3-dienecarbohydrazide, 5-(C6-12aryloxy)cyclopenta-1,3-dienecarboxylic acid, or 10 5-(C1-6alkyloxy)cyclopenta-1,3-dienecarboxylic acid, preferably 3,4,5-tris(benzyloxy)benzohydrazide, 3,4,5-tris(benzyloxy)benzoic acid, 3,4-bis(benzyloxy)-5-hydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzohydrazide, 3-(benzyloxy)-4,5-dihydroxybenzoic acid, or 3,4-bis(benzyloxy)-5-hydroxybenzoic acid. 15
9.
A process of preparing the surface passivated quantum dot as claimed in claim 1, the process comprising:
a. treating a first precursor solution and a second precursor solution to obtain a perovskite nanocrystal of formula ABX3; and
b. treating the perovskite nanocrystal of formula ABX3 with the conjugated 20 aromatic ligand of Formula L1 to obtain the surface passivated quantum dot.
10.
The process as claimed in claim 9, wherein the first precursor solution is obtained by mixing a first precursor compound, a first solvent and a first ligand (L2a); and the second precursor solution is obtained by mixing a second precursor compound, a second solvent and a second ligand (L2b). 25
11.
The process as claimed in claim 10, wherein the first precursor compound is selected from cesium carbonate, cesium chloride, cesium bromide, cesium iodide, methylammonium carbonate, methylammonium chloride, methylammonium bromide, methylammonium iodide, formamidinium carbonate, formamidinium chloride, formamidinium bromide, formamidinium 30 iodide, phenethylammonium carbonate, phenethylammonium chloride,
42
phenethylammonium bromide, or phenethylammonium iodide; and the second precursor compound is selected from lead chloride, lead bromide, lead iodide, tin chloride, tin bromide, or tin iodide.
12.
The process as claimed in claim 10, wherein the first solvent and the second solvent are independently selected from octadecene, mesitylene, squalane, 5 tetradecane, hexadecane, perfluorodecalin, or combinations thereof.
13.
The process as claimed in claim 10, wherein the first ligand (L2a) and the second ligand (L2b) are independently selected from oleic acid, oleylamine, lauric acid, stearic acid, phenethylamine, octanoic acid, octylamine, L-cysteine, octylphosphonic acid, didodecyldimethylammonium bromide, trioctyl 10 phosphine, ethylenediamine tetraacetic acid, citric acid, triphenyl phosphine oxide, or combinations thereof.
14.
The process as claimed in claim 9, wherein the first precursor solution is dried under nitrogen at a temperature in a range of 100 to 130℃, followed by heating to a temperature in a range of 140 to 160℃, prior to treating with the second 15 precursor solution.
15.
The process as claimed in claim 9, wherein the second precursor solution is heated to a temperature in a range of 180 to 220℃, prior to treating with the first precursor solution.
16.
The process as claimed in claim 9, wherein the perovskite nanocrystal of formula 20 ABX3 and the conjugated aromatic ligand of Formula L1 are taken in a mole ratio range of 1:28 to 1:60.
17.
The process as claimed in claim 9, wherein the surface passivated quantum dot exhibits photoluminescence emission wavelength in a range of 450 to 490 nm.
18.
Use of the surface passivated quantum dot as claimed in claim 1 in an 25 optoelectronic device configured to operate under humid conditions.
19.
The use as claimed in claim 18, wherein the device is a light-emitting diode, display, or sensor.
30