Conversion element, method for producing a conversion element, and light-emitting device

Abstract

A conversion element (1) is specified. The conversion element (1) comprises a substrate (2) and a conversion layer (3) comprising a polysiloxane (4), phosphor particles (5), and filler particles (6), wherein the conversion layer (3) comprises at most 35 vol% of the polysiloxane (4) and the conversion layer (3) comprises at least 25 vol% of the filler particles (6). Furthermore, a method for producing a conversion element and a light-emitting device with the conversion element are specified.

Description

[0001] 2023PF01825 April 29, 2025P2024,0112 WO N -1 –Description CONVERSION ELEMENT, METHOD FOR PRODUCING A CONVERSION ELEMENT, AND LIGHT-EMITTING DEVICE A conversion element, a method for producing a conversion element, and a light-emitting device are specified. It is an object to provide a conversion element with improved efficiency. In particular, a conversion element shall be provided which at least shows reduced cracking and / or delamination. Furthermore, it is an object to provide a conversion element having a smooth surface. Additionally, a method for producing such a conversion element shall be specified. It is also an object to provide a light-emitting device with improved efficiency. According to at least one embodiment, the conversion element comprises a substrate. In particular, the substrate is rigid. Thus, advantageously, the substrate provides mechanical stability for the conversion element. For example, the substrate is transparent to electromagnetic radiation in the UV, visible, and / or IR region of the electromagneticspectrum. The conversion element can be a self-supportingconversion element due to the substrate.In particular, a material of the substrate is selected from the group consisting of glass, polymer, polymer blend, and sapphire. The glass is, for example, borosilicate glass. For instance, a thickness of the substrate is between andincluding 70 micrometers and 200 micrometers. Here and in thefollowing, the thickness of an element such as the substrate2023PF01825 April 29, 2025P2024,0112 WO N -2 –is an extension of the respective element perpendicular to its main extension plane. Advantageously, the substrate comprising these materials and / or having the specified thickness offers mechanical stability. According to at least one embodiment, the conversion element comprises a conversion layer. In particular, the conversion layer is configured to convert electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range. The electromagnetic radiation of the first wavelength range is, for example, provided by a light- emitting semiconductor chip. In particular, the conversion layer is in direct mechanical contact with the substrate. In other words, no further layers are arranged between the conversion layer and the substrate. According to at least one embodiment of the conversion element, the conversion layer comprises a polysiloxane. In particular, the polysiloxane comprises or consists of M-units (R3SiO-), D-units (-OR2SiO-), and / or T-units (-ORSiO2-). In contrast to a silicone, the polysiloxane can comprise T- units. For instance, the polysiloxane is formed from a polysiloxane precursor which comprises the M-units, D-units,and / or T-units. It is possible that the polysiloxane is freeof Q-units (-OSiO3-). According to at least one embodiment of the conversion element, the conversion layer comprises phosphor particles. In particular, the phosphor particles convert theelectromagnetic radiation of the first wavelength range intoelectromagnetic radiation of the second wavelength range. In other words, wavelength converting properties of the2023PF01825 April 29, 2025P2024,0112 WO N -3 –conversion layer and thus also the conversion element arise from the phosphor particles.In particular, the phosphor particles comprise a ceramicphosphor and / or a quantum dot phosphor. The ceramic phosphor comprises, for instance, a material selected from the group consisting of a garnet, a nitride, an oxynitride, a SiAlONs, an oxynitridosilicate, a perovskite, a silicate, and combinations thereof. In particular, the phosphor is a garnet-type phosphor. For example, the phosphor is selected from the followinggroup: Ce3+ doped garnets such as YAG and LuAG, for example(Y, Lu,Gd,Tb) (Al1-x,Gax)5O 3+ 2+3 12:Ce ; Eu doped nitrides, forexample (Ca,Sr)AlSiN :Eu2+, Sr(Ca,Sr)Si Al N 2+3 2 2 6:Eu (SCASN),(Sr,Ca)AlSiN3*Si2N2O:Eu2+, (Ca,Ba,Sr)2Si5N8:Eu2+, SrLiAl3N4:Eu2+,SrLi Al O N :Eu2+; Ce3+2 2 2 2 doped nitrides, for example (Ca,Sr)Al(1-Si N :Ce 2+4x / 3) (1+x) 3 ; (x = 0,2 – 0,5); Eu doped sulfides,(Ba,Sr,Ca)Si 2+2O2N2:Eu , SiAlONs, nitrido-orthosilicates (forexample AE2-x-aRExEuaSi1-yO4-x-2yNx), orthosilicates(Ba,Sr,Ca)2SiO4:Eu2+; chlorosilicates (for exampleCa8Mg(SiO4)4Cl2:Eu2+); Mn4+ doped fluorides, for example(K,Na)2(Si,Ti)F6:Mn4+; Eu2+ or Ce3+ doped litho-silicates, suchas (Li,Na,K,Rb,Cs)(Li SiO ):E with 2+ 3+3 4 E = Eu , Ce , or(Sr,Li)Li AlO :Eu2+ or SrLi AlO :Eu2+; (B 2+3 4 3 4 a1-x-ySrxCay)SiO4:Eu (0^ x ^ 1, 0 ^ y ^ 1), (Ba Sr Ca ) 2+1-x-y x y 3SiO5:Eu (0 ^ x ^ 1, 0 ^ y^ 1), Li2SrSiO4:Eu2+, oxo-nitrides such as (Ba1-x-Sr Ca )Si O N :Eu2+ (0 ^ x ^ 1; 0 ^ y ^ 2+y x y 2 2 2 1), SrSiAl2O3N2:Eu ,Ba Ca Si ON :Eu2+ (0 ^ x ^ 1), ( 2+4-x x 6 10 Ba1-xSrx)Y2Si2Al2O2N5:Eu (0 ^x ^ 1), Sr Si Al O 2+x (6-y) y yN(8-y):Eu (0,05 ^ x ^ 0,5; 0,001 ^ y ^0,5), Si 2+ 2+6-zAlzOzN8-z:Eu (0 ^ z ^ 0,42), MxSi12-m-nAlm+nOnN16-n:Eu(M = Li, Mg, Ca, Y; x = m / v; v = valency of M, x ^ 2), MxSi12-2023PF01825 April 29, 2025P2024,0112 WO N -4 –m-nAlm+nOnN16-n:Ce3+, AE2-x-aRExEuaSi1-yO4-x-2yNx(AE = Sr, Ba, Ca, Mg; RE = rare earth element), AE2-x-aRExEuaSi1-yO4-x-2yNx(AE = Sr,Ba, Ca, Mg; RE = rare earth element), Ba 2+3Si6O12N2:Eu ornitrides such as La Si N 1: 3+ 3+3 6 1 Ce , (La1-xYx)3Si6N11:Ce , (Ba1-x-Sr Ca ) Si N :Eu2+, (Ca Sr Ba )AlSiN 2+y x y 2 5 8 