Method for producing a plurality of light-emitting devices and light-emitting device

Abstract

A method for producing a plurality of light-emitting devices is disclosed. The method comprises: - providing a plurality of light-emitting semiconductor chips on a substrate, - applying a precursor mixture on the plurality of light-emitting semiconductor chips, wherein the precursor mixture comprises a polysiloxane precursor, phosphor particles and a photoactive catalyst, - irradiating the precursor mixture in first regions to form a conversion layer in the first regions, wherein the conversion layer comprises a polysiloxane resin and the phosphor particles. Furthermore, a light-emitting device is disclosed. The light-emitting device in particular comprises a micro-LED.

Description

[0001] 2023PF01582 February 26, 2025P2023,1579 WO N -1 -Description METHOD FOR PRODUCING A PLURALITY OF LIGHT-EMITTING DEVICES AND LIGHT-EMITTING DEVICE A method for producing a plurality of light-emitting devices and a light-emitting device are specified. It is an object to provide a simple and efficient method for producing a plurality of light-emitting devices. Furthermore, a light-emitting device produced by such a method shall be specified. In particular, the light-emitting device shall have an increased efficiency.According to at least one embodiment, the method isconfigured to produce a plurality of light-emitting devices. In other words, executing the method leads to a production of a plurality of light-emitting devices. According to at least one embodiment of the method, a plurality of light-emitting semiconductor chips are provided on a substrate. In particular, the plurality of light- emitting semiconductor chips are arranged in a regularpattern on the substrate. For example, the substrate is acommon substrate. For instance, each light-emittingsemiconductor chip is spaced apart from its neighboring light-emitting semiconductor chips. Thus, a part of the substrate is free of light-emitting semiconductor chips.The substrate advantageously improves a mechanical stabilityof the plurality of light-emitting semiconductor chips.2023PF01582 February 26, 2025P2023,1579 WO N -2 -For example, the light-emitting semiconductor chips are produced on the substrate. Alternatively, it is possible that the light-emitting semiconductor chips are arranged on the substrate after their production. In particular, the substrate comprises or consists of a glass, a polymer, sapphire, and / or a semiconductor material. In particular, the light-emitting semiconductor chips each comprise a semiconductor layer sequence. The semiconductorlayer sequence comprises an active layer generating light.Here and in the following, light corresponds toelectromagnetic radiation in the ultraviolet to infrared range of the electromagnetic spectrum. The light-emitting semiconductor chip can emit light through a radiation exitsurface. For instance, the radiation exit surface is parallelto a main extension plane of the light-emitting semiconductor chip. According to at least one embodiment of the method, a precursor mixture is applied on the plurality of light- emitting semiconductor chips. In particular, the precursor mixture is applied to the radiation exit surfaces of the light-emitting semiconductor chips. For example, the precursor mixture is directly applied on the light-emitting semiconductor chips. That is, no further layer such as an adhesive layer is arranged between the precursor mixture and the light-emitting semiconductor chips. For instance, the precursor mixture is also applied to the part of the substrate free of the light-emitting semiconductor chips. According to at least one embodiment of the method, the precursor mixture comprises a polysiloxane precursor, phosphor particles, and a photoactive catalyst.2023PF01582 February 26, 2025P2023,1579 WO N -3 -Here and in the following, the polysiloxane precursor is acompound which forms a polysiloxane after being cured. In particular, the polysiloxane precursor comprises or consists of a polysiloxane. For example, a polysiloxane comprises orconsists of M-units (R3OSi-), D-units (-OR2SiO-), T-units (-OSiRO2-), and / or Q-units (-OSiO3-). In particular, the phosphor particles are particles of a phosphor material. The phosphor particles can convert the light emitted by the light-emitting semiconductor chip into electromagnetic radiation having another wavelength or wavelength range. The photoactive catalyst is in particular a catalyst which is active or activated under irradiation with electromagneticradiation. The catalyst increases a rate of a chemicalreaction, for example by decreasing an activation energy of the chemical reaction. According to at least one embodiment of the method, the precursor mixture is irradiated in first regions to form a conversion layer. In other words, the precursor mixture acts as a photoresist. In particular, the first regions correspond to regions of the precursor mixture covering the light-emitting semiconductor chips. For example, regions betweenthe light-emitting semiconductor chips are not irradiated.For instance, the first regions are selectively irradiated. This can be achieved by using a mask. The first regions are in particular free of the mask. In particular, during irradiating, the precursor mixture in the first regions is cured.2023PF01582 February 26, 2025P2023,1579 WO N -4 -According to at least one embodiment of the method, the conversion layer comprises a polysiloxane resin and the phosphor particles. In particular, the polysiloxane resin is formed from the polysiloxane precursor, for example by a polymerization reaction such as a condensation. The formation of the polysiloxane resin is induced by the photoactive catalyst. In particular, the photoactive catalyst or a reaction product thereof catalyzes the polymerization reaction of the polysiloxane precursor to the polysiloxaneresin. In other words, the formation of the polysiloxaneresin from the polysiloxane precursor is photoinitiated.According to at least one embodiment, the method forproducing a plurality of light-emitting devices comprises:- providing the plurality of light-emitting semiconductorchips on the substrate,- applying the precursor mixture on the plurality of light-emitting semiconductor chips, wherein the precursor mixturecomprises the polysiloxane precursor, phosphor particles andthe photoactive catalyst,- irradiating the precursor mixture in first regions to formthe conversion layer in the first regions, wherein theconversion