Method for producing a nanoparticle, nanoparticle, and optoelectronic device

Abstract

A method for producing a nanoparticle is provided, the method comprising: - providing a colloidal substrate particle, - forming a shell comprising a III / V compound semiconductor material on the substrate particle, wherein the substrate particle comprises a material being different from the III / V compound semiconductor material. Further, a nanoparticle and an optoelectronic device are provided.

Description

[0001] 2024PF00715 September 9, 2025

[0002] P2024, 0540 WO N

[0003] - 1 -

[0004] Description

[0005] METHOD FOR PRODUCING A NANOPARTICLE, NANOPARTICLE, AND OPTOELECTRONIC DEVICE

[0006] A method for producing nanoparticle, a nanoparticle, and an optoelectronic component are provided.

[0007] It is an object of at least one embodiment to provide an improved method for producing a nanoparticle. It is a further object of at least one embodiment to provide a nanoparticle with improved properties. It is a further object of at least one embodiment to provide an optoelectronic device with improved properties.

[0008] A method for producing a nanoparticle is specified. A nanoparticle is to be understood as a discrete structure. In particular, the nanoparticle is a solid. Here and in the following, the nanoparticle is a particle having a size in the nanometer range, for example between and including 1 nm and 100 nm. In particular, the nanoparticle comprises properties of a phosphor, i.e., it converts electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range. In other words, the nanoparticle has wavelength-converting properties. The nanoparticle can absorb the electromagnetic radiation of the first wavelength range and emit the electromagnetic radiation of the second wavelength range. The nanoparticle is, for instance, a quantum dot (QD) .

[0009] According to at least one embodiment, the method comprises the step of providing a colloidal substrate particle. Colloidal means that the substrate particle is present in a 2024PF00715 September 9, 2025

[0010] P2024, 0540 WO N

[0011] - 2 - fluid, for example in a solvent. In particular, there is a plurality of discrete substrate particles present in the fluid. Thus, according to at least one embodiment, a plurality of substrate particles is provided, and a plurality of nanoparticles is produced with the method. A substrate particle may comprise a size in the range of up to several nanometers .

[0012] According to at least one embodiment, the method further comprises the step of forming a shell comprising a III / V compound semiconductor material on the substrate particle. A shell is to be understood as a layer fully or partially surrounding the substrate particle or at least being attached to the substrate particle. The shell being formed on the substrate particle, comprises a common surface at least with parts of the substrate particle. In particular, the shell is chemically bonded to the substrate particle in the area of the common surface.

[0013] A III / V compound semiconductor material comprises at least one element of the third main group of the periodic system, for example B, Al, Ga, or In and at least one element of the fifth main group of the periodic system, for example, N, P or As. In particular, a III / V compound semiconductor material is a phosphide, and arsenide, or a nitride, for example the III / V compound semiconductor material is InP.

[0014] According to at least one embodiment, the substrate particle comprises a material being different from the III / V compound semiconductor material. This means in particular, that the material of the substrate particle is not a III / V compound semiconductor material. Thus, the shell comprising a III / V 2024PF00715 September 9, 2025

[0015] P2024, 0540 WO N

[0016] - 3 - compound semiconductor material is formed on a material being different from the III / V semiconductor material.

[0017] According to at least one embodiment, there is provided a method for producing a nanoparticle, the method comprising:

[0018] - providing a colloidal substrate particle,

[0019] - forming a shell comprising a III / V compound semiconductor material on the substrate particle, wherein the substrate particle comprises a material being different from the III / V compound semiconductor material.

[0020] Conventional methods for producing nanoparticles, in particular quantum dots (QDs) comprise the step of first nucleating a cluster of the desired compound semiconductor material, as for example InP, followed by the growth of these clusters by reacting them with additional precursors of the elements of the desired compound semiconductor material. Alternatively or additionally, growth of clusters takes place by coalescence of multiple clusters. However, nucleation of new clusters can still occur even while already formed clusters continue to grow. This nucleation of new clusters during the growth phase of already formed crystals contributes to increase the size distribution of the final QDs. A high size distribution, however, is undesirable since the emission wavelength of QDs is determined by their size. Thus, QDs with a high spread of size distribution have a spread in emission wavelengths too.

[0021] In particular, the conventional nucleation and growth process of III / V compound semiconductor nanoparticles can be chaotic and difficult to control and reproduce. Additionally, it is typical that further shells of semiconductor material are grown around the QDs, for example around InP QDs. If the InP 2024PF00715 September 9, 2025

[0022] P2024, 0540 WO N

[0023] - 4 - materials have a heterogeneous distribution of sizes, the subsequent shell reaction chemistry is also hampered and can result in further heterogeneity of the sizes. A heterogeneous distribution of sizes of QDs may prevent accurately determining the concentration of particles and leads also to problems in shelling where large particles may grow larger and small particles may grow smaller which contributes to an even higher size distribution.