1-x-y x y 3:Eu (0 ^ x ^ 1; 0 ^ y ^1), Sr(Sr Ca )A 2+1-x x l2Si2N6:Eu (0 ^ x ^ 0,2), Sr(Sr1-Ca )Al Si 3+ 2+x x 2 2N6:Ce (0 ^ x ^ 0,2) SrAlSi4N7:Eu , (Ba1-x-2+ 3+ySrxCay)SiN2:Eu (0 ^ x ^ 1; 0 ^ y ^ 1), (Ba1-x-ySrxCay)SiN2:Ce(0 ^ x ^ 1; 0 ^ y ^ 1), (Sr1-xCax)LiAl3N4:Eu2+ (0 ^ x ^ 1),(Ba1-x-ySrxCay)Mg2Al2N4:Eu2+ (0 ^ x ^ 1; 0 ^ y ^ 1), (Ba1-x-ySrxCay)Mg3SiN4:Eu2+ (0 ^ x ^ 1; 0 ^ y ^ 1).According to at least one embodiment of the conversion element, the conversion layer comprises filler particles. Advantageously, the filler particles can be used to increase a solids content in the conversion layer. Furthermore, the filler particles can change various properties of the conversion layer. For instance, the filler particles are used to adjust a thermal expansion coefficient (CTE) of the conversion layer. Thus, stress on the conversion layer can be advantageously reduced. According to at least one embodiment of the conversion element, the conversion layer comprises at most 35 vol% of the polysiloxane. According to at least one embodiment of the conversion element, the conversion layer comprises at least 25 vol% ofthe filler particles. This content of the filler particles inthe conversion layer is sufficient to adjust the thermal expansion coefficient.2023PF01825 April 29, 2025P2024,0112 WO N -5 –According to at least one embodiment, the conversion elementcomprises the substrate and the conversion layer comprisingthe polysiloxane, the phosphor particles, and the fillerparticles, wherein the conversion layer comprises at most 35vol% of the polysiloxane and the conversion layer comprisesat least 25 vol% of the filler particles. There is at least reduced cracking of the conversion layer due to the low content of the polysiloxane and the content ofthe filler particles in the conversion layer. Furthermore, atleast reduced delamination of the conversion layer from thesubstrate can be observed. Additionally, with the low polysiloxane content and the filler particles it is possible to obtain a conversion layer having a smooth surface. Thesmooth surface is desired, as less glue is necessary toattach the conversion element to a light-emitting semiconductor chip. According to at least one embodiment of the conversion element, the conversion layer comprises between and including 20 vol% and 40 vol%, in particular between and including 30 vol% and 35 vol% of the phosphor particles. According to at least one embodiment of the conversion element, the conversion layer comprises between and including 24 vol% and 35 vol%, in particular between and including 28vol% and 31 vol% of the polysiloxane. This content of thepolysiloxane in the conversion layer is advantageous to obtain reduced cracking and delamination of the conversion layer. According to at least one embodiment of the conversion element, the polysiloxane comprises T-units. A polysiloxane2023PF01825 April 29, 2025P2024,0112 WO N -6 –comprising the T-units, in particular, comprises a 3D network. For instance, the polysiloxane comprising T-units is formed with polymethylsiloxane. Advantageously, the polysiloxane comprising the T-units has an increased thermal stability. According to at least one embodiment of the conversion element, the polysiloxane comprises D-units and T-units. It is possible to add 30 vol% or more of a D-units polysiloxane to T-unit polysiloxanes. In other words, D-unit polysiloxanes and T-unit polysiloxanes show good compatibility. According to at least one embodiment of the conversion element, the polysiloxane comprises between and including 0vol% and 8 vol% of D-units. In other words, the polysiloxanein the conversion layer comprises a content of between and including 0 vol% and 8 vol% of D-units. That is, the polysiloxane can comprise a mixture of T-units and D-units or consist of such a mixture. Advantageously, a stiffness of thepolysiloxane is decreased due to the presence of the D-units.Thus, a more flexible polysiloxane is provided. This contributes to reduced cracking and delamination of the conversion layer. According to at least one embodiment of the conversion element, the polysiloxane comprises between and including 2vol% and 5 vol% of the D-units. In other words, thepolysiloxane in the conversion layer comprises a content of between and including 2 vol% and 5 vol% of D-units. This content of the D-units in the polysiloxane advantageously leads to a polysiloxane having the desired stiffness while still being flexible enough such that cracks and delaminationare reduced or prevented. Furthermore, if the D-units are2023PF01825 April 29, 2025P2024,0112 WO N -7 –present, a content of the T-units in the polysiloxane is reduced. This advantageously leads to less shrinkage of the conversion layer during production of the conversion element. According to at least one embodiment of the conversion element, the polysiloxane is formed from a polysiloxane precursor comprising polydimethylsiloxane. In particular, the polydimethylsiloxane has the following formula: According to at least one embodiment of the conversion element, the polydimethylsiloxane comprises a molecularweight between and including 400 g / mol and 2,000 g / mol, inparticular between and including 700 g / mold and 1,500 g / mol. According to at least one embodiment of the conversion element, the conversion layer comprises between and including 1 vol% to 6 vol%, in particular between and including 2 vol%and 4 vol% of fumed silica. In particular, fumed silicacomprises or consists of silica nanoparticles. For example, a surface area of the silica nanoparticles is between and including 100 m2 / g to 400 m2 / g. Advantageously, fumed silica alters a rheology of a slurry from which the conversion layer is formed. For instance, increasing a content of the fumed silica results in an increase of the viscosity and thixotropy of the slurry.2023PF01825 April 29, 2025P2024,0112 WO N -8 –According to at least one embodiment