layer comprises the polysiloxane resin and thephosphor particles. In particular, the steps of the methodare carried out in the order described. It is an idea of the present disclosure to provide a plurality of light-emitting devices in a simple and efficientmanner. The conversion layer can thereby be produced in sucha way that only the radiation exit surfaces of the light- emitting semiconductor chips are covered with the conversion layer. The region between the light-emitting semiconductor chips remains free of the conversion layer. Due to the2023PF01582 February 26, 2025P2023,1579 WO N -5 -irradiation of the precursor mixture only in the first regions it is possible to avoid the use of a sacrificiallayer, for example of a photoresist, to achieve that selectedregions remain free of the conversion layer. Furthermore, the plurality of light-emitting devices can be provided with the conversion layer, in particular at the same time, by a simple process. Advantageously, a pick and place process to individually provide each light-emitting semiconductor chip with a conversion layer can be avoided. Thus, the method described herein significantly reduces production costs of the light-emitting device.According to at least one embodiment of the method, theprecursor mixture is applied using spray coating, spincoating, doctor blading or stencil printing. Advantageously,these methods allow for a simple and efficient application ofthe precursor mixture on the plurality of light-emitting semiconductor chips. According to at least one embodiment of the method, the phosphor is a ceramic phosphor and / or a quantum dot phosphor.In particular, the ceramic phosphor is a garnet phosphor or anitride phosphor. The phosphor emits light in the blue to infrared spectral range. For example, the ceramic phosphor is selected from the following group:Ce3+ and / or Gd3+ doped garnets like YAG and LuAG, for example(Y, Lu,Gd,Tb) 3+ 2+3(Al1-x,Gax)5O12:Ce ; Eu doped nitrides, forexample (Ca,Sr)AlSiN :Eu2+, Sr(Ca,Sr)Si Al N :Eu2+3 2 2 6 (SCASN),(Sr,Ca)AlSiN3*Si2N2O:Eu2+, (Ca,Ba,Sr)2Si5N8:Eu2+, SrLiAl3N4:Eu2+,SrLi Al O N :Eu2+ 3+2 2 2 2 ; Ce doped nitrides, for example (Ca,Sr)Al(1-2+4x / 3)Si(1+x)N3:Ce; (x = 0,2 – 0,5); Eu doped sulfides,2023PF01582 February 26, 2025P2023,1579 WO N -6 -(Ba,Sr,Ca)Si2O2N2:Eu2+, SiAlONs, nitride orthosilicates (e.g.AE RE Eu Si O N ), orthosilicates (Ba,Sr 2+2-x-a x a 1-y 4-x-2y x ,Ca)2SiO4:Eu ;chlorosilicates (e.g. Ca 2+ 4+8Mg(SiO4)4Cl2:Eu ); Mn dopedfluorides, for example (K,Na) 4+ 2+ 3+2(Si,Ti)F6:Mn ; Eu or Cedoped litho-silicates, such as (Li,Na,K,Rb,Cs)(Li3SiO4):Ewith E = Eu2+, Ce3+, or (Sr,Li)Li AlO :Eu2+ o 2+3 4 r SrLi3AlO4:Eu ;and mixtures thereof. Additionally or alternatively, the ceramic phosphor is selected from the following group:(Ba1-x-ySrxCay)SiO4:Eu2+ (0 ^ x ^ 1, 0 ^ y ^ 1), (Ba1-x-Sr Ca ) SiO :Eu2+ (0 ^ x ^ 1 2+y x y 3 5 , 0 ^ y ^ 1), Li2SrSiO4:Eu , oxo-nitrides such as (Ba 2+1-x-ySrxCay)Si2O2N2:Eu (0 ^ x ^ 1; 0 ^ y ^1), SrSiAl 2+ 2+2O3N2:Eu , Ba4-xCaxSi6ON10:Eu (0 ^ x ^ 1), (Ba1-Sr )Y Si2Al2O2N5:Eu2+ (0 ^ x 2+x x 2 ^ 1), SrxSi(6-y)AlyOyN(8-y):Eu (0,05^ x ^ 0,5; 0,001 ^ y ^ 0,5), Si Al O 2+6-z z zN8-z:Eu (0 ^ z ^ 0,42),MxSi12-m-nAlm+nOnN16-n:Eu2+(M = Li, Mg, Ca, Y; x = m / v; v =valency of M, x ^ 2), M 3+xSi12-m-nAlm+nOnN16-n:Ce , 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 earthelement), Ba Si O N :Eu2+ or nitrides su 3+3 6 12 2 ch as La3Si6N11:Ce ,(La1-xYx)3Si6N11:Ce3+, (Ba1-x-ySrxCay)2Si5N8:Eu2+, (Ca1-x-Sr Ba )AlSi 2+y x y N3:Eu (0 ^ x ^ 1; 0 ^ y ^ 1), Sr(Sr1-Ca )Al Si N :Eu2+ ( 3+x x 2 2 6 0 ^ x ^ 0,2), Sr(Sr1-xCax)Al2Si2N6:Ce (0 ^ x^ 0,2) SrAlSi 2+ 2+4N7:Eu , (Ba1-x-ySrxCay)SiN2:Eu (0 ^ x ^ 1; 0 ^ y^ 1), (Ba x-ySrxCay)SiN 3+1- 2:Ce (0 ^ x ^ 1; 0 ^ y ^ 1), (Sr1-Ca )LiAl N :Eu2+ (0 ^ x ^ 1), (Ba Sr Ca )Mg Al N : 2+x x 3 4 1-x-y x y 2 2 4 Eu (0 ^ x^ 1; 0 ^ y ^ 1), (Ba Sr Ca )Mg SiN 2+1-x-y x y 3 4:Eu (0 ^ x ^ 1; 0 ^ y ^1), and mixtures thereof.2023PF01582 February 26, 2025P2023,1579 WO N -7 -Additionally or alternatively, the phosphor is selected fromthe following group: La3Ga5GeO14:Cr3+, ScBO3:Cr3+,Gd2Sc2Ga3O12:Cr3+, Mg2SiO4:Cr3+, and mixtures thereof. According to at least one embodiment, the method further comprises removing the precursor mixture in second, non- irradiated regions. This process can also be called developing. In particular, the precursor mixture has not formed the conversion layer in the second, non-irradiated regions. For example, the second, non-irradiated regions were covered with the mask. To remove the precursor mixture, the precursor mixture is, for example, washed away with a solvent. The solvent can be selected from the group consisting of alcohols, esters, ketones, and mixtures thereof. An example for an alcohol is isopropanol. As ester, for instance, butyl acetate is used. The ketone can be acetone. According to at least one embodiment, the method further comprises singulating into a plurality of light-emitting devices. For instance, the substrate is singulated. In particular, singulation is preformed using dicing and / or sawing. For example, singulating occurs in the second, non- irradiated regions. In other words, singulating is performed between the light-emitting semiconductor chips. For instance, the substrate is divided into smaller parts by singulation. According to at least one embodiment, the method further comprises heating the precursor mixture. Advantageously, heating is performed to accelerate the formation of the polysiloxane resin from the polysiloxane precursor. In particular, the heating is performed during or after irradiating the precursor mixture. During heating a2023PF01582 February 26, 2025P2023,1579 WO N -8 -temperature of between and including 50°C and 150°C, in particular between and including 75°C and 125°C, is applied to the precursor mixture. According to at least one embodiment of the method, the photoactive catalyst generates an acid or a base upon irradiation. In other words, the photoactive catalyst is aphotoacid generator or a photobase generator. The photoacidgenerator is a chemical compound which undergoes a chemicalreaction under irradiation such that an acid is formed. The photobase generator is a chemical compound which undergoes a chemical reaction under irradiation such that a base is formed. In particular, the acid is a Lewis acid or a Bronsted acid and the base is a Lewis base or a Bronsted base. For example, the acid or the base catalyzes the polymerization of the polysiloxane precursor to the polysiloxane resin. In other words, it is not the photoactive catalyst itself that catalyzes the polymerization but its irradiation product. As the acid or the base are only formed in the first regions which are irradiated, the polymerization only occurs in the first regions. Accordingly, only in the first regions the conversion layer is formed. According to at least one embodiment of the method, the precursor mixture comprises 0.01 wt.