Sol-gels as binders for the production of conversion elements

Abstract

Method for producing a conversion element (2) comprising the steps: - Hydrolysis of at least one metal precursor in a solvent, - optionally adding a catalyst to the hydrolyzed metal precursor, - optionally adding at least one additive to the hydrolyzed metal precursor, - Preparation of a sol-gel by condensing the at least one hydrolyzed metal precursor, - Dispersing at least one phosphor in the sol-gel, and - Applying the fluorescent sol-gel dispersion directly onto a light-emitting layer (3).

Description

[0001] The text describes the use of a sol-gel for the fabrication of a conversion element, a method for the fabrication of a conversion element, a conversion element, an optoelectronic semiconductor device, and the use of a conversion element.

[0002] A conversion element typically consists of phosphor particles embedded in a silicon matrix and arranged on the light-emitting layer (or chip). However, the use of silicon is limited due to its instability towards blue light, particularly in high-power or high-flux LED applications. Additional disadvantages arise from light extraction from the light-emitting layer (or chip) due to silicon's low refractive index (approximately 1.5). Prior art can be found in DE 10 2017 104 135 A1, DE 196 25 622 A1, and DE 10 2017 104 128 A1.

[0003] As an alternative to a silicone matrix, water glass (potassium silicate) is also used as a matrix material for phosphor particles in the prior art. The water glass is applied to the light-emitting, passivated layer (or the chip) and cured at temperatures below 400 °C. In an alternative embodiment from the prior art, water glass is applied together with the phosphor particles to a glass substrate, thus coating it. Nevertheless, the refractive index of water glass is very similar to that of silicone.

[0004] High-flux LED applications require phosphors, which are generally produced in the form of ceramic platelets and are stable at high sintering temperatures. These ceramic platelets are manufactured by sintering suitable starting materials at high temperatures (> 1500 °C). Due to the required high-temperature stability of the ceramic platelets, only cool white and amber phosphors and phosphor mixtures can be used to produce them. Generally, the phosphors are applied in powder form in a compact layer to create a thin layer of the desired thickness. This layer is then die-cut into the desired platelet shape, and the phosphors are subjected to a high sintering temperature of over 1500 °C to fuse the phosphor particles together, thus producing ceramic platelets.

[0005] Applying high temperatures to stamped ceramic plates used as conversion elements can cause the plates to warp, leading to incomplete or imprecise coverage of the light-emitting layer (or chip). This warping can also result in uneven thermal bonding of the conversion element to the light-emitting layer (or chip) via silicone adhesive. Consequently, this can lead to reliability issues due to insufficient heat dissipation.

[0006] The object of the present invention was therefore to overcome the disadvantages of the prior art and to provide a use of a sol-gel for the production of a conversion element, a new method for the production of a conversion element, a new conversion element, an optoelectronic semiconductor device, and the use of a new conversion element.

[0007] The object of the present invention is achieved by using a sol-gel for the production of a conversion element according to claim 1, a method for producing a conversion element according to claim 2, a conversion element according to claim 9, a conversion element according to claim 10, an optoelectronic semiconductor device according to claim 14, and the use of a conversion element according to claim 15. Advantageous further developments and embodiments are the subject of the dependent patent claims.

[0008] The present invention relates to the use of a sol-gel for the production of a conversion element, wherein the sol-gel comprises: - at least one metal precursor, - at least one solvent and - possibly at least one additive.

[0009] In the context of the present invention, a conversion element is an optoelectronic component by means of which light of a certain wavelength can be converted into light of at least a second wavelength.

[0010] In one embodiment, light of a specific wavelength (e.g., blue light) is converted into yellow and / or green light.

[0011] In another embodiment, light of a specific wavelength (e.g. blue light) is converted into red light.

[0012] Within the scope of the present invention, a sol is understood to be a dispersion of a “polymer-like” solid phase in a liquid phase.

[0013] Within the scope of the present invention, a gel is understood to be a viscous mass that is formed when the particles of a sol are further polymerized.