of the conversion element, the filler particles comprise a material selected from the group consisting of silica, siloxane, modifiedsiloxane, and combinations thereof. In particular, silicapowder, siloxane powder, modified siloxane powder, andcombinations thereof are used as filler particles. A typical CTE value for polymethylsiloxane is about 120 x 10-6 / K, whereas the CTE value for borosilicate glass is about 3.3 x 10-6 / K. Thus, a large thermal expansion mismatch between the conversion layer and the substrate of theconversion element is possible. This thermal expansionmismatch can result in stress on the conversion element andtherefore lead to cracking and delamination. A typical CTEvalue for fused silica is, for example, 0.5 x 10-6 / K. Thus,filler particles comprising the above-described material can decrease an overall CTE value of the conversion layer. As a result, the thermal expansion mismatch between conversion layer and substrate is decreased and cracking and delamination of the conversion layer are advantageously reduced or prevented. In particular, high purity filler particles, that is filler particles with only traces of impurities or even no impurities, are used. This advantageously ensures that the filler particles show a low absorption of the electromagnetic radiation of the first wavelength range and the electromagnetic radiation of the second wavelength range. According to at least one embodiment of the conversion element, the conversion layer comprises between and including 25 vol% to 45 vol%, in particular between and including 30vol% and 40 vol% of the filler particles. This content of the2023PF01825 April 29, 2025P2024,0112 WO N -9 –filler particles is particularly efficient in reducing theformation of cracks and delamination. According to at least one embodiment of the conversion element, the filler particles have a spherical shape. Advantageously, such filler particles lead to an improved packing of the filler particles in the conversion layer. This can lead to a conversion layer having a smooth surface. According to at least one embodiment of the conversion element, the filler particles have a d50 value of between and including 0.3 micrometers and 10 micrometers, in particular between and including 0.5 micrometers and 8 micrometers, for example between and including 0.8 micrometers and 4micrometers. Here and in the following, the d50 value is themean or average particle size. In other words, 50% of the particles are smaller than the d50 value and 50% are bigger. Advantageously, the filler particles with the d50 value of between and including 0.3 micrometers and 10 micrometers show an improved particle packing in the conversion layer and a reduced surface roughness of the conversion layer can be observed with filler particles having the above-mentioned d50 value. According to at least one embodiment of the conversion element, the filler particles comprise first filler particles having a d50 value of between and including 0.8 micrometers and 1 micrometer, second filler particles having a d50 value of between and including 1.5 micrometers and 2 micrometers, and third filler particles having a d50 value of 4micrometers. In other words, filler particles of threedifferent sizes are used in the conversion layer. This2023PF01825 April 29, 2025P2024,0112 WO N -10 –further improves the packing of the filler particles and the surface roughness of the conversion layer. According to at least one embodiment of the conversion element, the conversion layer comprises an average surface roughness (Sa) of at most 0.8 micrometers, in particular atmost 0.5 micrometers. In particular, the average surfaceroughness is determined on a surface of the conversion layer facing away from the substrate. The average surface roughness (Sa) is described in the ISO 25178 standard and is defined asthe average deviation of individual heights and depths from amean height plane. According to at least one embodiment of the conversion element, the conversion layer comprises a peak surface roughness (Sp) of at most 4 micrometers, in particular atmost 2.5 micrometers. In particular, the peak surfaceroughness is determined on a surface of the conversion layer facing away from the substrate. The peak surface roughness (Sp) is also described in the ISO 25178 standard. Inpractical terms, the peak surface roughness (Sp) correspondsto a highest height above the average surface height. According to at least one embodiment of the conversion element, a thickness of the conversion layer is between and including 20 micrometers and 50 micrometers, in particularbetween and including 25 micrometers and 35 micrometers. Inparticular, this thickness applies to white light-emitting device applications. Furthermore, a method for producing a conversion element is specified. In particular, the method is used to produce the conversion element described herein. Thus, features,2023PF01825 April 29, 2025P2024,0112 WO N -11 –embodiments and advantages described in combination with the conversion element also apply to the method and vice versa. According to at least one embodiment of the method, a slurry is provided. In particular, the slurry comprises a polysiloxane precursor, phosphor particles, and filler particles. For example, the constituents of the slurry are mixed together to form the slurry. According to at least one embodiment of the method, the slurry is applied on a substrate. In particular, the slurry is applied using tape casting, spin coating, spray coating, or slot die casting. According to at least one embodiment of the method, the slurry is cured to form a conversion layer. In particular, curing already occurs at room temperature, that is at atemperature between and including 20 °C and 25 °C. However,it is also possible that an increased temperature is used for curing. During curing, a polysiloxane is formed from the polysiloxane precursor. According