% to 0.5 wt.% of the photoactive catalyst. Advantageously, this amount of the photoactive catalyst is sufficient to form the polysiloxane resin from the polysiloxane precursor. According to at least one embodiment, the photoactive catalyst is selected from the following group of photoacidgenerators: salts of trifluoromethanesulfonic acid such astriphenylsulfonium trifluoromethane sulfonate, (4-2023PF01582 February 26, 2025P2023,1579 WO N -9 -methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, and (4-phenoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, salts of hexafluorophosphonic acidsuch as triphenylsulfonium hexafluorophosphate and tri-p-tolylsulfonium hexafluorophosphate, trichloromethyltriazines such as 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine, arylsulfonate esters, iminosulfonates,imidosulfonates, and mixtures thereof.According to at least one embodiment, the photoactive catalyst is selected from the following group of photobase generators: esters or salts of biguanidine such as 1,2- diisopropyl-3-[bis(dimethylamino)methylene]guanidium 2-(3- benzoylphenyl) propionate, 9-anthrylmethyl N,N- diethylcarbamate, or 1,2-dicyclohexyl-4,4,5,5- tetramethylbiguanidium n-butyltriphenylborate, or esters of tetramethyl guanidine, such as 2-(2-nitrophenyl) propyloxycarbonyl tetramethylguanidine, and mixtures thereof. According to at least one embodiment of the method, UV to blue light is used for irradiating the precursor mixture. In particular, the photoactive catalyst generates the acid or the base upon irradiation with light in the UV to blue spectral region. For instance, the light used for irradiating comprises wavelengths in the region of between and including 200 nanometers to 500 nanometers. The light to be used for irradiation can be dependent on the photoactive catalyst used. For example, UV light is used for irradiating theprecursor mixture. The UV light can be UV-A light, inparticular having wavelengths in a region between andincluding 315 nanometers to 400 nanometers, and / or UV-Blight, in particular having wavelengths in a region betweenand including 250 nanometers to 315 nanometers. In other2023PF01582 February 26, 2025P2023,1579 WO N -10 -words, the photoactive catalyst can be a UV-A activated photoacid or photobase generator or a UV-B activated photoacid or photobase generator. According to at least one embodiment of the method, the precursor mixture comprises a component selected from the group consisting of fillers, adhesion promoters, surfactants, solvents, and combinations thereof. In particular, the fillers are inert fillers, that is fillersthat do not react under the conditions used for forming thepolysiloxane resin from the polysiloxane precursor. For example, the precursor mixture comprises between andincluding 5 wt.% and 50 wt.% of the fillers. Examples offillers include silicone dioxide such as fused silica, cristobalite, or quartz, as well as zirconium dioxide. Advantageously, the adhesion promoters and the surfactants are added to increase an adhesion between the polysiloxane precursor and the phosphor as well as between the polysiloxane precursor and the light-emitting semiconductorchip. For example, the precursor mixture comprises betweenand including 5 wt.% and 10 wt.% of the adhesion promotersand / or the surfactants. Examples of adhesion promoters areorganic alkoxysilanes, such as allyltrimethylethoxysilane ormethyltriethoxysilane, alcohols such as octyl alcohol oroctadecyl alcohol, or amines, such as octylamine oroctadecylamine. In particular, the solvent can be used to adjust a viscosity of the precursor mixture. For example, the precursor mixture comprises between and including 5 wt.% and 50 wt.% of the solvents. The solvent is, for instance, selected from the2023PF01582 February 26, 2025P2023,1579 WO N -11 -group consisting of alcohols such as isopropanol, esters such as butyl acetate, ketones such as acetone, and mixtures thereof. According to at least one embodiment of the method, the polysiloxane precursor is a polysilsesquioxane having the formula (RSiO1.5)n, wherein R is a carbon-containing functional group selected from the group consisting of alkyl groups, alkenyl groups, and aryl groups. In particular, R is selected from the group consisting of methyl, ethyl, phenyl or benzyl. For example, R is methyl or phenyl. In particular,polysilsesquioxanes have a cage-like or polymeric structurewith Si-O-Si linkages and tetrahedral Si vertices. According to at least one embodiment of the method, the polysiloxane precursor, in particular the polysilsesquioxane, is thermoplastic. A thermoplastic compound is, for example, a polymer that becomes pliable at a certain elevated temperature and solidifies upon cooling. The temperature at which the thermoplastic compound becomes pliable is called the softening point. According to at least one embodiment of the method, the polysiloxane precursor is a solid at room temperature. Hereand in the following, room temperature is a temperaturebetween and including 20°C and 25°C. The polysiloxane precursor which is a solid at room temperature can be easily handled during preparation of the precursor mixture. According to at least one embodiment of the method, the polysiloxane precursor has a softening point between and including 30°C and 150°C, in particular between and including 50°C and 100°C.2023PF01582 February 26, 2025P2023,1579 WO N -12 -According to at least one embodiment of the method, the polysiloxane precursor has a molecular weight between and including 1000 g / mol and 10000 g / mol, in particular betweenand including 1000 g / mol and 5000 g / mol. For example, such amolecular weight leads to a polysiloxane precursor which is solid at room temperature. According to at least one embodiment of the method, the polysiloxane precursor comprises between and including 1 wt.% and 15 wt.% of reactive groups, in particular between andincluding 3 wt.% and 6 wt.