Filter element, optoelectronic component, method for producing a filter element and method for producing an optoelectronic component

Abstract

The invention relates to a filter element which has, for electromagnetic radiation with wavelengths of up to 750 nm, a transmission of less than 10% and, for electromagnetic radiation with wavelengths of greater than 850 nm, a transmission of more than 10%, wherein the filter element comprises a mixture containing at least one dye and a polysiloxane, in which Si atoms are interlinked only via one O atom in each case. The invention also relates to an optoelectronic component, for example a micro LED, having a filter element, to a method for producing a filter element, and to a method for producing an optoelectronic component.

Description

[0001] Description

[0002] FILTER ELEMENT, OPTOELECTRONIC COMPONENT, METHOD FOR PRODUCING A FILTER ELEMENT AND METHOD FOR PRODUCING AN OPTOELECTRONIC COMPONENT

[0003] A filter element, an optoelectronic component, a method for producing a filter element and a method for producing an optoelectronic component are specified.

[0004] The object of at least one embodiment is to specify a filter element with improved properties. The object of at least one further embodiment is to specify an optoelectronic component with improved properties. The object of at least one further embodiment is to specify a method for producing a filter element with improved properties. The object of at least one further embodiment is to specify a method for producing an optoelectronic component with improved properties. These objects are achieved by a filter element, an optoelectronic component and by methods according to the independent claims. Further embodiments of the filter element, the component and the methods are the subject of dependent claims.

[0005] A filter element is specified. Here and in the following, a filter element is understood to be a component that can filter, i.e. block, electromagnetic radiation. The filter element can, for example, be intended to be used in an optoelectronic component. In particular, the filter element can block electromagnetic radiation of a specific wavelength range, i.e. be opaque to this electromagnetic radiation. Accordingly, the filter element can only be transparent to radiation of a wavelength range that differs from this specific wavelength range. The geometry of such a filter element is in principle not restricted as long as it enables the filter function of the element.

[0006] According to at least one embodiment, the filter element has a transmission of less than 10%, in particular less than 5%, for example less than 2%, for electromagnetic radiation with wavelengths of up to 750 nm, in particular from 350 nm to 750 nm, and a transmission of more than 10%, in particular more than 20%, for example more than 50%, for electromagnetic radiation with wavelengths greater than 850 nm. This means that the filter element is permeable to radiation from the IR range and at the same time blocks radiation from the UVvis range or filters out radiation with wavelengths from the UVvis range from the total radiation that passes through the filter element.

[0007] According to at least one embodiment, the filter element comprises a mixture containing a polysiloxane in which Si atoms are linked to one another only via one O atom each, and at least one dye. In particular, the filter element consists of a mixture containing a polysiloxane in which Si atoms are linked to one another only via one O atom each, and at least one dye. The mixture is thus the material of the filter element.

[0008] A polysiloxane in which Si atoms are linked to one another only via one O atom each is understood to be a polysiloxane formed from -Si-O-Si chains or a -Si-O-Si network. The Si atoms contained in the polysiloxane are linked to one another only via O atoms and not via other atoms or groups. In particular, the polysiloxane is free of -Si-CH2-CH2-Si bonds.

[0009] The polysiloxane can in particular be a condensation-curing polysiloxane.

[0010] A -Si-O-Si network can be two- or three-dimensional. For example, -Si-O-Si chains can be linked to form rings, conductors, or ladder-like structures. Complete or incomplete cage structures formed from -Si-O-Si chains are also conceivable. A polysiloxane described here can, for example, have the following structural formulas I to VI:

[0011] IV V VI

[0012] "R" here and below represents an organic radical which may be selected, for example, from alkyl groups and aryl groups. The alkyl group selected may be, for example, methyl, ethyl, propyl and butyl, in particular methyl.