[0014] A sol-gel according to the present invention is understood to be a mixture between the two phase states of the sol and the gel, wherein all conceivable percentage proportions of the two phase states are possible. For example, the term sol-gel is also used here when the proportion of sol is 100% and the proportion of gel is 0%, as well as when the proportion of sol is 0% and the proportion of gel is 100%.

[0015] Within the scope of the present invention, the sol-gel serves as an adhesive for the existing particles, in particular for the phosphor particles.

[0016] In general, during a sol-gel reaction, a metal precursor is hydrolyzed by the solvent, and the hydrolyzed metal precursor then condenses with further hydrolyzed metal precursor molecules, releasing water. This polycondensation reaction of multiple metal precursor molecules leads to the formation of metal oxides and an increase in the viscosity of the mixture.

[0017] In simplified terms, the reaction can proceed as follows, with the stoichiometry being shown only as an example: MX + ROH → M-OR + HX (I) M-OR + H + + H2O → M-OH + ROH (II)

[0018] MX refers to a metal halide. ROH is an alcohol. M-OH is the hydrolyzed metal precursor.

[0019] When a metal alkoxide is used as a metal precursor, a catalyst is often present during the hydrolysis of the metal precursor. This catalyst can be an acid.

[0020] In simplified terms, the reaction to form the sol-gel in one embodiment proceeds as follows, with the stoichiometries being merely exemplary: M-OR + M-OH → MOM + ROH (III)

[0021] The general formula M-OR is a metal alkoxide, M-OH is a hydrolyzed metal precursor, and MOM represents the basic structure of the sol-gel.

[0022] In general terms, the metal precursor can be a metal halide or a metal alkoxide.

[0023] The metals of the metal precursor are preferably selected from the alkaline earth, transition metals, metalloids, or boron group. In particular, the metal of the metal precursor may be selected from group 2, 4, 5, 12, 13, or 14 of the periodic table of elements.

[0024] Metal halides can be chlorides, bromides, or iodides of the metals.

[0025] In one embodiment, the metal salt is selected from the group consisting of metal halides, metal acetates and metal oxalates.

[0026] In one embodiment, the metal alkoxide is selected from the group consisting of metal alkoxides, alkyl metal alkoxides and aryl metal alkoxides.

[0027] An alkoxide is a compound with the general formula M(RO) n , where M = metal ion, R = alkyl, aryl and n = valence of the metal ion.

[0028] The metal alkoxides can be methoxides, ethoxides, butoxides, propoxides, isopropoxides, etc. of the metals.

[0029] The metal alkoxides can also be partially alkylated. In this case, at least one alkoxide group is replaced by an alkyl group. The presence of at least one alkyl group can lead to stabilization of the hydrolyzed metal precursor and to stabilization of the sol-gel.

[0030] Examples of metal precursors are tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), triethoxymethylsilane (MeTEOS) and trimethoxymethylsilane (MeTMOS).

[0031] Further examples of metal precursors within the scope of the present invention are InCl3, SnCl4, SbCl5, Zn(OAc)2, ZnCl 2, ZnBr2, zinc methoxide, Sb(OAc)3, In(OAc)3, Sn(OAc)4, AlCl3, aluminum isopropoxide, TiCl4, titanium(IV) ethoxide, NbCl5, niobium ethoxide, BaCl2, barium isopropoxide.

[0032] In one embodiment, at least one metal precursor is selected from the group consisting of metal halides, metal acetates, metal oxalates, metal alkoxides, alkyl metal alkoxides and aryl metal alkoxides.

[0033] In one embodiment, the sol-gel comprises various metal precursors.

[0034] In one embodiment, the sol-gel comprises a compound as a metal precursor.

[0035] By selecting suitable metal precursors, the refractive index of the conversion element formed from the sol-gel can be adjusted. A higher refractive index than, for example, that of silicon would increase the light extraction from the light-emitting layer (or the chip).