%. For example, the reactive groupsin the polysiloxane precursor undergo a condensation reaction during formation of the polysiloxane resin. In particular, the reactive groups undergo a cross-linking reaction in the presence of the acid or the base formed from the photoactive catalyst or in the presence of the photoactivated photoactive catalyst. For instance, the reactive groups are hydroxy groups and / or alkoxy groups. According to at least one embodiment of the method, a reflective resin is applied in the second, non-irradiated regions, in particular after the conversion layer is formed. The reflective resin comprises, for example, a further polysiloxane resin and reflective particles. The further polysiloxane resin is in particular different from the polysiloxane resin of the conversion layer. The reflective particles can comprise a material selected from the group consisting of SiO2, TiO2, ZrO2, BaSO4, and combinations thereof. Furthermore, a light-emitting device is specified. In particular, the light-emitting device is produced by the2023PF01582 February 26, 2025P2023,1579 WO N -13 -method described herein. Thus, embodiments, features, and advantages described in combination with the method also apply to the light-emitting device and vice versa. According to at least one embodiment, the light-emitting device comprises a light-emitting semiconductor chip. The light-emitting semiconductor chip is in particular configured to emit light of a first wavelength range. The light-emitting semiconductor chip comprises, for example, a semiconductor layer sequence. The semiconductor layer sequence can comprise an active region which is able to produce light. The light is emitted via a radiation exit surface, for example. The light- emitting semiconductor chip is, for example, a light-emitting diode (LED) or a laser diode. According to at least one embodiment, the light-emitting device further comprises a conversion layer. The conversion layer in particular converts the light emitted by the light- emitting semiconductor chip, that is the light of the first wavelength range, into light of a second wavelength range. The second wavelength range is at least partially different from the first wavelength range. According to at least one embodiment of the light-emitting device, the conversion layer is in direct mechanical contact with the light-emitting semiconductor chip. In particular, the conversion layer is directly applied on the radiation exit surface of the light-emitting semiconductor chip. In other words, no further layers such as adhesive layers are arranged between the light-emitting semiconductor chip and the conversion layer.2023PF01582 February 26, 2025P2023,1579 WO N -14 -According to at least one embodiment of the light-emitting device, the conversion layer is formed from the precursor mixture described herein. According to at least one embodiment of the light-emitting device, the conversion layer comprises a polysiloxane resin. In particular, the polysiloxane resin is formed from the polysiloxane precursor described herein. According to at least one embodiment of the light-emittingdevice, the conversion layer comprises phosphor particles.The phosphor particles can convert the light emitted by thelight-emitting semiconductor chip to light of the second wavelength range. In other words, the phosphor particles are a reason for the wavelength-converting properties of the conversion layer. According to at least one embodiment of the light-emitting device, the conversion layer comprises traces of a photoactive catalyst and / or traces of degradation products of a photoactive catalyst. “Traces” means that detectable quantities of the photoactive catalyst and / or the degradation products of the photoactive catalyst are present in the conversion layer. However, the detectable quantities in the conversion layer do not affectthe properties of the conversion layer. For example, tracesmeans an amount of the photoactive catalyst and / or the degradation products of the photoactive catalyst of at most 0.5 wt.% of the conversion layer. According to at least one embodiment, the light-emitting device comprises the light-emitting semiconductor chip and2023PF01582 February 26, 2025P2023,1579 WO N -15 -the conversion layer, wherein the conversion layer is in direct mechanical contact with the light-emitting semiconductor chip, and wherein the conversion layer comprises the polysiloxane resin, phosphor particles and traces of the photoactive catalyst and / or traces of degradation products of the photoactive catalyst. As the conversion layer is directly arranged on the light- emitting semiconductor chip, a heat transfer between the light-emitting semiconductor chip and the conversion layer isimproved. This advantageously leads to a more reliable light-emitting device. The light-emitting device can be used for various applications, for example for automotive and mobility applications, industrial applications, medical and health applications, mobile phones and wearables, as well aslighting applications. In particular, the light-emittingdevice can be used in static forward lighting, dynamic forward lighting, static signaling, dynamic signaling,functional illumination, ambient lighting, displaybacklighting, projection, and general lighting. According to at least one embodiment, the light-emitting device emits white light. In particular, the white light comprises the light of the first wavelength range and the light of the second wavelength range. For example, for an emission of white light, the conversion layer comprises Gd and / or Ce doped YAG. According to at least one embodiment, the light-emitting device emits amber light. In particular, the amber light comprises the light of the first wavelength range and the2023PF01582 February 26, 2025P2023,1579 WO N -16 -light of the second wavelength range. For an emission of amber light, the conversion layer comprises, for example, (Sr,Ba)2Si5N8:Eu2+as phosphor particles. According to at least one embodiment of the light-emitting device, the light-emitting semiconductor chip is configuredto emit light in the ultraviolet (UV) to blue spectral range.According to at least one embodiment of the light-emitting device, at least one of the degradation products of the photoactive catalyst is an acid or a base. In particular, the degradation products of the photoactive catalyst are generated from the photoactive catalyst by irradiation with UV to blue light. According to at least one embodiment of the light-emitting device, the light-emitting semiconductor chip is a mini-LED or a micro-LED. As a broad definition, a micro-LED could be seen as any light-emitting diode with a particularly small size. Micro- LEDs 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 ofa semiconductor layer sequence, of the radiation exit surfaceof smaller than or equal to 70 micrometers, for examplesmaller than or equal to 50 micrometers. For example, amicro-LED is a light-emitting diode with a removed growthsubstrate, such that a thickness of the micro-LED is in the range between and including, for example, 1.5 micrometers and2023PF01582 February 26, 2025P2023,1579 WO N -17 -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. In contrast, the growth substrate may still adhere to the mini-LEDs, resulting in a thickness of approximately between and including 50 micrometers and 100 micrometers. 