[0013] A dye is understood here and below to be a material that, due to its chemical structure, can absorb and possibly also emit electromagnetic radiation. In the present component, the dye in the filter element is responsible for its filtering function. In other words, the at least one dye absorbs electromagnetic radiation with wavelengths of up to 750 nm, thus making the filter element opaque to this UV-visible radiation.

[0014] According to at least one embodiment, a filter element is specified which has a transmission of less than 10% for electromagnetic radiation with wavelengths of up to 750 nm and a transmission of more than 10% for electromagnetic radiation with wavelengths greater than 850 nm, wherein the filter element comprises a mixture containing at least one dye and a polysiloxane in which Si atoms are linked to one another only via one O atom each.

[0015] Particularly in the automotive sector, IR radiation emitting or IR radiation detecting components are used in which the UVvis portion of the electromagnetic radiation must be suppressed, for example to reduce the so-called red glow effect. Until now, UVvis suppression has been achieved by additional optical elements which contain a thermoplastic material in addition to the filtering dyes. Thermoplastic materials are sufficiently stable under the conditions to which an optical element applied on a second level is exposed. However, this solution increases the complexity of the entire system and also the manufacturing costs. On the other hand, thermoplastics, just like epoxy materials, would degrade under the conditions typical in IR radiation emitting or detecting components if they were integrated into these components.

[0016] The filter element described here, which can block UVvis radiation, is suitable for being integrated into an optoelectronic component, i.e. for being arranged at the first level in a component. This is made possible by the fact that the filter element has a high (photo-)thermal stability due to the polysiloxane it contains, in which, as described above, Si atoms are only linked to one another via one O atom each. The polysiloxane occupies an intermediate position between an organic and an inorganic material and has a higher stability than common matrix materials such as epoxy, thermoplastics or standard silicones, which contain Si-CH2-CH2-Si bonds in their network. The polysiloxane described here therefore has a polymer network or polymer chains that are better compatible with dyes and solvents than thermoplastics or epoxy.

[0017] In addition, the polysiloxane exhibits a high polarity, which particularly supports the solubility of dyes that are soluble in polar solvents. Since dyes that block UV-visible radiation and are transparent to IR radiation can be soluble in polar solvents, the mixture containing at least one dye and the polysiloxane provides a filter element that is well suited for use in optoelectronic components in the automotive sector.

[0018] According to at least one embodiment, in the polysiloxane each Si atom is linked to at least 2.5 O atoms, in particular at least three O atoms. In the case of a chain-like structure each Si atom within the structure is thus linked, for example, via two O atoms to two further Si atoms and furthermore has at least one OH or OR radical. The fourth linkage of the Si atom can then be either to a further OH or OR radical or to an R radical (see formula I). ​​In a two- or three-dimensionally linked polysiloxane each Si atom is linked via an O atom to two or three further Si atoms and the third and / or fourth bond of the Si atom can then be either to a further OH or OR radical or to an R radical (see formulas II to VI). It is also possible to link a Si atom via one O atom each to four further Si atoms.

[0019] Due to this structure of the polysiloxane, it has a low proportion of organic radicals R and a high proportion of Si-O bonds, which, among other things, leads to its high stability. In addition, the polysiloxane described here is more polar and has a higher polarizability than conventional silicones, which have a -Si-CC-Si network and / or a lower proportion of Si-O bonds compared to the polysiloxane described here. The polysiloxane described here can therefore be easily mixed with dyes that are soluble in polar solvents. According to at least one embodiment, the mixture is free of alcohol. Alternatively, small proportions of alcohol used in the preparation of the mixture can be present in the mixture.

[0020] According to at least one embodiment, the mixture contains at least two different dyes. The mixture can therefore contain a dye system which is tailored to absorb electromagnetic radiation in the range up to 750 nm, in particular in the range from 350 nm to 750 nm, and thus not transmit it through the filter element. The desired wavelengths can be filtered by superimposing the absorption behavior of the individual dyes. According to at least one embodiment, the at least one dye is a commercial dye. Commercial dyes or dye systems can therefore be used in the mixture.

