WO2020043661A1

WO2020043661A1 - Method for synthesizing a semiconducting material

Info

Publication number: WO2020043661A1
Application number: PCT/EP2019/072704
Authority: WO
Inventors: Inbal DAVIDI; Amir Holtzman; Yael NISENHOLZ; Shany NEYSHTADT; David MOCATTA; Alex IRZH
Original assignee: Merck Patent Gmbh
Priority date: 2018-08-28
Filing date: 2019-08-26
Publication date: 2020-03-05
Also published as: TW202020116A

Abstract

The present invention relates to a method for synthesizing a semiconducting nanosized material.

Description

Method for synthesizing a semiconducting material

Field of the invention

The present invention relates to a method for synthesizing a

semiconducting nanosized material comprising high optical density, a semiconducting nanosized material obtainable by the method, optical medium and an optical device.

The present invention also relates to a semiconducting nanosized material comprising high performance, a method for synthesizing said

semiconducting nanosized, optical medium and an optical device.

Background Art

Quantum dots have large potential for use in display technologies due to their high quantum yields and narrow emission line-widths, which allow a large color gamut to be attained. Cadmium based quantum dots have traditionally given the highest quantum yields and the lowest emission line- widths. However, recent health and safety regulations have limited the use of cadmium and so cadmium free alternatives are preferred.

Unfortunately, the leading cadmium free alternative, InP, shows significantly larger line widths than cadmium-based materials. Spectroscopic evidence of single InP quantum dot line widths show that they are comparable to cadmium-based materials. This fact suggests that the cause of the large line-widths exhibited by InP based quantum dots ensembles is the inhomogeneous broadening stemming from the large size distribution of the InP quantum dots. The inhomogeneous broadening in InP has two contributing factors one is the use of the highly reactive

tris(trimethylsilyl)phosphine (PTMS) as the phosphorous precursor in most syntheses. The reactivity of the PTMS makes it hard to separate the nucleation and growth stages which is necessary to produce quantum dots with narrow size distributions like those achieved with cadmium based materials.

In the field of semiconductors for displays, several Parameters are of great importance: QY, FWHM, self- absorption and the amount of light absorbed per mg of material (OD/mg) at A=450nm where the blue LED in displays emits. Most of the research done on InP based NPs is with zinc

chalcogenide Shell (ZnSe, ZnS or ZnSeS alloy) due to the high QY (type 1 materials), relative low FWHM and the absorption of the Zn chalcogenide Shell.

Due to this most syntheses of InP core/shell dots give an FWHM for the final photoluminescence peak of >40nm. One paper by X. Yang et al. gives an FWHM of 38nm¹. In these syntheses the FWHM of the final core/shell is largely determined by the size distribution of the InP cores and this ultimately limits the FWHM breadth.

Similarly, a document published by P. Ramasamy et al. discloses core/shell quantum dots having an InZnP core².

On top of this the quantum yield of the final InP/ZnS or InP/ZnSe quantum dots is partially determined by the lattice mismatch between the InP core and the ZnS or ZnSe shell. This mismatch can be tuned by controlling the amount of zinc in the InP core³.

Recently a method for synthesizing InP quantum dots is reported⁴. This method uses InP magic sized clusters (MSCs) as single source precursors (SSP) instead of the PTMS and indium-carboxylate.

Using InGaP alloy (band gap=1.8-1.9eV) as the shell of InP cores (band gap=1.34eV) or synthesizing InZnGaP cores and GaP as shell (band gap=2.26eV) also produces type I kind of NPs (Figure 1 )⁵·⁶. Using GaP as buffer layer between InP based cores and ZnS/ZnSe/ZnSeS shell produces Quantum Dots (QD) with high Quantum Yield (QY). ^{7 - 13} Furthermore, some documents describe that the shape of the QD may have an influence of the optical density per mg (OD/mg) of the QD. ^{14 16}

Prior Art:

I . X. Yang et al., Adv. Mater., 2012, 24, 4180

2. Ramasamy et al ., Chem Mater, 2017, 29, 6893

3. F. Pietra et al., ACS Nano, 2016, 10 (4), pp 4754-4762)

4. D. Gary et al., Chem. Mater., 2015, 1432

5. Qiang Fluang et al., J. Mater. Chem. A, 2015, 3, 15824-15837

6. US 2018/0047878 A1

7. F. Pietra et al., Chem. Mater. 2017, 29, 5192-5199

8. WO 2017/074897 A1

9. Sungwoo Kim et al., JACS 2012, 134, 3804-3809

10. US 8,784,703 B2

I I . CN 107338048 A

12. US 9,153,731 B2

13. Park et al. Scientific Reports 2016, 6, 30094, DOI: 10.1038/srep30094

14. Z. Hens and I. Moreels, J. Mater. Chem., 2012, 22, 10406

15. A. Achtstein et al., J. Phys. Chem. C, 2015, 119, 20156, DOI:

10.1021 /acs.jpcc.5b06208

16. I. Angeloni et al., ACS Photonics, 2016, 3, 58,

DOI: 10.1021/acsphotonics.5b00626

Quantum dots obtainable according to prior art documents could be used. However, it is a permanent desire to improve the features of these quantum dots. Therefore, it is an object of embodiments of the present invention to provide quantum dots having a high quantum yield, a high absorption, improved color purity and efficiency. It is a further object of embodiments of the present invention to provide quantum dots having a high optical density. A further object of embodiments of the present invention is providing quantum dots having an improved stability and lifetime.

It is an object of embodiments of the present invention to provide an efficient and/or cheap method for production of improved quantum dots.

The above objective is accomplished by quantum dots and a method for producing the same according to the present invention.

Summary of the invention

Surprisingly, the inventors have found that a method for synthesizing a semiconducting nanosized material comprising high optical density with all the features of present claim 1 solves one or more of the problems mentioned above.

Consequently, the present invention provides a method for synthesizing a semiconducting nanosized material comprising high optical density, wherein the method comprises the steps of i) providing a first cation core precursor and a first anion core precursor or a semiconducting nanosized material being obtainable by reacting the first cation core precursor and the first anion core precursor; ii) providing a second precursor; iii) reacting the second precursor with the first cation core precursor and the first anion core precursor or reacting the second precursor with a nanosized material being obtainable by reacting the first cation core precursor and the first anion core precursor in order to achieve a semiconducting nanosized material comprising at least three components iv) reacting the semiconducting nanosized material comprising at least three components with a third cation precursor in order to achieve a

semiconducting nanosized material comprising high optical density characterized in that the first cation core precursor is a source of an element of the group 13 of the periodic table, preferably a salt of an element of the group 13 of the periodic table, more preferably the element of the group 13 is In, Ga or a mixture of thereof; the first anion core precursor is a source of an element of the group 15 of the periodic table, preferably the element of the group 15 is P, As or a mixture of thereof; the second precursor is a Zn, or a Cd source, preferably a material selected from one or more members of the group consisting of Zinc salts and Cadmium salts or mixtures thereof, preferably Zinc halogenides, Cadmium halogenides, Zinc carboxylates and Cadmium carboxylates or mixtures thereof, more preferably ZnC , ZnBr2, Zn , Zn(02CR)2, wherein R is Ci to Ci9, even more preferably Zinc acetate, Zinc myristate, Zinc oleate, Zinc laurate, Zinc stearate; and the third cation precursor is a Ga source, preferably a material selected from Gallium salts, preferably Gallium halogenides, and Gallium

carboxylates or mixtures thereof, more preferably GaCb, GaBr3, Gab,

Ga(0₂CR)3, wherein R is Ci to Cig,even more preferably Gallium acetate, Gallium myristate, Gallium laurate, Gallium stearate and Gallium oleate. Preferably said method of the present invention solves all the problems mentioned above at the same time. In another aspect, the present invention relates to a method for

synthesizing a semiconducting nanosized material comprising high optical density being based on magical sized clusters (MSCs).

In another aspect, the present invention also relates to a semiconducting nanosized material, preferably a semiconducting light emitting nanosized material, more preferably quantum dots (QD) being obtainable by a method for synthesizing a semiconducting nanosized material comprising high optical density. In another aspect, the present invention also relates to a semiconducting nanosized material comprising with all the features of present claim 1 solves one or more of the problems mentioned above.

Consequently, the present invention provides a semiconducting nanosized material, wherein the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 0.6, preferably at least 0.9, more preferably at least 1.0.

Preferably said semiconducting light emitting nanosized material of the present invention solves all the problems mentioned above at the same time.

In another aspect, the present invention relates to a method for

synthesizing a semiconducting nanosized material of the present invention. Preferably the semiconducting nanosized material comprising high performance being based on magical sized clusters (MSCs). In another aspect, the present invention further relates to composition comprising at least one semiconducting nanosized material of the present invention comprising high optical density, and at least one additional material, preferably the additional material is selected from the group consisting of organic light emitting materials, inorganic light emitting materials, charge transporting materials, scattering particles, host materials, nanosized plasmonic particles, photo initiators, and matrix materials.

In another aspect, the present invention further relates to formulation composition comprising or consisting of at least one semiconducting nanosized material of the present invention comprising high optical density, and at least one solvent.

In another aspect, the present invention also relates to use of the

semiconducting nanosized material comprising high optical density, or the composition, or the formulation, in an electronic device, optical device or in a biomedical device.

In another aspect, the present invention relates to an optical medium comprising at least one semiconducting nanosized material comprising high optical density.

In another aspect, the present invention also relates to an optical device comprising at least one optical medium of the present invention.

Detailed description of the invention

The present invention provides a method for synthesizing a semiconducting nanosized material comprising high optical density, wherein the method comprises the steps of i) providing a first cation core precursor and a first anion core precursor or a semiconducting nanosized material being obtainable by reacting the first cation core precursor and the first anion core precursor;

ii) providing a second precursor;

iii) reacting the second precursor with the first cation core precursor and the first anion core precursor or reacting the second precursor with a nanosized material being obtainable by reacting the first cation core precursor and the first anion core precursor in order to achieve a semiconducting nanosized material comprising at least three

components; and

iv) reacting the semiconducting nanosized material comprising at least three components with a third cation precursor in order to achieve a

semiconducting nanosized material comprising high optical density characterized in that

the first cation core precursor is a source of an element of the group 13 of the periodic table, preferably a salt of an element of the group 13 of the periodic table, more preferably the element of the group 13 is In, Ga or a mixture of thereof, and even more preferably the element of the group 13 is In;

the first anion core precursor is a source of an element of the group 15 of the periodic table, preferably the element of the group 15 is P, As or a mixture of thereof;

the second precursor is a Zn, or a Cd source, preferably a material selected from one or more members of the group consisting of Zinc salts and Cadmium salts or mixtures thereof, preferably Zinc halogenides, Cadmium halogenides, Zinc carboxylates and Cadmium carboxylates or mixtures thereof, more preferably ZnC , ZnBr2, Zn , Zn(02CR)2, wherein R is Ci to Ci9, even more preferably Zinc acetate, Zinc myristate, Zinc oleate, Zinc laurate, Zinc stearate; and

the third cation precursor is a Ga source, preferably a material selected from Gallium salts, preferably Gallium halogenides, and Gallium

carboxylates or mixtures thereof, more preferably GaCb, GaBr3, Gab, Ga(0₂CR)3, wherein R is Ci to Cig.even more preferably Gallium acetate, Gallium myristate, Gallium laurate, Gallium stearate and Gallium oleate.

Preferably, the method can include further steps, e.g. for providing a shell preferably comprising ZnS, ZnSe and/or ZnSeS as disclosed below in more detail.

In an embodiment of the present invention, the first cation core precursor, the first anion core precursor and the second precursor can be mixed and reacted to a semiconducting nanosized material comprising at least three components in one step. The expression“reacted to a semiconducting nanosized material comprising at least three components in one step” means that the product is formed using the three precursors without forming intermediate products which could be isolated but the three precursors are mixed and reacted, preferably at the same time.

Consequently, in that embodiment, the three precursors are preferably different.

Preferably, the first cation core precursor for forming a semiconducting nanosized material comprising at least three components is a source of an element of the group 13 of the periodic table, preferably a salt of an element of the group 13 of the periodic table, more preferably the element of the group 13 is In, Ga or a mixture of thereof, even more preferably the element of the group 13 is In.

Preferably, the reaction mixture comprises at least 0.01 % by weight of the first cation core precursor, more preferably at least 0.05 % by weight, even more preferably at least 0.1 % by weight, even more preferably at least 0.5 % by weight. Preferably, the reaction mixture comprises at most 20 % by weight of the first core cation precursor, more preferably at most 10 % by weight, even more preferably at most 5 % by weight. Preferably, the reaction mixture comprises the first cation core precursor in a range of from 0.01 to 10 % by weight, more preferably from 0.05 to 5% by weight, even more preferably 0.07 to 2.5 % by weight, most preferably 0.1 to 2% by weight, based on the total weight of the mixture.

Preferably, the preparation of the semiconducting nanosized material comprising at least three components is achieved by a reaction mixture comprising an indium precursor preferably being selected from the group consisting of indium carboxylates, more preferably indium carboxylates having 2 to 30 carbon atoms, preferably 4 to 24 carbon atoms, even more preferably 8 to 20 carbon atoms, most preferably 10 to 16 carbon atoms.

The indium carboxylate is preferably selected from the group consisting of indium myristate, indium laurate, indium palmitate, indium stearate and indium oleate. The indium precursor, preferably the indium carboxylate can be used as a complex.

Preferably, the first anion core precursor for forming a semiconducting nanosized material comprising at least three components is a source of an element of the group 15 of the periodic table, preferably the element of the group 15 is P, As or a mixture of thereof, more preferably the element of the group 15 is P.

Preferably, the reaction mixture comprises at least 0.01 % by weight of the first anion core precursor, more preferably at least 0.05 % by weight, even more preferably at least 0.07 % by weight, even more preferably at least 0.1 % by weight. Preferably, the reaction mixture comprises at most 20 % by weight of the first anion core precursor, more preferably at most 10 % by weight, even more preferably at most 5 % by weight.

Preferably, the reaction mixture comprises the first anion core precursor in a range of from 0.01 to 20 % by weight, more preferably from 0.05 to 10% by weight, even more preferably 0.07 to 7.5 % by weight, most preferably 0.1 to 5% by weight, based on the total weight of the mixture.

Preferably, the preparation of the semiconducting nanosized material comprising at least three components is achieved by a reaction mixture comprising a phosphorus precursor being selected from the group consisting of organic phosphine compounds, preferably alkyl silyl phosphine compounds having 1 to 3 silicon atoms preferably alkyl silyl phosphine compounds having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms, even more preferably 1 to 4 carbon atoms, most preferably 1 or 2 carbon atoms in the alkyl groups or aryl silyl phosphine compounds, preferably aryl silyl phosphine compounds having 1 -3 silicon atoms preferably aryl silyl phosphine compounds having 6 to 30 carbon atoms, preferably 6 to 18 carbon atoms, even more preferably 6 to 12 carbon atoms, most preferably 6 or 10 carbon atoms in the aryl groups.

In a specific embodiment, the preparation of the semiconducting nanosized material comprising at least three components is preferably achieved by a reaction mixture comprising a phosphorus precursor and an indium precursor being different to the phosphorus precursor and the molar ratio of the phosphorus precursor to the indium precursor is preferably in the range of 1 :3 to 1 :1 , preferably 1 :2.5 to 1 :1 , even more preferably 1 :2 to 1 :1.

Preferably, the phosphorous precursor comprises

tris(trimethylsilyl)phosphine and similar materials having an aryl, and/or alkyl group instead of the methyl unit, such as tris(triphenylsilyl)phosphine, tris(triethylsilyl)phosphine, tris(diphenylmethylsilyl)phosphine,

tris(phenyldimethylsilyl)phosphine, tris(triphenylsilyl)phosphine,

tris(triethylsilyl)phosphine, tris(diethylmethylsilyl)phosphine,

tris(ethyldimethylsilyl)phosphine. Preferably, the second precursor for forming a semiconducting nanosized material comprising at least three components is a Zn or a Cd source, preferably a material selected from one or more members of the group consisting of Zinc salts and Cadmium salts or mixtures thereof, preferably Zinc halogenides, Cadmium halogenides, Zinc carboxylates and Cadmium carboxylates or mixtures thereof, more preferably ZnCh, ZnBr2, Znh, Zn(02CR)2, wherein R is a Ci to C25 group, preferably a C1 to C19 group, even more preferably Zinc acetate, Zinc myristate, Zinc oleate, Zinc laurate, Zinc stearate. Zn compounds are preferred over Cd compounds.

The expression “C1 to C25 group, preferably C1 to C19 group” means residues comprising 1 to 25 carbon atoms and 1 to 19 carbon atoms, respectively. Preferably, the C1 to C25 group, preferably C1 to C19 group is an alkyl residue or an aromatic residue, such as methyl, ethyl, hexyl, heptyl, octanyl, nonanyl, decanyl, undecanyl, dodecanyl, tridecanyl, tetradecanyl, pentadecanyl, hexadecanyl, heptadecanyl, octadecanyl, nonadecanyl, phenyl, methylphenyl, ethylphenyl.

Preferably, the reaction mixture comprises at least 0.01 % by weight of the second precursor, more preferably at least 0.05 % by weight, even more preferably at least 0.1 % by weight, even more preferably at least 0.5 % by weight. Preferably, the reaction mixture comprises at most 20 % by weight of the second precursor, more preferably at most 10 % by weight, more preferably at most 7.5 % by weight, even more preferably at most 5 % by weight.

Preferably, the reaction mixture comprises the second precursor in a range of from 0.01 to 20 % by weight, more preferably from 0.05 to 10% by weight, even more preferably 0.07 to 7.5 % by weight, most preferably 0.1 to 5% by weight, based on the total weight of the mixture. Preferably, the reaction mixture for obtaining the semiconducting nanosized material comprising at least three components comprises a solvent, preferably a solvent exhibiting a boiling point of 250 °C or more, more preferably a solvent exhibiting a boiling point in the range from 250 °C to 500 °C, preferably in the range from 300 °C to 480 °C, more preferably it is from 350 °C to 450 °C, even more preferably it is from 370 °C to 430 °C.

It can be provided that the solvent is preferably selected from amines, aldehydes, alcohols, ketones, ethers, esters, amides, sulfur compounds, nitro compounds, hydrocarbons, halogenated hydro-carbons (e.g.

chlorinated hydrocarbons), aromatic or heteroaromatic hydrocarbons, halogenated aromatic or heteroaromatic hydrocarbons and/or (cyclic) siloxanes, preferably cyclic hydrocarbons, terpenes, epoxides, ketones, ethers and esters; more preferably the solvent is selected from one or more members of the group consisting of squalenes, squalanes, heptadecanes, octadecanes, octadecenes, nonadecanes, icosanes, henicosanes, docosanes, tricosanes, pentacosanes, hexacosanes, octacosanes, nonacosanes, triacontanes, hentriacontanes, dotriacontanes,

tritriacontanes, tetratriacontanes, pentatriacontanes, hexatriacontanes, oleylamines, and trioctylamines, even more preferably squalene, squalane, heptadecane, octadecane, octadecene, nonadecane, icosane, henicosane, docosane, tricosane, pentacosane, hexacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, oleylamine, and trioctylamine, even more preferably squalane, pentacosane, hexacosane, octacosane, nonacosane, or triacontane, even more preferably squalane, pentacosane, or hexacosane.