[0024] The inventors found out that the problematic nucleation phase and cluster stage during the production of nanoparticles comprising III / V compound semiconductor materials can be avoided by starting with a scaffold material in the form of colloidal substrate particles. Thus, no nucleation of the III / V compound semiconductor material takes place, but a controlled growth of a shell comprising the III / V compound semiconductor material on the substrate particle. Thus, a domain size of III / V compound semiconductor material may be controlled as well as the total number of formed nanoparticles .

[0025] The conventional nucleation method of III / V compound semiconductor nanoparticles and its problems as mentioned above, make it hard to control the total number of the synthesized nanoparticles and therefore the final size of the nanoparticles cannot be determined. Ambiguity around the number of QDs in a synthesis is especially challenging during growth of, for example, wider band gap shells on the QDs.

[0026] The addition of a known number of controlled substrate particles as scaffolds or seeds, comprised of a different material than the III / V compound semiconductor material, allows for precise control of the number of nanoparticles 2024PF00715 September 9, 2025

[0027] P2024, 0540 WO N

[0028] - 5 - present during the III / V growth reaction and also during subsequent shelling with other materials such as ZnSe or ZnS, for example. Additionally providing conditions that prevent the independent nucleation of III / V materials may enhance this effect.

[0029] According to at least one embodiment, the material of the substrate particle is chosen from II / VI compound nanocrystals, inorganic clusters of elements chosen from group II and / or group VI of the periodic table, inorganic clusters of mixtures of elements chosen from group II / VI compound semiconductor materials and III / V compound semiconductor materials, and organic molecules, in particular organic molecules having at least two ligand sites. II / VI compound nanocrystals may comprise at least one element of the second main group of the periodic table and at least one element of the sixth main group of the periodic table. For example, II / VI compound nanocrystals are chosen from ZnSe, ZnS, ZnSeS, ZnSe / ZnS core / shell structures, ZnTeS, and ZnTeSe. Examples for inorganic clusters of mixtures of elements chosen from group II / VI compound semiconductor materials and III / V compound semiconductor materials are Zn3P2, In2S3 or Ga2S2. Further examples are oxide materials such as SiO2, TiO2, ZrO2, In2O2, ZnO, or BiVCg . Organic molecules may, for example, be branched hydrocarbons with terminal ligands such as primary amines or carboxylic acids, for example EDTA (ethylenediaminetetraacetic acid) , substituted planar molecules, substituted fullerenes, graphenes, and carbon nanotubes, or polymers such as polystyrene spheres. An alternative to having ligands on the organic molecule would be to chemically bond the organic substrate particle to a ligand already attached to the group III metal. 2024PF00715 September 9 , 2025

[0030] P2024 , 0540 WO N

[0031] - 6 -

[0032] The substrate particles as mentioned above , are easier to be synthesi zed, puri fied, and fully characteri zed . Thus , their si ze distribution can be controlled, and the particle concentration can be well known . This facilitates the method and enables the production of nanoparticles with a small si ze distribution .

[0033] According to at least one embodiment , the shell is formed completely around the substrate particle . In other words , the shell fully surrounds or encapsulates the substrate particle . Thus , an electromagnetic radiation-emitting complex may be formed, the complex comprising the substrate particle and the shell formed thereon . In dependence of the nature of the substrate particle , it may be electromagnetic radiationemitting itsel f or not . For example , the produced nanoparticle may comprise the shell of I I I / V compound semiconductor material being able to absorb electromagnetic radiation of a first wavelength range and the substrate particle of another semiconductor material being able to emit electromagnetic radiation of a second wavelength range . Alternatively or addtionally, the shell surrounding the substrate particle may be shelled itsel f with further compound semiconductor materials .

[0034] According to at least one embodiment , the shell is formed adj acent to the substrate particle . Even such a produced structure may comprise the electromagnetic radiation-emitting properties as explained above , in this case the shell covers the substrate particle , only partially .

[0035] According to at least one embodiment , the shell is chemically bonded to the substrate particle . "Chemically bonded" 2024PF00715 September 9 , 2025

[0036] P2024 , 0540 WO N

[0037] - 7 - comprises , for example , a covalent bonding, a non-covalent bonding or even a weak interaction like a van-der-Waals bonding . A chemical bonding may be created by an addition reaction of material of the shell with the substrate particle or by an exchange reaction such as a cation exchange or a Z- type ligand exchange .