[0021] According to at least one embodiment, the at least one dye is soluble in polar solvents. Thus, the dye or dyes are more soluble in the polysiloxane described here than in conventional silicones which have -Si-CC-Si- bonds. In addition, the solubility of the dye or dyes can be further increased because they are soluble in polar solvents such as alcohols. This can further facilitate the production of the mixture of the at least one dye with the polysiloxane by increasing the solubility of the dye or the dye system in a precursor material of the polysiloxane by adding a polar solvent such as alcohol. According to at least one embodiment, the concentration of the at least one dye in the filter element is less than or equal to 5 wt%.If more than one dye is contained in the filter element, the total concentration of all dyes is less than or equal to 5% by weight. This dye content is sufficient to ensure reliable filter function.

[0022] According to at least one embodiment, the filter element has a geometric shape selected from a lens, a plate, or a volume encapsulation. The filter element can thus be used in various configurations, for example, in an optoelectronic component.

[0023] An optoelectronic component is specified. The filter element described above is suitable and configured for use in an optoelectronic component. All features disclosed in connection with the filter element therefore also apply to the optoelectronic component, and vice versa.

[0024] According to at least one embodiment, the optoelectronic component comprises a semiconductor chip which is configured to emit or detect electromagnetic radiation in a wavelength range from 780 nm to 3000 nm.

[0025] The semiconductor chip can comprise an epitaxially grown semiconductor layer sequence with an active zone suitable for generating or detecting electromagnetic radiation during operation. For this purpose, the active zone has, for example, a pn junction, a double heterostructure, a single quantum well, or a multiple quantum well structure. The semiconductor chip is, for example, a light-emitting diode chip or a laser diode chip. The component can thus be, for example, a light-emitting diode (LED) or a laser.

[0026] The wavelength range from 780 nm to 3000 nm characterizes the wavelength range of infrared (IR) radiation. The optoelectronic component described here is thus designed to emit or detect IR radiation.

[0027] According to at least one embodiment, the optoelectronic component further comprises a filter element as described above.

[0028] According to at least one embodiment, the filter element is arranged in the beam path of the optoelectronic component. This means that the electromagnetic radiation generated by the semiconductor chip is coupled into the filter element before exiting the optoelectronic component and is then decoupled from the filter element again, or that the electromagnetic radiation detected by the semiconductor chip is first coupled into the filter element and then decoupled from the filter element again before it strikes the semiconductor chip. For both alternatives, the filter element can be arranged directly on the semiconductor chip or at a distance from it.

[0029] According to at least one embodiment, an optoelectronic component is specified, comprising a semiconductor chip which is configured to emit or detect electromagnetic radiation in a wavelength range from 780 nm to 3000 nm, and a filter element according to the above embodiments which is arranged in the beam path of the optoelectronic component.

[0030] The combination of the filter element described here with the semiconductor chip of the optoelectronic component results in effective blocking of UV-visible radiation, while the filter element exhibits high (photo)stability and thus a high degree of reliability in its filtering function, even under operating conditions. This not only filters out unwanted UV-visible radiation from the total radiation, but also suppresses undesirable effects such as the red glow effect.

[0031] According to at least one embodiment, the filter element is a volume encapsulation that encloses free outer surfaces of the semiconductor chip. Free outer surfaces of the semiconductor chip are understood to mean all surfaces that are not in physical contact with other components of the optoelectronic device, such as a substrate, a housing or electrical connections. “Enclosing” is understood to mean direct contact between the free outer surface of the semiconductor chip and the volume encapsulation, so that the semiconductor chip and the volume encapsulation have a common interface at least in some regions. Due to the high (photo)stability of the polysiloxane in the filter element or the volume encapsulation, the filter element has a high level of stability and a long service life even when arranged directly on the semiconductor chip, while at the same time providing a reliable filter function thanks to the dyes it contains.Furthermore, the mixture contained in the filter element is well suited for volume encapsulation due to the polysiloxane. In particular, the mixture can be encapsulated before the polysiloxane cures and then cured at the target location, i.e., on the semiconductor chip.