[0036] In the process according to the invention, the metal precursor is hydrolyzed in the solvent.

[0037] The solvents used in the present invention can be selected from the group consisting of water, alcohols, and mixtures thereof. Preferred alcohols are ethanol, methanol, isopropanol, butanol, isobutanol, and benzyl alcohol. Particularly preferred alcohols as solvents are methanol and ethanol.

[0038] In another embodiment, the sol-gel can comprise at least one additive.

[0039] The additives can be chosen in such a way that they have a particularly beneficial effect on the properties of the sol-gel.

[0040] In one embodiment, the at least one additive may be selected from the group consisting of metals or oxides and mixtures thereof, in particular in the form of nanoparticles, nanowires, nanoplatelets and mixtures thereof.

[0041] The metals in question could be silver, gold, platinum, or alloys thereof.

[0042] According to the present invention, nanoparticles have a size of approximately 2 to approximately 200 nm. In one embodiment, the nanoparticles have a size of approximately 2 nm to approximately 100 nm. In another embodiment, the nanoparticles have a size of approximately 2 nm to approximately 50 nm. In a further embodiment, the nanoparticles have a size of approximately 3 nm to approximately 20 nm.

[0043] According to the present invention, nanowires have a length of approximately 150 nm to approximately 1 µm. In one embodiment, the nanowires have a length of approximately 300 nm to approximately 800 nm. In another embodiment, the nanowires have a length of approximately 500 nm to approximately 700 nm.

[0044] According to the present invention, nanowires have a diameter of approximately 3 nm to approximately 50 nm. In one embodiment, the nanowires have a diameter of approximately 5 nm to approximately 40 nm. In another embodiment, the nanowires have a diameter of approximately 10 nm to approximately 20 nm.

[0045] In one embodiment, the aforementioned lengths of the nanowires can be combined with the respective diameters. Thus, a nanowire can have a length of approximately 150 nm to approximately 1 µm and a diameter of approximately 3 nm to approximately 50 nm.

[0046] According to the present invention, nanoplatelets have an edge length of approximately 150 nm to approximately 1 µm. In one embodiment, the nanoplatelets have an edge length of approximately 200 nm to approximately 800 nm. In another embodiment, the nanoplatelets have an edge length of approximately 400 nm to approximately 600 nm.

[0047] According to the present invention, nanoplatelets have a thickness of approximately 3 nm to approximately 50 nm. In one embodiment, the nanoplatelets have a thickness of approximately 5 nm to approximately 40 nm. In another embodiment, the nanoplatelets have a thickness of approximately 10 nm to approximately 20 nm.

[0048] In one embodiment, the respective edge lengths of the nanoplatelets can be combined with the respective thicknesses. Thus, a nanoplatelet can have an edge length of approximately 150 nm to approximately 1 µm and a thickness of approximately 3 nm to approximately 50 nm.

[0049] For example, the refractive index can be increased by adding a nanomaterial. Suitable nanomaterials can be nanoparticles, nanorods, nanowires, or nanolayers. These can be made from TiO2, ZrO2, BaTiO3, SrTiO3, TCO, Al2O3, Nb2O5, HfO2, ZnO, and the like.

[0050] Oxide nanoparticles may also be present as additives. Examples include Al₂O₃, SiO₂, TiO₂, ZrO₂, ZnO, etc. Such oxides can contribute to stabilizing the conversion element and lowering the processing temperature.

[0051] To improve thermal conductivity, particles and wires can be added as additives to the conversion element. Examples of suitable materials include diamond (~2200-3320 W / m·K), SiC (~270-490 W / m·K), GaP (~100-110 W / m·K), and AlN (~285 W / m·K). However, other materials with similar conductivity values ​​can also be used.

[0052] The additives can consist of either a single substance or a combination of several. The additives are selected to achieve the desired properties in a particularly advantageous way.

[0053] In one embodiment, the sol-gel further comprises at least one phosphor, wherein the phosphor may be selected from the group consisting of garnet phosphors, nitridosilicate phosphors and mixtures thereof.