[0038] According to at least one embodiment , forming the shell comprises the steps of

[0039] - reacting the substrate particle with a first precursor to form a monolayer of a first element on the substrate particle ,

[0040] - reacting the substrate particle with a second precursor to form a monolayer of a second element on the monolayer of the first element , wherein one of the first and second precursor is chosen from a precursor of a group I I I element and the other one of the first and second precursor is chosen from a precursor of a group V element .

[0041] A precursor means here a chemical compound which is able to undergo a chemical reaction while forming the target compound, in this case a monolayer of the first or second element . "Reacting" here in and in the following means , that the first precursor and the colloidal substrate particle or the second precursor and the monolayer of the first element undergo chemical reactions in order to form a chemical bond between the substrate particle and the first precursor or the monolayer of the first element and the second precursor while forming the first element from the first precursor or the second element from the second precursor . 2024PF00715 September 9, 2025

[0042] P2024, 0540 WO N

[0043] - 8 -

[0044] A monolayer consists of one of the first or second element, i.e. of one of a group III element or group V element, wherein additional ligands may still be bonded to or associated with the first or second element. These ligands serve for the addition of the next element, i.e., for the formation of the next monolayer. When the monolayer of the second element is formed on the monolayer of the first element, the III / V compound semiconductor material is thus formed .

[0045] When forming the shell by conducting the above mentioned steps, the III / V compound semiconductor material of the shell can be synthesized on the substrate particle while avoiding a direct reaction of the first and second precursors in solution, i.e. the group III and group V elements present in a molecular, or free salt form. Instead, the first precursor reacts with the substrate particle wherein the first element is incorporated onto the surface of the substrate particle, and the second precursor reacts with the surface of the monolayer of the first element being already present on the substrate particle. Thus, the precursors are subsequently added and, thus, the group III and group V elements are subsequently attached to the surface. In particular, the first precursor and the second precursor are not present at the same time. Thus, the III / V compound semiconductor material is grown. When avoiding the direct reaction of the first and second precursors, a nucleation reaction and a subsequent growth that is not controllable can be avoided. Thus, nanoparticles with a small size distribution can be produced .

[0046] According to at least one embodiment, a precursor of a group

[0047] III element is chosen from Indium ( I I I ) oleate and Indium 2024PF00715 September 9, 2025

[0048] P2024, 0540 WO N

[0049] 9

[0050] (III) halides and a precursor of a group V element is chosen from tris (diethylamino) phosphine, tris (trimethylsilyl) phosphine, tris (triethylsilyl) phosphine, and tris ( tripropylsilyl ) phosphine . Suitable solvents which may be used are chosen from coordinating solvents like alkyl phosphines or alkyl amines, and non-coordinating solvents like octadecene or squalane.

[0051] According to at least one embodiment, the method further comprises alternately reacting the substrate particle with the first and second precursors to form a plurality of alternating monolayers of the first element and of the second element. In other words, the above-mentioned method steps for forming the shell can be repeated in order to increase the thickness of the shell. As the growth of the shell takes place on the substrate particle, a uniform size of nanoparticles can be realized, in case of forming a plurality of shells on a plurality of nanoparticles.

[0052] According to at least one embodiment, forming the shell is conducted at a temperature chosen from a range of including 150°C to 250°C. For example, the temperature is chosen from a range of including 170°C to 190°C. These temperatures contribute to mild reaction conditions which additionally help to avoid nucleation of the first and second precursors during the growth of the shell.

[0053] According to at least one embodiment, during forming the shell a product of first precursors and second precursors being present at once is so low, that independent clusters of elements of group III and elements of group V cannot be formed. A product of first precursors and second precursors means in particular a product of concentrations of the first 2024PF00715 September 9 , 2025

[0054] P2024 , 0540 WO N

[0055] - 10 - and second precursors . I f the reaction between the substrate particle and the , for example , first precursor is complete there is no first precursor present anymore , when the second precursor is added . In this case , the product of first precursors and second precursors is equal to zero . However, i f the reaction is not fully completed, there might still be some first precursor present when the second precursor is added . Therefore , reducing the product of the concentrations of the first and second precursors may prevent the nucleation of clusters of elements of group I I I and elements of group V .

[0056] Reducing the product of the first precursor and the second precursor can be reali zed, for example , by carefully controlling the stoichiometry of the precursor addition . In particular, for reacting the substrate particle with the first precursor j ust enough first precursor is added to react with the surface of the substrate particle . Adding j ust enough first precursor for forming a monolayer of the first element may be reali zed by careful calculations considering the number and si ze of substrate particles being present in the reaction solution . The number and si ze of substrate particles may be estimated, for example , via their absorption coef ficient . The thickness of the monolayer of the first or second element to be formed can be also added to these calculations . The increase in volume when the monolayer grows by that distance may then be determined . Finally, a precise number of moles of the first element for a first monolayer can be added to the reaction solution, followed by an equimolar amount of second precursor . Thus , the product of concentrations may remain low at all times during the forming of the shell , in particular, the product can be kept low to prevent nucleation of the I I I / V material by inj ecting each precursor at a rate that remains below the reaction rate at 2024PF00715 September 9, 2025

[0057] P2024, 0540 WO N

[0058] - li the surface of the substrate particle or the surface of the growing shell. This way of reducing the product of concentration while forming the shell may be called layer-by layer approach to nanocrystal growth.