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 size 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 the use in data communication or pixelated lighting applications. According to at least one embodiment, the light-emitting device further comprises a reflective layer. In particular, the reflective layer is arranged adjacent to the light- emitting semiconductor chip and the conversion layer. For example, the reflective layer is in direct mechanical contact with the light-emitting semiconductor chip and the conversion layer. For instance, only side surfaces of the light-emitting semiconductor chip and the conversion layer are covered with the reflective layer. For example, the reflective layer comprises a polysiloxane resin and reflective particles. In particular, the polysiloxane is a silicone. Here and in the following, a silicone is a polysiloxane which mainly consists of D-units (-OR2SiO-). The reflective particles, for example, compriseor consist of a material selected from the group consistingof TiO2, SiO2, ZrO2, BaSO4, and combinations thereof.2023PF01582 February 26, 2025P2023,1579 WO N -18 -According to at least one embodiment of the light-emitting device, the reflective layer is flush with the conversion layer. This advantageously allows for a compact design of the light-emitting device. Advantageous embodiments and developments of the method for producing a plurality of light-emitting devices and the light-emitting device will become apparent from the exemplary embodiments described below in conjunction with the figures. In the figures: Figures 1A to 1F schematically show steps of a method for producing a plurality of light-emitting devices according to an exemplary embodiment.Figures 2A to 2G schematically show steps of a method forproducing a plurality of light-emitting devices according to an exemplary embodiment.Figure 3 shows an absorption spectrum of phosphor particles.Figure 4 shows a transmission spectrum of a mixture of a polysiloxane precursor and a filler. Figure 5 shows Fourier transform infrared (FT-IR) spectra of a precursor mixture at different irradiation states.Figure 6 shows a dependency of an area of a Si-OH peak in anFT-IR spectrum from the time after irradiating.2023PF01582 February 26, 2025P2023,1579 WO N -19 -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.In a first step of a method for producing a light-emittingdevice 10 according to an exemplary embodiment, shown in Figure 1A, a plurality of light-emitting semiconductor chips 2 are provided on a substrate 1. The light-emitting semiconductor chips 2 on the substrate 1 form a wafer. The wafer arises, for example, from the production of the light- emitting semiconductor chips 2. Alternatively, the wafer is an artificial wafer. The substrate 1 can be opaque or transparent. For example, the substrate 1 comprises or consists of a glass, a plastic, or a semiconductor material. The light-emitting semiconductor chips 2 comprise a semiconductor layer sequence with an active layer and emitfor example light in the UV to blue spectral range. Thelight-emitting semiconductor chips 2 are arranged in aregular grid on the substrate 1. The light-emittingsemiconductor chips 2 can be micro-LEDs or mini-LEDs. Presently, a reflective layer 7 is arranged between the light-emitting semiconductor chips 2. The reflective layer 7 comprises, for example, a silicone and reflective particles, for example comprising SiO2, TiO2, or ZrO2. The reflective layer 7 is flush with the light-emitting semiconductor chips 2.2023PF01582 February 26, 2025P2023,1579 WO N -20 -In a next step, a precursor mixture 3 is directly applied on the plurality of semiconductor chips 2, as shown in Figure 1B. For example, the precursor mixture 3 is applied by spray coating, spin coating, doctor blading or stencil printing. The precursor mixture 3 comprises a polysiloxane precursor 31. The polysiloxane precursor 31 is a polysilsesquioxane(RSiO1.5)n, wherein R is selected from methyl or phenyl. Thepolysilsesquioxane is a thermoplastic compound which is solid at room temperature. In particular, the polysiloxaneprecursor 31 has a softening point between and including 50°Cand 100°C and / or a molecular weight between and including1000 and 10000 g / mol. The polysiloxane precursor 31 containshydroxy groups and / or alkoxy groups which can undergo a crosslinking reaction in the presence of an acid or a base. The polysiloxane precursor 31 comprises, for example, between and including 3 wt.% and 6 wt.% of the hydroxy groups and / oralkoxy groups, which are reactive groups.The precursor mixture 3 further comprises phosphor particles 4. The phosphor particles 4 are for example Gd and / or Ce doped YAG to achieve a light-emitting device 10 emittingwhite light. For an emission of green light Ce doped LuAG orLuYAG can be used as phosphor particles 4. A light-emittingdevice 10 emitting amber light can be achieved with Eu doped(Sr,Ba)2Si5N8as phosphor particles 4. Additionally or alternatively, phosphors emitting in the infrared and / or near infrared spectral range such as La3Ga5GeO14:Cr3+, ScBO3:Cr3+, Gd3Sc2Ga3O12:Cr3+, and Mg2SiO4:Cr3+can be used. The precursor mixture 3 further comprises a photoactivecatalyst (not shown). The photoactive catalyst is, forexample, a photoacid or a photobase. As the photoacid atrichloromethyltriazine or a trifluoromethanesulfonic acid2023PF01582 February 26, 2025P2023,1579 WO N -21 -salt can be used. The precursor mixture 3 comprises 0.01 wt.% to 0.5 wt.