[0054] In one embodiment, the at least one phosphor is selected from the group consisting of oxide-based phosphors (e.g. yttrium aluminum garnet (YAG), lutetium aluminum garnet (LuAG)) or nitride- and oxynitride-based phosphors (e.g. α-SiAlON, β-SiAlON, SCASN, CASN) and mixtures thereof.

[0055] Table 1 shows exemplary embodiments of sol gels: Table 1 Sol-Gel No. Metal precursor(s) solvent Additive(s) 1 TMOS / MeTMOS Water / EtOH SiO2 nanoparticles 2 TEOS / MeTEOS Ethanol SiO2 nanoparticles 3 TMOS / MeTMOS Water ZrO2 nanoparticles 4 TEOS / MeTEOS Ethanol / Methanol ZrO2 nanoparticles

[0056] Furthermore, the present invention relates to a method for manufacturing a conversion element comprising the steps of: - Hydrolysis of at least one metal precursor in a solvent, - optionally adding a catalyst to the hydrolyzed metal precursor, - optionally adding at least one additive to the hydrolyzed metal precursor, - Preparation of a sol-gel by condensing the at least one hydrolyzed metal precursor, - dispersing at least one phosphor in the sol-gel.

[0057] The metal precursor, solvent, catalyst, additive and phosphor can be selected as described above.

[0058] The refractive index of the resulting conversion element can be adjusted by selecting the metal precursor(s) as well as the additives. For example, the refractive index can be further increased by adding suitable nanoparticles. For instance, adding nanoparticles with a high refractive index can enhance the light extraction from the conversion element. Examples of nanoparticles that can increase the refractive index include TiO₂, ZrO₂, BaTiO₃, ITO (indium tin oxide), TCO, Al₂O₃, and Nb₂O. 5, TiO2, ZrO2, BaTiO3, SrTiO3, Al2O3, Nb2O5, HfO2, ZnO, and the like.

[0059] Transparent conductive oxides (TCOs) are transparent conductive oxides. In particular, TCOs comprise doped In₂O₃, SnO₂, ZnO, or CdO. Preferably, the oxides are doped with Sn, Zn, Al, Ga, or In. Specifically, the oxides are doped with 1 to 40 mol%, such as In₂O₃ doped with 3 mol% Sn or In₂O₃ doped with 10 mol% Sn (both described as ITOs). Other examples of TCOs are ITO (indium tin oxide), ATO (antimony-doped tin oxide), IZO (indium zinc oxide), AZO (antimony-doped zinc oxide), IMO (indium-doped molybdenum oxide), IGO (indium-doped gallium oxide), and mixtures thereof.

[0060] In a further step of the process according to the invention, a sol-gel is produced by condensing the at least one hydrolyzed metal precursor.

[0061] As described above, in a sol-gel reaction, a metal precursor is hydrolyzed by the solvent, and the hydrolyzed metal precursor condenses with further hydrolyzed metal precursor molecules, releasing water. This polycondensation reaction of multiple metal precursor molecules leads to the formation of metal oxides and an increase in the viscosity of the mixture.

[0062] In a further step, at least one phosphor is dispersed in the sol-gel, thus producing a phosphor-sol-gel dispersion.

[0063] As mentioned above, at least one phosphor can be selected from the group consisting of garnet phosphors, nitridosilicate phosphors and mixtures thereof.

[0064] In one embodiment, the at least one phosphor is selected from the group consisting of oxide-based phosphors (e.g. yttrium aluminum garnet (YAG), lutetium aluminum garnet (LuAG)) or nitride- and oxynitride-based phosphors (e.g. α-SiAlON, β-SiAlON, SCASN, CASN) and mixtures thereof.

[0065] The phosphor can be in the form of a particle, flake, powder, etc. It is typically found in particle sizes ranging from 3 nm to 30 µm, and more precisely, from 3 µm to 25 µm.