[0059] According to at least on embodiment, simultaneous coinjection of both first and second precursors, i.e., for example group III and group V precursors, can also be used to grow the III / V shell layer if the injection rate is kept below the reaction rate at the substrate particle surface. This will avoid a build up of precursor that would lead to a high precursor concentration and subsequent III / V nucleation.

[0060] According to at least one embodiment, a purifying step is performed after each formation of a monolayer. The purifying step may be performed in addition or as an alternative to the above-mentioned calculations in order to reduce the product of concentrations of the precursors. The purifying step can be performed, for example, by completely exchanging the reaction solvent. In this alternative the first or second precursor may also be added in excess, as unbound precursors are removed during the purifying step. The purifying step can in particular be realized if a nucleation of the first and second element is hard to suppress, or if there is ambiguity about the number of substrate particles.

[0061] According to at least one embodiment, forming the shell comprises reacting the substrate particle with monomers of the III / V compound semiconductor material. Thus, first the monomers of the III / V compound semiconductor material are formed and then reacted with the substrate particle. Even in this alternative, a nucleation and uncontrolled growth of the first and second element may be prevented. 2024PF00715 September 9, 2025

[0062] P2024, 0540 WO N

[0063] 12

[0064] According to at least one embodiment, the III / V compound semiconductor material is InP. Thus, an efficient luminescent material may be produced with the method as described herein.

[0065] According to at least one embodiment, wherein at least one additional shell is formed on the shell. The material of the additional shell may be chosen from semiconductor materials or insulating materials. Thus, with the additional shell together the shell may form a core / shell / shell structure, for example .

[0066] Furthermore, a nanoparticle is provided. In particular, the nanoparticle can be produced with a method as described herein. Therefore, all features and embodiments mentioned with respect to the method also apply for the nanoparticle and vice versa.

[0067] According to at least one embodiment, the nanoparticle comprises

[0068] - a substrate particle, and

[0069] - a shell comprising a III / V compound semiconductor material on the substrate particle, wherein the substrate particle comprises a material being different from the III / V compound semiconductor material.

[0070] The nanoparticle can form a core / shell structure if the substrate particle is, for example a semiconductor material. The substrate particle in the nanoparticle can be detected by elemental analysis, for example. Alternatively, the nanoparticle may comprise at least one additional shell, such that the shell comprising a III / V compound semiconductor material on the substrate particle forms a core itself. The 2024PF00715 September 9, 2025

[0071] P2024, 0540 WO N

[0072] - 13 - nanoparticle may have a size in the range of including 1 nm to including 100 nm. It may be able to convert electromagnetic radiation by absorbing electromagnetic radiation of a first wavelength range and emitting electromagnetic radiation of a second wavelength range.

[0073] The nanoparticle comprises an emission wavelength that can be adjusted according to its application by adjusting its size. Additionally, if a plurality of such nanoparticles is provided, they have a small distribution of their sizes, as the III / V compound semiconductor material, for example InP, and optionally additional shells on the III / V compound semiconductor material are grown in a controlled manner.

[0074] According to at least one embodiment, the material of the substrate particle is chosen from II / VI compound nanocrystals, inorganic clusters of elements chosen from group II and / or group VI, inorganic clusters of mixtures of elements chosen from group II / VI compound semiconductor materials and III / V compound semiconductor materials, and organic molecules, in particular organic molecules having at least two ligand sites. II / VI compound nanocrystals may comprise at least one element of the second main group of the periodic table and at least one element of the sixth main group of the periodic table. For example, II / VI compound nanocrystals are chosen from ZnSe, ZnS, ZnSeS, ZnSe / ZnS core / shell structures, ZnTeS, and ZnTeSe. Examples for inorganic clusters of mixtures of elements chosen from group II / VI compound semiconductor materials and III / V compound semiconductor materials are Zn3P2, In2S2or Ga2S2. Further examples are oxide materials such as SiO2, TiO2, ZrO2, In2O2, ZnO, or BiVO4. Organic molecules may, for example, be branched hydrocarbons with terminal ligands such as primary 2024PF00715 September 9, 2025

[0075] P2024, 0540 WO N

[0076] - 14 - amines or carboxylic acids, for example EDTA (ethylenediaminetetraacetic acid) , substituted planar molecules, substituted fullerenes, graphenes, and carbon nanotubes, or polymers such as polystyrene spheres. An alternative to having ligands on the organic molecule would be to chemically bond the organic substrate particle to a ligand already attached to the group III metal. These substrate particles can either support the luminescent properties of the nanoparticle or they are small enough to have no negative influence on the luminescent properties of the nanoparticle.