Preferably, an alkane, more preferably a squalane is used as a solvent for the preparation of the semiconducting nanosized material comprising at least three components. Preferably, an alkane having 6 to 46 carbon atoms, more preferably 8 to 40 carbon atoms, even more preferably 12 to 34 carbon atoms, most preferably 16 to 30 carbon atoms is used as a solvent. More preferably, the alkane being used as a solvent is a decane, dodecane, tetradecane, hexadecane, octadecane, eicosane. docosane, tetracosane, hexamethyltetracosane. The alkane may be linear or branched with branched alkanes such as squalane being preferred.

In an embodiment of the present invention, the preparation of the

semiconducting nanosized material comprising at least three components is preferably achieved by a reaction mixture comprising a solvent and the solvent comprises at least one alkene, preferably an alkene having 6 to 36 carbon atoms, more preferably 8 to 30 carbon atoms, even more preferably 12 to 24 carbon atoms, most preferably 16 to 20 carbon atoms. More preferably, the alkene is a 1 -alkene, such as 1-decene, 1 -dodecene, 1 - Tetradecene, 1 -hexadecene, 1 -octadecene, 1-eicosene. 1 -docosene. The alkene may be linear or branched.

Preferably, the reaction mixture comprises at least 10 % by weight of a solvent, more preferably at least 50 % by weight, even more preferably at least 70 % by weight, even more preferably at least 80 % by weight. The residual is provided by the further components of the reaction mixture as described above and below. These amounts preferably apply to at least one, more preferably to at least two and even preferably to all of the different reaction steps for achieving the semiconducting nanosized material comprising high optical density of the present invention.

Preferably, the reaction mixture comprises a solvent in a range of from 60 to 99.5 % by weight, more preferably from 70 to 99% by weight, even more preferably 80 to 98 % by weight, based on the total weight of the mixture. These amounts preferably apply to at least one, more preferably to at least two and even preferably to all of the different reaction steps for achieving the semiconducting nanosized material comprising high optical density of the present invention. Preferably the reaction mixture for obtaining the semiconducting nanosized material comprises a ligand. Therefore, the reaction mixture of the first step, the second step or the reaction mixture comprising a first cation core precursor, a first anion core precursor and a second precursor preferably comprises a ligand.

The surface ligands in common use include phosphines and phosphine oxides such as Trioctylphosphine oxide (TOPO), Trioctylphosphine (TOP), and Tributylphosphine (TBP); phosphonic acids such as

Dodecylphosphonic acid (DDPA), Tetradecylphosphonic acid (TDPA), Octadecylphosphonic acid (ODPA), and Hexylphosphonic acid (HPA);

amines such as Oleylamine, Dedecyl amine (DDA), Tetradecyl amine (TDA), Hexadecyl amine (HDA), and Octadecyl amine (ODA), Oleylamine (OLA), alkenes, such as 1 -Octadecene (ODE), thiols such as hexadecane thiol and hexane thiol; mercapto carboxylic acids such as mercapto propionic acid and mercaptoundecanoicacid; carboxylic acids such as oleic acid, stearic acid, myristic acid; acetic acid and a combination of any of these. Polyethylenimine (PEI) also can be used preferably.

The ligands mentioned above, especially the acids, can be used in acidic form and/or as a salt. The person skilled in the art will be aware that the ligand will bind to the core in an appropriate manner, e.g. the acids may get deprotonated.

Examples of surface ligands have been described in, for example, the laid- open international patent application No. WO 2012/059931 A.

Preferably, the QD comprise a carboxylate ligand, more preferably a carboxylate ligand having 2 to 30 carbon atoms, preferably 4 to 26 carbon atoms, even more preferably 8 to 22 carbon atoms, most preferably 10 to 18 carbon atoms, even more preferably a carboxylate ligand selected from the group consisting of myristate, palmitate, laurate, stearate, oleate; and/or a phosphorus containing ligand, such as phosphine ligands, preferably alkyl phosphine ligands having 3 to 108 carbon atoms, e. g. Trioctylphosphine (TOP), phosphine oxide ligands, preferably alkyl phosphine oxide having 3 to 108 carbon atoms and/or phosphonate ligands, more preferably an alkyl phosphonate ligand having 1 to 36 carbon atoms, preferably 6 to 30 carbon atoms, even more preferably 10 to 24 carbon atoms, most preferably 12 or 20 carbon atoms in the alkyl group even more preferably a phosphonate ligand selected from the group consisting of octadecylphosphonate, dodecylphosphonate, tetradecylphosphonate, hexadecylphosphonate;

and/or amines, preferably primary or secondary amines having 1-36 carbon atoms, preferably 6 to 30.

In view of the ligands mentioned above, carboxylate ligands such as stearate and oleate and phosphine ligands, such as Trioctylphosphine oxide (TOPO), Trioctylphosphine (TOP), and Tributylphosphine (TBP) are preferred.

Preferably, the second precursor is reacted with the first cation core precursor and the first anion core precursor or a nanosized material being obtainable by reacting the first cation core precursor and the first anion core precursor at a reaction temperature in the range from 100 °C to 500 °C, preferably in the range from 120 °C to 450 °C, more preferably it is from 130 °C to 400 °C, further more preferably from 150 °C to 380°C.

In a further embodiment, second precursor is reacted with the first cation core precursor and the first anion core precursor at a temperature in the range from 60 °C to 250 °C, preferably in the range from 80 °C to 220 °C, more preferably it is from 110 °C to 200 °C to allow a creation and growth of the semiconducting nanosized material, preferably semiconducting nanosized cluster in the mixture. In a preferred embodiment, said first cation core precursor and said second precursor are reacted to a nanosized material in a first step and the nanosized material of the first step is reacted with the second precursor in a second step to obtain a semiconducting nanosized material comprising at least three components.

Preferably, the nanosized material of the first step is purified before the nanosized material of the first step is reacted with a second precursor. The purification step can be performed as disclosed below.

In one embodiment, the nanosized material of the first step is preferably injected to a composition comprising the second precursor. In a further embodiment, the nanosized material of the first step is preferably injected to a composition comprising the second precursor in at least two portions, more preferably in at least three portions. This embodiment is especially useful for obtaining a semiconducting nanosized material comprising high optical density having a peak maximum in the photoluminescence spectrum at a wavelength in the range of 520 nm to 600 nm as disclosed in more detail below.

In further embodiment, a composition comprising the second precursor is preferably injected to the nanosized material of the first step. In a further embodiment, a composition comprising the second precursor is preferably injected to the nanosized material of the first step in at least two portions, more preferably in at least three portions. This embodiment is especially useful for obtaining a semiconducting nanosized material comprising high optical density having a peak maximum in the photoluminescence spectrum at a wavelength in the range of range of 610 nm to 800 nm as disclosed in more detail below.

Preferably, the nanosized material of the first step is reacted with the second precursor in a concentration of at least 0.1 mg/ml, preferably at least 0.5 mg/ml, more preferably at least 1.0 mg/ml, based on the concentration of the nanosized material obtainable in the first step.

Preferably, the nanosized material of the first step is reacted with the second precursor in a concentration in a range of from 0.5 to 30 mg/ml, more preferably from 1 to 20 mg/ml, even more preferably 1 to 15 mg/ml,.

Preferably, the nanosized material of the first step is reacted with the second precursor wherein the weight ratio of the nanosized material of the first step to the second precursor is in a range of 10:1 to 1 :20, preferably 2.5:1 to 1 :10, more preferably 1 :1.5 to 1 :6.

In a further embodiment, the molar ratio of second precursor to the first anion core precursor is preferably in the range of 10:1 to 1 :15, preferably 10:1 to 1 :10, more preferably 10:1 to 1.5:1.

Preferably, the molar ratio of second precursor to the nanosized material of the first step based on the content of the element of the group 15 is in the range of 50:1 to 1 :10, preferably 10:1 to 1 :5, more preferably 5.5:1 to 1 :1.3, even more preferably 5.5:1 to 1.1 :1.

Preferably, the molar ratio of second precursor to the nanosized material of the first step based on the content of the element of the group 13 is in the range of 10:1 to 1 :10, preferably 10:1 to 1 :2, more preferably 7:1 to 1 :1.

Preferably, the molar ratio of second precursor to the nanosized material of the first step based on the content of the element of the group 15 is in the range of 5 to 150, preferably 5 to 120, more preferably 10 to 120, even more preferably 15 to 110.

Preferably, the reaction mixture comprises at least 0.1 % by weight of the nanosized material of the first step, more preferably at least 0.25 % by weight, even more preferably at least 0.5 % by weight, even more preferably at least 1.0 % by weight. Preferably, the reaction mixture comprises at most 20 % by weight of the nanosized material of the first step, more preferably at most 10 % by weight, even more preferably at most 5 % by weight.

Preferably, the reaction mixture comprises the nanosized material of the first step in a range of from 0.1 to 20 % by weight, more preferably from 0.25 to 15 % by weight, even more preferably from 0.5 to 10 % by weight, most preferably from 0.5 to 5 % by weight, based on the total weight of the mixture.

It can be provided that the reaction temperature of the first step is preferably adjusted or kept in the range from 60 °C to 250 °C, preferably in the range from 80 °C to 220 °C, more preferably it is from 110 °C to 200 °C to allow a creation and growth of the semiconducting nanosized material in the mixture.

Preferably, the temperature of the reaction mixture of the first step, wherein a first cation core precursor and a first anion core precursor are reacted, is kept in the temperature range for from 1 second to 3 hours, preferably from 5 seconds to 2.5 hours, more preferably from 20 seconds to 180 minutes, even more preferably from 30 seconds to 120 minutes, further more preferably from 45 seconds to 90 minutes, the most preferably from 60 seconds to 60 minutes.

In an embodiment of the present method, the second precursor is preferably reacted with the first cation core precursor and the first anion core precursor or a nanosized material being obtainable by reacting the first cation core precursor and the second precursor at a reaction temperature in the range from 250 °C to 500 °C, preferably in the range from 280 °C to 450 °C, more preferably it is from 300 °C to 400 °C, further more preferably from 340 °C to 400°C.

In a specific embodiment of the present invention the temperature of the reaction mixture of the second step, wherein a second precursor and the reaction product of the first step are reacted is preferably kept in the temperature range for from 1 second to 3 hours, preferably from 5 seconds to 2.5 hours, more preferably from 20 seconds to 180 minutes, even more preferably from 30 seconds to 120 minutes, further more preferably from 45 seconds to 90 minutes, the most preferably from 60 seconds to 60 minutes.

In a preferred embodiment, the semiconducting nanosized material comprising at least three components are prepared by the use of clusters comprising indium phosphide, preferably magic sized clusters comprising indium phosphide, more preferably the semiconducting nanosized material comprising at least three components are prepared by the use of magic sized clusters essentially consisting of indium phosphide (MSC InP). Magic sized clusters (MSC) are well known in the art. MSC have a well-defined composition and exhibit remarkable thermodynamic stability relative to similar sizes.

Preferably, a cluster material, more preferably a magical size cluster (MSC) is formed in said first step, wherein a first cation core precursor and a first anion core precursor are reacted, preferably a magical size cluster comprising indium phosphide (MSC InP). Preferably, the cluster material, more preferably the magical size cluster (MSC) being formed in said first step comprises size of 2.0 nm or below, preferably of 1.5 nm or below. The size is measured according to the method mentioned above and below (High Resolution Transmission Electron Microscopy; HRTEM) and is based on the arithmetic mean (number average). Preferably, the preparation of the magical size cluster (MSC) is formed in said first step is achieved at a temperature of 80°C or above, preferably 100 °C or above, more preferably 105 °C or above. Preferably, the preparation of the magical size cluster (MSC) is formed in said first step is achieved at a temperature in the range of 80 to 145°C, preferably 105 to 140 °C, more preferably 105 to 120 °C.

Preferably, the preparation of the magical size cluster (MSC) is achieved in the presence of a carboxylate compound, more preferably carboxylate compound having 2 to 30 carbon atoms, preferably 4 to 26 carbon atoms, even more preferably 8 to 22 carbon atoms, most preferably 10 to 18 carbon atoms. Preferably, carboxylate compound comprises a linear, branched, saturated or unsaturated hydrocarbon residue having 1 to 29 carbon atoms, preferably 3 to 25 carbon atoms, even more preferably 7 to 21 carbon atoms, most preferably 9 to 17 carbon atoms being attached to the carboxyl group. More preferably, the carboxylate compound is a saturated

carboxylate compound. The carboxylate compound could be added to the reaction mixture as a free acid or as a salt. Preferably, the carboxylate compound is added as a precursor, preferably an indium precursor wherein preferred indium precursors are disclosed above and below. The InP magic size cluster (MSC) being useful as starting material for the preparation of semiconducting nanosized material comprising at least three components, preferably quantum dots can be prepared by any method known in the art. Preferably, the preparation of the MSC InP is achieved by a reaction mixture comprising a phosphorus precursor as mentioned above. In addition to a phosphorus precursor, the preparation of the MSC InP is preferably achieved by a reaction mixture comprising an indium precursor as mentioned above. In a specific embodiment, the preparation of the MSC InP being useful for preparation of the semiconducting nanosized material comprising at least three components is preferably achieved by a reaction mixture comprising a phosphorus precursor and an indium precursor being different to the phosphorus precursor and the molar ratio of the phosphorus precursor to the indium precursor is preferably in the range of 1 :3 to 1 :1 , preferably 1 :2.5 to 1 :1 , even more preferably 1 :2 to 1 :1.

Surprising improvements can be obtained using a high reaction

temperature for the preparation of the MSC InP being useful as starting material for the preparation of the semiconducting nanosized material comprising at least three components. Preferably, the preparation of the MSC InP is achieved at a temperature 80°C or above, more preferably 100°C or above, more preferably temperature 110°C or above, even more preferably 115°C or above. Preferably, the preparation of the MSC InP is achieved at a temperature in the range of 80 to 180°C, more preferably 100 to 170°C, even more preferably 110 to 160°C, even more preferably 115 to 140°C.

Preferably, the MSC InP being useful as starting material for the

preparation of the semiconducting nanosized material comprising at least three components exhibits an Exciton Peak of at least 370 nm, preferably at least 380 nm, in the absorbance spectrum measured at 25° using a toluene solution. These data concern the MSC InP being achieved by the methods

mentioned above and below and being preferably used as a starting material for the preparation of QD having the features mentioned above and below and preferably comprising a shell. Preferably, the QD having a shell exhibits an Exciton Peak of between 400-650nm, preferably between 440-600nm, in the absorption spectrum measured at 25° using a toluene solution.

The preparation of the nanosized material in a first step by reacting a first cation core precursor and a first anion core precursor, the preparing a semiconducting nanosized material, preferably semiconducting nanosized cluster by providing at least a first cation core precursor, and a first anion core precursor and/or the preparation of an magical size cluster is preferably achieved using a solvent. The solvent is not specifically restricted. Preferably, the solvent is selected from the compounds mentioned above. Preferably a non-coordinating solvent is used. Preferably, an alkane, more preferably a squalane is used as a solvent for the preparation of the nanosized material in a first step by reacting a first cation core precursor and a first anion core precursor, the preparing of a semiconducting nanosized material, preferably semiconducting nanosized cluster by providing at least a first cation core precursor, and a first anion core precursor and/or the preparation of an magical size cluster. Preferably, an alkane having 6 to 46 carbon atoms, more preferably 8 to 40 carbon atoms, even more preferably 12 to 34 carbon atoms, most preferably 16 to 30 carbon atoms is used as a solvent. More preferably, the alkane being used as a solvent is a decane, dodecane, tetradecane, hexadecane, octadecane, eicosane. docosane, tetracosane, hexamethyltetracosane.

The alkane may be linear or branched with branched alkanes such as squalane being preferred.

In an embodiment of the present invention, the preparation of the

nanosized material in a first step by reacting a first cation core precursor and a first anion core precursor, the preparing of a semiconducting nanosized material, preferably semiconducting nanosized cluster by providing at least a first cation core precursor and a first anion core precursor and/or the preparation of an magical size cluster is preferably achieved by a reaction mixture comprising a solvent and the solvent comprises at least one alkene, preferably an alkene having 6 to 36 carbon atoms, more preferably 8 to 30 carbon atoms, even more preferably 12 to 24 carbon atoms, most preferably 16 to 20 carbon atoms. More preferably, the alkene is a 1 -alkene, such as 1-decene, 1 -dodecene, 1 -Tetradecene, 1 - hexadecene, 1 -octadecene, 1-eicosene. 1 -docosene. The alkene may be linear or branched.

In an embodiment of the present invention, the preparation of the

nanosized material in a first step by reacting a first cation core precursor and a first anion core precursor, the preparing of a semiconducting nanosized material, preferably semiconducting nanosized cluster by providing at least a first cation core precursor and a first anion core precursor and/or the preparation of an magical size cluster is preferably achieved by a reaction mixture comprising a solvent and the solvent comprises at least one aromatic solvent, preferably toluene. Regarding the preparation step of the semiconducting nanosized material comprising at least three components and the MSC InP being useful as starting material for the preparation of the semiconducting nanosized material comprising at least three components, alkanes and/or alkenes are preferred in view of the other solvents mentioned above, more preferable a squalane is used.

In another embodiment, a purification step is preferably performed for purifying a particulate material before performing an additional reaction step. That is, the nanosized material obtained in a first step by reacting a first cation core precursor and a first anion core precursor, the

semiconducting nanosized material, preferably semiconducting nanosized cluster being obtained by providing at least a first cation core precursor, and a first anion core precursor and/or the magical size cluster being used as starting material is preferably purified before any subsequent reaction and/or modification is performed. The purification is described in more detail above and below.

The purification is preferably performed by adding a solvent to the mixture obtained in the first reaction step comprising a particulate material and preferably precipitating a particulate material. The particulate material is preferably the nanosized material obtained in a first step by reacting a first cation core precursor and a first anion core precursor, the semiconducting nanosized material, preferably semiconducting nanosized cluster being obtained by providing at least a first cation core precursor and a first anion core precursor and/or the magical size cluster being used as starting material, and/or a semiconducting nanosized material comprising a shell as disclosed in more detail below.

In a specific embodiment, the semiconducting nanosized material comprising at least three components is preferably purified before the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor in order to achieve a semiconducting nanosized material comprising high optical density.

According to a further embodiment, the nanosized material comprising at least three components and the third cation precursor are preferably mixed at a temperature below 150°C and heated after the mixing.

Preferably, the mixture of the nanosized material comprising at least three components and the third cation precursor are heated to a temperature in the range of 100°C to 350°C, preferably 150°C to 300°C, more preferably 180°C to 280°C, even more preferably 200°C to 250°C. Preferably, the reaction mixture comprises at least 0.01 % by weight of the third cation precursor, more preferably at least 0.05 % by weight, even more preferably at least 0.1 % by weight, even more preferably at least 0.5 % by weight. Preferably, the reaction mixture comprises at most 30 % by weight of the third cation precursor, more preferably at most 20 % by weight, even more preferably at most 15 % by weight.

Preferably, the reaction mixture comprises the third cation precursor in a range of from 0.01 to 30 % by weight, more preferably from 1 to 20% by weight, even more preferably 2 to 15 % by weight, based on the total weight of the mixture.