to at least one embodiment, the method for producing the conversion element comprises- providing a slurry comprising a polysiloxane precursor,phosphor particles, and filler particles,- applying the slurry on a substrate,- curing the slurry to form a conversion layer,wherein the conversion layer comprises at most 35 vol% of apolysiloxane formed from the polysiloxane precursor, and theconversion layer comprises at least 25 vol% of the fillerparticles. In particular, the method steps are performed inthe order given.2023PF01825 April 29, 2025P2024,0112 WO N -12 –Advantageously, the method for producing the conversion element is simple and efficient. Even though the filler particles are present in the slurry, the slurry can be handled like other slurries used to produce a conversionlayer. Thus, advantageously, no specific setup is necessaryfor the method. According to at least one embodiment of the method, the slurry further comprises fumed silica. In particular, the slurry comprises between and including 1 vol% and 6 vol% of the fumed silica. According to at least one embodiment of the method, the slurry further comprises a solvent. In particular, the solvent is removed during curing. According to at least one embodiment of the method, the slurry further comprises a hardener. In particular, the hardener acts as a catalyst during curing of the slurry. For example, traces of the hardener remain in the conversion layer after curing. Thus, the use of the hardener can be detected. For instance, the hardener is selected such that noprecipitation, and / or no gelation of the slurry occurs priorto curing. According to at least one embodiment of the method, curing the slurry comprises a first curing at room temperature and a second curing at a temperature above room temperature. In other words, the curing comprises two steps which differ in their temperature.2023PF01825 April 29, 2025P2024,0112 WO N -13 –In particular, the first curing is conducted in an environment having a controlled humidity. For example, a relative humidity during the first curing is between and including 40% and 60%, for example about 50%. For instance, the first curing occurs for a time between and including 2 days and 7 days. In particular, a highest temperature reached during the second curing is between and including 150 °C and 250 °C, in particular between and including 180 °C and 220 °C, for example about 200 °C. For instance, during the second curing the temperature is increase with a ramp rate. It is also possible that during the second curing the temperature is held at an intermediate temperature which is between room temperature and the highest temperature. The intermediate temperature is for example between and including 50 °C and 80 Advantageously, using two different curing steps improves thethermal stability of the conversion layer. The second curingcan decrease the formation of cracks and delamination. According to at least one embodiment of the method, the ramp rate during the second curing is between and including 0.3°C / min and 1 °C / min, for example about 0.5 °C / min. This ramprate is slower compared to other methods. With the described ramp rate it is advantageously possible to obtain a conversion layer having less cracks and showing less delamination. Furthermore, a light-emitting device is specified. In particular, the light-emitting device comprises the conversion element described herein. Thus, features,2023PF01825 April 29, 2025P2024,0112 WO N -14 –embodiments, and advantages described in combination with the conversion element and the method for producing the conversion element also apply to the light-emitting device and vice versa. According to at least one embodiment, the light-emitting device comprises a semiconductor chip. In particular, the semiconductor chip is configured to generate electromagneticradiation of a first wavelength range. For example, thesemiconductor chip is a light-emitting diode (LED). For instance, the semiconductor chip comprises a semiconductor layer sequence formed from a semiconductor material. The semiconductor layer sequence comprises an active layer which is configured to generate the electromagnetic radiation of the first wavelength range. The generated electromagnetic radiation can be emitted through a radiation exit surface of the light-emitting semiconductor chip. According to at least one embodiment, the light-emitting device comprises the conversion element described herein. In particular, the conversion element converts the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range. The first wavelength range and the second wavelength range are, for example, at least partially different. In particular, the conversion element is arranged on the radiation exit surface of the light-emitting semiconductor chip. For example, the conversion element is arranged in such a way that the conversion layer is arranged between the light-emitting semiconductor chip and the substrate.2023PF01825 April 29, 2025P2024,0112 WO N -15 –Advantageously, the light-emitting device has an improved efficiency. In particular, the light-emitting device shows a higher brightness compared to other light-emitting devices. The increased brightness can be traced back to the decreased surface roughness of the conversion layer. According to at least one embodiment, the light-emitting device emits mixed light of the first wavelength range and the second wavelength range. However, it is also possible that the light-emitting device mainly emits the electromagnetic radiation of the second wavelength range. According to at least one embodiment of the light-emitting device, an adhesive layer is arranged between the light- emitting semiconductor chip and the conversion element. Dueto the low surface roughness, that is the smooth surface ofthe conversion layer, an adhesive layer having a lower thickness compared to other light-emitting