[0077] According to at least one embodiment, the III / V compound semiconductor material comprises InP. Thus, the nanoparticle is an InP quantum dot, for example.

[0078] According to at least one embodiment, the nanoparticle comprises at least one additional shell on the shell. The additional shell may comprise a semiconductor material or an insulating material.

[0079] Furthermore, an optoelectronic component is provided. The optoelectronic component comprises nanoparticles as described herein. Thus, all features and embodiments disclosed with respect to the nanoparticle or to the method for producing the nanoparticle also apply to the optoelectronic component and vice versa.

[0080] According to at least one embodiment, the optoelectronic component comprises:

[0081] - a semiconductor chip, and

[0082] - a conversion element on the semiconductor chip, 2024PF00715 September 9 , 2025

[0083] P2024 , 0540 WO N

[0084] - 15 - wherein the conversion element comprises nanoparticles as described herein .

[0085] The optoelectronic component may be a light emitting diode ( LED) and the semiconductor chip a LED chip, or a laser diode and the semiconductor chip a laser diode chip, for example . The semiconductor chip is , in particular, configured to emit electromagnetic radiation of a first wavelength range (primary radiation) . For example , the first wavelength range is in the ultraviolet to blue spectral range .

[0086] The conversion element on the semiconductor chip may be applied directly, with a mechanical contact on the semiconductor chip, or spaced with respect to the semiconductor chip . For example , there may be an adhesive layer between the semiconductor chip and the conversion element .

[0087] The conversion element comprises nanoparticles as described herein . According to an embodiment , the conversion element consists of the nanoparticles . According to an alternative embodiment , the nanoparticles are embedded in a matrix material . A matrix material may be chosen, for example , from silicone or epoxy .

[0088] The conversion element converts the electromagnetic radiation of the first wavelength range into electromagnetic radiation of the second wavelength range ( secondary radiation) . In particular, the second wavelength range is at least partially di f ferent from the first wavelength range . The second wavelength range comprises wavelengths may have a lower energy compared to wavelengths in the first wavelength range . The wavelength conversion properties of the conversion 2024PF00715 September 9 , 2025

[0089] P2024 , 0540 WO N

[0090] 16 element arise from the nanoparticles being present in the conversion element as the nanoparticles convert the electromagnetic radiation of the first wavelength range into electromagnetic radiation of the second wavelength range .

[0091] Due to the improved properties of the nanoparticles , the optoelectronic component has a small distribution of the converted emitted radiation, and, thus , the desired emission of the component can be easily adj usted . Thus , the component can be used for display applications , for example in mobile displays or automotive displays .

[0092] According to at least one embodiment , the semiconductor chip comprises or is a micro-LED ( LED : light-emitting diode ) .

[0093] As a broad definition, a micro-LED could be seen as any light-emitting diode with a particularly small si ze . MicroLEDs may comprise a width, a length, a thickness and / or a diameter smaller than or equal to 100 micrometers , in particular smaller than or equal to 70 micrometers , for example smaller than or equal to 50 micrometers . In particular, micro-LEDs , for example rectangular micro-LEDs , have an edge length, in particular in plan view of layers of the semiconductor layer sequence , of a radiation exit surface of smaller than or equal to 70 micrometers , for example smaller than or equal to 50 micrometers . For example , a micro-LED is a light-emitting diode with a growth substrate removed, such that a thickness of the micro-LED is in the range between and including, for example , 1 . 5 micrometers and 10 micrometers . For example , the micro-LED is provided on a wafer having releasable retaining structures . The micro-LED can be detached from the wafer in a non-destructive manner . 2024PF00715 September 9 , 2025

[0094] P2024 , 0540 WO N

[0095] - 17 -

[0096] In particular, micro-LEDs are mainly used in displays . The micro-LEDs form pixels or subpixels and emit light of a defined color . Small pixel si zes and a high density with close distances make micro-LEDs suitable , among others , for small monolithic displays for augmented reality applications , especially data glasses . In addition, other applications are being developed, in particular regarding their use in data communication or pixelated lighting applications .

[0097] Advantageous embodiments and developments of the method for producing a nanoparticle , of the nanoparticle and of the optoelectronic device will become apparent from the exemplary embodiments described below in conj unction with the figures .

[0098] In the figures :

[0099] Figure 1 shows the chemical reaction scheme for producing a nanoparticle according to a reference example .

[0100] Figures 2 to 6 show chemical reaction schemes for producing nanoparticles according to exemplary embodiments .