% of the photoactive catalyst. In addition to the phosphor particles 4, the precursor mixture 3 may also comprise fillers, adhesion promotors, surfactants and / or solvents. In particular, these materials influence rheologic properties of the precursor mixture 3. Asthe solvent, for example isopropanol, acetone, butyl acetateand mixtures thereof can be used. As shown in Figure 1C, a mask 8 is arranged above the precursor mixture 3. In this way first regions 51 and secondregions 52 are generated. The first regions 51 correspond tothe light-emitting semiconductor chips 2, whereas the secondregions 52 presently correspond to regions of the reflective layer 7. The precursor mixture 3 is irradiated with UV to blue light through the mask 8. In this way, the photoactive catalyst is activated and an acid or a base is generated. The acid or the base catalyzes a reaction of the polysiloxane precursor 31 to a polysiloxane resin 61. The reaction of the polysiloxane precursor 31 to the polysiloxane resin 61 can be described as curing. To aid curing of the polysiloxane precursor 31, the precursor mixture 3 can be heated, for example during or after irradiating the precursor mixture 3.If the trichloromethyltriazine is used as the photoactivecatalyst, the photoactive catalyst can be activated with UV-Alight. The trichloromethylriazine undergoes the followingreaction in the presence of water under irradiation:2023PF01582 February 26, 2025P2023,1579 WO N -22 - If the trifluoromethanesulfonic acid salt is used as thephotoactive catalyst, the photoactive catalyst can be activated with UV-B light. A possibletrifluoromethanesulfonic acid salt and the UV-light-inducedreaction are shown below. The result after irradiating is shown in Figure 1D. Afterirradiating a conversion layer 6 with the polysiloxane resin61 is formed in the first regions 51, whereas thepolysiloxane precursor 31 remains unreacted in the second regions 52. Thus, in the second, non-irradiated regions 52, the precursor mixture 3 is still present. The conversion layer 6 is developed by removing the unreacted precursor mixture 3, as shown in Figure 1E. The precursor mixture 3 is washed away with a solvent such as isopropanol, acetone, butyl acetate and mixtures thereof. The conversion layer 6 is only arranged in the first regions 51, that is on the light-emitting semiconductor chips 2. The second regions 52 are free of the conversion layer 6. After developing the conversion layer 6, further material of the reflective layer 7 is arranged between the semiconductor chips 2. The2023PF01582 February 26, 2025P2023,1579 WO N -23 -reflective layer then completely fills a space between theconversion layers 6 such that the reflective layer 7 is flushwith the conversion layers 6. To produce individual light-emitting devices 10, singulation is performed, for example by dicing or sawing. The singulation occurs in the second regions 52. A finished light-emitting device 10 is shown in Figure 1F. The light- emitting device 10 comprises the substrate 1 and the light- emitting semiconductor chip 2 arranged on the substrate 1. The conversion layer 6 comprising the polysiloxane resin 61made from the polysiloxane precursor 31 described above andcomprising the phosphor particles 4 is arranged directly onthe light-emitting semiconductor chip 2. Side faces of the light-emitting semiconductor chip 2 and the conversion layer 6 are surrounded by the reflective layer 7. The reflective layer 7 is in particular in direct mechanical contact with the conversion layer 6 and the light-emitting semiconductor chip 2. The reflective layer 7 is flush with the conversion layer 6. The conversion layer 6 comprises traces of the photoactive catalyst and / or traces of the acid or the base generated from the photoactive catalyst. Another exemplary embodiment of the method for producing a light-emitting device 10 is disclosed in Figures 2A to 2G. As shown in Figure 2A, a plurality of light-emitting semiconductor chips 2 are arranged on a substrate 1. Thelight-emitting semiconductor chips 2 and the substrate 1 canbe configured as described in combination with Figure 1A. Contact pads 9 are arranged between the light-emittingsemiconductor chips 2. The contact pads 9 are arranged on thesubstrate 1. In contrast to Figure 1A, no reflective layer 72023PF01582 February 26, 2025P2023,1579 WO N -24 -is present between the light-emitting semiconductor chips 2 on the substrate. A precursor mixture 3 is applied on the plurality of light-emitting semiconductor chips 2, as shown in Figure 2B. Theprecursor mixture 3 covers the light-emitting semiconductor chips 2, the contact pads 9 and a part of the substrate 1 free of the light-emitting semiconductor chips 2 and the contact pads 9. The precursor mixture 3 is in direct contact with the light-emitting semiconductor chips 2, the substrate 1 and the contact pads 9. The precursor mixture 3 can comprise the same constituents as described in combination with Figure 1B. That is, the precursor mixture 3 comprises a polysiloxane precursor 31, phosphor particles 4, a photoactive catalyst, and optionally fillers, adhesion promotors, surfactants, solvents, and combinations thereof.A mask 8 is arranged above the precursor mixture 3, as shownin Figure 2C. The precursor mixture 4 is irradiated through the mask 8, for example with UV light. In first regions 51, which correspond to the light-emitting semiconductor chips 2, the precursor mixture 3 is not covered with the mask 8. Insecond regions 52, which correspond to spaces between thelight-emitting semiconductor chips 2, the precursor mixture 3 is covered with the mask. Due to the irradiation, the polysiloxane precursor 31 reacts to form a polysiloxane resin 61. In this way, conversion layers 6 are formed on the light-emitting semiconductor chips 2, as shown in Figure 2D. During irradiation, the photoactive catalyst liberates an acid or a base. The acid or the base catalyzes the reaction of the polysiloxane precursor 31 to the polysiloxane resin 61.2023PF01582 February 26, 2025P2023,1579 WO N -25 -As irradiation is only performed in the first regions 51, the reaction of the polysiloxane precursor 31 to the polysiloxane resin 61 only occurs in the first regions 51. Thus, the conversion layer 6 is only formed in the first regions 51, that is on the light-emitting semiconductor chips 2. The conversion layers 6 are developed by removing the unreacted precursor mixture 3 in the second, non-irradiatedregions 52, as shown in Figure 2E. To remove the precursormixture 3, a solvent as described in combination with Figure1E is used. Removing the unreacted precursor mixture 3 exposes the contact pads 9 and side faces of the light- emitting semiconductor chips 2. As shown in Figure 2F, a reflective layer 7 is applied in the second regions 52. The reflective layer 7 comprises a silicone and reflective particles, for example comprising or consisting of