Preferably, the semiconducting nanosized material comprising at least three components is reacted with the third cation precursor in a

concentration of at least 0.1 mg/ml, preferably at least 0.5 mg/ml, more preferably at least 1.0 mg/ml, semiconducting nanosized material comprising at least three components.

concentration in a range of from 0.5 to 30 mg/ml, more preferably from 1 to 20 mg/ml, even more preferably 1 to 15 mg/ml, most preferably 1 to

10mg/ml. According to one embodiment, wherein the third cation precursor is preferably added in multiple steps. This first embodiment preferably provides quantum dots having an absorption at a high wavelength and a low full width half maximum (FWHM). In view of prior art particles having the same wavelength, the present particles comprise very high optical density and/or high quantum yield (QY). In a preferred embodiment wherein the semiconducting nanosized material comprising at least three

components is reacted with a third cation precursor wherein the third cation precursor is added in multiple steps, the FWHM is preferably at most 60 nm, more preferably of at most 50 nm and/or the particles show emission and preferably comprise a quantum yield (QY) of at least 2 %, more preferably at least 10 % and even more preferably at least 20 %. In addition thereto, the present invention enables the use of the same starting materials as for particles having lower wavelength. In order to achieve higher wavelength the third cation precursor is added in multiple steps while for lower wavelength the third cation precursor is added in exactly one step. This imparts cost advantages and is less time consuming. Furthermore, the quality control is improved.

According to a further embodiment the third cation precursor is preferably added in exactly one step. This second embodiment preferably provides quantum dots having an absorption at a low wavelength (blue shift) and a low full width half maximum (FWFIM). In view of prior art particles having the same wavelength, the present particles comprise very high optical density and/or high quantum yield (QY). Furthermore, in view of particles having an absorption at a high wavelength, the particles being achieved by adding the third cation precursor in exactly one step show lower full width half maximum (FWFIM) values, higher high optical density and higher quantum yield (QY). In a preferred embodiment wherein the

semiconducting nanosized material comprising at least three components is reacted with a third cation precursor wherein the third cation precursor is added in exactly one step, the FWFIM is preferably at most 60 nm, more preferably of at most 50 nm and/or the particles show emission and preferably comprise a quantum yield (QY) of at least 2 %, more preferably at least 10 % and even more preferably at least 20 %. In addition thereto, the present invention enables the use of the same starting materials as for particles having higher wavelength. In order to achieve higher wavelength the third cation precursor is added in multiple steps while for lower wavelength the third cation precursor is added in exactly one step. This imparts cost advantages and is less time consuming. Furthermore, the quality control is improved.

In a specific embodiment of the present invention the temperature of the reaction mixture of the step, wherein a third cation precursor and a semiconducting nanosized material comprising at least three components are reacted is preferably kept in the temperature range for from 1 second to 3 hours, preferably from 5 seconds to 2.5 hours, more preferably from 20 seconds to 180 minutes, even more preferably from 30 seconds to 120 minutes, further more preferably from 45 seconds to 90 minutes, the most preferably from 60 seconds to 60 minutes.

Preferably, the molar ratio of third cation precursor to the first anion core precursor is below 1 :1 , preferably below 10:1 , more preferably below 100:1 while the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor. Low concentration of the first anion core precursor are preferably achieved by a purification step before the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor.

Preferably, the molar ratio of third cation precursor to the first anion core precursor is in the range of 1000:1 to 1 :1 , preferably 500:1 to 10:1 , more preferably 250:1 to 100:1 while the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor. Low concentration of the first anion core precursor are preferably achieved by a purification step before the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor. Preferably, the concentration the first anion core precursor is below 1 mg/ml, preferably below 0.5 mg/ml, more preferably below 0.1 mg/ml while the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor. Low concentration of the first anion core precursor are preferably achieved by a purification step before the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor.

Embodiments comprising a low amount of first anion core precursor while the semiconducting nanosized material comprising at least three

components is reacted with a third cation precursor provide particles having low full width half maximum (FWHM), very high optical density and/or high quantum yield (QY). In a preferred embodiment wherein the

semiconducting nanosized material comprising at least three components is reacted with a third cation precursor at a low amount of first anion core precursor, the FWHM is preferably at most 60 nm, more preferably of at most 50 nm and/or the particles show emission and preferably comprise a quantum yield (QY) of at least 2 %, more preferably at least 10 % and even more preferably at least 20 %.

In an embodiment of the present invention, no source of P, As or a mixture of thereof is preferably added for reacting the semiconducting nanosized material comprising at least three components with a third cation precursor, more preferably no source of an element of the group 15 of the periodic table is added. This first embodiment preferably provides quantum dots having an absorption at a low wavelength (blue shift) and a low full width half maximum (FWHM).

In an embodiment of the present invention, a third anion precursor is added for reacting the semiconducting nanosized material comprising at least three components with a third cation precursor, preferably a source of an element of the group 15 of the periodic table, preferably the element of the group 15 is P, As or a mixture of thereof. Preferably, the molar ratio of third cation precursor to the third anion precursor is in the range of 10:1 to 1 :10, more preferably 10:1 to 1 :1 , even more preferably 7:1 to 2:1. Preferably, the concentration the third anion precursor is above 0.1 mg/ml, more preferably above 0.5 mg/ml, even more preferably above 1.0 mg/ml while the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor. This second embodiment, wherein a third anion precursor is added, preferably provides quantum dots having an absorption at a high

wavelength and a low full width half maximum (FWHM). It should be noted that a controlled addition of a third anion precursor provides the opportunity to avoid an additional growth of InP parts in the layer achieved by the reaction step wherein the third precursor is reacted.

Preferably, the method comprises the steps of

a) providing a lll-V semiconducting nanosized material;

b) providing a second precursor;

c) reacting the lll-V nanosized material with the second precursor in order to achieve a semiconducting nanosized material comprising at least three components;

d) providing a third cation precursor;

e) reacting the semiconducting nanosized material comprising at least three components with the third cation precursor, preferably in order to achieve a semiconducting nanosized material comprising high optical density.

Preferably, the reaction mixture comprises at least 0.1 % by weight of the lll-V semiconducting nanosized material, more preferably at least 0.25 % by weight, even more preferably at least 0.5 % by weight, even more preferably at least 1.0 % by weight. Preferably, the reaction mixture comprises at most 20 % by weight of the lll-V semiconducting nanosized material, more preferably at most 10 % by weight, even more preferably at most 5 % by weight.

Preferably, the reaction mixture comprises the lll-V semiconducting nanosized material in a range of from 0.1 to 20 % by weight, more preferably from 0.25 to 15 % by weight, even more preferably from 0.5 to 10 % by weight, most preferably from 0.5 to 5 % by weight, based on the total weight of the mixture.

In a specific embodiment, the lll-V semiconducting nanosized material is preferably injected to a composition comprising the second precursor. Preferably, the lll-V semiconducting nanosized material is injected to a composition comprising the second precursor in at least two portions, more preferably in at least three portions. This embodiment is especially useful for obtaining a semiconducting nanosized material comprising high optical density having a peak maximum in the photoluminescence spectrum at a wavelength in the range of 520 nm to 600 nm as disclosed in more detail below.

In a further embodiment, a composition comprising the second precursor is preferably injected to the lll-V semiconducting nanosized material.

Preferably, a composition comprising the second precursor is injected to the lll-V semiconducting nanosized material in at least two portions, more preferably in at least three portions. This embodiment is especially useful for obtaining a semiconducting nanosized material comprising high optical density having a peak maximum in the photoluminescence spectrum at a wavelength in the range of range of 610 nm to 800 nm as disclosed in more detail below. Preferably, the lll-V semiconducting nanosized material is reacted with the second precursor in concentration of at least 0.1 mg/ml, preferably at least 0.5 mg/ml, more preferably at least 1.0 mg/ml, based on the concentration of the lll-V semiconducting nanosized material.

Preferably, the lll-V semiconducting nanosized material is reacted with the second precursor in a concentration in a range of from 0.5 to 200 mg/ml, more preferably from 1 to 100 mg/ml, even more preferably 1 to 50 mg/ml. Preferably, the lll-V semiconducting nanosized material is reacted with the second precursor wherein the weight ratio of the lll-V semiconducting nanosized material to the second precursor is in a range of 10:1 to 1 :20, preferably 2.5:1 to 1 :10, more preferably 1 :1.5 to 1 :6. Preferably, the lll-V semiconducting nanosized material is reacted with the second precursor wherein the weight ratio of the lll-V semiconducting nanosized material to the second precursor is in a range 0.01 to 1 , more preferable is 0.01 to 0.8, even more preferred range is 0.01 to 0.6, most preferable is 0.05 to 0.6.

Preferably, the molar ratio of second precursor to the lll-V semiconducting nanosized material based on the content of the element of the group V is in the range of 10:1 to 1 :10, preferably 10:1 to 1 :5, more preferably 5.5:1 to 1 :1.3, even more preferably 5.5:1 to 1.1 :1.

Preferably, the lll-V semiconducting nanosized material is a cluster material, more preferably a magical size cluster (MSC) comprising size of 4.0 nm or below, more preferably of 2.0 nm or below, even more preferably of 1.5 nm or below. The size is measured according to the method mentioned above and below (High Resolution Transmission Electron Microscopy; HRTEM) and is based on the arithmetic mean (number average). Preferably, the lll-V semiconducting nanosized material is a lll-V cluster selected from the group consisting of InP, InAs, InSb, GaP, GaAs, and GaSb clusters, more preferably InP cluster.

More preferably, the lll-V semiconducting nanosized material is a lll-V magic sized cluster (MSC) selected from the group consisting of InP, InAs, InSb, GaP, GaAs, and GaSb magic sized clusters (MSC), preferably InP magic sized cluster (MSC InP), more preferably, it is ln3₇P₂o(0₂CR¹)si, wherein said O2CR¹ of said ln3₇P₂o(0₂CR¹)si is -0₂CCH₂Phenyl, or a substituted or unsubstituted fatty acid such as hexanoate, heptanoate, octanoate, nonanoate, decanoate, undecanoate, dodecanoate,

tridecanoate, tetradecanoate, pentadecanoate, hexadecanoate,

heptadecanoate, octadecanoate, nonadecanoate, icosanoate, myristate, laurate, palmitate, stearate, or oleate.

Preferably, the lll-V semiconducting nanosized material is based on a nanocrystal core, which consists solely of fused 6-membered rings with all phosphorus atoms coordinated to four indium atoms in a pseudo- tetrahedral arrangement. The nanocrystal core preferably have the formula [ln_2i P₂O]³⁺, [ln₄₂P₄o]⁶⁺, [InesPeop, [ln₈₄P8o]¹²⁺, [I^h ₉₅R9o]¹⁵⁺, [I^h ₃iR₃o]³⁺,

[ln_4iP₄₀]³⁺, [InsiPsop, [IneiPeop, [I^h ₇iR₇o]³⁺, [I^h ₈iR₈o]³⁺, [I^h ₉iR₉o]³⁺. In this preferred embodiment the subset of atoms preferably possesses a C2 rotation axis that bisects two phosphorus atoms and a single indium atom located at the center of the particle, and measures approximately 1.3 nm ^c 1.0 nm x 1.0 nm. A dihedral angle of 160 ± 3° is consistent along the longest straight In-P . The average In-P bond length in the [ln2iP2o]³⁺. core is 2.528 A (min 2.479 A, max 2.624 A), and the average P- In-P bond angle is 109.2° (min 97.7°, max 119.9°). Preferably, an additional 16 indium atoms are singly bound to this core through surface-exposed phosphorus atoms, with an average bond length of 2.482 A (min 2.450 A, max 2.515 A). Preferably, the sum of the single-bond covalent radii for In and P is 2.53 A and it is preferably inferred that the bonding in the inorganic core of this cluster may be best viewed as covalent in nature, with differences in bond lengths between In-P in the core and In-P at the surface arising from internal strain. The structure is preferably assessed using single-crystal X- ray diffraction at 25°C as well known in the art. (see J. Am. Chem. Soc.

2016, 138, 1510-1513). It should be noted that the core of the present QD may comprise additional InP or areas having another structure. Preferably, the area comprising the preferred structure as mentioned above is at least 30% by volume, more preferably at least 50% by volume and even more preferably at least 70 % by volume.

Preferably, the lll-V semiconducting nanosized material, preferably semiconducting nanosized cluster, more preferably the lll-V magic sized cluster (MSC), comprises an Indium based carboxylate ligand, preferably ln(0₂CR¹)3, wherein said O2CR¹ of said ln(0₂CR¹)3 is -0₂CCH₂Phenyl, or a substituted or unsubstituted fatty acid such as hexanoate, heptanoate, octanoate, nonanoate, decanoate, undecanoate, dodecanoate,

tridecanoate, tetradecanoate, pentadecanoate, hexadecanoate,

Preferably, the second precursor is reacted with the lll-V semiconducting nanosized material, preferably semiconducting nanosized cluster at a reaction temperature in the range from 250 °C to 500 °C, preferably in the range from 280 °C to 450 °C, more preferably it is from 300 °C to 400 °C, further more preferably from 340 °C to 400°C.

Preferably, the temperature of the reaction mixture wherein the second precursor is reacted with the lll-V semiconducting nanosized material, is kept in said temperature range for from 1 second to 3 hours, preferably from 5 seconds to 2.5 hours, more preferably from 20 seconds to 180 minutes, even more preferably from 30 seconds to 120 minutes, further more preferably from 45 seconds to 90 minutes, the most preferably from 60 seconds to 60 minutes.

Preferably, the lll-V semiconducting nanosized material, preferably semiconducting nanosized cluster comprises a ligand.

Preferably, the ligand of the lll-V semiconducting nanosized material, preferably semiconducting nanosized cluster is selected from one or more members of the group consisting of carboxylic acids, metal carboxylate ligands, phosphines, phosphonic acids, metal-phosphonates, amines, quaternary ammonium carboxylate salts, metal phosphonates and metal halides, preferably carboxylic acids such as oleic acid, acetic acid, stearic acid, myristic acid, lauric acid, carboxylates such as metal stearate, metal oleate, metal myristate, metal laurate, metal phenylate, metal acetate, more preferably indium myristate, or indium acetate; preferably phosphines and phosphine oxides such as Trioctylphosphine oxide (TOPO),

Trioctylphosphine (TOP), and Tributylphosphine (TBP); phosphonic acids such as Dodecylphosphonic acid (DDPA), Tetradecylphosphonic acid (TDPA), Octadecylphosphonic acid (ODPA), and Hexylphosphonic acid (HPA); amines such as Oleylamine, Dodecyl amine (DDA), Tetradecyl amine (TDA), Hexadecyl amine (HDA), and Octadecyl amine (ODA), Oleylamine (OLA), alkenes, such as 1 -Octadecene (ODE), thiols such as hexadecane thiol and hexane thiol; mercapto carboxylic acids such as mercapto propionic acid and mercaptoundecanoicacid; and a combination of any of these.

According to a preferred embodiment, the nanosized material of the first step and/or the lll-V semiconducting nanosized material is used as a single source precursor. In a preferred embodiment a nanosized material being obtained in a first step by reacting a first cation core precursor and a first anion core precursor as mentioned above and below, preferably magic sized clusters essentially consisting of indium phosphide (MSC InP) or a III- V semiconducting nanosized material is degraded and/or solved by appropriate reaction temperatures in order to provide a source for the first cation core precursor and the first anion core precursor. According to this embodiment of the present invention, the first cation core precursor and the first anion core precursor being provided by degrading the nanosized material of the first step and/or the lll-V semiconducting nanosized material is reacted with the second precursor.

In a preferred embodiment of the method wherein the nanosized material being obtained in a first step by reacting first cation core precursor and a first anion core precursor as mentioned above and below and/or the lll-V semiconducting nanosized material is used as a single source precursor the degraded single source precursor forms a nucleation particles with the second precursor. In an additional step the nucleation particles are enlarged by a growing step. Preferably, this could be achieved by a temperature profile and by adding additional educts.

Preferably, a composition comprising the second precursor is heated up to a temperature in the range of from 250 °C to 500 °C, preferably in the range from 280 °C to 450 °C, more preferably it is from 300 °C to 400 °C, further more preferably from 340 °C to 400°C and a nanosized material of the first step and/or a lll-V semiconducting nanosized material is injected to a composition comprising the second precursor. After the injection of the nanosized material of the first step and/or the lll-V semiconducting nanosized material, the temperature of the reaction mixture is preferably lowered for growing the particles to a desired volume. Preferably the growing is performed by stepwise adding further nanosized material of the first step and/or lll-V semiconducting nanosized material. The growing of the particles is preferably achieved in a temperature range of 140 °C to 450 °C, preferably in the range from 200 °C to 400 °C, more preferably it is from 260 °C to 350 °C. The nucleation step is preferably achieved in a reaction time from 1 second to 15 minutes, preferably from 1 second to 14 minutes, more preferably from 10 seconds to 12 minutes, even more preferably from 10 seconds to 10 minutes, further more preferably from 10 seconds to 5 minutes, the most preferably from 10 seconds to 120 seconds.

The growing step is preferably achieved in a reaction time from 1 second to 3 hours, preferably from 5 seconds to 2.5 hours, more preferably from 20 seconds to 180 minutes, even more preferably from 30 seconds to 120 minutes, further more preferably from 45 seconds to 90 minutes, the most preferably from 60 seconds to 60 minutes.

Preferably the semiconducting nanosized material comprising at least three components being obtained in step iii) is purified before the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor.

Preferably, the semiconducting nanosized material comprising at least three components being obtained in step iii) is reacted with the third cation precursor in a concentration of at least 0.1 mg/ml, preferably at least 0.5 mg/ml, more preferably at least 1.0 mg/ml, semiconducting nanosized material comprising at least three components.

Preferably, the semiconducting nanosized material comprising at least three components being obtained in step iii) is reacted with the third cation precursor in a concentration in a range of from 0.5 to 30 mg/ml, more preferably from 1 to 20 mg/ml, even more preferably 1 to 15 mg/ml, most preferably 1 to 10mg/ml.

In an embodiment of the present invention, the Zn concentration in outer layer of the semiconducting nanosized material comprising at least three components is preferably in the range of 0.1 to 10, more preferably 0.1 to 4, even more preferably 0.1 to 0.4.

In an embodiment of the present invention, the Zn concentration of the outer layer is preferably higher than the Zn concentration of the core.

Preferably, it can be provided that the semiconducting nanosized material comprising at least three components comprises an inner core consisting essentially of InP and an outer core of InZnP.

In an embodiment of the present invention, no source of P, As or a mixture of thereof is added for reacting the semiconducting nanosized material comprising at least three components with a third cation precursor, preferably no source of an element of the group 15 of the periodic table is added. This first embodiment preferably provides quantum dots having an absorption at a low wavelength (blue shift) and a low full width half maximum (FWHM).

In a further embodiment of the present invention, a third anion precursor is added for reacting the semiconducting nanosized material comprising at least three components with a third cation precursor, preferably a source of an element of the group 15 of the periodic table, preferably the element of the group 15 is P, As or a mixture of thereof. Preferably, the concentration the third anion precursor is above 0.1 mg/ml, preferably above 0.5 mg/ml, more preferably above 0.8 mg/ml while the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor. This second embodiment, wherein a third anion precursor is added, preferably provides quantum dots having an absorption at a high

wavelength, a low full width half maximum (FWHM) and a high quantum yield (QY). It should be noted that a controlled addition of a third anion precursor provides the opportunity to avoid an additional growth of InP parts in the layer achieved by the reaction step wherein the third precursor is reacted. Furthermore, the FWHM is preferably lower in comparison to conventional methods wherein the first cation core precursor is present while reacting the semiconducting nanosized material comprising at least three components with a third cation precursor.