[0101] Figure 7 shows a schematic cross section of an optoelectronic device according to an exemplary embodiment .

[0102] In the exemplary embodiments and figures , similar or similarly acting constituent parts are provided with the same reference signs . The elements illustrated in the figures and their si ze relationships among one another should not be regarded as true to scale . Rather, individual elements may be represented with an exaggerated si ze for the sake of better representability and / or for the sake of better understanding . 2024PF00715 September 9 , 2025

[0103] P2024 , 0540 WO N

[0104] - 18 -

[0105] The following examples and the reference example refer to the production of InP nanoparticles . However, the method described herein is also applicable to the production of nanoparticles containing other I I I / V compound semiconductor materials as well .

[0106] Figure 1 shows a chemical reaction scheme for producing nanoparticles , in this reference example InP containing nanoparticles , according to a reference example . This conventional method for the production of InP takes place via nucleation . First indium precursors IPr and phosphorus precursors PPr are heated to initially form monomers Mm which quickly coalesce to form somewhat stable clusters C or nuclei of InP (magic si ze clusters ) . The monomers Mm may still comprise ligands from the precursors ( indicated by bonding lines in figure 1 ) . The InP clusters C then grow into larger nanocrystals NC by either coalescing with each other, reacting with additional monomers Mm, or with additional indium precursors IPr or with additional phosphorus precursors PPr . Thus , during the growth, indium precursors IPr and phosphorus precursors PPr are always present at a time which makes the growths di f ficult to control .

[0107] Nanocrystals NC with a broad distribution of particle si zes are the result .

[0108] The indium precursors IPr are , for example , Indium ( I I I ) oleates or Indium ( I I I ) halides . The phosphorus precursors PPr are , for example , tris ( diethylamino ) phosphine or tris ( trimethylsilyl ) phosphine . Generally, the phosphorus precursors PPr comprise moieties R like amines or trimethylsilyl and the indium precursors IPr comprise ligands L like oleates , phosphonates or halides . The first or second element , in this example In and P, are associated to free 2024PF00715 September 9 , 2025

[0109] P2024 , 0540 WO N

[0110] 19 electron pairs of the ligands or comprise a free electron pair ( as indicated in figure 1 ) .

[0111] The following exemplary embodiments use the same precursors IPr and PPr as explained with respect to the reference example . However, the formation of the clusters C is avoided, for example , by applying mild reaction conditions . For example , the methods according to the exemplary embodiments are conducted at a temperature of about 180 ° C which provides mild reaction conditions . Additionally, before adding any reactants as the indium precursor IPr and the phosphorus precursor PPr, the necessary amount of the reactants is carefully calculated in order to have no or a low product of concentrations of the precursors IPr and PPr .

[0112] Furthermore , all exemplary embodiments proceed with IPr preceding PPr . Thus , in these exemplary embodiments IPr is the first precursor and PPr is the second precursor . However, the growth of the shell 11 could also begin by reacting the phosphorus precursor PPr with a substrate particle 2 , in particular with metal ions or atoms on the surface of the substrate particle 2 . In other words , PPr could be the first precursor and IPr could be the second precursor, even i f not explicitly shown here .

[0113] The exemplary embodiments according to figures 2 to 6 show the production of nanoparticles 1 each comprising substrate particles 2 and a shell 11 . However, additional shells might be formed on the shell 11 even i f not explicitly shown here .

[0114] Figure 2 shows a chemical reaction scheme for producing nanoparticles 1 according to an exemplary embodiment . Here a nanocrystal is used as a substrate particle 2 , i . e . as a 2024PF00715 September 9 , 2025

[0115] P2024 , 0540 WO N

[0116] - 20 - scaf fold . The nanocrystal is not made of InP but has a di f ferent composition as the InP shell to be produced . The nanocrystal may be a ZnSe nanocrystal , for example . An indium precursor IPr is reacted with the substrate particle 2 to form an indium coated substrate particle 2c . The reaction of IPr with the substrate particle 2 can either be an addition reaction where IPr reacts with a non-metal on the surface of the substrate particle 2 , or a displacement of a metal ion from the surface of the substrate particle 2 ( cation exchange or Z-type ligand exchange ) . The native ligands L from the indium precursor IPr will generally still be present and stabili zing the coated substrate particle 2c coated with a monolayer of In . This indium coated nanocrystal can then be reacted with phosphorus precursor PPr to form a monolayer of P on the monolayer of In and, thus , a shell 11 of InP on the nanocrystalline substrate particle 2 . Repeated alternating additions of indium and phosphorus precursors IPr and Ppr can be used to produce more monolayers of InP and, thus , to grow a thicker shell 11 on the substrate particle 2 resulting in nanoparticle 1 comprising the substrate particle 2 and the shell 11 comprising InP as I I I / V compound semiconductor material .