[0032] According to at least one embodiment, the volume encapsulation has a thickness selected from the range of 100 pm to 700 pm, in particular 200 pm to 500 pm. With such a thickness, the concentration of the dye in the mixture can be selected to be low, since the radiation passing through the filter element travels a longer path length.

[0033] According to at least one embodiment, the filter element is a lens that is arranged directly or at a distance from the semiconductor chip. The filter element is thus shaped in the form of a lens that is arranged on the semiconductor chip. In a direct arrangement, the lens can have a common interface with the semiconductor chip or can be attached thereto by means of an adhesive layer. In a spaced-apart arrangement, the lens can be applied, for example, to the edges of a housing enclosing the semiconductor chip, likewise with or without an adhesive layer. A potting resin or a cavity can then be present between the semiconductor chip and the housing. If the filter element is shaped as a lens, this can be produced in a separate process step, for example by potting it in a mold, and after the polysiloxane has hardened, it can be arranged as a finished element at the desired location in the optoelectronic component.For example, shaping the filter element as a lens can improve the light extraction from the optoelectronic component.

[0034] According to at least one embodiment, the filter element is a plate that is arranged directly or at a distance from the semiconductor chip. The filter element is thus shaped in the form of a plate that is arranged on the semiconductor chip. In a direct arrangement, the plate can have a common interface with the semiconductor chip or can be attached thereto by means of an adhesive layer. In a spaced-apart arrangement, the plate can be applied, for example, to the edges of a housing enclosing the semiconductor chip, likewise with or without an adhesive layer. A potting resin or a cavity can then be present between the semiconductor chip and the plate.If the filter element is shaped as a platelet, this can be produced in a separate process step, for example by casting it into a mold, and after the polysiloxane has hardened, it can be arranged as a finished element at the desired location in the optoelectronic component.

[0035] Both a lens and a plate can have a smaller thickness than, for example, a volume encapsulation. The plate can, for example, have a thickness of up to 150 pm, and the lens a thickness of up to 200 pm. Accordingly, the concentration of the at least one dye can be selected to be higher in order to ensure the filter function, since the filter element shaped as a lens or plate represents a shorter path length for the electromagnetic radiation passing through. According to at least one embodiment, the optoelectronic component is an LED, in particular a micro-LED. In the case of micro-LEDs, a growth substrate is generally removed, so that typical heights are, for example, in the range 1.5 pm to 10 pm. In principle, a micro-LED does not necessarily have to have a rectangular radiation emission surface. In general, for example, an LED with a radiation emission surface in which, in a plan view of the semiconductor chip orFor the filter element, any lateral extent of the radiation emission surface is less than or equal to 100 pm or less than or equal to 70 pm. The edge length of rectangular micro-LEDs can thus, for example, be less than or equal to 70 pm or less than or equal to 50 pm—particularly in a top view of the semiconductor chip or the filter element. Such micro-LEDs are usually provided on wafers with holding structures that can be removed without damaging the micro-LED.

[0036] Furthermore, a method for producing a filter element is specified. In particular, a filter element as described above can be produced using the method. All features and embodiments disclosed in connection with the filter element and the optoelectronic component thus also apply to the method, and vice versa.

[0037] According to at least one embodiment, the method is used to produce a filter element which has a transmission of less than 10%, in particular less than 5%, for example less than 2%, for electromagnetic radiation with wavelengths of up to 750 nm, and a transmission of more than 10%, in particular more than 20%, for example more than 50%, for electromagnetic radiation with wavelengths greater than 850 nm. The filter element produced by the method is thus permeable to radiation from the IR range and at the same time blocks radiation from the UVvis range or filters out radiation with wavelengths from the UVvis range from the total radiation passing through the filter element.