devices is attained. Furthermore, due to the smooth surface of the conversion layer, squeeze-out of material of the adhesivelayer can be minimized or prevented. Both effects improve thebrightness and thus the efficiency of the light-emitting device. According to at least one embodiment, the light-emitting device emits white light. Advantageously, such a light- emitting device can be used in automotive exterior lighting such as headlamps. According to at least one embodiment, the light-emitting device emits amber light. Advantageously, such a light-2023PF01825 April 29, 2025P2024,0112 WO N -16 –emitting device can be used in automotive exterior lighting such as indicators. Advantageous embodiments and developments of the conversion element, the light-emitting device, and the method for producing a conversion element will become apparent from the exemplary embodiments described below in conjunction with the figures. In the figures: Figure 1 shows a schematic sectional view of a conversion element according to an exemplary embodiment. Figure 2 shows a scanning electron microscopy (SEM) image of a cross-section of a conversion element according to an exemplary embodiment. Figures 3A and 3B show optical images of a surface of a conversion element according to a comparative example and an exemplary embodiment.Figures 4A and 4B show optical images of a surface of aconversion element according to a comparative example and an exemplary embodiment.Figures 5A and 5B show SEM images of a surface of aconversion element according to a comparative example and an exemplary embodiment.Figures 6A and 6B show SEM images of a surface of aconversion element according to a comparative example and an exemplary embodiment.2023PF01825 April 29, 2025P2024,0112 WO N -17 –Figure 7 schematically shows steps of a method for producing a conversion element according to an exemplary embodiment. Figure 8 shows a temperature profile used during a method for producing a conversion element according to an exemplary embodiment. Figures 9A and 10A show optical images of a surface of a conversion element according to exemplary embodiments. Figures 9B and 10B show optical images of a surface of a conversion element according to exemplary embodiments. Figures 9C and 10C show SEM images of a surface of a conversion element according to exemplary embodiments. Figure 11 shows a schematic sectional view of a light- emitting device according to an exemplary embodiment. 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 size relationships among one another should not be regarded as true to scale. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and / or for the sake of better understanding. Figure 1 shows an exemplary embodiment of a conversion element 1. The conversion element 1 comprises a substrate 2, for example formed with borosilicate glass and having a thickness of about 100 micrometers. A conversion layer 3 is in direct mechanical contact to the substrate 2. The2023PF01825 April 29, 2025P2024,0112 WO N -18 –conversion layer 3 comprises a polysiloxane 4, phosphor particles 5 and filler particles 6. Additionally, the conversion layer 3 can comprise between and including 2 vol% and 4 vol% fumed silica (not shown). A thickness of the conversion layer 3 is between and including 25 micrometers and 35 micrometers. The conversion layer 3 comprises between and including 28 vol% and 31 vol% of the polysiloxane 4. The polysiloxane 4 comprises T-unit and between and including 2 vol% and 5 vol% D-units. The polysiloxane is formed from polymethylsiloxane (T-units) and polydimethylsiloxane (D-units). The filler particles 6 comprise or consist of silica, siloxane, modified siloxane, and combinations thereof. The conversion layer 3 comprises between and including 30 vol% and 40 vol% of the filler particles 6. The filler particles 6 have a d50 value of between and including 0.8 micrometers and 4 micrometers. A SEM image of a polished cross-section of a conversion element 1 according to an exemplary embodiment is shown in figure 2. The conversion element 1 comprises a substrate 2 and a conversion layer 3 as described in combination with figure 1. Presently, the thickness of the conversion layer 3 is about 30 micrometers. The filler particles 6 have a spherical shape. The filler particles 6 and the phosphor particles 5 are homogeneously distributed throughout the conversion layer 3. The phosphor particles 5 convert electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range. Thus, the conversion element 1 is2023PF01825 April 29, 2025P2024,0112 WO N -19 –able to convert the electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range. Compared to the exemplary embodiment of figure 1, the conversion layer 3 presently comprises filler particles 6 comprising first, second, and third filler particles. The first, second, and third filler particles differ in their d50 value. The d50 value of the first filler particles is between and including 0.8 micrometers and 1 micrometer, the d50 value of the second filler particles is between and including 1.5 micrometers and 2 micrometers, and the d50 value of the third filler particles is about 4 micrometers. Due to the differently sized filler particles 6 packing of the fillerparticles 6 is improved, which leads to a smoother surface ofthe conversion layer 3. Figures 3A to 6B arise from conversion elements 1 each having a substrate 2 and a conversion layer 3. Figures 3A and 3B show an optical image of a conversion element 1. Figure 3A shows a conversion element 1 according to a comparative example, whereas figure 3B arises from a conversion element 1 according to an exemplary embodiment. Figures 3A and 3B show a surface of the conversion layer 3facing away from the substrate 2. The surface was stainedwith black ink to provide information regarding cracking in the conversion layer 3. Darkened regions arise from cracks in the conversion