It can be provided that the molar ratio of the lll-V semiconducting nanosized material based on the content of the element of the group V to the third cation precursor is below 1 :2, preferably below 1 :1 , more preferably below 2:1 , even more preferably below 5:1.

Preferably, the molar ratio of the lll-V semiconducting nanosized material based on the content of the element of the group V to the third cation precursor is in the range of 1 :2 to 100:1 , preferably 2:1 to 40:1 , more preferably 5:1 to 20:1.

Preferably, the molar ratio of the lll-V semiconducting nanosized material based on the content of the element of the group III to the third cation precursor is below 1 :2, preferably below 1 :1 , more preferably below 2:1 , even more preferably below 5:1.

Preferably, the molar ratio of the lll-V semiconducting nanosized material based on the content of the element of the group III to the third cation precursor is in the range of 1 :2 to 100:1 , preferably 2:1 to 40:1 , more preferably 5:1 to 20:1.

Preferably, the nanosized material comprising at least three components and the third cation precursor are mixed at a temperature below 150°C and heated after the mixing. It can be provided that the mixture of the nanosized material comprising at least three components and the third cation precursor are heated to a temperature in the range of 100°C to 350°C, preferably 150°C to 300°C, more preferably 180°C to 280°C, even more preferably 200°C to 250°C.

The preferred embodiments as mentioned above and below concerning a reaction comprising the steps i) to iv) and a) to e) for the production of nanosized material comprising high optical density can be adopted and apply to all embodiments, respectively.

According to a further aspect of the method of the present invention, a shell of a semiconductor and/or an additional shell is grown onto the

semiconducting nanosized material being obtained by reacting the semiconducting nanosized material comprising at least three components with a third cation precursor as mentioned above and below. That is, if the product of the steps i) to iv) and/or a) to e) is considered as a core particle, a shell is made onto that product. Furthermore, if the product of the steps i) to iv) and/or a) to e) is considered as a core/shell particle, an additional shell is made onto the core/shell particle as obtained according to the steps i) to iv) and/or a) to e) as mentioned above. That is in the second case a particle comprising at least two shells is achieved. The additional shell may comprise one or multiple layers. Furthermore, the additional shell may have a gradient structure. The shell of a semiconductor and/or an additional shell as mentioned above and below can be considered as outer shell. The outer shell may comprise one, two or more layers, preferably of ZnS, ZnSe and/or ZnSeS. Furthermore, the outer shell may comprise a concentration gradient of the different components.

The growing of a shell of a semiconductor and/or an additional shell is different to a reaction of the third precursor with the first and second precursor, a nanosized material of the first step, or a lll-V semiconducting nanosized cluster as mentioned above and below based on the used reaction mixtures and the reaction procedure.

According to the present invention, the term ^"core / shell structure^” means the structure having a core part and at least one shell part covering said core.

In some embodiments of the present invention, said core / shell structure can be core / one shell layer structure, core / double shells structure or core / multishell structure.

According to the present invention, the term ^"multishell ^" stands for the stacked shell layers consisting of three or more shell layers.

Each stacked shell layers of double shells and / or multishell can be made from same or different materials.

In some embodiments of the present invention, a quantum dot shell may comprise a shell of a semiconductor material comprising ll-VI, lll-V, or IV-IV semiconductors, or a combination of any of these.

In some embodiments, as a combination, ternary or quaternary materials of II, III, IV, V, VI materials of the periodic table can be used.

Preferably, the shell comprises or consists of a 1 ^st element of group 12 of the periodic table and a 2^nd element of group 16 of the periodic table, preferably, the 1 ^st element is Zn, and the 2^nd element is S, Se and/or the shell comprises or a consisting of a 1^st element of group 13 of the periodic table and a 2^nd element of group 15 of the periodic table, preferably, the 1 ^st element is In, and the 2^nd element is P, more preferably the shell comprises or a consisting of InP, GaP, ZnS, ZnSe or combinations of these materials, especially alloys of these materials, even more preferably ZnSe or ZnS or the shell comprises a mixture of ZnS and ZnSe. In an embodiment, the mixture of ZnS and ZnSe is achieved by a multi-layer structure comprising at least one layer of ZnS and a further layer of ZnSe. In a further

embodiment the mixture of ZnS and ZnSe is achieved by a structure wherein ZnS and ZnSe are present in one layer (alloy of ZnSeS).

For example, CdSe/CdS, CdSeS/CdZnS, CdSeS/CdS/ZnS, ZnSe/CdS, CdSe/ZnS, InP/ZnS, ZnSe, ZnS, InP/ZnSe, InP/ZnSe/ZnS, InZnP/ZnS, InZnPS/ ZnS, InZnP/ZnSe/ZnS, ZnSe/CdS, ZnSe/ZnS, GaP/ZnS,

GaP/ZnSe, GaP/ZnSe/ZnS, GaZnP/ZnS, GaZnPS/ ZnS, GaZnP/ZnSe/ZnS, InGaP/ZnS, InGaP/ZnSe, InGaP/ZnSeS, InGaP/ZnSe/ZnS,

InGaP/ZnSe/ZnSeS/ZnS, InGaP/ZnSeS/ZnS. ZnSe/ZnS, ZnSe/ZnSeS/ZnS, only ZnS. InGaZnP/ZnSe/ZnS, InGaZnP/ZnS, InGaZnP/ZnSe/ZnSeS/ZnS, InGaZnP/ZnSeS/ZnS, InGaZnP/ZnSe/ZnS, or combination of any of these, can be used preferably. Preferably, the semiconducting material does not comprise Cd, more preferably the semiconducting material of the shell comprises ZnS, ZnSe and/or ZnSeS.

In some embodiments of the present invention, said shell comprises group 12 and group 16 elements of the periodic table. Preferably the shell comprises InP, ZnS, ZnSe and/or ZnSeS, more preferably ZnS, ZnSe and/or ZnSeS, even more preferably ZnSeS and/or ZnS. Preferred embodiments regarding the shell are specified above and below. Especially preferred embodiments comprise an alloy shell of ZnSeS and/or a multilayer structure comprising layers of ZnS, ZnSe and/or ZnSeS.

According to a specific embodiment, the shell preferably comprises at least 10 % by weight, more preferably at least 20 % by weight, even more preferably at least 40 % by weight, even more preferably at least 60 % by weight and most preferably at least 80 % by weight ZnS based on the total weight of the shell. In a further embodiment, the shell preferably comprises at least 20 % by weight, more preferably at least 40 % by weight, even more preferably at least 60 % by weight, even more preferably at least 80 % by weight and most preferably at least 90 % by weight ZnS in a specific layer of the shell. According to a further embodiment, the shell preferably comprises at least 10 % by weight, more preferably at least 20 % by weight, even more preferably at least 40 % by weight, even more preferably at least 60 % by weight and most preferably at least 80 % by weight and most preferably at least 80 % by weight ZnSeS based on the total weight of the shell. In a further embodiment, the shell preferably comprises at least 20 % by weight, more preferably at least 40 % by weight, even more preferably at least 60 % by weight, even more preferably at least 80 % by weight and most preferably at least 90 % by weight ZnSeS in a specific layer of the shell. According to a further embodiment, the shell preferably comprises at least 10 % by weight, more preferably at least 20 % by weight, even more preferably at least 40 % by weight, even more preferably at least 60 % by weight and most preferably at least 80 % by weight ZnSe based on the total weight of the shell. In a further embodiment, the shell preferably comprises at least 20 % by weight, more preferably at least 40 % by weight, even more preferably at least 60 % by weight, even more preferably at least 80 % by weight and most preferably at least 90 % by weight ZnSe in a specific layer of the shell. Preferably the semiconducting nanosized material being obtainable by reacting the semiconducting nanosized material comprising at least three components with a third cation precursor according to the method of the present invention is purified before a shell of a semiconductor is grown onto the semiconducting nanosized material being obtained by reacting the semiconducting nanosized material comprising at least three components with a third cation precursor. Preferably, the purification is performed by adding a solvent to the mixture and preferably precipitating the semiconducting nanosized material being obtained by reacting the semiconducting nanosized material comprising at least three components with a third cation precursor as mentioned above and below. In an embodiment of the invention, the shell preferably has a thickness in the range of 0.3nm to 20nm, preferably 0.5 nm to 10nm, more preferably 1 to 5.0 nm, measured by taking images on a 120kV TEM and measuring the size, e.g. the diameter of the quantum material for a sample of more than 50 particles and provided as arithmetic mean (number average). The measurement is preferably performed using ImageJ software or the software mentioned below. Preferably, the shell thickness is calculated by subtracting the shelled particle thickness from the literature value of the MSCs e. g. 1.0 or 1 3nm and/or the particle being used for shelling.

Furthermore, the particle size of the shelled particles can be determined as mentioned above before shelling.

In some embodiments of the invention, the size of the overall structures of the quantum dots, is from 1 nm to 100 nm, more preferably, it is from 1.5 nm to 30 nm, even more preferably, it is from 2 nm to 10 nm, even more preferably, it is from 3 nm to 8 nm. The size is measured according to the method mentioned above and below (High Resolution Transmission Electron Microscopy; HRTEM) and is based on the arithmetic mean (number average). The starting material for a preparing a semiconducting nanosized material having a shell preferably comprises a ligand as mentioned above and below.

The preparation of the shell is preferably achieved using a solvent. The solvent is not specifically restricted. Preferably, the solvent is selected from aldehydes, alcohols, ketones, ethers, esters, amides, sulfur compounds, nitro compounds, phosphorus compounds, hydrocarbons, halogenated hydro-carbons (e.g. chlorinated hydrocarbons), aromatic or heteroaromatic hydrocarbons, halogenated aromatic or heteroaromatic hydrocarbons and/or (cyclic) siloxanes, preferably cyclic hydrocarbons, terpenes, epoxides, ketones, ethers and esters. Preferably a non-coordinating solvent is used.

Preferably, an alkane, more preferably a squalane is used as a solvent for achieving a shell. Preferably, an alkane having 6 to 46 carbon atoms, more preferably 8 to 40 carbon atoms, even more preferably 12 to 34 carbon atoms, most preferably 16 to 30 carbon atoms is used as a solvent. More preferably, the alkane being used as a solvent is a decane, dodecane, tetradecane, hexadecane, octadecane, eicosane. docosane, tetracosane, hexamethyltetracosane. The alkane may be linear or branched with branched alkanes such as squalane being preferred

In an embodiment of the present invention, the preparation of the shell is preferably achieved by a reaction mixture comprising a solvent and the solvent comprises at least one alkene, preferably an alkene having 6 to 36 carbon atoms, more preferably 8 to 30 carbon atoms, even more preferably 12 to 24 carbon atoms, most preferably 16 to 20 carbon atoms. More preferably, the alkene is a 1 -alkene, such as 1-decene, 1 -dodecene, 1 - Tetradecene, 1 -hexadecene, 1 -octadecene, 1-eicosene. 1 -docosene. The alkene may be linear or branched. In a further embodiment of the present invention, the preparation of the shell is preferably achieved by a reaction mixture comprising a solvent and the solvent comprises at least one phosphorus compound, such as phosphine compounds, preferably alkyl phosphine compounds having 3 to 108 carbon atoms, phosphine oxide compounds, preferably alkyl phosphine oxide having 3 to 108 carbon atoms and/or phosphonate compounds, more preferably an alkyl phosphonate compounds having 1 to 36 carbon atoms, preferably 6 to 30 carbon atoms, even more preferably 10 to 24 carbon atoms, most preferably 12 or 20 carbon atoms in the alkyl group.

Preferably, Trioctylphosphine (TOP) is used as a solvent for the preparation of a shell. Regarding the preparation step of the shell, alkenes, e. g. octadecene, and/or alkanes, e. g. squalane, are preferred in view of the other solvents mentioned above. In a further preferred embodiment, the solvent for the preparation of the shell comprises a mixture of an alkene and a phosphorus compound. In another preferred embodiment, the solvent for the

preparation of the shell comprises a mixture of an alkane and a phosphorus compound.

Preferably, the reaction mixture for the preparation of the shell comprises at least 10 % by weight of a solvent, more preferably at least 50 % by weight, even more preferably at least 70 % by weight, even more preferably at least 90 % by weight. The residual is provided by the further components of the reaction mixture as described above and below.

Preferably, the reaction mixture for the preparation of the shell comprises an amine, preferably the reaction mixture comprises from 1 % to 95 % by weight of an alkane and/or an alkene, more preferably from 10 % to 90 % by weight, even more preferably from 30 % to 85 % by weight. The residual is provided by the further components of the reaction mixture as described above and below.

Preferably, the preparation of the shell is achieved by a reaction mixture comprising a solvent and the solvent exhibits a boiling point of at least 150°C, preferably of at least 200°C, more preferably of at least 250°C, even more preferably of at least 300°C.

Preferably, the preparation of the shell is achieved at a temperature above 110 °C, preferably in the range of 110 to 500 °C, more preferably above 150 °C, even more preferably above 200°C and most preferably above 250°C. In an embodiment of the present invention, the preparation of the shell is preferably achieved at a temperature in the range of 120 to 450 °C, more preferably in the range of 150 to 400 °C, even more preferably in the range of 180 to 360 °C.

In a specific embodiment of the present invention, the shell is preferably prepared by mixing a first cation shell precursor and a semiconducting nanosized material obtainable by reacting a semiconducting nanosized material with a third cation precursor as mentioned above and below and heating up the obtained mixture and then adding a first anion shell precursor, preferably the first cation shell precursor comprises an element of group 12 of the periodic table and the first anion shell precursor comprises an element of group 16 of the periodic table. Preferably, the first cation shell precursor comprises Zn, and the first anion shell precursor comprises S and/or Se. In a further embodiment the first cation shell precursor comprises an element of group 13 of the periodic table and a the first anion shell precursor comprises an element of group 15 of the periodic table, preferably, first cation shell precursor comprises In, and the first anion shell precursor comprises P. Preferred embodiments regarding the first cation shell precursors and first anion shell precursor concerning the preparation of the shell are provided below.

In the embodiment wherein a mixture of a a first cation shell precursor and a semiconducting nanosized material obtainable by reacting a

semiconducting nanosized material with a third cation precursor as mentioned above and below is made and heated up, the mixture is preferably made and maintained at a temperature below 150°C, more preferably below 100°C, even more preferably below, 60°C. The heating of the mixture before adding the first anion shell precursor is preferably achieved at a high energy input. The addition of the first anion shell precursor is preferably achieved before the high reaction temperatures as mentioned above and below are achieved. Preferably, the first anion shell precursor is added to the reaction mixture at a temperature in the range of 60 °C to 140 °C, more preferably 70 °C to 120 °C and even more preferably at a range in the temperature of 80 °C to 100 °C.

In a further embodiment of the present invention, the shell is preferably prepared by mixing a first anion shell precursor and a semiconducting nanosized material obtainable by reacting a semiconducting nanosized material with a third cation precursor as mentioned above and below and heating up the obtainable mixture and then adding a first cation shell precursor, preferably the first cation shell precursor comprises an element of group 12 of the periodic table and the first anion shell precursor comprises an element of group 16 of the periodic table. Preferably, the first cation shell precursor comprises Zn, and the first anion shell precursor comprises S and/or Se, or the first cation shell precursor comprises an element of group 13 of the periodic table and the first anion shell precursor comprises an element of group 15 of the periodic table, preferably, the first cation shell precursor comprises In, and the first anion shell precursor comprises P. Preferred embodiments regarding the first cation shell precursors and first anion shell precursor concerning the preparation of the shell are provided below.

In the embodiment wherein a mixture of a a first anion shell precursor and a semiconducting nanosized material obtainable by reacting a

semiconducting nanosized material with a third cation precursor as mentioned above and below is made and heated up, the mixture is preferably made and maintained at a temperature below 150°C, more preferably below 100°C, even more preferably below, 60°C. The heating of the mixture before adding the first cation shell precursor is preferably achieved at a high energy input. The addition of the first cation shell precursor is preferably achieved before the high reaction temperatures as mentioned above and below are achieved. Preferably, the first cation shell precursor is added to the reaction mixture at a temperature in the range of 60 °C to 140 °C, more preferably 70 °C to 120 °C and even more preferably at a range in the temperature of 80 °C to 100 °C. In a further embodiment of the present invention, the shell is preferably prepared by mixing a first cation shell precursor, a first anion shell precursor and a semiconducting nanosized material obtainable by reacting a semiconducting nanosized material with a third cation precursor as mentioned above and below and heating up the obtainable mixture.

Preferably, the first cation shell precursor comprises an element of group 12 of the periodic table and the first anion shell precursor comprises an element of group 16 of the periodic table. Preferably, the first cation shell precursor comprises Zn, and the first anion shell precursor comprises S and/or Se, or the first cation shell precursor comprises an element of group 13 of the periodic table and the first anion shell precursor comprises an element of group 15 of the periodic table, preferably, the first cation shell precursor comprises In, and the first anion shell precursor comprises P. Preferred embodiments regarding the first cation shell precursors and first anion shell precursor concerning the preparation of the shell are provided below.

Preferably, the semiconductor precursor comprises a Zn compound and/or an In compound, preferably a Zn carboxylate, more preferably a zinc carboxylate having 2 to 30 carbon atoms, preferably 4 to 26 carbon atoms, even more preferably 8 to 22 carbon atoms, most preferably 10 to 18 carbon atoms, even more preferably a zinc carboxylate selected from the group consisting of Zn myristate, Zn palmitate, Zn laurate, Zn stearate, Zn oleate and/or an indium carboxylates, more preferably indium carboxylates having 2 to 30 carbon atoms, preferably 4 to 24 carbon atoms, even more preferably 8 to 20 carbon atoms, most preferably 10 to 18 carbon atoms even more preferably a indium carboxylate selected from the group consisting of In myristate, In palmitate, In laurate, In stearate, In oleate. Preferably, the semiconductor precursor comprises a S compound, preferably a sulfur solution, a sulfur suspension, a alkylthiol, e. g.

octanethiol, a alkylsilyl sulfur, and/or a alkylsilyl sulfur, e. g. bis(trimethyl silyl) sulfur, a Se compound, preferably a Se solution, Se suspension, alkylselenol, e. g. octaneselenol, and/or a alkylsilyl selenium, e. g.

bis(trimethyl silyl) selenium, and/or an P compound, preferably an alkylsilyl phosphine more preferably tris(trimethylsilyl)phosphine. Preferably a sulfur solution, more preferably a S solution comprising a phosphorus containing solvent, e.g. trioctylphosphine is used as a semiconductor precursor.

Preferably, a Se suspension comprising a hydrocarbon solvent, e.g. an 1 - alkene, such as 1 -octadecene and/or an organic phosphine compounds, preferably alkyl phosphine compounds having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms, even more preferably 1 to 4 carbon atoms, most preferably 1 or 2 carbon atoms in the alkyl groups or aryl phosphine compounds having 6 to 30 carbon atoms, preferably 6 to 18 carbon atoms, even more preferably 6 to 12 carbon atoms, most preferably 6 or 10 carbon atoms in the aryl groups is used as a semiconductor precursor.