[0066] In an alternative embodiment, the at least one phosphor is added to the hydrolyzed metal precursor and the sol-gel is then produced.

[0067] In another embodiment, the fluorescent sol-gel dispersion is applied to a light-emitting layer.

[0068] In another embodiment, the fluorescent sol-gel dispersion is applied to a hydrophobic layer. This hydrophobic layer can be Teflon or silicone.

[0069] The fluorescent sol-gel dispersion can be applied to the light-emitting layer or the hydrophobic layer using various techniques known in the prior art. Examples include stamping, screen printing, and the like. In general, all methods normally suitable for applying polymer-like adhesives are conceivable.

[0070] Fluorescent sol-gel dispersions are preferably applied directly to the light-emitting layer. Compared to water glass, as known from the prior art, fluorescent sol-gel dispersions have a significantly lower pH value. The high pH value of water glass can damage the light-emitting layer, meaning that direct coating with water glass-based conversion elements is only possible on light-emitting layers passivated with silicon dioxide.

[0071] In another embodiment, the pH value of the fluorescent sol-gel dispersion can be adjusted by changing the composition of the sol-gel, which makes the fluorescent sol-gel dispersion suitable for a wide variety of applications.

[0072] In another embodiment, the fluorescent sol-gel dispersion, in particular together with the light-emitting layer or the hydrophobic layer, is heated.

[0073] In a further step, the product can be heated to a temperature in the range of 150 °C to 600 °C. A temperature in the range of 150 °C to 350 °C is preferred, and a temperature in the range of 200 °C to 250 °C is particularly preferred.

[0074] The temperature is preferably selected depending on the materials used. For example, the temperature can be chosen based on the metal precursors, the solvent, or the additives. Additives can, for instance, lower or raise the temperature.

[0075] Heating further accelerates the elimination of water and / or alcohol molecules, and thus the polycondensation in the sol-gel reaction. This increases the viscosity of the fluorescent sol-gel dispersion.

[0076] Heating the fluorescent sol-gel dispersion hardens it and transforms it into a solid layer or matrix, i.e., a metal oxide layer in which the fluorescent substance(s) is / are embedded. The metal oxides thus form a kind of binder for the fluorescent substances. The solid layer encompassing the embedded fluorescent substance(s) then forms the conversion element.

[0077] The composition of the sol-gel thus determines the composition of the metal oxide formed.

[0078] In one embodiment, the metal of the resulting metal oxide is selected from the group consisting of alkaline earth metals, transition metals, metalloids, or boron. In particular, the metal of the metal oxide can be selected from group 2, 4, 5, 12, 13, or 14 of the periodic table of elements.

[0079] Particularly preferred are the metal oxides formed from the corresponding sol-gel SiO2, Al2O3, TiO2, ZnO, TCO, Nb2O5, ZrO2, etc.

[0080] The oxides can be present in pure form or in a mixture of different oxides.

[0081] In one embodiment, the at least one metal oxide is selected from the group consisting of SiO2, Al2O3, TiO2, ZnO, the TCO class (transparent and electrically conductive oxides) (such as ITO, ATO, IZO, AZO, IMO, IGO and mixtures thereof), Nb2O5, ZrO2, HfO2, BaTiO3, SrTiO3, and mixtures thereof.

[0082] Particularly preferred metal oxides are SiO2, Al2O3, TiO2, metal oxides of the TCO class, Nb2O5, ZrO2, HfO2 or mixtures thereof.

[0083] The metal oxides are specifically selected to have a desired refractive index. For example, TiO2 has a refractive index of 2.4, while SiO2 has a refractive index of 1.5. The higher the refractive index, the greater the light extraction, which is particularly advantageous.

[0084] The metal oxides, such as SiO2, exist in an amorphous or crystalline structure within the metal oxide. In the context of the present invention, an amorphous structure is understood to be a structure that lacks order and exhibits only short-range order, but no long-range order, of the individual atoms. The opposite of an amorphous structure is a crystalline structure.