TiO2, SiO2, ZrO2, and mixtures thereof. The reflective layer 7 is flush with the conversion layers 6 on the light-emitting semiconductor chips 2. The light-emitting devices 10 are singulated such that thelight-emitting device 10 shown in Figure 2G is produced. Thelight-emitting device 10 comprises the substrate 1, the light-emitting semiconductor chip 2, the conversion layer 6 and the reflective layer 7. The reflective layer 7 surrounds the light-emitting semiconductor chip 2 and the conversion layer 6 in a lateral direction. Presently, the reflective layer 7 is in direct mechanical contact with the light- emitting semiconductor chip 2, the contact pad 9, the substrate 1, and the conversion layer 6. The reflective layer 7 is flush with the conversion layer 6. The conversion layer2023PF01582 February 26, 2025P2023,1579 WO N -26 -6 is in direct mechanical contact with the light-emitting semiconductor chip 2. In particular, the conversion layer 6 is arranged only on a main emission surface of the light- emitting semiconductor chip 2. Side faces of the light- emitting semiconductor chip 2 are free of the conversion layer 6. The conversion layer 6 comprises the polysiloxane resin 61 formed from the polysiloxane precursor 31, the phosphor particles 4, and traces of the photoactive catalyst and / or traces of the acid or the base generated from the photoactive catalyst. The phosphor particles 4 are homogeneously distributed in the conversion layer 6. Alternatively, the phosphor particles 4 can have a gradient. For example, a concentration of the phosphor particles 4 increases towards the light-emitting semiconductor chip 2.Figure 3 shows an absorption spectrum C1 of phosphorparticles 4. In Figure 3, the absorption coefficient C isplotted against the wavelength in nanometers. The absorptioncoefficient C is given in arbitrary units. The phosphorparticles comprise Ce and / or Gd doped YAG (Y3Al5O12). Figure 3further shows regions UV-A und UV-B corresponding to the UV-A and UV-B spectral ranges. It can be seen from this figure that phosphor particles 4 comprising Ce and / or Gd doped YAG have two windows of transparency in the UV spectral range. These two windows coincide with the light which can be used to generate an acid or a base from the photoactive catalyst. Thus, the phosphor particles 4 do not interfere with anactivation of the photoactive catalyst by irradiation with UVlight, in particular UV-A or UV-B light.2023PF01582 February 26, 2025P2023,1579 WO N -27 -In Figure 4 a transmission spectrum T1 of a mixturecomprising a polysiloxane precursor 31 and fillers comprisingfumed silica is shown. The transmission T of the mixture in % is plotted against the wavelength in nanometers. Regions UV-A and UV-B corresponding to the UV-A and UV-B spectral ranges are also shown in Figure 4. It can be seen from this figure that the mixture is transmissive for UV-A light and at least partially transmissive for UV-B light. Thus, the polysiloxane precursor 31 and fillers comprising fumed silica do not interfere with an activation of the photoactive catalyst byirradiation with UV light, in particular UV-A or UV-B light.Figure 5 shows Fourier transform infrared (FT-IR) spectra 5-1and 5-2 of a precursor mixture 3 at different irradiationstates. In Figure 5, the normalized absorption B is plottedagainst the frequency in cm-1. FT-IR spectrum 5-1 arises from a non-irradiated precursor mixture 3 comprising apolysiloxane precursor 31 (4.0 g), butyl acetate (1.0 g) assolvent, and a trichloromethyltriazine (4 mg) as photoactivecatalyst. The precursor mixture 3 is applied on an attenuated total reflection (ATR) crystal and the solvent is evaporated. A halogen lamp providing light with a wavelength range of 350 nanometers to 550 nanometers with a power of 20 mW is used toirradiate the precursor mixture 3 for 30 seconds at atemperature of 100°C. After the irradiation the FT-IR spectrum 5-2 is recorded. A comparison of the FT-IR spectra 5-1 and 5-2 shows that the area of the peak resulting from the Si-OH group is reduced after irradiation. This means that the polysiloxane precursor 31 is reacted to a polysiloxane resin 61 via a condensation reaction of the Si-OH groups. This proves that the photoactive catalyst was activated and an acid was produced2023PF01582 February 26, 2025P2023,1579 WO N -28 -from the photoactive catalyst. The acid then catalyzed the reaction from the polysiloxane precursor 31 to the polysiloxane resin 61.Figure 6 shows a dependency of an area of a Si-OH peak in anFT-IR spectrum from the time after irradiating. In Figure 6the area of the Si-OH peak (A(OH)) in an FT-IR spectrum compared to an area of the Si-O-Si peak (A(Si-O-Si)) in an FT-IR spectrum is plotted against the time T. Until the start S, the peak area of the Si-OH peak did notchange even though the precursor mixture 3 described incombination with Figure 5 was kept at 100°C. Thus, anincreased temperature alone is not able to induce the reaction from the polysiloxane precursor 31 to the polysiloxane resin 61. At the start S the precursor mixture 3 was irradiated with a halogen lamp emitting light with a wavelength range of 350nanometers to 550 nanometers while the temperature of theprecursor mixture 3 was still kept at 100°C. The precursor mixture 3 was irradiated for 30 seconds. As can be seen from Figure 6, the area of the Si-OH peak decreases after the start S of irradiation. After about 6 minutes, the area of the Si-OH peak was constant again. After the 6 minutes about 50% of the Si-OH groups had reacted. Thus, the polysiloxane resin 61 was formed from the polysiloxane precursor 31 in the precursor mixture 3. The features and exemplary embodiments described in connection with the figures can be combined with each other according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the2023PF01582 February 26, 2025P2023,1579 WO N -29 -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 provisional patent application 63 / 570,661, the disclosure content of which 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] 2023PF01582 February 26, 2025P2023,1579 WO N -30 -References1 substrate2 light-emitting semiconductor chip3 precursor mixture31 polysiloxane precursor4 phosphor particle51 first region52 second region6 conversion layer61 polysiloxane resin7 reflective layer8 mask9 contact pad10 light-emitting device5-1, 5-2 FT-IR spectrumA areaA1 time-dependent areaB normalized absorptionC absorption coefficientC1 absorption spectrumν frequencyS startT1 transmission spectrumT transmissiont time