Preferably, an organic phosphine compound as mentioned above regarding the InP precursor, e.g. tris(trimethylsilyl)phosphine and similar materials having an aryl, and/or alkyl group instead of the methyl unit, such as tris(triphenylsilyl)phosphine, tris(triethylsilyl)phosphine,

tris(diphenylmethylsilyl)phosphine, tris(phenyldimethylsilyl)phosphine, tris(triphenylsilyl)phosphine, tris(triethylsilyl)phosphine,

tris(diethylmethylsilyl)phosphine, tris(ethyldimethylsilyl)phosphine dissolved in an organic solvent, preferably octadecene or squalane is used as a semiconductor precursor. It can be provided that at least a first cation shell precursor and a first anion shell precursor, optionally in a solvent, are preferably used to form a shell layer onto the semiconducting nanosized material being reacted with a third cation precursor, wherein said first cation shell precursor is a salt of an element of the group 12 of the periodic table and the first anion shell precursor is a source of an element of the group 16 of the periodic table, more preferably said first cation shell precursor is selected from one or more member s of the group consisting of Zn-stearate, Zn-myristate, Zn- oleate, Zn-laurate, Zn-palmitate, Zn-acetylacetonate, Cd-stearate, Cd- myristate, Cd-oleate, Cd-laurate, Cd-palmitate, Cd-acetylacetonate a metal halogen represented by chemical formula (V) and a metal carboxylate represented by chemical formula (VI),

MX²n (V) wherein M is Zn²⁺, or Cd²⁺, preferably M is Zn²⁺, X² is a halogen selected from the group consisting of Cl , Br and I , n is 2,

[M(0₂CR¹) (0₂CR²)] - (VI) wherein M is Zn²⁺, or Cd²⁺, preferably M is Zn²⁺;

R¹ is a linear alkyl group having 1 to 30 carbon atoms, a branched alkyl group having 4 to 30 carbon atoms, a linear alkenyl group having 2 to 30 carbon atoms, or a branched alkenyl group having 4 to 30 carbon atoms, preferably R¹ is a linear alkyl group having 1 to 30 carbon atoms, or a linear alkenyl group having 2 to 30 carbon atoms, more preferably, R¹ is a linear alkyl group having 5 to 25 carbon atoms, or a linear alkenyl group having 6 to 25 carbon atoms, even more preferably R¹ is a linear alkyl group having 10 to 20 carbon atoms, or a linear alkenyl group having 10 to 20 carbon atoms, furthermore preferably R¹ is a linear alkenyl group having 10 to 20 carbon atoms, R² is a linear alkyl group having 1 to 30 carbon atoms, a branched alkyl group having 4 to 30 carbon atoms, a linear alkenyl group having 2 to 30 carbon atoms, or a branched alkenyl group having 4 to 30 carbon atoms, preferably R² is a linear alkyl group having 1 to 30 carbon atoms, or a linear alkenyl group having 2 to 30 carbon atoms, more preferably R² is a linear alkyl group having 5 to 25 carbon atoms, or a linear alkenyl group having 6 to 25 carbon atoms, even more preferably R² is a linear alkyl group having 10 to 20 carbon atoms, or a linear alkenyl group having 10 to 20 carbon atoms, furthermore preferably R² is a linear alkenyl group having 10 to 20 carbon atoms, and preferably said anion shell precursor is selected from one or more members of the group consisting of Trioctylphosphine : Se,

Tributylphosphine : Se, Trioctylphosphine : S, Tributylphosphine : S, and thiols.

Preferably, the molar ratio of total shell precursors used in the shelling step and total semiconducting material being shelled and used in the shelling step is 6 or more, preferably in the range from 7 to 30, more preferably from 8 to 30, even more preferably from 9 to 27.

Furthermore, it can be provided said first anion shell precursor and a second anion shell precursor are added sequentially in in the shelling step.

Preferably, said first anion shell precursor is Trioctylphosphine : Se, or Tributylphosphine : Se, and the second anion shell precursor is

Trioctylphosphine : S, Tributylphosphine : S, or a thiol. Preferably, the shelling step is carried out at the temperature in the range from 150°C to 350°C, preferably in the range from 160°C to 340 °C, more preferably in the range from 170°C to 330°C, even more preferably from 180°C to 320°C.

In another embodiment, the semiconducting nanosized material comprising a high optical density being preferably prepared by a reaction mixture comprising a carboxylate compound in a first reaction step A) is reacted with a semiconductor precursor in a second reaction step B).

Preferably, the carboxylate compound being used in the first reaction step A) has 2 to 30 carbon atoms, preferably 4 to 26 carbon atoms, even more preferably 8 to 22 carbon atoms, most preferably 10 to 18 carbon atoms. More preferably, the carboxylate compound being used in the first reaction step A) is a saturated carboxylate compound. The carboxylate compound could be added to the reaction mixture as a free acid or as a salt.

Preferably, the carboxylate compound is added as a precursor, preferably an indium precursor wherein preferred indium precursors are disclosed above and below.

According to a further embodiment, the second reaction step B) is performed by heating up a composition comprising a first cation shell precursor, preferably Zn compound and/or an In compound, to a

temperature above 50°C, preferably above 90°C and a composition comprising the reaction product from the first reaction step A) and a first anion shell precursor, preferably a S and/or a Se and/or a P compound are injected into the composition comprising a first cation shell precursor. Preferably, the second reaction step B) is performed by heating up a composition comprising a first cation shell precursor, preferably Zn compound and/or an In compound, to a temperature in the range of 50°C to 400 °C, and a composition comprising the reaction product from the first reaction step A) and a first anion shell precursor, preferably a S and/or a Se and/or a P compound are injected into the composition comprising a first precursor.

The composition comprising the reaction product from the first reaction step A) and a first anion shell precursor, preferably a S and/or a Se and/or a P is preferably kept to a temperature below 120°C, more preferably below 100°C, before mixing.

According to another embodiment, the second reaction step B) is performed by heating up a composition comprising the reaction product from the first reaction step A) and a first cation shell precursor, preferably Zn compound and/or an In compound, to a temperature above 50°C, preferably above 70°C, more preferably above 80 °C and a composition comprising a first anion shell precursor, preferably a S and/or a Se and/or a P compound, is injected into the composition comprising a first cation shell precursor. The heating of the composition comprising the reaction product from the first reaction step A), a first cation shell precursor and a first anion shell precursor is heated thereafter to the reaction temperatures as mentioned above and below. Preferably, the heating of the composition comprising the reaction product from the first reaction step A) and a first cation shell precursor starts at a temperature below 50°C, more preferably below 40°C. The temperature of the composition comprising a first anion shell precursor is preferably below 50°C, more preferably below 40°C before injection. In a preferred embodiment, the injection of the composition comprising a first anion shell precursor to the composition comprising the reaction product from the first reaction step A) and a first cation shell precursor is preferably achieved at a temperature in the range of 60 °C to 140 °C, more preferably 70 °C to 120 °C and even more preferably at a range in the temperature of 80 °C to 100 °C. The composition comprising the reaction product from the first reaction step A), a first cation shell precursor and a first anion shell precursor is heated thereafter to the reaction temperatures as mentioned above and below, preferably above 150°C, more preferably above 200°C and even more preferably above 250°C.

According to another embodiment, the second reaction step B) is performed by heating up a composition comprising a first anion shell precursor, preferably a S and/or a Se and/or a P compound, to a

temperature above 200°C, preferably above 250°C and a composition comprising the reaction product from the first reaction step A) and a first cation shell, preferably Zn compound and/or an In compound, is injected into the composition comprising a second precursor.

temperature in the range of 200°C to 400°C, more preferably to a temperature in the range of 250°C to 350°C and a composition comprising the reaction product from the first reaction step A) and a first cation shell, preferably Zn compound and/or an In compound, is injected into the composition comprising a second precursor.

The composition comprising the reaction product from the first reaction step A) and a first cation shell, preferably Zn compound and/or an In compound, is preferably kept to a temperature below 120°C, more preferably below 100°C, before mixing.

According to another embodiment, the second reaction step B) is performed by heating up a composition comprising a first cation shell, preferably Zn compound and/or an In compound, a first anion shell precursor, preferably a S and/or a Se and/or a P compound, and reaction product from the first reaction step A) to a temperature above 50°C, preferably above 90°C, more preferably to a temperature in the range of 50°C to 450 °C, more preferably in the range of 200 to 400 °C. Preferably, a composition comprising a first cation shell precursor, preferably Zn compound and/or an In compound, is added to the reaction mixture for performing the second reaction step B). Preferably, a composition comprising a first anion shell precursor, preferably a S and/or a Se and/or a P compound, is added to the reaction mixture for performing the second reaction step B). In this embodiment, the first cation shell precursor and first anion shell precursor is additionally added to the composition comprising a first precursor, preferably Zn compound and/or an In compound, a first anion shell precursor, preferably a S and/or a Se and/or a P compound, and reaction product from the first reaction step A) in multiple portions. The addition of first cation shell precursor and/or first anion shell precursor to a reaction mixture for achieving a shell layer provides astonishing

improvements concerning the shell thickness without imparting a high FWHM value (broad particle size distribution). In addition thereto, the addition of first cation shell precursor and/or first anion shell precursor provides the opportunity to achieve a multi-layer shell having different compositions such as ZnSe/ZnS, ZnSeS/ZnS, ZnS/ZnSe and/or

ZnS/ZnSeS multi-layer structure. Furthermore, two layers comprising different ZnSeS composition can be achieved.

The reaction product of the first reaction step A) can be purified before performing the second reaction step B) for preparing a shell. Preferred embodiments regarding the purification, especially the adding of a solvent and the precipitation are provided above and added by reference thereto.

In another aspect, the present invention also relates to a method for preparing quantum dots comprising a core / shell structure, wherein the method comprises following steps (a), (b) and (c) in this sequence.

(a) synthesis of a core in a solution (b) removing the extra ligands from the core

(c) coating the core with at least one shell layer using said solution obtained in step (b).

In some embodiments of the present invention, the surface of the quantum dots can be over coated with one or more kinds of surface ligands.

Without wishing to be bound by theory it is believed that such a surface ligands may lead to disperse the nanosized material in a solvent more easily. In addition, the surface ligand may improve the features of the quantum dots such as efficiency, quantum yield, wavelength of the peak maximum and full width half maximum (FWHM).

According to a specific embodiment of the method of the present invention, the semiconducting nanosized material being obtained by reacting the semiconducting nanosized material comprising at least three components with a third cation precursor being used as starting material for the shelling reaction preferably comprises a ligand, preferably a carboxylate ligand, more preferably a carboxylate ligand having 2 to 30 carbon atoms, preferably 4 to 26 carbon atoms, even more preferably 8 to 22 carbon atoms, most preferably 10 to 18 carbon atoms, even more preferably a carboxylate ligand selected from the group consisting of myristate, palmitate, laurate, stearate, oleate.

In a specific embodiment of the present invention, the semiconducting nanosized material comprising at least three components and/or any nanosized material being produced or used to obtain the semiconducting nanosized material can be purified. This purification can be done as intermediate step or to obtain a purified quantum dots according to the present invention. According to a special embodiment, the purification can be achieved by dispersing 0.1 to 10 equivalents of the crude solution in 1 equivalent of a solvent (by volume), preferably a hydrocarbon solvent, e. g. toluene, hexane, pentane or chloroform. Then, 0.5 to 20 equivalents (by volume) of a cleaning solution such as a ketone, alcohol, preferably acetone, methanol, ethanol or propanol, more preferably an alcohol, e. g. ethanol is preferably added to the composition. The resultant suspension is preferably centrifuged for a time and at a speed sufficient for a useful precipitation.

E.g. good results are achieved with 5 min at a speed of 5000 rpm.

In some embodiments of the present invention, the cleaning solution comprises one compound selected from one or more members of the group consisting of ketones, such as, methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols, such as, methanol, ethanol, propanol, butanol, hexanol, cyclo hexanol, ethylene glycol; and pentane; halogenated hydrocarbons, such as chloroform;

xylene and toluene.

In a preferred embodiment of the present invention, the cleaning solution comprises three parts the crude solution with the QDs, the solvent and the anti-solvent. The solvent is typically a non-polar compound preferably an alkane or a benzene derivative such as toluene or a halogenated hydrocarbon, more preferably toluene, chloroform, hexane and pentane. The anti-solvent is typically a polar compound such as an alcohol, ester or nitrogen containing compound, preferably methanol, ethanol, isopropanol, butanol, ethyl acetate and acetonitrile. The ratios of the crude, solvent and anti-solvent are in the ranges of 2.5:2.5:1 to 1 :20:80.

In a preferred embodiment of the present invention, the cleaning solution comprises one or more of ketones to more effectively remove unreacted core precursors from the composition comprising a particulate material as mentioned above or any other reaction composition and remove e. g. the ligands leftovers.

More preferably, the cleaning solution contains one or more of ketones selected from the group consisting of methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone, and cyclohexanone, and one more solvent selected from halogenated hydrocarbons, preferably chloroform, acetonitrile, ethyl acetate, xylene or toluene to remove unreacted core precursors from the composition comprising a particulate material as mentioned above or any other reaction composition and remove e. g. the ligands leftovers in the solution effectively.

Preferably, the cleaning solution contains one or more of ketones selected from methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone, and cyclohexanone, and chloroform.

In a preferred embodiment, a filtration step is performed before a cleaning solution is added. More preferably, the cleaning solution contains one or more of alcohols selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol and cyclohexanol, and one more solvent selected from

hydrocarbons, preferably aromatic hydrocarbons, e. g. toluene to remove unreacted core precursors from the composition comprising a particulate material as mentioned above or any other reaction composition and remove e. g. the ligands leftovers in the solution effectively. The mixing ratio is preferably in the ranges as provided above.

More preferably, the cleaning removes the extra ligands and the unreacted precursor. ln another aspect, the present invention further relates to the use of the semiconducting nanosized material comprising high optical density, preferably the quantum dots (QD) of the present invention, the composition of the present invention or the formulation of the present invention in an electronic device, optical device or in a biomedical device.

A further subject matter of the present invention is the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) being obtainable by a method of the present invention as described above and below.

Thus, the present invention provides a semiconducting nanosized material, wherein the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 0.6, preferably at least 0.9, more preferably at least 1.0.

Preferably, the semiconducting light emitting nanosized material is essentially free of lead (Pb), more preferably said ssemiconducting light emitting nanosized material comprises InP. The expression“essentially free of lead” means that the particles do not comprise essential amounts of Pb, more preferably the particles comprise less than 500 ppm, more preferably less than 100 ppm, even more preferably less than 10 ppm and even more preferably less than 5 ppm Pb.

Preferably, the semiconducting light emitting nanosized material is essentially free of cadmium (Cd). The expression“essentially free of cadmium” means that the particles do not comprise essential amounts of Cd, more preferably the particles comprise less than 500 ppm, more preferably less than 100 ppm, even more preferably less than 10 ppm and even more preferably less than 5 ppm Cd. Preferably the semiconducting light emitting nanosized material of the present invention, preferably the quantum dots exhibit a triangular shape. Semiconducting light emitting nanosized material of the present invention, preferably the quantum dots exhibiting a triangular shape provide

astonishing improvements in optical density. Particles exhibiting a triangular shape have low full width half maximum (FWHM), very high optical density and/or high quantum yield (QY). In a preferred embodiment wherein the semiconducting nanosized material exhibiting a triangular shape, the FWHM is preferably at most 60 nm, more preferably of at most 50 nm and/or the particles show emission and preferably comprise a quantum yield (QY) of at least 2 %, more preferably at least 10 % and even more preferably at least 20 %. Particles exhibiting a triangular shape have a surface with triangular shaped segments. In a preferred embodiment, the length of the three edges are in a similar range. That is, preferably the ratio of the longest edge to the shortest edge is 10:1 or smaller, preferably 5:1 or smaller, more preferably 2:1 and even more preferably 3:2 or smaller.

Preferably, the particles exhibiting a triangular shape have a pyramidal shape. The pyramid may be skew or regular, preferably the pyramid is essentially regular such that the pyramid has a high symmetry. Preferably the edges of the triangles have essentially the same length as mentioned above. The base of the pyramid is preferably triangle (tetrahedron), square, pentagonal, hexagonal, more preferably triangle or square. The edge of the triangular shaped segments are preferably in the range of 0.5 to 10 nm, more preferably 1 to 8 nm and even more preferably 2 to 6 nm.

Semiconducting light emitting nanosized material of the present invention, preferably the quantum dots exhibiting a triangular shape are preferably achieved by using the methods and materials as herein disclosed in more detail. Especially the selection of the ligands, the solvents, the temperature profile and/or the use of single source precursors provide particles having a triangular shape. The Examples provide hints in more detail. Figure 1 shows a TEM image of the particles as being obtained according to the Examples. A higher magnification of the TEM image is provided in Figure 2. The evaluation of the images is preferably achieved by using Fiji-lmageJ program using appropriate parameters for defining noise and setting the resolution of the measurement (e.g. set watershed for irregular structures; segmentation: circular window radius about 30 [pixels], rolling ball radius about 200 [pixels], minimum OTB intensity difference 8bit about 20; shape constraints: minimal area about 30 [pixels²], minimal feret min [pixels]). Furthermore, the program ImageJ provides a table comprising the calculated parameters including a theoretical diameter of a hypothetical circle surrounding the shape being accepted as a particle. Using this theoretical diameter supports the calculation of the edges as mentioned above and provides appropriate arithmetic mean (number average) values.

Preferably, the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 1.4, preferably at least 1.6, more preferably at least 1.7 based on inorganics. The Optical density per mg based on inorganics can be achieved as mentioned in the Examples.

Preferably, the semiconducting nanosized material comprising high performance, preferably quantum dots (QD) preferably have a relative quantum yield of at least 20%, more preferably at least 35% and even more preferably at least 50%. The relative quantum yield can be measured by calculating the ratio of the emission counts of the QD and useful dye. The type of the dye depends on the emission of the QD as shown above and below.

According to a preferred embodiment, the semiconducting nanosized material comprising high optical density, preferably the quantum dots may comprise a core / shell structure. Consequently, the QD may comprise a shell of a semiconductor. Quantum dots (QD) are well known in the art as described above.

Conventionally QD are a nanosized light emitting semiconductor material. According to the present invention, the term“nanosized” means the size in between 0,1 nm and 999 nm.

Thus, according to the present invention, the term ^"a nanosized light emitting semiconductor material^" is taken to mean that the light emitting material which size of the overall diameter is in the range from 0.5 nm to 999 nm. And in case of the material has elongated shape, the length of the overall structures of the light emitting material is in the range from 0.5 nm to 999 nm.

According to the present invention, the term“nano sized” means the size of the semiconductor material itself without ligands or another surface modification, which can show the quantum size effect.

According to the present invention, a type of shape of the core of the nanosized light emitting material, and shape of the nanosized light emitting material to be synthesized are not particularly limited.

For examples, spherical shaped, elongated shaped, star shaped, polyhedron shaped, pyramidal shaped, tetrapod shaped, tetrahedron shaped, platelet shaped, cone shaped, and irregular shaped nanosized light emitting materials can be synthesized.

Preferably the semiconducting light emitting nanosized material of the present invention, preferably the quantum dots exhibit a triangular shape. Semiconducting light emitting nanosized material of the present invention, preferably the quantum dots exhibiting a triangular shape provide

Preferably, the particles exhibiting a triangular shape have a pyramidal shape. The pyramid may be skew or regular, preferably the pyramid is essentially regular such that the pyramid has a high symmetry. Preferably the edges of the triangles have essentially the same length as mentioned above. The base of the pyramid is preferably triangle (tetrahedron), square, pentagonal, hexagonal, more preferably triangle or square. The edge of the triangular shaped segments are preferably in the range of 0.5 to 10 nm, more preferably 1 to 8 nm and even more preferably 2 to 6 nm. The size is measured according to the method mentioned above and below

(Transmission Electron Microscopy; TEM) and is based on the arithmetic mean (number average) considering that the edges are two-dimensional data of a three-dimensional particle.