[0038] According to at least one embodiment, the method comprises the step of providing a dye solution comprising at least one dye dissolved in an alcohol. The dye solution can therefore also comprise more than one dye. In particular, the dye solution comprises a dye system which is coordinated such that it does not transmit radiation from the range up to 750 nm, in particular 350 nm to 750 nm. The alcohol can, for example, be selected from a group comprising methanol, ethanol, (iso-)propanol, 2-ethylhexanol, or polyhydric alcohols. Polyhydric alcohols are, for example, ethanediol or glycerol.

[0039] To prepare the dye solution, the at least one dye and the alcohol are mixed so that the at least one dye dissolves in the alcohol, in particular homogeneously.

[0040] According to at least one embodiment, the method further comprises the step of adding a precursor material for a polysiloxane, in which Si atoms are linked to one another only via one O atom each, to produce a homogeneous starting mixture. In the homogeneous starting mixture, the dye is present in particular homogeneously dissolved in the precursor material and the alcohol. A precursor material is understood to be a material which is converted into the polysiloxane by curing. The starting material can thus contain monomers or oligomers which are converted into the polysiloxane by a polymerization reaction. During curing, the precursor material therefore polymerizes and forms one-dimensional chains or two- or three-dimensional networks. The polymerization can take place, for example, via condensation reactions of the precursor material.Since the precursor material is added to the at least one dye dissolved in alcohol and a homogeneous starting mixture is produced, a good mixing of the at least one dye in the precursor material takes place, so that after curing the at least one dye is evenly distributed in the polysiloxane.

[0041] According to at least one embodiment, the method further comprises the step of casting and curing the homogeneous starting mixture. The desired shape of the subsequent filter element can be formed by casting, and the curing transforms the starting mixture into the filter element.

[0042] According to at least one embodiment, the method produces a filter element which has a transmission of less than 10% for electromagnetic radiation with wavelengths of up to 750 nm and a transmission of more than 10% for electromagnetic radiation with wavelengths of greater than 850 nm, the method comprising the steps of:

[0043] Providing a dye solution containing at least one dye dissolved in an alcohol, adding a precursor material for a polysiloxane in which Si atoms are linked to one another only via one O atom each, to produce a homogeneous starting mixture,

[0044] Pouring and curing the homogeneous starting mixture.

[0045] The process can be used to easily produce a filter element which has a high level of (photo) stability and a filter function for the UVvis range of the electromagnetic spectrum. In addition, the filter element has a good filter function because the dyes responsible for the filter function are evenly distributed in the polysiloxane. This is due to the high polarity of the precursor material and the polysiloxane together with the alcohol in which at least one dye is highly soluble. In addition, the filter element is produced in a simple, cost-effective and efficient manner because, for example, only one casting is carried out to achieve the desired geometry of the filter element.

[0046] This makes the filter element ideal for use in optoelectronic components designed to emit or detect electromagnetic radiation in a wavelength range from 780 nm to 3000 nm and where blocking of UVvis radiation is necessary, for example to suppress the red glow effect.

[0047] According to at least one embodiment, the starting mixture has an alcohol content selected from the range of less than 20% by weight, in particular less than 10% by weight. The exact concentration of the alcohol can be matched to the solubility behavior of the at least one dye. This ensures good dissolution of the at least one dye and unimpairs the processing of the starting mixture. According to at least one embodiment, the dye solution further contains a catalyst. This can be selected, for example, from phosphoric acid esters and their derivatives. Other acids or bases can also be suitable as catalysts. A catalyst can accelerate the polymerization during the curing of the precursor material of the polysiloxane and / or lead to a more complete polymerization.During polymerization, a condensation reaction takes place, which can be promoted by a catalyst. According to at least one embodiment, the catalyst content in the starting mixture is less than 1 wt.%.