Claims

2023PF01582 February 26, 2025P2023,1579 WO N -31 -Claims 1. A method for producing a plurality of light-emitting devices (10) comprising:- providing a plurality of light-emitting semiconductor chips(2) on a substrate (1),- applying a precursor mixture (3) on the plurality of light-emitting semiconductor chips (2), wherein the precursormixture (3) comprises a polysiloxane precursor (31), phosphorparticles (4), and a photoactive catalyst,- irradiating the precursor mixture (3) in first regions (51)to form a conversion layer (6) in the first regions (51),wherein the conversion layer (6) comprises a polysiloxane resin (61) and the phosphor particles (4).

2. The method according to the previous claim, furthercomprising removing the precursor mixture (3) in second, non-irradiated regions (52).

3. The method according to any of the previous claims,further comprising singulating into a plurality of light-emitting devices (10).

4. The method according to any of the previous claims, the method further comprising heating the precursor mixture (3).

5. The method according to any of the previous claims, wherein the photoactive catalyst generates an acid or a base upon irradiation.

6. The method according to any of the previous claims, wherein the precursor mixture (3) comprises 0.01 wt.% to 0.5 wt.% of the photoactive catalyst.2023PF01582 February 26, 2025P2023,1579 WO N -32 -7. The method according to any of the previous claims,wherein UV to blue light is used for irradiating theprecursor mixture (3).

8. The method according to any of the previous claims, wherein the precursor mixture (3) comprises a component selected from the group consisting of fillers, adhesion promoters, surfactants, solvents, and combinations thereof.

9. The method according to any of the previous claims,wherein the polysiloxane precursor (31) is apolysilsesquioxane having the formula (RSiO1.5)n, wherein R is a carbon-containing functional group selected from the group consisting of alkyl groups, alkenyl groups, and aryl groups.

10. The method according to any of the previous claims, wherein the polysiloxane precursor (31) is thermoplastic.

11. The method according to any of the previous claims, wherein the polysiloxane precursor (31) is a solid at room temperature.

12. The method according to any of the previous claims, wherein the polysiloxane precursor (31) has a softening point between and including 30°C and 150°C.

13. The method according to any of the previous claims, wherein the polysiloxane precursor (31) has a molecular weight between and including 1000 g / mol and 10000 g / mol.2023PF01582 February 26, 2025P2023,1579 WO N -<sub>33 -14. The method according to any of the previous claims, wherein the polysiloxane precursor (31) comprises between and including 1 wt.% and 15 wt.% of reactive groups.

15. A light-emitting device (10) comprising:- a light-emitting semiconductor chip (2) and- a conversion layer (6), wherein- the conversion layer (6) is in direct mechanical contactwith the light-emitting semiconductor chip (2), and wherein- the conversion layer (6) comprises a polysiloxane resin(61), phosphor particles (4) and traces of a photoactivecatalyst and / or traces of degradation products of aphotoactive catalyst.

16. The light-emitting device (10) according to the previousclaim, wherein at least one of the degradation products ofthe photoactive catalyst is an acid or a base.

17. The light-emitting device (10) according any of claims 15and 16, wherein the light-emitting semiconductor chip (2) isa mini-LED or a micro-LED.

18. The light-emitting device (10) according to any of claims15 to 17, further comprising a reflective layer (7), whereinthe reflective layer (7) is flush with the conversion layer (6).

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