[0117] Figure 3 shows a chemical reaction scheme for producing nanoparticles 1 according to another exemplary embodiment . The general approach corresponds to the method as explained with respect to figure 2 . However, instead of a nanocrystal as a substrate particle 2 , here an inorganic cluster of a di f ferent composition than the I I I / V compound semiconductor material of the shell 11 to be produced is used as the substrate particle 2 . The inorganic cluster may have properties intermediate between those of molecules and nanocrystals . The inorganic cluster may be , for example , an 2024PF00715 September 9 , 2025

[0118] P2024 , 0540 WO N

[0119] 21

[0120] I I / VI material , wherein M in figure 3 stands for the metal for the element of group VI . X remains in the nanoparticle 1 and is in the beginning coated by In which replaces M ( coated substrate particle 2c ) . After the addition of phosphorus precursor PPr and alternating additional precursors IPr and PPr, X is surrounded by the formed shell 11 of InP .

[0121] Figure 4 shows a chemical reaction scheme for producing nanoparticles 1 according to another exemplary embodiment . The general approach corresponds to the method as explained with respect to figure 2 . However, instead of a nanocrystal as a substrate particle 2 , here a molecular substrate particle 2 is used . The molecular substrate particle 2 comprises ligands L and an organic moiety R, wherein R may be chosen from branched hydrocarbons and L may be chosen from primary amines or carboxylic acids . For example , EDTA is used as the substrate particle 2 . Such molecules are able to bind multiple indium atoms when being reacted with indium precursor IPr . These indium rich molecular coated substrate particles 2c are then reacted with phosphorus precursors PPr to generate InP domains . After several cycles of alternate addition of IPr and PPr a shell 11 of InP is grown on the molecule , i . e . the substrate particle 2 . The molecular substrate particle 2 remains present during the further growth of the shell 2 , and thus during the formation of nanoparticle 1 .

[0122] Figure 5 shows a chemical reaction scheme for producing nanoparticles 1 according to another exemplary embodiment . The general approach corresponds to the method as explained with respect to figure 2 , wherein all substrate particles 2 as explained with respect to figures 2 to 4 could be used . 2024PF00715 September 9 , 2025

[0123] P2024 , 0540 WO N

[0124] - 22 -

[0125] Here , the resulting shell 11 of InP does not encapsulate the substrate particle 2 , but instead grows alongside it .

[0126] Figure 6 shows a chemical reaction scheme for producing nanoparticles 1 according to another exemplary embodiment . Here , indium and phosphorus precursors IPr and PPr are reacted first to form a InP monomer Mm . But due to the mild reaction conditions and the presence of a substrate particle 2 , there does not appear any cluster formation . Instead, the monomers M reacts with the surface of the substrate particle 2 . Any of the substrate particles 2 explained with respect to figures 2 to 4 can be used in this exemplary embodiment .

[0127] Figure 7 shows a schematic cross-section of an optoelectronic component 100 according to an exemplary embodiment . The optoelectronic component 100 comprises a semiconductor chip 10 being for example an LED or micro-LED . The semiconductor chip 10 comprises an epitaxial semiconductor layer sequence with active layer 12 . The semiconductor chip 10 is configured to generate electromagnetic radiation of a first wavelength range in the active layer 12 , which exits the semiconductor chip 10 via a radiation exit surface .

[0128] A conversion element 20 is arranged on the semiconductor chip 10 , in particular, on the radiation exit surface of the semiconductor chip 10 . The conversion element 20 comprises a plurality of nanoparticles 1 according to any of the exemplary embodiments as explained with respect to figures 2 to 4 . In this example , the conversion element 20 is arranged directly on the semiconductor chip 10 , that is without an adhesive layer arranged in between . The nanoparticles 1 convert the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength 2024PF00715 September 9 , 2025

[0129] P2024 , 0540 WO N

[0130] - 23 - range which is at least partially di f ferent from the first wavelength range .

[0131] In this example , the nanoparticles 1 are embedded in a matrix material 21 . Exemplary matrix materials are epoxy, polysiloxane or silica . Alternatively, the conversion element 20 can be free of matrix material 21 and, thus , consist of nanoparticles 1 .

[0132] The conversion element 20 as shown in figure 7 has the form of a layer . However, it could also be a casting that partially surrounds the conversion element 20 .

[0133] The optoelectronic component 100 has a small distribution of emission wavelengths due to the small si ze distribution of the nanoparticles 1 .

[0134] The features and exemplary embodiments described in connection with the figures can be combined with each other according to further exemplary embodiments , even i f not all combinations are explicitly described . Furthermore , the exemplary embodiments described in connection with the figures may have alternative or additional features as described in the general part .