[0085] In one embodiment, a particularly stable, crack-free, or crack-minimized matrix is ​​produced by using metal precursors substituted with at least one alkyl group. An example of such a metal precursor is CH3Si(OEt)₂. 3.

[0086] Heating can be done in an oven or using a hot plate.

[0087] The use of a sol-gel is particularly advantageous for lowering the curing temperature, or more generally the sintering temperature, as conventionally used in the production of (ceramic) conversion elements. Conventional temperatures for the production of (ceramic) conversion elements are above 1500 °C. By using the sol-gel, the curing or sintering temperature, and thus the temperature for the production of conversion elements, can be reduced to well below 1500 °C, for example, to a temperature in the range between 150 °C and 600 °C, preferably in the range of 150 °C to 350 °C.

[0088] Such low temperatures allow the production of conversion elements with a wide variety of phosphors. For example, (ceramic) conversion elements with a single phosphor, as well as with a mixture of two or more phosphors (e.g., two or three), can be produced. Using a method according to the invention, conversion elements can be manufactured in which the light color can be optimally adjusted. For example, it is possible to produce LEDs that emit warm white light using the conversion elements according to the invention.

[0089] For example, the inventive method can be used to produce conversion elements with phosphors that have a higher efficiency than those known in the prior art. In methods for producing conversion elements known in the prior art, the phosphors must be selected, in particular, according to the criterion that they can withstand the high sintering temperatures used to produce the conversion element without damage. With the present method, which allows the use of lower curing temperatures, phosphors can also be selected that may not be stable at higher temperatures but exhibit higher efficiency.

[0090] The curing temperature can be chosen depending, for example, on the selected metal precursor, but also on the optional additives present.

[0091] The resulting metal oxides of the conversion elements are generally stable with respect to temperature, light, and humidity. Compared to potassium silicate as a binder for phosphors, the sol-gel dispersion is stable with respect to humidity and contains less ionic species (such as potassium oxide). +, Al 3+ ) in the conversion element is significantly lower.

[0092] An additional advantage of the sol-gel dispersion described here over potassium silicate is that, when producing conversion elements from potassium silicate, dilution of the potassium silicate solution is necessary to prevent excessively rapid hardening. This results in a highly porous potassium silicate matrix capable of absorbing adjacent reflector material (e.g., TiO2).

[0093] When using sol-gel dispersion, the porosity of the resulting matrix can be reduced. Increasing the sol concentration of the metal oxide precursors can minimize absorption from the adjacent layer. Curing can be achieved through heat treatment rather than machining the sol.

[0094] Table 1 shows exemplary combinations for carrying out methods according to the invention for the production of conversion elements. Table 1 Procedure No. Metal precursor(s) solvent catalyst(s) Additive(s) Fluorescent material(s) 1 TMOS / MeTMOS Water / Ethanol HCl SiO2 nanoparticles LuAG, SCASN 2 TEOS / MeTEOS Ethanol HCl SiO2 nanoparticles YAG, α-SiAlON, β-SiAlON 3 TMOS / MeTMOS Water HCl ZrO2 nanoparticles YAG, α-SiAlON 4 TEOS / MeTEOS Ethanol / Methanol HCl ZrO2 nanoparticles YAG, α-SiAlON

[0095] Table 1 contains: SCASN phosphors are phosphors of the formula ((Sr,Ca)SiAlN3:Eu). YAG are yttrium aluminum garnet phosphors. CASN are nitride silicates of the formula CaAlSiN3:Eu 2+ .

[0096] Furthermore, the present invention relates to a conversion element which was produced according to an embodiment of a method according to the invention.

[0097] In one embodiment, the conversion element is a ceramic plate made from the sol-gel as described above.

[0098] The conversion element can be formed by heating the sol-gel and thus by the formation of the corresponding metal oxide. Typical heating temperatures range from approximately 80 °C to approximately 600 °C.

[0099] Furthermore, the present invention relates to a conversion element comprising: - at least one metal oxide, - at least one fluorescent material, and - possibly at least one additive.