In some embodiments of the present invention, the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) preferably have a relative quantum yield of at least 20%, more preferably at least 35% and even more preferably at least 50% measured by calculating the ratio of the emission counts of the QD and the dye coumarin 153 (CAS 53518-18-6) and multiplying by the QY of the dye (54.4%) measured at 25°C.

In some embodiments of the present invention, the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) preferably have a relative quantum yield of at most 90 %, more preferably at most 85 %, even more preferably at most 75 % and even more preferably at most 70 % measured by calculating the ratio of the emission counts of the QD and the dye coumarin 153 (CAS 53518-18-6) and multiplying by the QY of the dye (54.4%) measured at 25°C.

In specific embodiments of the present invention, the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) preferably have a relative quantum yield in the range of 5 % to 90 %, more preferably in the range of 15 to 85 %, even more preferably in the range of 30 to 80 % and even more preferably in the range of 40 to 70 % measured by calculating the ratio of the emission counts of the QD and the dye coumarin 153 (CAS 53518-18-6) and multiplying by the QY of the dye (55%) measured at 25°C.

The relative quantum yield is preferably calculated using absorbance and emission spectrum (excited at 350 nm), obtained using Shimadzu UV-1800 and Jasco FP-8300 spectrophotometer, using the following formula, with coumarin 153 dye in ethanol is used as a reference, with a quantum yield of 55%

wherein the symbols have the following meaning

QY = Quantum Yield of the sample

QY _ref = Quantum Yield of the reference/standard

n = the refractive index of the sample solvent (especially ethanol) n_ref = the refractive index of the reference/standard

I = the integral of the sample emission intensity as measured on the

Jasco. Calculated as Jl dv with I intensity, v =wavelength.

A = is the percentage absorbance of the sample. The percentage of the sampling light that the sample absorbs.

I _ref = the integral of the reference emission intensity as measured on the Jasco. Calculated as Jl dv with I intensity, v =wavelength. A_ref = is the percentage absorbance of the reference. The

percentage of the sampling light that the reference absorbs.

The absorbance and emission spectrum is achieved at a temperature of about 25°C.

In some embodiments of the present invention, the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) preferably have a relative quantum yield of at least 20%, more preferably at least 35% and even more preferably at least 50% measured by calculating the ratio of the emission counts of the QD and the dye DCM (CAS 51325-91-8) and multiplying by the QY of the dye (43.5%) measured at 25°C. In some embodiments of the present invention, the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) preferably have a relative quantum yield of at most 90 %, more preferably at most 85 %, even more preferably at most 75 % and even more preferably at most 70 % measured by calculating the ratio of the emission counts of the QD and the dye DCM (CAS 51325-91 -8) and multiplying by the QY of the dye (43.5%) measured at 25°C.

In specific embodiments of the present invention, the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) preferably have a relative quantum yield in the range of 5 % to 90 %, more preferably in the range of 15 to 85 %, even more preferably in the range of 30 to 80 % and even more preferably in the range of 40 to 70 % measured by calculating the ratio of the emission counts of the QD and the dye DCM (CAS 51325-91-8) and multiplying by the QY of the dye (43.5%) measured at 25°C.

In some embodiments of the present invention, the semiconducting nanosized material comprising high performance, preferably quantum dots (QD) preferably have a relative quantum yield of at least 20%, more preferably at least 35% and even more preferably at least 50% measured by calculating the ratio of the emission counts of the QD and the dye coumarin 450 (CAS: 26078-25-1 ) and multiplying by the QY of the dye (65%) measured at 25°C, preferably in cyclohexane. In some embodiments of the present invention, the semiconducting nanosized material comprising high performance, preferably quantum dots (QD) preferably have a relative quantum yield of at most 90 %, more preferably at most 85 %, even more preferably at most 75 % and even more preferably at most 70 % measured by calculating the ratio of the emission counts of the QD and the dye coumarin 450 (CAS: 26078-25-1 ) and multiplying by the QY of the dye (65%) measured at 25°C, preferably in cyclohexane.

In specific embodiments of the present invention, the semiconducting nanosized material comprising high performance, preferably quantum dots (QD) preferably have a relative quantum yield in the range of 5 % to 90 %, more preferably in the range of 15 to 85 %, even more preferably in the range of 30 to 80 % and even more preferably in the range of 40 to 70 % measured by calculating the ratio of the emission counts of the QD and the dye coumarin 450 (CAS: 26078-25-1 ) and multiplying by the QY of the dye (65%) measured at 25°C, preferably in cyclohexane.

Further details for measuring the QY are provided above concerning the dyes, e.g. coumarin 153 dye, DCM dye and coumarin 450 dye. The coumarin 153 dye is preferably used for green particles preferably having a peak maximum in the photoluminescence spectrum at a wavelength in the range of 500 nm to 580 nm as disclosed in more detail below. The DCM dye (4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran; CAS 51325-91 -8) is preferably used for red particles preferably having a peak maximum in the photoluminescence spectrum at a wavelength in the range of above 580 nm, preferably in the range above 580 nm to 700 nm as disclosed in more detail below. The coumarin 450 dye is preferably used for blue particles preferably having a peak maximum in the photoluminescence spectrum at a wavelength below 500 nm as disclosed in more detail below.

In a specific embodiment, the semiconducting nanosized material comprising high optical density, preferably quantum dots (QD) has a full width half maximum (FWHM) of at most 80 nm, preferably of at most 60 nm measured at 25° using a toluene solution, preferably a full width half maximum (FWHM) in the range of 30 to 50 nm, more preferable 30 to 45nm most preferably 35 to 45nm at 25° using a toluene solution.

Preferably, the semiconducting light emitting nanosized material, preferably quantum dots (QD) exhibit a peak maximum in the photoluminescence spectrum at a wavelength above 500 nm.

In an embodiment of the present invention the semiconducting light emitting nanosized material preferably exhibits a peak maximum in the

photoluminescence spectrum at a wavelength in the range of 520 nm to 600 nm.

In a further embodiment of the present invention the semiconducting light emitting nanosized material preferably exhibits a peak maximum in the photoluminescence spectrum at a wavelength in the range of 610 nm to 800 nm.

In a preferred embodiment, the semiconducting nanosized material comprising high optical density, preferably the quantum dots (QD) preferably exhibit a peak maximum in the photoluminescence spectrum at a wavelength in the range of 402 to 600 nm and a full width half maximum (FWHM) in the range of 10 nm to 80 nm, preferably in the range of 25 nm to 70, more preferably in the range of 30 nm to 60 nm, even more preferably in the range of 35nm to 55nm measured at 25°C using a toluene solution.

Preferably, the determination of the full width half maximum (FWHM) is made with an appropriate data base preferably comprising at least 10, more preferably at least 20 and even more preferably at least 50 data points. The determination is preferably performed by using LabVIEW Software

(LabVIEW 2017; May 2017) with the following Vis (Virtual Instrument): 1. 'Peak detector' for finding center wavelength and y-value (counts).

The following parameters are preferably used: width: 10, threshold: maximum value of input data divided by 5.

2. Dividing the counts (y-value) at the center wavelength value (see item 1 ) by 2 giving the y-value for the half-width of the peak. The two points having this half-width y-value are found and the difference between their two wavelength values are taken to give the FWHM parameter.

In a very preferred embodiment, the semiconducting nanosized material comprising high optical density, preferably the QD preferably exhibit a peak maximum in the photoluminescence spectrum at a wavelength above 400 nm and a full width half maximum (FWHM) in the range of 10 nm to 80 nm, preferably in the range of 25 nm to 70, more preferably in the range of 30 nm to 60 nm, even more preferably in the range of 40nm to 55nm

measured at 25°C using a toluene solution.

Preferably, the data concerning the peak maximum in the

photoluminescence is obtained using a toluene solution of quantum material with an optical density (OD) of 0.09 at the excitation wavelength of 350nm on a JASCO spectrofluorometer. The FWHM of full-width-half- maximum is the width of the exciton peak measured at half the maximum emission counts.

Preferably, the semiconducting nanosized material comprising high optical density, preferably QD exhibit a ratio of the peak maximum to the peak minimum in the absorption spectrum of at least 1.0, more preferably at least 1.25, even more preferably of at least 1.5 and even more preferably of at least 1.7 measured at 25°C using a toluene solution having an optical density (OD) of 0.09. The ratio of the peak maximum to the peak minimum is the ratio of the OD of the first exciton peak and the trough on the lower wavelength side of that peak. Preferably, the ratio of the peak maximum to the peak minimum in the absorption spectrum is related to the first exciton peak.

Preferably, the peak maximum of the semiconducting nanosized material comprising high optical density, preferably QD in the absorption spectrum is at a wavelength above 385 nm, more preferably above 390 nm. Preferably, the QD exhibit an Exciton peak maximum in the absorption spectrum at a wavelength in the range of 400 to 650 nm, more preferably in the range of 410 to 600nm, in the absorption spectrum measured at 25° using a toluene solution.

Preferably, the semiconducting nanosized material comprising high optical density, preferably the QD are based on indium zinc phosphide (InZnP). Therefore, the present QD preferably comprise a measurable amount of InZnP. Preferably, the QD comprise a centre area of InZnP. More preferably, the centre area of the semiconducting nanosized material comprising high optical density, preferably of InZnP comprises a size, e.g. a diameter in the range of 0.8 to 6.0 nm, preferably 1.0 nm to 5.0 nm, more preferably 2.0 to 4.0 nm. The size of the particles can be obtained by methods well known in the art. The particle size distribution is preferably assessed with Gatan Digital Micrograph software using images obtained from High Resolution Transmission Electron Microscopy (HRTEM) and provided as arithmetic mean (number average). The sample preparation for performing the HRTEM can be performed by any conventional method. Preferably, the sample is purified before the measurement. E.g. 0.05 ml of the crude sample is dissolved with 0.2ml toluene and precipitated with 0.2-0.4ml ethanol using centrifuge. The solid is re-dissolved with 1 -2ml toluene. Few drops are deposited on Cu/C TEM grid. The grid is dried in vacuum at 80°C for 1 5h to remove the residues of the solvent as well as possible organic residues. HRTEM and/or other TEM measurements are preferably carried out on a Tecnai F20 G2 machine equipped with EDAX Energy Dispersive X-Ray Spectrometer. In an embodiment of the present invention, the core of the semiconducting light emitting nanosized material according to the invention comprises InGaP and the molar ratio of In to Ga is in the range of 0.1 to 10.

In an embodiment of the present invention, the semiconducting light emitting nanosized material comprises a core and a shell and the volume ratio of the core to the shell is in the range of 0.1 to 10. This data preferably applies to particles having a core of InP, InZnP, InGaP or InGaZnP and a shell of ZnS, ZnSe, ZnSeS and/or ZnS/ZnSe. In a further embodiment of the present invention, the semiconducting light emitting nanosized material preferably comprises a core, a first

intermediate layer and at least one outer shell.

Preferably, the core comprises InP or InZnP and the first intermediate layer comprises GaP, InZnP, InGaP or InZnGaP.

In a specific embodiment, the core preferably comprises InP and the first intermediate layer comprises GaP, InZnP, InGaP or InZnGaP. In a preferred embodiment, the core preferably comprises InP and the first intermediate layer preferably comprises GaP wherein the Ga to In ratio is below 100. Preferably the Ga to In ratio is above 0.1 , preferably above 0.5. These values concern the whole amount of In and Ga in the

Semiconducting light emitting nanosized material.

In a preferred embodiment, the core preferably comprises InP and the first intermediate layer preferably comprises InZnP wherein the Zn to In ratio in the core is below 1 , preferably below 0.5 and more preferably below 0.1. Preferably the Zn to In ratio in the intermediate layer is above 0.1 , preferably above 0.2 and more preferably above 0.3. Preferably, the In to Zn ratio in the intermediate layer is below 2, preferably below 1 and more preferably below 0.4.

In a specific embodiment, the core preferably comprises InZnP and the first intermediate layer comprises GaP, InGaP or InZnGaP. Preferably, the Zn to In ratio in the core is below 10, preferably below 2 and GaP the In to Ga ratio of the first intermediate layer is below 10, preferably below 5 and more preferably below 2.

It can be provided that the volume ratio of the core to the first intermediate layer is in the range of 0.1 to 1 , preferably in the range of 0.2 to 0.8.

In a further embodiment of the present invention, the semiconducting light emitting nanosized material preferably comprises a core, a first

intermediate layer, a second intermediate and at least one outer shell. Preferably, the core comprises InP and the first intermediate layer comprises InZnP and the second intermediate layer comprises GaP, InGaP or InZnGaP.

In an embodiment of the invention, the core of the semiconducting light emitting nanosized material comprises a size, e.g. a diameter in the range of 0.8 to 6.0 nm, preferably 1.0 nm to 5.0 nm, more preferably 2.0 to 4.0 nm.

In an embodiment of the invention, the shell preferably has a thickness in the range of 0.3nm to 20nm, preferably 0.5 nm to 10nm, more preferably 1 to 5.0 nm, measured by taking images on a 120kV TEM and measuring the size, e.g. the diameter of the quantum material for a sample of more than 50 particles and provided as arithmetic mean (number average). The measurement is preferably performed using ImageJ software or the software mentioned below. Preferably, the shell thickness is calculated by subtracting the shelled particle thickness from the literature value of the MSCs e. g. 1.0 or 1 3nm and/or the particle being used for shelling.

In some embodiments of the invention, the size of the overall structures of the quantum dots, is from 1 nm to 100 nm, more preferably, it is from 1.5 nm to 30 nm, even more preferably, it is from 2 nm to 10 nm, even more preferably, it is from 3 nm to 8 nm. The size is measured according to the method mentioned above and below (High Resolution Transmission Electron Microscopy; HRTEM) and is based on the arithmetic mean

(number average) considering that the edges are two-dimensional data of a three-dimensional particle.

According to an embodiment of the present invention, said semiconducting light emitting nanoparticle preferably comprising a core and at least one shell layer, wherein the semiconducting light emitting nanoparticle preferably has the self-absorption value 0.6 or less, preferably, in the range from 0.60 to 0.1 , more preferably, from 0. 55 to 0.15, even more preferably, from 0.50 to 0.2. The Self-absorption value is calculated preferably according to the following procedure:

According to the present invention, the optical density (hereafter ^"OD^") of the semiconducting nanosized materials is preferably measured using Shimadzu UV-1800, double beam spectrophotometer, using toluene baseline, in the range between 350 and 750 nm. The photoluminescence spectra (hereafter ^"PL^”) of the semiconducting nanosized materials is preferably measured using Jasco FP fluorimeter, in the range between 460 and 850 nm, using 450 nm excitation. The OD(A) and PL (A) are the measured optical density and the photoluminescence at wavelength of A.

ODi represented by the formula (I) is the optical density normalized to the optical density at 450 nm, and ai represented by formula (II) is the absorption corresponding to the normalized optical density.

on, = OD(A)

OD(_/ 1 450 nm)

(I)

-Oi

a_{ = 1 10 (II)

The self-absorption value of the semiconducting nanosized materials represented by formula (III) is preferably calculated based on the OD and PL measurement raw data.

It is believed that lower-self absorbance of the semiconducting nanosized materials is expected to prevent the QY decrease in high emitter

concentrations.

Preferably, the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 0.6, preferably at least 0.9, more preferably at least 1.0. The Optical density per mg can be achieved as mentioned in the Examples. Preferably, the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 1.4, preferably at least 1.6, more preferably at least 1.7 based on inorganics. The Optical density per mg based on inorganics can be achieved as mentioned in the Examples.

In another aspect, the present invention further relates to a composition comprising or consisting of at least one semiconducting nanosized material of the present invention comprising high optical density, preferably the QD of the present invention, preferably semiconducting light emitting

nanoparticle of the present invention and at least one additional material, preferably the additional material is selected from the group consisting of organic light emitting materials, inorganic light emitting materials, charge transporting materials, scattering particles, host materials, nanosized plasmonic particles, photo initiators, and matrix materials.

Preferably, said composition comprises a plurality of semiconducting nanosized materials of the present invention.

A further embodiment of the present invention is a formulation comprising or consisting of at least one semiconducting nanosized material of the present invention comprising high optical density, preferably the QD of the present invention, and at least one solvent. Preferred solvents are mentioned above and below. Preferably, the solvent is selected from one or more members of the group consisting of aromatic, halogenated and aliphatic hydrocarbon solvents, more preferably selected from one or more members of the group consisting of toluene, xylene, ethers,

tetrahydrofuran, chloroform, dichloromethane and heptane, purified water, ester acetates, alcohols, sulfoxides, formamides, nitrides, ketones. Preferably, said formulation comprises a plurality of semiconducting nanosized materials of the present invention. Preferably, the semiconducting nanosized material comprising high optical density have properties of a semiconducting light emitting nanoparticle.

- Optical medium

In another aspect, the present invention further relates to an optical medium comprising at least one semiconducting nanosized material of the present invention, a composition according to the present invention or a

combination of any of these. Preferably, the optical medium comprises an anode and a cathode, and at least one organic layer comprising at least one semiconducting nanosized material according to the present invention, or at least one composition according to the present invention or a combination of any of these, preferably said one organic layer is a light emission layer, more preferably the medium further comprises one or more layers selected from the group consisting of hole injection layers, hole transporting layers, electron blocking layers, hole blocking layers, electron blocking layers, and electron injection layers.

Preferably, the optical medium comprises at least one organic layer wherein said the organic layer comprises at least one semiconducting light emitting nanosized material according to the present invention, and a host material, preferably the host material is an organic host material.

Preferably, said optical medium comprises a plurality of semiconducting nanosized materials of the present invention.

In some embodiments of the present invention, the optical medium can be an optical sheet, for example, a color filter, color conversion film, remote phosphor tape, or another film or filter.

According to the present invention, the term ^"sheet^” includes film and / or layer like structured mediums. - Optical device

In another aspect, the invention further relates to an optical device comprising at least one optical medium of the present invention. in some embodiments of the present invention, the optical device can be a liquid crystal display device (LCD), Organic Light Emitting Diode (OLED), backlight unit for an optical display, Light Emitting Diode device (LED),

Micro Electro Mechanical Systems (here in after“MEMS”), electro wetting display, or an electrophoretic display, a lighting device, and / or a solar cell.

Preferable embodiments

According to the present invention, surprisingly, the inventors have found that a semiconducting nanosized material comprising with all the features of following preferable embodiment 1 solves one or more of the problems mentioned above.

Embodiment 1. Semiconducting light emitting nanosized material, wherein the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 0.6, preferably at least 0.9, more preferably at least 1.0.

Further preferable embodiments are discloses hereafter.

Embodiment 2. Semiconducting light emitting nanosized material according to embodiment 1 , wherein said semiconducting light emitting nanosized material is essentially free of lead (Pb) and/or free of cadmium (Cd), more preferably said ssemiconducting light emitting nanosized material comprises InP. Embodiment 3. Semiconducting light emitting nanosized material according to embodiment 1 or 2, wherein the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 1.4, preferably at least 1.6, more preferably at least 1.7 based on inorganics.

Embodiment 4. Semiconducting light emitting nanosized material according to one or more of embodiments 1 to 3, wherein the

semiconducting light emitting nanosized material has a full width half maximum (FWHM) of at most 60 nm measured at 25° using a toluene solution, preferably a full width half maximum (FWHM) in the range of 30 to 50 nm.