layer 3. The exemplary embodiment of figure 3B shows no darkened regions, in contrast to the comparative example of figure 3Awhich shows a significant number of darkened regions. This2023PF01825 April 29, 2025P2024,0112 WO N -20 –shows that the conversion layer 3 of the comparative example has cracks in it, whereas the conversion layer 3 of the exemplary embodiment is free of cracks. Figures 4A and 4B also show optical images of a conversion element 1 according to a comparative example (figure 4A) andan exemplary embodiment (figure 4B). The optical images weretaken through the substrate 2 of the conversion elements 1. Coaxial lighting was used to detect delamination of theconversion layer 3 from the substrate 2. Bright regions showwhere the conversion layer 3 has delaminated from the substrate 2. Figure 4A shows some bright regions. Accordingly, in the conversion element 1 according to the comparative example delamination of the conversion layer 3 from the substrate 2 has occurred. In contrast, figure 4B does not show any bright regions. Thus, the conversion element 1 of the exemplary embodiment is free of delamination of the conversion layer 3 from the substrate 2. Figures 5A and 5B show SEM images of a surface of a conversion element 1 according to a comparative example (figure 5A) and an exemplary embodiment (figure 5B). The SEM images have been taken in the back-scatter mode of SEM. The surface of the analyzed conversion element 1 is the surface of the conversion layer 3 facing away from the substrate 2. It can be clearly seen from figure 5A that cracks are present in the conversion layer 3 of the comparative example. Additionally, the phosphor particles 5 and the filler particles 6 are visible. Constituents of the conversion layer3, that is the phosphor particles 5 and the filler particles2023PF01825 April 29, 2025P2024,0112 WO N -21 –6, are also visible in the conversion layer 3 of theexemplary embodiment. At the same time, it can be seen that filler particles 6 having different d50 values have been used and a content of the filler particles 6 is comparativelyhigher in the exemplary embodiment. Figure 5B does not showany cracks in the conversion layer 3. Furthermore, only small sections of the phosphor particles 5 can be observed in the exemplary embodiment. Figures 6A and 6B show SEM images of a surface of a conversion element 1 according to a comparative example (figure 6A) and an exemplary embodiment (figure 6B). The surface of the analyzed conversion element 1 is the surface of the conversion layer 3 facing away from the substrate 2. The SEM images have been taken in the topography mode of SEM. Information regarding the topography of the conversion layer3 can be provided with the topography mode of SEM.It can be seen from figure 6A that the surface of the conversion layer 3 comprises peaks and valleys which arise from the phosphor particles 5. In contrast, valleys between the phosphor particles 5 in the exemplary embodiment shown in figure 6B are filled with the filler particles 6. Thus, a surface roughness of the conversion layer 3 is decreased in the exemplary embodiment. In other words, the conversion layer 3 of the exemplary embodiment has a smoother surface than the comparative example. A method for producing a conversion element 1 according to an exemplary embodiment is schematically shown in figure 7. In a first step S1, a polysiloxane precursor, phosphor particles 5 and filler particles 6 are mixed to form a slurry. Apart from these constituents, the slurry can further comprise a2023PF01825 April 29, 2025P2024,0112 WO N -22 –hardener, a solvent, and fumed silica. The filler particles 6 comprise silica, siloxane, or modified siloxane. The mixing of the constituents of the slurry is performed using planetary centrifugal mixing. To ensure dispersion of the phosphor particles 5 and the filler particles 6 in the slurry, 3-roll milling can be performed. Afterwards, it is possible to use planetary centrifugal mixing again to further mix and homogenize the slurry. In a step S2, the slurry is applied to a substrate 2, for example comprising or consisting of a glass such as borosilicate glass. The slurry is applied to the substrate 2 using tape casting. Curing of the slurry occurs in a step S3. Presently, curing comprises a first curing at room temperature and a second curing at a temperature above room temperature. During the first curing, the slurry is cured at room temperature for 2 days to 7 days at a relative humidity of about 50%. During the second curing, the slurry is cured at about 200 °C in an oxygen containing environment. The maximal temperature of about 200 °C is reached using a temperature profile. Due to the curing, the polysiloxane precursor goes through achemical reaction to form a polysiloxane 4. In this way, aconversion layer 3 is formed from the slurry.During the second curing the temperature profile T2 as shownin figure 8 can be used. Figure 8 shows a temperature in °Cdependent on a time in minutes. Curve T1 belongs to a temperature profile used during a method for producing a conversion element 1 according to a comparative example. Curve T2 belongs to a temperature profile used during a method for producing a conversion element 1 according to an2023PF01825 April 29, 2025P2024,0112 WO N -23 –exemplary embodiment. Figure 8 shows that a slower ramp rate,for example of about 0.5 °C / min, is used during the secondcuring according to the exemplary embodiment. This ensures that no cracking or delamination occurs in the conversionlayer 3 as stress on the conversion layer 3 during heating ofthe conversion element 1 is decreased. Using the method described herein, it is possible to produce a plurality of conversion elements 1. For this, singulation takes place after curing. Singulation can be performed using a dicing saw. Table 1 shows details on a formulation of the conversion layer 3 and of the curing