[0135] The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments . Rather, the invention encompasses any new feature and also any combination of features , which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments , even i f this feature or this 2024PF00715 September 9, 2025

[0136] P2024, 0540 WO N

[0137] - 24 - combination itself is not explicitly specified in the patent claims or exemplary embodiments.

[0138] This patent application claims the priority of US patent application 63 / 700,769, the disclosure content of which is hereby incorporated by reference.

[0139] 2024PF00715 September 9 , 2025

[0140] P2024 , 0540 WO N

[0141] - 25 -

[0142] References

[0143] 1 nanoparticle

[0144] 2 substrate particle 2c coated substrate particle

[0145] 10 semiconductor chip

[0146] 11 shell

[0147] 12 active layer

[0148] 20 conversion element 21 matrix material

[0149] 100 optoelectronic component

[0150] IPr indium precursor

[0151] PPr phosphorus precursor

[0152] Mm monomer C cluster

[0153] NO nanocrystal

Claims

2024PF00715 September 9, 2025P2024, 0540 WO N- 26 -Claims1. A method for producing a nanoparticle (1) , the method comprising :- providing a colloidal substrate particle (2) ,- forming a shell (11) comprising a III / V compound semiconductor material on the substrate particle (2) , wherein the substrate particle (2) comprises a material being different from the III / V compound semiconductor material.

2. The method according to the preceding claim, wherein the material of the substrate particle (2) is chosen from II / VI compound nanocrystals, inorganic clusters of elements chosen from group II and / or group VI, inorganic clusters of mixtures of elements chosen from group II / VI compound semiconductor materials and III / V compound semiconductor materials, and organic molecules.

3. The method according to any of the preceding claims, wherein the shell (11) is formed completely around the substrate particle (2) .

4. The method according to any of claims 1 or 2, wherein the shell (11) is formed adjacent to the substrate particle (2) .

5. The method according to any of the preceding claims, wherein the shell (11) is chemically bonded to the substrate particle ( 2 ) .

6. The method according to any of the preceding claims, wherein forming the shell (11) comprises the steps of2024PF00715 September 9, 2025P2024, 0540 WO N27- reacting the substrate particle (2) with a first precursor to form a monolayer of a first element on the substrate particle,- reacting the substrate particle (2) with a second precursor to form a monolayer of a second element on the monolayer of the first element, wherein one of the first and second precursor is chosen from a precursor of a group III element and the other one of the first and second precursor is chosen from a precursor of a group V element.

7. The method according to the preceding claim, further comprising alternately reacting the substrate particle (2) with the first and second precursors to form a plurality of alternating monolayers of the first element and of the second element .

8. The method according to any of the preceding claims, wherein forming the shell (11) is conducted at a temperature chosen from a range of 150°C to 250°C.

9. The method according to any of claims 6 to 8, wherein during forming the shell (11) a product of first precursors and second precursors being present at once is so low, that independent clusters of elements of group III and elements of group V cannot be formed.

10. The method according to any of claims 6 to 9, wherein a purifying step is performed after each formation of a monolayer .2024PF00715 September 9, 2025P2024, 0540 WO N- 28 -11. The method according to any of the claims 1 to 5, wherein forming the shell (11) comprises reacting the substrate particle (2) with monomers of the III / V compound semiconductor material.

12. The method according to any of the preceding claims, wherein the III / V compound semiconductor material is InP.

13. The method according to any of the preceding claims, wherein at least one additional shell is formed on the shell (11) •14. A nanoparticle (1) , comprising:- a substrate particle (2) , and- a shell (11) comprising a III / V compound semiconductor material on the substrate particle (2) , wherein the substrate particle (2) comprises a material being different from the III / V compound semiconductor material.

15. The nanoparticle (1) according to the preceding claim, wherein the material of the substrate particle (2) is chosen from II / VI compound nanocrystals, inorganic clusters of elements chosen from group II and / or group VI, inorganic clusters of mixtures of elements chosen from group II / VI compound semiconductor materials and III / V compound semiconductor materials, and organic molecules.

16. The nanoparticle (1) according to any of the preceding claims 14 or 15, wherein the III / V compound semiconductor material comprises InP.

17. The nanoparticle (1) according to any of claims 14 to 16, comprising at least one additional shell on the shell (11) .2024PF00715 September 9, 2025P2024, 0540 WO N- 29 -18. An optoelectronic device (100) , comprising:- a semiconductor chip (10) , and- a conversion element (20) on the semiconductor chip (10) , wherein the conversion element (20) comprises nanoparticles (1) according to any of claims 14 to 17.

19. The optoelectronic device (100) according to the preceding claims, wherein the semiconductor chip comprises a micro-LED.

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