Embodiment 5. Semiconducting light emitting nanosized material according to one or more of embodiments 1 to 4, wherein the

semiconducting light emitting nanosized material has a quantum yield of at least 20%, more preferably at least 35% and even more preferably at least 50%.

Embodiment 6. Semiconducting light emitting nanosized material according to one or more of embodiments 1 to 5, wherein the

semiconducting light emitting nanosized material exhibits a peak maximum in the photoluminescence spectrum at a wavelength above 500 nm.

Embodiment 7. Semiconducting light emitting nanosized material according to one or more of embodiments 1 to 6, wherein the

semiconducting light emitting nanosized material comprises a core and a shell, preferably the shell comprises ZnS, ZnSe and/or a mixture of these materials.

Embodiment 8. Semiconducting light emitting nanosized material according to embodiment 7, wherein the core comprises InP, InZnP, InGaP or InGaZnP. Embodiment 9. Semiconducting light emitting nanosized material according to embodiment 7, wherein the core comprises InGaP and the molar ratio of In to Ga is in the range of 0.1 to 10. Embodiment 10. Semiconducting light emitting nanosized material according to one or more of embodiments 7 to 9, wherein the volume ratio of the core to the shell is in the range of 0.1 to 10.

Embodiment 11. Semiconducting light emitting nanosized material according to one or more of embodiments 7 to 10, wherein the

semiconducting light emitting nanosized material comprises a core, a first intermediate layer and an outer shell.

Embodiment 12. Semiconducting light emitting nanosized material according to embodiment 11 , wherein the core comprises InP or InZnP and the first intermediate layer comprises GaP, InGaP or InZnGaP.

Embodiment 13. Semiconducting light emitting nanosized material according to embodiment 11 , wherein the core comprises InP and the first intermediate layer comprises InZnP.

Embodiment 14. Semiconducting light emitting nanosized material according to embodiment 11 , wherein the core comprises InZnP and the first intermediate layer comprises GaP, InGaP or InZnGaP.

Embodiment 15. Semiconducting light emitting nanosized material according to one or more of embodiments 11 to 14, wherein the

semiconducting light emitting nanosized material comprises a core, a first intermediate layer, a second intermediate and an outer shell.

Embodiment 16. Semiconducting light emitting nanosized material according to embodiment 15 wherein the core comprises InP and the first intermediate layer comprises InZnP and the second intermediate layer comprises GaP, InGaP or InZnGaP.

Embodiment 17. Semiconducting light emitting nanosized material according to one or more of embodiments 1 to 16, wherein the

semiconducting light emitting nanosized material comprises a triangular shape.

Embodiment 18. Method for preparing a semiconducting nanosized material according to one or more of embodiments 1 to 17 wherein a core is produced and a shell is applied onto the core.

Embodiment 19. Composition comprising at least one semiconducting nanosized material comprising at least three components according to embodiment 18,

and at least one additional material, preferably the additional material is selected from the group consisting of organic light emitting materials, inorganic light emitting materials, charge transporting materials, scattering particles, host materials, nanosized plasmonic particles, photo initiators, and matrix materials.

Embodiment 20. Formulation comprising or consisting of at least one semiconducting nanosized material comprising at least three components according to embodiment 18 or the composition according to embodiment 19, and at least one solvent.

Embodiment 21. Use of the semiconducting nanosized material comprising at least three components according to any one of claims according to embodiment 18, or the composition according to claim 19, or the formulation according to embodiment 20 in an electronic device, optical device or in a biomedical device. Embodiment 22. An optical medium comprising at least one

semiconducting nanosized material comprising at least three components according to embodiment 18 or the composition according to embodiment 19.

Embodiment 23. An optical device comprising at least one optical medium according to embodiment 22.

Definition of Terms

The term“semiconductor” means a material which has electrical

conductivity to a degree between that of a conductor (such as copper) and that of an insulator (such as glass) at room temperature.

The term“organic” means any material containing carbon atoms or any compound that containing carbon atoms ionically bound to other atoms such as carbon monoxide, carbon dioxide, carbonates, cyanides, cyanates, carbides, and thiocyanates.

The term“emission” means the emission of electromagnetic waves by electron transitions in atoms and molecules.

The term“material” means any compound and/or substance having the features additionally mentioned for specifying the expression material.

The term“cluster” means a material having a specific composition of the different components. The expression“quantum dot” means a semiconducting nanosized material being useful for any application. That is a quantum dot is designed as a material which can be used for the preparation of an optical media and/or the optical devices.

The expression“semiconducting nanosized material comprising high optical density” means a material having semiconducting properties and having a nanosize as mentioned above and below, preferably the semiconducting nanosized material comprising high optical density comprises at least three components for forming a semiconductor, such as InZnP, InGaP, GaZnP, etc as mentioned above and below. Preferred semiconducting nanosized material comprising high optical density can be used as quantum dots. However, the expression“semiconducting nanosized material comprising high optical density” includes any pre-product for obtaining quantum dots.

Advantages

The quantum dots according to the invention and the optical media and/or the optical devices, obtainable therefrom are distinguished over the prior art by one or more of the following surprising advantages:

1 . The optical media and/or the optical devices obtainable using the

quantum dots according to the invention exhibit very high stability and a very long lifetime compared with optical media and/or optical devices obtained using conventional quantum dots. 2. The quantum dots according to the invention can be processed using conventional methods, so that cost advantages can also be achieved thereby.

The quantum dots according to the invention are not subject to any particular restrictions, enabling the workability of the present invention to be employed comprehensively. 4. The quantum dots according to the invention provide a high color purity and a low FWHM.

5. The quantum dots according to the invention can be produced in a very rapid and easy manner using conventional methods, so that cost advantages can also be achieved thereby.

6. The quantum dots according to the invention are less toxic than

conventional formulations and have a high environmental

acceptability.

7. The quantum dots according to the invention show a high emission in the visual range of the electromagnetic radiation. 8. The quantum dots according to the invention show a high quantum yield.

9. The quantum dots according to the invention show a high absorption.

10. The quantum dots according to the invention show a low self- absorption.

11. The quantum dots according to the invention show a high optical density per mg.

12. The formation of InP quantum dots using InP MSCs as the precursor (which we term the“SSP Reaction”; SSP = single source precursor) results in the formation of InP QD populations with improved size distribution and better max/min ratios. When a shell of ZnSe is put onto these InP QDs very narrow FWHMs have been reached, 38nm.

Flowever, the Quantum Yield (QY) of such shell materials is affected by the lattice mismatch between the InP and ZnSe or ZnS shell. One way to tune the lattice mismatch is to add Ga to the InZnP QD being obtainable by the reaction mentioned above.

Adding Zn Precursors to the SSP reaction and/or adding Zn to the InP MSCs and forming InZnP MSCs allows Zn to be introduced into the

SSP reaction allows the formation of InZnP quantum dots. These quantum dots provide astonishing improvements to particles containing Ga allowing the lattice mismatch of the final InZnGaP QDs and/or InZnP/GaP QDs to be tuned to give higher QYs whilst maintaining smaller particle size distribution and lower FWHM.

The improvements achieved by using the InP MSC as single source

precursor or similar starting materials are maintained in the following steps. That is, the present QD have very narrow FWHMs.

13. The present invention allows better control over the reaction and flexibility of the nature of the cores. Especially, the band gap can be controlled by the degree of alloying of Ga in the shell and the thickness of the shell.

14. The addition of Ga should blue-shift the optical properties of the QD.

Therefore, InZnGaP QDs with similar CWL to InZnP QDs will need to be larger. This could result in QDs that have a higher absorption at 450nm or any other wavelength.

15. The present QD are more stable due to their larger size.

16. The present QD are cheaper based on the lower Indium content per particle.

17. The present method provides compositions having a very high

concentration of semiconducting nanosized material comprising high optical density, preferably quantum dots (QD). The high

concentrations provide cost advantages with regard to the processing and the handling of the QD. Furthermore, these high concentrations are achieved without specific steps conventionally used for increasing the concentration.

18. The present method enables the use of very high concentrated

reaction compositions for obtaining the present semiconducting nanosized material comprising high optical density. Therefore, the present method provides additional cost advantages.

19. The present method provides compositions having a very low content of by-products and semiconducting nanosized materials having a very defined composition and structure based on the lowering of by- products and precursors during the manufacturing process.

20. The present QD of the present invention are very clean and comprise very low amounts of by-products and precursors which is a very useful feature especially with regard to OLED applications and other uses having the need for high purity starting materials.

These above-mentioned advantages are not accompanied by an undue impairment of the other essential properties. There is no prior art reporting the formation of InZnP QDs and/or InGaP QDs using the SSP reaction. There is prior art which describes the synthesis of InZnP quantum dots and further shelling of these particles. However, they do not use the MSCs as the InP source. In this invention, preferably specific MSCs are used and these are injected at high

temperature together with InP MSCs to form InZnP QDs. No prior art teaches a Ga treatment of InZnP cores made using the SSP reaction. It should be pointed out that variations of the embodiments described in the present invention fall within the scope of this invention. Each feature dis- closed in the present invention can, unless this is explicitly excluded, be replaced by alternative features which serve the same, an equivalent or a similar purpose. Thus, each feature disclosed in the present invention is, unless stated otherwise, to be regarded as an example of a generic series or as an equivalent or similar feature.

All features of the present invention can be combined with one another in any way, unless certain features and/or steps are mutually exclusive. This applies, in particular, to preferred features of the present invention. Equally, features of non-essential combinations can be used separately (and not in combination).

It should furthermore be pointed out that many of the features, and in par- ticular those of the preferred embodiments of the present invention, are themselves inventive and are not to be regarded merely as part of the em- bodiments of the present invention. For these features, independent pro- tection can be sought in addition or as an alternative to each invention presently claimed.

The teaching on technical action disclosed in the present invention can be abstracted and combined with other examples.

The invention is explained in greater detail below with reference to a working example, but without being restricted thereby.

Working Examples

Working Example 1 : Synthesizing InP magic size clusters (MSC) Preparation of IndVIA from Indium acetate and Myristic acid (MA):

In this synthesis, 4.65g of indium acetate and 13.25g of myristic acid are weighed into a 500ml flask equipped with a reflux condenser. The apparatus is vacuumed with stirring at 100°C for 6.5h to evaporate acetic acid under reduced pressure.

The solution is re-heated to 100°C and evacuated for 2h in the same conditions. Total vacuum time at 100°C is 8.5h, to produce the ln(MA)3 solution.

Afterward, the flask is filled with argon, and a 100ml portion of dry toluene is added. Synthesis of InP MSCs from InOVlA solution and PtTMSls:

In Glovebox (GB), 2.33ml (2.0g) of P(TMS)3 are added to 50ml of toluene in a vial equipped with a septum. The ln(MA)3 flask is heated to 110°C and the P(TMS)3 solution is injected. When the improvement in the peak max/min is stopped, P(TMS)3 solution (1 ml P(TMS)3 in 10.2ml toluene) is added in the following order:

• 2ml P(TMS)3 solution is added after 12 min

• 2ml P(TMS)3 solution is added after 20 min

• 2ml P(TMS)3 solution is added after 32 min

· 0.5ml P(TMS)3 solution is added after 45 min

After 53 min the solution is cooled, sample is stored in GB.

Purification of InP MSCs:

Clusters are cleaned x5 times: 1. In GB clusters solution is transferred into 750ml centrifuge tube (equipped with Teflon film). The crude MSCs is precipitated using centrifuge: 2700G, 7 min.

2. In GB, ~180ml of supernatant (containing toluene) are precipitated with 130ml acetonitrile in GB. centrifuge: 2700G, 7 min.

3. In GB, 20ml of toluene with 15ml acetonitrile are added to the

precipitant in the tube. After precipitation 24ml of toluene are added to dissolve the MSCs. The mixture is transferred into two 50ml tubes (equipped with Teflon film). 16ml of acetonitrile are added (8ml to each tube). Solution became turbid. Centrifuge: 7 min, 5000 rpm.

4. In GB, 17ml toluene are added to the precipitant which is combined into one 50ml tube. 12ml acetonitrile are added and the solution became turbid. Centrifuge: 7 min, 5000 rpm.

5. In GB, 7ml of toluene are added to the precipitant in the tube. 4ml of acetonitrile are added. Centrifuge: 7 min, 5000 rpm.

The precipitant is dissolved in 14 ml of squalane.

Working Example 2: Synthesizing InZnP SSP cores

Preparation of stock solution of 0.117M ZntStk in squalane

1.48g of Zinc Stearate (Zn(St)2) and 20ml of distilled squalane where put into a 50ml round- bottom flask, which is connected to a Schlenk line via a condenser. The flask is heated to 110°C for 2 hours under vacuum and then cooled down to RT by removing the mantle and blowing air by fan; the turbid solution is stored in GB.

Preparation of the injection solution:

1 75ml of distilled squalane are mixed in GB with 1 7ml of InP MSCs solution. Preparation of the additions solution:

6.1 ml of distilled squalane are mixed in GB with 1 8ml of InP MSCs solution and 15.1 ml of the 0.117M Zn(St)2 solution.

Formation of InZnP QDs:

0.8325g of zinc stearate where put into a 100ml round-bottom flask. The flask is connected to condenser and is vacuumed. 15ml of distilled squalane is injected into the flask and vacuumed at 110°C with stirring for 2h, then the flask is heated to 375°C under Ar. 3ml of the injection solution are injected into the flask. After 1 min the flask is cooled down fast to 200°C by removing the mantle, and blowing air by fan; The flask is then re-heated to 265°C, and then 2.5ml portions of the additions solution are injected at the following times (in minutes, counted from the initial injection): 20, 24,

28, 32, 36, 40, 44. After 48 min the flask is cooled down to RT by removing the mantle and blowing air by fan. The crude is stored in GB. InZnP cores cleaning:

In GB, 6.25ml of crude InZnP cores are transferred into 50ml tube and are dissolved with 9.2ml toluene. The cores are precipitated with 15.8ml EtOH. Centrifuge: 5000rpm, 5min. The paste is precipitated again by dissolving with 5.26ml toluene and 9.2ml EtOH. Centrifuge: 5000rpm, 5min. The cores are stored in GB overnight. Total inorganics mass (according to TGA): 20mg.

Working Example 3: Synthesizing shells.

Preparation of gallium oleate stock solution

In GB, 0.684g GaCI3 are weighted into a 100ml round bottom flask with 4.77ml of pumped oleic acid (OIAc) and 30ml of pumped 1 -octadecene (ODE). The solution became brown-orange immediately after addition of the OIAc. The flask is mounted on a Schlenk line and is vacuumed at

140°C for ~1 h. Then the solution is cooled to RT, filled with Ar and stored in GB.

Preparation of Selenium-trioctylphosphine (Se-TOP) 1 M stock solution:

In GB, 3.16g of Se powder is weighted into 50ml vial with 40ml

trioctylphosphine (TOP). The solution is mixed at room temperature until it became clear. Preparation of Sulfur-trioctylphosphine (S-TOP) 1 M stock solution:

1.29g of S powder is weighted into 50ml vial and 40ml TOP are added in GB. The solution is mixed at room temperature until it became clear. Preparation of zinc stearate (Zn(st2) stock solution:

7.58g of zinc stearate powder is weighted into 50ml vial and 35ml of pumped ODE are added in GB. The solution is sonicated for few minutes every time before use to form homogeneous suspension.

GaP Shell:

In GB, cleaned InZnP cores (20mg of InZnP dots) are dissolved with 1 ,5ml toluene and are transferred into 50ml round bottom flask with 0.23ml Ga(OIAc)3 in ODE and 7ml ODE. The flask is mounted on schlenk line and pumped for ~30min at 50°C. Then the mixture is heated to 200°C under Ar for 1 h. The flask is cooled to 150°C and 0.0085ml of P(TMS)3 in 1 ml ODE is injected. Then the mixture is re-heated to 200°C for additional 1 h. The flask is cooled to RT.

Growth of ZnSeS Shell:

The solution of Zn(stealate)2 in pumped ODE is sonicated for around15min and 2ml of the suspension is injected into the flask at RT. The flask is heated to 300°C and at 90°C 0.35ml of TOP-Se and 0.35ml of TOP-S is injected. The reaction is kept at 300°C for 20min and cooled to RT.

Central Wavelength in Photoluminescence spectrum (CWI__PL)=599nm, Quantum Yield (QY)=65%

Working Example 4: Without injection of P(TMS)-¾ in GaP Shell.

The same as Working Example 3, but without injection of P(TMS)3. After 1 h at 200°C the reaction is cooled down and the ZnSeS Shell is performed. CWLPL =577nm, QY=53%, FWHM=46nm

Working Example 5: Ga:P mole ratio 2:1

The same as Working Example 3, but with multiple amounts of Ga(OIAc)3 solution (0.46ml instead of 0.23ml).

CWLPL =591 nm, QY=56%

Working Example 6: Multiple amounts of Ga and P

The same as Working Example 3, but with multiple amounts of Ga(OIAc)3 solution (0.46ml instead of 0.23ml) and P(TMS)3 (0.017ml in 1 ml ODE instead of 0.0085ml).

CWLPL =607nm, QY=60% Working Example 7: triple amounts of Ga and P The same as Working Example 3, but with triple amounts of Ga(OIAc)3 solution (0.69ml instead of 0.23ml) and P(TM3)3 (0.0255ml in 1 ml ODE instead of 0.0085ml).

CWLPL =620nm, QY=60%

Working Example 8: Producing ZnSe Shell only.

The same as Working Example 3, but with multiple amounts of Se-TOP and without injecting S-TOP.

CWLPL =657nm.

Working Example 9: Producing ZnS Shell only. The same as Working Example 3, but with multiple amounts of S-TOP and without injecting Se-TOP.

CWLp_L=608nm

Working Example 10: Synthesizing GaP Shell using GaCI-_¾ and tris- dialkylaminophosphine

GaP shell

To a round bottom flask in GB, GaCb in the appropriate amounts is added to cleaned InZnP SSPs dots with 7ml of pumped oleylamine (OLAm). The flask is mounted on schlenk line and pumped for ~30min at 50°C. then the mixture is heated to 200-300°C for an hour. After the reaction with the Ga, the temperature is lowered to 180°C and tris-dialkylaminophosphine is injected into the solution. The flask is maintained at this temperature for another hour and then cooled down to RT. ZnSeS shell

The same as Working Example 3.

Working Example 11 : Preparation of InZnP/lnGaP/GaP Core/Shell

In GB, cleaned InZnP cores (21 33mg inorganics according to TGA) are dissolved with 1 ,2ml toluene and are transferred into 50ml round bottom flask with 0.23ml Ga(OIAc)3 in ODE (from GaCb), 0.026g ln(OAc)3 and 7ml ODE. The flask is mounted on schlenk line and pumped for ~30min at 50°C. Then the mixture is heated to 200°C under Ar for 30min. The flask is cooled to 150°C and 0.0085ml of P(TMS)3 in 1 ml ODE is injected. Then the mixture is re-heated to 200°C for additional 30min, after which another portion of 0.23ml Ga(OIAc)3 solution is injected at 200°C. After 30min another portion of 0.0085ml P(TMS)3 in 1 ml ODE is injected at 150°C. The flask is maintained at 200°C for additional 30min and is cooled to RT.