which can be used in the method for producing a conversion element 1. Table 1 also denotes if cracking or delamination occurred for the obtained conversion elements 1. The contents of the constituents of the conversion layer 3 are given in vol%. Table 1 Component COMP EMB-1 EMB-2 EMB-3 EMB-4 EMB-5 EMB-6 EMB-7T-unit 35 30.5 34.2 26.1 26.3 25.1 24.6 22.5siloxane D-unit 05.5 0 4.7 4.7 4.1 4 3.7siloxane fumed silica 12 6 6.8 4.2 3.1 2 2 2filler 15 26 27 30 30.9 37.8 39.4 42.8particles phosphor 35 32 32 35 35 31 30 31particles temperature T1 T2 T2 T2 T2 T2 T2 T2profile cracking yes no -- no no no no minordelamination yes yes -- no no no no no2023PF01825 April 29, 2025P2024,0112 WO N -24 –Sa < 0.5 no yes no yes yes yes yes nomicrometers The delamination for the exemplary embodiment EMB-1 occurred only after intensive mechanical handling. The exemplary embodiments EMB-1 to EMB-7 show all improved properties with regard to cracking, delamination and / or surface roughness compared to the comparative example COM. In particular, the exemplary embodiments EMB-3 to EMB-6 show no cracking, nodelamination, and an average surface roughness Sa of lessthan 0.5 micrometers. Table 2 provides additional data for the conversion elements 1 according to the comparative example COMP and the exemplary embodiments EMB-4 and EMB-6. Table 2 COMP EMB-4 EMB-6Sa about 0.9 micrometers 0.46 micrometers 0.28 micrometersSp about 5 micrometers 2.8 micrometers 1.75 micrometersFigures 9A and 10A show optical images of a surface of aconversion element 1 according to the exemplary embodimentsEMB-4 (figure 9A) and EMB-6 (figure 10A). A surface of the conversion layer 3 of the conversion elements 1 was stained with black ink. However, no darkened regions as shown in figure 3A can be observed. Thus, the exemplary embodiments EMB-4 and EMB-6 are free of cracks in the conversion layer 3.This can be explained by the presence of the D-units in thepolysiloxane 4 and a high content of the filler particles 6 in the conversion layer 3, as well as the use of temperature profile T2 during production of the conversion element 1.2023PF01825 April 29, 2025P2024,0112 WO N -25 –Figures 9B and 10B show optical images of a surface of aconversion element according to exemplary embodiments EMB-4(figure 9B) and EMB-6 (figure 10B). The optical images were taken through the substrate 2 of the conversion elements 1. Coaxial lighting was used to detect delamination of the conversion layer 3 from the substrate 2. Bright regions show where the conversion layer 3 has delaminated from the substrate 2. However, in contrast to the comparative example shown in figure 4A, no bright regions could be detected. Accordingly, the exemplary embodiments EMB-4 and EMB-6 do not show delamination of the conversion layer 3 from the substrate 2. The reduced delamination can be explained by the presence of the D-units in the polysiloxane 4 and a high content of the filler particles 6 of the conversion layer 3, as well as the use of the temperature profile T2 during production of the conversion element 1. Figures 9C and 10C show SEM images of a surface of aconversion element according to exemplary embodiments EMB-4(figure 9C) and EMB-6 (figure 10C). The SEM images were taken in the topography mode. Both exemplary embodiments EMB-4 and EMB-6 show a smoother surface of the conversion layer 3 compared to the comparative example shown in figure 6A. This is due to high content of the filler particles 6 in the conversion layer 3. Figure 11 shows a schematic cross-section of a light-emitting device 7 according to an exemplary embodiment. The light- emitting device 7 comprises a conversion element 1. The conversion element 1 can have the structure of any of the exemplary embodiments described above for the conversion elements 1. The conversion element 1 is arranged on a light- emitting semiconductor chip 8 such that the conversion layer2023PF01825 April 29, 2025P2024,0112 WO N -26 –3 faces the light-emitting semiconductor chip 8. In other words, the conversion layer 3 is arranged between the light- emitting semiconductor chip 8 and the substrate 2 of the conversion element 1. The conversion element 1 is attached to the light-emitting semiconductor chip 8 via an adhesive layer 9. As the conversion layer 3 has a low surface roughness, an amount of adhesive used for the adhesive layer can be reduced compared to other light-emitting devices 7. Furthermore, squeeze-outof the adhesive can be minimized or prevented. This leads toan increased brightness of the light-emitting device 7. The light-emitting semiconductor chip 8 comprises a semiconductor layer sequence 81 formed with a semiconductor material. The semiconductor layer sequence 81 comprises an active layer 82 which is configured to generate electromagnetic radiation of a first wavelength range. The electromagnetic radiation of the first wavelength range is emitted via a radiation exit surface of the light-emitting semiconductor chip. The conversion element 1 is arranged on the radiation exit surface. The conversion element 1 converts the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range. The light-emitting device 7 can then emit mixed light of the electromagnetic radiation of the first wavelength range and the electromagnetic radiation of the second wavelength range. For example, the light-emitting device 7 can emit white light. The features and exemplary embodiments described in connection with the figures can be combined with each other2023PF01825 April 29, 2025P2024,0112 WO N -27 –according to further exemplary embodiments, even if 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. This patent application claims the priority of US provisionalpatent application 63 / 654,629, the disclosure content ofwhich is hereby incorporated by reference. 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 if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