[0048] According to at least one embodiment, the starting material of the polysiloxane has at least three reactive leaving groups. Reactive leaving groups are understood to be substituents on the Si atom that are, in principle, suitable for reaction and thus for polymerization. According to one embodiment, reactive leaving groups are selected from OH groups and OR groups, where R is an organic radical such as alkyl or aryl. For example, the leaving groups are methoxy groups, where R can also be selected from longer alkyl groups.

[0049] According to at least one embodiment, the at least one dye is soluble in polar solvents. Thus, it can be readily dissolved in the alcohol and the precursor material of the polysiloxane, producing a homogeneous starting mixture. According to at least one embodiment, curing is carried out at a temperature selected from the range 120°C to 220°C, for example 150°C. At this temperature, crosslinking of the precursor material can be initiated, i.e., the precursor material can react to form the polysiloxane, for example by means of a condensation reaction.

[0050] According to at least one embodiment, the step of adding a starting material is carried out with mixing and degassing. This ensures a good and uniform distribution of the at least one dye in the precursor material and thus also in the filter element produced therefrom.

[0051] According to at least one embodiment, the casting process involves molding the homogeneous starting mixture into a volume casting. This step can be carried out, for example, by applying the starting mixture directly to the element to be enclosed, for example, a semiconductor chip, before curing.

[0052] According to at least one embodiment, the casting process involves shaping the homogeneous starting mixture into a lens. For this purpose, the starting mixture can be cast, for example, into a mold with lens-shaped recesses, where curing subsequently takes place. The resulting lenses can then be removed from the mold and placed at the desired location in a component.

[0053] According to at least one embodiment, the casting process involves forming the homogeneous starting mixture into platelets. For this purpose, the starting mixture can be cast, for example, into a mold with platelet-shaped recesses, where curing subsequently takes place. The resulting platelets can then be removed from the mold and placed at the desired location in a component.

[0054] Furthermore, a method for producing an optoelectronic component is specified. In particular, an optoelectronic component as described above can be produced using the method. All features and embodiments disclosed in connection with the filter element, the component, or the method for producing a filter element thus also apply to the method for producing an optoelectronic component, and vice versa.

[0055] According to at least one embodiment, the method comprises the steps:

[0056] Providing a semiconductor chip which is configured to emit or detect electromagnetic radiation in a wavelength range from 780 nm to 3000 nm, producing a filter element on the semiconductor chip using a method according to one of the embodiments described above, or producing a filter element using a method according to one of the embodiments described above and arranging the filter element on the semiconductor chip.

[0057] When producing a filter element on the semiconductor chip using a method according to one of the embodiments described above, the steps explained above for producing a homogeneous starting mixture are carried out separately, while the encapsulation takes place directly onto the semiconductor chip, where the homogeneous starting mixture is also cured. Using this embodiment of the method, for example, the optoelectronic component with a filter element can be produced in the form of a volume encapsulation.

[0058] When producing a filter element using a method according to one of the embodiments described above and arranging the filter element on the semiconductor chip, the filter element can be produced completely separately and only after its completion can it be arranged on the semiconductor chip directly or at a distance, with or without an additional adhesive layer. This embodiment is suitable, for example, for producing an optoelectronic component with a filter element shaped as a lens or plate.

[0059] With both variants, the process produces an optoelectronic component which can be used in the automotive sector due to the high stability and reliability of the filter function.

[0060] An optoelectronic component described here can be used, for example, in high-speed detectors for IR radiation, in rain sensors, smoke detectors, IR remote controls and IR data transmission systems or in proximity sensors.

[0061] Further advantageous embodiments and developments of the filter element, the component, and the method will become apparent from the exemplary embodiments described below in conjunction with the figures. Figure 1 shows a schematic sectional view of an optoelectronic component according to an exemplary embodiment.

[0062] Figure 2 shows a schematic sectional view of an optoelectronic component according to an embodiment.