Working Example 12: Preparation of InZnP/lnGaP/GaP/ZnSexSi-x

Core/Shell/Shell.

After InZnP/lnGaP core/shell crude is cooled to RT, 2ml of unpumped Zn(st)2 in ODE is injected into the flask after sonication of 15min. The flask is heated to 300°C and at 90°C 0.35ml of TOP-Se 1 M and 0.35ml of TOP-S 1 M is injected. The reaction is kept at 300°C for 20min and cooled to RT.

Working Example 13: Preparation of InGaP Cores. Preparation gallium oleate stock solution in ODE:

In a glove box, 0.89g GaCb (99.999% trace metal basis) are weighted into a 250ml round bottom flask with 6.37ml oleic acid and 40ml ODE. The flask is mounted on a Schleck line and is vacuumed at 50°C for few minutes.

Then the flask is heated to 140°C for ~1 h under Ar. The flask is cooled to room temperature and stored in glove box.

Preparation of the injection solution:

Clean InP MSCs are dissolved in squalane.

Preparation of the additions solution: Squalane is mixed in GB with InP MSCs solution and Ga(OIAc)3 solution in ratio Gain 0.5-5.

Formation of InGaP CDs: InGaP SSP cores are synthesized in the following method: 1 16ml of the Ga(OIAc)3 in ODE solution and 8.84ml of distilled squalane are placed in a 100ml round-bottom flask. The flask is connected to a Schlenk line and vacuumed for 5 minutes, then the flask is heated to 375°C under argon. 3ml of the injection solution is injected into the flask. After 1 min the flask is cooled down fast to 200°C by removing the mantle, and blowing air by fan. The flask is then re-heated to 265°C, and then 2.5ml portions of the additions solution is injected at the following times (in minutes, counted from the initial injection): 20, 24, 28, 32, 36, 40, 44. After 48 min and the flask is cooled down to room temperature by removing the mantle and blowing air by fan. Working Example 14. Preparation of ln_xZn„Gai-»P Cores.

Preparation of stock solution of 0.117M ZntStk in squalane: 1 48g of Zn Stearate and 20ml of distilled squalane are put into a 50ml round-bottom flask, which is connected to a schlenk line via a

condenser. The flask is heated to 110°C for 2 hours under vacuum and then cooled down to room temperature by removing the mantle and blowing air by fan; the turbid solution is stored in glove box.

Synthesis of Preparation of ln_xZnvGai_-vP Cores

InZnGaP SSP cores are synthesized in the following method: The same as Working Example 11 but adding Zn precursor solution (such as Zn-stearate and others) with the Ga solution in the appropriate ratio (0<y<1 ).

Working Example 15: Preparation of InGaP/GaP or ln_xZn„Gai-»P/GaP Core/Shell

GaP shell are synthesized according to the following method: In GB, cleaned cores (20mg of dots) are dissolved with 1 5ml toluene and transferred into 50ml round bottom flask with Ga(OIAc)3 in ODE and 7ml ODE. The flask is mounted on schlenk line and pumped for ~30min at 50°C. Then the mixture is heated to 200°C under Ar for 1 h. The flask is cooled to 150°C and P(TMS)3 in ODE is injected. Then the mixture is re- heated to 200°C for additional 1 h. The flask is cooled to RT.

Working Example 16: Preparation of InGaP/GaP/ ZnSe_xSi-_x or ln_xZn„Gai-»P/GaP/ ZnSe_xSi-_x Core/Shell/Shell ZnSe_xSi_-x shell are synthesized according to the procedure in Working Example 12 on the appropriate core shell NPs (on InGaP/GaP or ln_xZn_yGai- yP/GaP).

Working Example 17: InZnP/GaP/ZnSeS core-shell

Cores cleaning:

In GB, 12.64ml of crude InZnP cores (EPW=517nm, Zn:ln=0.54 ratio according to EDS, 63.99mg inorganics according to TGA) are transferred into 2, 50ml tubes (6.32ml in each tube) and are dissolved with 20.96ml toluene (10.48ml in each tube). The cores are precipitated with 31.6ml EtOH (15.8ml in each tube). Centrifuge: 5000rpm, 5min. The paste in the two tubes is combined into one tube and precipitated again by dissolving with 13.95ml toluene and precipitated with 18.96ml EtOH. Centrifuge:

5000rpm, 5min. GaP shell:

In GB, cleaned InZnP cores (63.99mg inorganics according to TGA) are dissolved with 3ml anhydrous toluene and are transferred into 250ml round bottom flask with 0.69ml Ga(OIAc)3 in ODE 0.126M and 21 mL ODE. The flask is mounted on Schlenk line and pumped for around 30min at 50°C.

Then the mixture is heated to 200°C under Ar for 1 h. The flask is cooled to 150°C and 0.0255ml of P(TMS)3 in 3ml ODE is injected. Then the mixture is re-heated to 200°C for additional 1 h. The flask is cooled to RT. Growth of ZnSeS shell: The solution of Zn(st)2 in ODE (0.325g Zn(st)2 in 1.5ml ODE) is sonicated for 15min and 6ml of the suspension is injected into the flask at RT. The flask is heated to 300°C and at 90°C 1 ml of TOP-Se (1 M) and 1 ml of TOP- S (1 M) is injected. The reaction is kept at 300°C for 20min and cooled to RT. CWI__PL=609nm, QY=60%

Cleaning InZnP/GaP/ZnSeS for OD/mq measurements:

0.7ml crude are diluted with toluene and filtered through 0.2mI_ PTFE filter. After evaporation of the toluene under Ar flow, 0.5ml toluene is added and the solution is precipitated with 1 5ml EtOH. Centrifuge: 5min, 5000rpm. The solid is re-dissolved with 0.5ml toluene and precipitated again with 1 ml EtOH. Centrifuge: 5min, 5000rpm.

Working Example 18: InZnP/lnGaP/ZnSeS core-shell

InGaP shell: In GB, cleaned InZnP cores (EPW=517nm, Zn:ln=0.54 ratio according to EDS, 63.99mg inorganics according to TGA) are dissolved with 3.5ml anhydrous toluene and are transferred into 250ml round bottom flask with 0.69ml Ga(OIAc)3 in ODE 0.126M and 21 ml ODE. The flask is mounted on Schlenk line and pumped for ~30min at 50°C. Then the mixture is heated to 200°C under Ar for 1 h. The flask is cooled to RT.

Growth of ZnSeS shell:

The second shell of ZnSeS is synthesized in the same manner as in Working Example 17.

CWI_PL=575nm, QY=53% Cleaning InZnP/lnGaP/ZnSeS for OD/mq measurements:

The cleaning process is the same as in Working Example 17.

Working Example 19: InZnP/lnGaP/ZnSeS core-shell

Cores cleaning:

In GB, 6ml of crude InZnP cores are transferred into 50ml tube and are dissolved with 9ml toluene. The cores are precipitated with 15ml EtOH. Centrifuge: 5000rpm, 5min. The paste is precipitated again by dissolving with 5.1 ml toluene and precipitated with 8.7ml EtOH. Centrifuge: 5000rpm, 5min. The cores are dissolved with 4ml toluene and the solution is divided into 2 vials containing 2.67ml (32mg of inorganics according to TGA). The solutions are dried under Ar and are stored in GB overnight.

InGaP shell:

In GB, cleaned InZnP cores (EPW=546nm, Zn:ln= 0.21 ratio according to EDS, 32.00mg inorganics according to TGA, 32.00mg inorganics according to TGA) are dissolved with 1 5ml toluene and are transferred into 50ml round bottom flask with 0.23ml Ga(OIAc)3 in ODE 0.126M and 7ml ODE. The flask is mounted on Schlenk line and pumped for ~30min at 50°. Then the mixture is heated to 200°C under Ar for 30min. The flask is cooled to RT.

Growth of ZnSeS shell:

The second shell of ZnSeS is synthesized in the same manner as in Working Example 17 CWLp_L=587nm, QY=48%

Cleaning InZnP/lnGaP/ZnSeS for OD/mq measurements:

1 ml crude is diluted with 2ml toluene in GB and are filtered with 0.2mI PTFE filter. The filter is washed with additional 3ml toluene and the toluene is dried under vacuum. Then the solution is diluted with 1 2ml toluene and precipitated with 4ml EtOH. Centrifuge: 5min, 5000rpm. The paste is re- dissolved with 0.5ml toluene and precipitated again with 1 ml EtOH.

Working Example 20: InZnP/lnGaP/ZnSeS core-shell Cores cleaning:

In GB, 18ml of crude InZnP cores (EPW=539, Zn:ln= 0.13 ratio according to EDS, 32.00mg inorganics according to TGA) are transferred into 3, 50ml tubes (6ml crude in each tube) and are dissolved with 27ml toluene (9ml in each tube). The cores are precipitated with 45ml EtOH (15ml in each tube). Centrifuge: 5000rpm, 5min. The paste is precipitated again by dissolving with 15.3ml toluene (5.1 ml in each tube) and precipitated with 26.1 ml EtOH (8.7ml in each tube). Centrifuge: 5000rpm, 5min. The cores are re- dissolved with 14ml toluene and combined into one tube. The solution is divided into 5 vials containing 2.78ml (32mg of inorganics according to TGA). The solutions are dried under Ar and are stored in GB overnight.

InGaP/ZnSeS shells: The synthesis is the same as in Working Example 19.

CWI__PL=590nm, QY=44% Cleaning InZnP/lnGaP/ZnSeS for OD/mq measurements:

The cleaning process is the same as in Working Example 19.

Comparative Example 1 : InZnP/ZnSeS core-shell

Cores cleaning:

In GB, 50ml of crude InZnP cores (EPW=517nm, Zn:ln=0.54 ratio according to EDS, 32.00mg inorganics according to TGA) are transferred into 750ml tube and are dissolved with 100ml toluene. The cores are precipitated with 25ml EtOH. Centrifuge: 4600G, 10min. The paste is precipitated again by dissolving with 45ml toluene and precipitated with 75ml EtOH. Centrifuge: 2700G, 7min. The solution is divided into 21 vials containing 2.8ml (21 33mg of inorganics) the solutions are dried under Ar and are stored in GB overnight. Growth of ZnSeS shell:

In GB, InZnP cores (32mg of inorganics according to TGA) are dissolved with 2.25ml toluene and transferred into 100ml flask. The flask is mounted on a Schleck line and toluene is pumped for ~30min at 50°C. A solution of unpumped Zn(st)2 in ODE (0.325g Zn(st)2 in 1 5ml ODE) is sonicated for 15min and 2ml of the suspension is injected into the flask at RT. The flask is heated to 300°C and at 90°C 0.35ml of TOP-Se (1 M) and 0.35ml of TOP- S (1 M) is injected. The reaction is kept at 300°C for 20min and cooled to RT. CWI__PL=577nm, QY=52%

Cleaning InZnP/lnGaP/ZnSeS for OD/mq measurements: The cleaning process is the same as in Working Example 19.

Measuring OD/mq Crude material is filtered and then precipitated from a mixture of solvent: anti-solvent (in our materials it is toluene: EtOH twice or any other precipitation method that will remove the solvent and the access ligands).

The solid is dried over vacuum until all solvents residues are evaporated (drying by Ar is not enough).

The solid is re-dissolved with a known volume of toluene to form a clear solution. If the solution is not clear another method of precipitation is needed or filtration.

Mq/ml measurement: A known volume of the NPs solution is measured in TGA to find the mg/ml, which in our measurements is around 30-80 mg/ml. A known volume of the solution is put in the crucible (40mI) and the method in TGA will evaporate the solvent to know the exact mass of the dried sample and the amount of organic material in the sample.

OD/ml measurement: A known volume of the NPs solution is diluted to -0.03-0.05 OD/ml and then the OD at 450nm is measured in

spectrophotometer. The OD should be under 1.5 but above 0.03 (to follow Bear-Lambert law). Pay attention the solution is not dispersive.

The OD/mg is calculated from OD/ml divided by mass/ml.

Summary of the OD/mq

Working Example 21 : Synthesizing InZnP cores

Preparation of the injection solution: 0.39 ml of InP MSCs solution in squalane (containing 66 mg of solid content) are mixed with 1.48 ml of degassed squalane in GB. Preparation of the additions solution:

In GB 1.25 g of zinc stearate and 0.39 ml of InP MSCs solution (containing 66 mg of solid content) are put into 5 ml of degassed squalane, and these are mixed thoroughly in a conditioning mixer.

Formation of InZnP QDs:

In GB 6 ml of degassed squalane are put into 50ml 4-neck flask with magnetic stirrer. The flask is connected to schlenk line and heated to 375C under argon.

1.5 ml of the injection solution are then injected into the flask. After 1 minute, portions of 0.5ml of the additions solution are injected into the flask with intervals of 20 seconds, each injection lasted 5 seconds. After 6 additions the mantle is removed, and the flask is cooled by fan. The solution is stored in GB.

The formed InZnP cores had an absorption peat at 575nm and emission peak at 605nm, with FWHM of 47nm and QY of 10%. EDS measurement after cleaning showed zinc content of 25%.

Claims

Patent Claims

1. Method for synthesizing a semiconducting nanosized material

comprising high optical density, wherein the method comprises the steps of i) providing a first cation core precursor and a first anion core precursor or a semiconducting nanosized material being obtainable by reacting the first cation core precursor and the first anion core precursor; ii) providing a second precursor; iii) reacting the second precursor with the first cation core precursor and the first anion core precursor or reacting the second precursor with a nanosized material being obtainable by reacting the first cation core precursor and the first anion core precursor in order to achieve a semiconducting nanosized material comprising at least three

components; iv) reacting the semiconducting nanosized material comprising at least three components with a third cation precursor in order to achieve a semiconducting nanosized material comprising high optical density; characterized in that the first cation core precursor is a source of an element of the group 13 of the periodic table, preferably a salt of an element of the group 13 of the periodic table, more preferably the element of the group 13 is In, Ga or a mixture of thereof; the first anion core precursor is a source of an element of the group 15 of the periodic table, preferably the element of the group 15 is P, As or a mixture of thereof; the second precursor is a Zn, or a Cd source, preferably a material selected from one or more members of the group consisting of Zinc salts and Cadmium salts or mixtures thereof, preferably Zinc halogenides, Cadmium halogenides, Zinc carboxylates and Cadmium carboxylates or mixtures thereof, more preferably ZnC , ZnBr2, Zn , Zn(0₂CR)₂, wherein R is Ci to C19, even more preferably Zinc acetate,

Zinc myristate, Zinc oleate, Zinc laurate, Zinc stearate; and the third cation precursor is a Ga source, preferably a material selected from Gallium salts, preferably Gallium halogenides, and Gallium carboxylates or mixtures thereof, more preferably GaCb, GaBr3, Gab,

Ga(0₂CR)3, wherein R is C1 to Cig,even more preferably Gallium acetate, Gallium myristate, Gallium laurate, Gallium stearate and Gallium oleate.

2. Method according to claim 1 , wherein said cation core precursor and said first anion core precursor are reacted to a nanosized material in a first step and the nanosized material of the first step is reacted with the second precursor in a second step to obtain a semiconducting nanosized material comprising at least three components.

3. Method according to claim 1 or 2, wherein the third cation precursor is added in multiple steps.

4. Method according to claim 1 or 2, wherein the third cation precursor is added in exactly one step.

5. Method according to one or more of claims 1 to 4, the method comprises the steps of

a) providing a lll-V semiconducting nanosized material;

b) providing a second precursor;

d) providing a third cation precursor;

e) reacting the semiconducting nanosized material comprising at least three components with the third cation precursor.

6. Method according to one or more of claims 1 to 5, wherein the

semiconducting nanosized material comprising at least three

components is purified before the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor.

7. Method according to one or more of claims 1 to 6, wherein the

concentration the first anion core precursor is below 1 mg/ml, preferably below 0.5 mg/ml, more preferably below 0.1 mg/ml while the semiconducting nanosized material comprising at least three

components is reacted with a third cation precursor.

8. Method according to one or more of claims 1 to 7, wherein no source of P, As or a mixture of thereof is added for reacting the semiconducting nanosized material comprising at least three components with a third cation precursor, preferably no source of an element of the group 15 of the periodic table is added.

9. Method according to one or more of claims 1 to 7, wherein a third anion precursor is added for reacting the semiconducting nanosized material comprising at least three components with a third cation precursor, preferably a source of an element of the group 15 of the periodic table, preferably the element of the group 15 is P, As or a mixture of thereof.

10. Method according to claim 9, wherein the concentration the third anion precursor is above 0.1 mg/ml, preferably above 0.5 mg/ml, more preferably above 1.0 mg/ml while the semiconducting nanosized material comprising at least three components is reacted with a third cation precursor.

11. Method according to one or more of claims 1 to 10, wherein the

concentration of the second precursor, preferably the Zn concentration in outer layer of the semiconducting nanosized material comprising at least three components is in the range of 0.1 to 10, preferably 0.1 to 4, more preferably 0.1 to 0.4.

12. Method according to one or more of claims 1 to 11 , wherein the

concentration of the second precursor, preferably the Zn concentration of the outer layer is higher than the concentration of the second precursor, preferably the Zn concentration of the core.

13. Method according to one or more of claims 1 to 12, wherein the

nanosized material comprising at least three components and the third cation precursor are mixed at a temperature below 150°C and heated after the mixing.

14. Method according to claim 1 to 13, wherein the mixture of the

nanosized material comprising at least three components and the third cation precursor are heated to a temperature in the range of 100°C to 350°C, preferably 150°C to 300°C, more preferably 180°C to 280°C, even more preferably 200°C to 250°C.

15. Method according to one or more of claims 2 to 14, wherein the nanosized material of the first step is purified before the second reaction step is performed.

16. Method according to one or more of claims 2 to 15, wherein said

nanosized material of the first step and/or said lll-V semiconducting nanosized material is used as a single source precursor.

17. Method according to one or more of claims 1 to 16, wherein a shell of a semiconductor and/or an additional shell is grown onto the

semiconducting nanosized material being obtained by reacting the semiconducting nanosized material comprising at least three components with a third cation precursor, preferably the shell comprises InP, ZnS, ZnSe and/or ZnSeS, more preferably ZnS, ZnSe and/or ZnSeS.

18. Semiconducting nanosized material comprising at least three

components obtainable by a method according to one or more of claims 1 to 17.

19. Semiconducting light emitting nanosized material, wherein the

semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 0.6, preferably at least 0.9, more preferably at least 1.0.

20. Semiconducting light emitting nanosized material according to claim 19, wherein said ssemiconducting light emitting nanosized material is essentially free of lead (Pb) and/or free of cadmium (Cd), more preferably said ssemiconducting light emitting nanosized material comprises InP.

21. Semiconducting light emitting nanosized material according to claim 19 or 20, wherein the semiconducting light emitting nanosized material exhibits an Optical density per mg of at least 1.4, preferably at least

1.6, more preferably at least 1.7 based on inorganics.

22. Composition comprising at least one semiconducting nanosized

material according to any one of claims 18 to 21

23. Formulation comprising or consisting of at least one semiconducting nanosized material according to any one of claims 18 to 21 or the composition according to claim 22, and at least one solvent.

24. Use of the semiconducting nanosized material according to any one of claims 18 to 21 or the composition according to claim 22, or the formulation according to claim 20 in an electronic device, optical device or in a biomedical device.

25. An optical medium comprising at least one semiconducting nanosized material according to any one of claims 18 to 21 or the composition according to claim 22.

26. An optical device comprising at least one optical medium according to claim 25.