[0002] 2023PF01825 April 29, 2025P2024,0112 WO N -28 –References1 conversion element2 substrate3 conversion layer4 polysiloxane5 phosphor particle6 filler particle7 light-emitting device8 semiconductor chip81 semiconductor layer sequence82 active layer9 adhesive layer

Claims

2023PF01825 April 29, 2025P2024,0112 WO N -29 –Claims 1. A conversion element (1) comprising- a substrate (2) and- a conversion layer (3) comprising a polysiloxane (4),phosphor particles (5), and filler particles (6), wherein- the conversion layer (3) comprises at most 35 vol% of thepolysiloxane (4), and- the conversion layer (3) comprises at least 25 vol% of thefiller particles (6).

2. The conversion element (1) according to the previous claim, wherein the conversion layer (3) comprises between and including 24vol% and 35 vol% of the polysiloxane (4).

3. The conversion element (1) according to any of the previous claims, wherein- the polysiloxane (4) comprises T-units, and- the polysiloxane (4) comprises between and including 0 vol%and 8 vol% of D-units.

4. The conversion element (1) according to the previous claim, wherein the polysiloxane (4) comprises between and including 2 vol% and 5 vol% of the D-units.

5. The conversion element (1) according to any of the previous claims, wherein the conversion layer (3) comprises between and including 1 vol% to 6 vol% of fumed silica.2023PF01825 April 29, 2025P2024,0112 WO N -30 –6. The conversion element (1) according to any of the previous claims, wherein the filler particles (6) comprise a material selected from the group consisting of silica, siloxane, modified siloxane, and combinations thereof.

7. The conversion element (1) according to any of the previous claims, wherein the conversion layer (3) comprises between and including 25vol% to 45 vol% of the filler particles (6).

8. The conversion element (1) according to any of the previous claims, wherein the filler particles (6) have a spherical shape.

9. The conversion element (1) according to any of the previous claims, wherein the filler particles (6) have a d50 value of between andincluding 0.3 micrometers and 10 micrometers.

10. The conversion element (1) according to any of the previous claims, whereinthe filler particles (6) comprise first filler particleshaving a d50 value of between and including 0.8 micrometers and 1 micrometer, second filler particles having a d50 value of between and including 1.5 micrometers and 2 micrometers,and third filler particles having a d50 value of 4micrometers.

11. The conversion element (1) according to any of the previous claims, wherein the conversion layer (3) comprises an average surface roughness (Sa) of at most 0.8 micrometers.2023PF01825 April 29, 2025P2024,0112 WO N -<sub>31 –12. The conversion element (1) according to any of the previous claims, wherein the conversion layer (3) comprises a peak surface roughness (Sp) of at most 4 micrometers.

13. A method for producing a conversion element (1) comprising- providing a slurry comprising a polysiloxane precursor,phosphor particles (5), and filler particles (6),- applying the slurry on a substrate (2),- curing the slurry to form a conversion layer (3),wherein- the conversion layer (3) comprises at most 35 vol% of apolysiloxane (4) formed from the polysiloxane precursor, and- the conversion layer (3) comprises at least 25 vol% of thefiller particles (6).

14. The method according to claim 13, wherein the slurry further comprises fumed silica.

15. The method according to claim 13 or 14, whereincuring the slurry comprises a first curing at room temperature and a second curing at a temperature above room temperature.

16. The method according to claim 15, wherein a ramp rate during the second curing is between and including 0.3 °C / min and 1 °C / min.

17. A light-emitting device (7) comprising- a semiconductor chip (8) configured to generateelectromagnetic radiation of a first wavelength range, and2023PF01825 April 29, 2025P2024,0112 WO N -<sub>32 –- a conversion element (1) according to any of claims 1 to12, wherein the conversion element (1) converts the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range.

18. The light-emitting device (7) according to claim 17, wherein the light-emitting device (7) emits white light.

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