[0100] The metal oxide, the phosphor, and the additive are substances as described above. The metal oxide is particularly advantageously produced by a sol-gel reaction as described herein.

[0101] Table 2 shows exemplary embodiments of conversion elements. Table 2 Conversion element no. Metal oxide(s) Fluorescent material(s) Additive(s) 1 SiO2 LuAG, SCASN ZrO2 2 Al2O3 YAG, α-SiAlON, β-SiAlON TiO2 3 ZrO2 YAG, α-SiAlON no 4 Al2O3 YAG, α-SiAlON SiO2

[0102] Furthermore, the present invention relates to an optoelectronic semiconductor component comprising: - at least one light-emitting layer and - at least one conversion element according to the present invention.

[0103] For the purposes of this invention, an optoelectronic semiconductor component is understood to be, for example, an LED (light emitting diode).

[0104] According to the present invention, a light-emitting layer is provided. This can be, for example, a light-emitting chip, e.g., indium-doped gallium nitride.

[0105] Furthermore, the present invention relates to the use of a conversion element according to the present invention in an optoelectronic semiconductor device.

[0106] Further advantageous embodiments and developments of the invention will result from the exemplary embodiments described below in conjunction with the figures. Figures Fig. Figure 1 shows an optoelectronic semiconductor device Fig. Figure 2 shows an example of a sol-gel reaction

[0107] Fig. Figure 1 shows an exemplary embodiment of an optoelectronic semiconductor device (1). A conversion element (2) is directly connected to a light-emitting layer (3) (e.g., gallium nitride). The conversion element is, for example, TiO2 in whose structure LuAG and / or YAG is incorporated as a phosphor.

[0108] Fig.Figure 2 shows an example of a sol-gel reaction. The metal precursor titanium tetrachloride is hydrolyzed using ethanol and water. Only the substitution of a chloride group by an ethoxy or hydroxy group is shown as an example. As the reaction progresses, all chloride groups can be replaced. Further reaction involves the polycondensation of the metal precursor with the elimination of ethanol, thus forming the sol-gel. Further removal of the solvent (here, ethanol), for example by heating, leads to the formation of a metal oxide and thus a matrix into which the phosphors (not shown here) can be embedded.

[0109] The invention is not limited to the description provided by means of the exemplary embodiments. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the claims, even if that feature or combination itself is not explicitly stated in the claims or exemplary embodiments. Reference symbol list 1 optoelectronic semiconductor device 2 Conversion element 3 light-emitting layers

Claims

[1] Method for producing a conversion element (2) comprising the steps: - Hydrolysis of at least one metal precursor in a solvent, - optionally adding a catalyst to the hydrolyzed metal precursor, - optionally adding at least one additive to the hydrolyzed metal precursor, - Preparation of a sol-gel by condensing the at least one hydrolyzed metal precursor, - Dispersing at least one phosphor in the sol-gel, and - Applying the fluorescent sol-gel dispersion directly onto a light-emitting layer (3). [2] Method for producing a conversion element (2) according to claim 1, wherein the metal precursor is selected from the group consisting of metal halides or metal alkoxides. [3] Method for producing a conversion element (2) according to claim 1 or 2, wherein the phosphor is selected from the group consisting of garnet phosphors, nitridosilicate phosphors and mixtures thereof. [4] Method for producing a conversion element (2) according to any one of claims 1 to 3, further comprising the step: - Heating the fluorescent sol-gel dispersion. [5] Method for producing a conversion element (2) according to claim 4, wherein the temperature is selected between 150 °C and 600 °C, preferably between 150 °C and 350 °C, more preferably between 200 °C and 250 °C. [6] Conversion element (2) manufactured according to any one of claims 1 to 5. [7] Optoelectronic semiconductor device (1) comprising: at least one light-emitting layer (3) and at least one conversion element (2) according to claim 6. [8] Use of a conversion element (2) according to claim 6 in an optoelectronic semiconductor device (1)

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