[0063] Figure 3 shows a schematic sectional view of an optoelectronic component according to an embodiment.

[0064] Figure 4 shows a schematic sectional view of process steps for producing a filter element according to an embodiment.

[0065] Figure 5 shows the solubility behavior of a mixture of a filter element according to an embodiment and comparative examples.

[0066] Identical, similar, or functionally identical elements are provided with the same reference symbols in the figures. The figures and the relative sizes of the elements depicted in the figures are not to be considered to scale. Rather, individual elements, particularly layer thicknesses, may be exaggerated for clarity and / or clarity.

[0067] Figures 1 to 3 each show optoelectronic components 100 in a schematic sectional view. Each shows a semiconductor chip 10 arranged in a housing 30. For the sake of clarity, further elements, such as electrical connections, are not shown.

[0068] The semiconductor chip 10 is designed to emit or detect electromagnetic radiation with wavelengths from 780 nm to 3000 nm. The optoelectronic components 100 shown in Figures 1 to 3 are thus, for example, light-emitting diodes or detectors, wherein they emit or detect IR radiation. Furthermore, the optoelectronic components of Figures 1 to 3 each contain a filter element 20 which has a transmission of less than 10% for electromagnetic radiation with wavelengths of up to 750 nm and a transmission of more than 10% for electromagnetic radiation with wavelengths greater than 850 nm. The filter element 20 is therefore permeable to IR radiation emitted or detected by the semiconductor chip 10, but opaque to UVvis radiation, which is blocked.

[0069] The filter element 20 contains a mixture of at least one dye and a polysiloxane. It can also contain a plurality of dyes, forming a dye system having the desired filter properties. The polysiloxane contains chains or a two- or three-dimensional network of -Si-O-Si units. This means that each Si atom in the polysiloxane is connected to one, two, three, or even four further Si atoms via an O atom. In particular, the polysiloxane is free of -Si-CH2-CH2-Si units.

[0070] A linear polysiloxane can, for example,

[0071] Structural formula I , a cyclic polysiloxane the structural formula II , a ladder-shaped polysiloxane the

[0072] Structural formula III , a cage-shaped polysiloxane which

[0073] Structural formula IV, a cage-like polysiloxane which

[0074] Structural formula V, and a ladder-like polysiloxane which

[0075] Structural formula VI:

[0076] Such a filter element can be manufactured as follows: the at least one dye or the

[0077] Dye systems containing a large number of dyes which together achieve the desired filter function are dissolved in an alcohol, for example 2-ethylhexanol, and mixed with a catalyst such as a phosphoric acid ester. A precursor material for a polysiloxane described here is added to this dye solution and everything is mixed well and degassed to obtain a homogeneous starting mixture. This can then be cast and cured, wherein the casting can take place directly onto a semiconductor chip 10 to produce a filter element 20 of a component 100 shaped as a volume casting 21, where the starting material is then cured, or separately in molds to obtain, for example, filter elements 20 in the form of lenses or platelets. The starting material is then cured in these molds, removed from the respective mold and only in the finished state is the lens 23 or platelet 22 arranged in the component 100.In both cases, curing takes place at temperatures of 120 ° C to 220 ° C, for example at 150 ° C .

[0078] In the exemplary embodiment shown in Figure 1, the optoelectronic component 100 contains the filter element 20, which is designed as a volume encapsulation 21 arranged in the housing 30 and enclosing free outer surfaces of the semiconductor chip 10. The volume encapsulation 21 and the semiconductor chip 10 thus have common interfaces. In particular, the volume encapsulation fills the housing 30 up to its upper edge.

[0079] The dye, which is well distributed in the polysiloxane, has the desired optical properties, i.e., the filter function in the UV-visible range, while the polysiloxane has high (photo)stability. Thus, the filter element 20 in the form of the volume encapsulation 21 is well suited for use in the optoelectronic component 100, where it can filter UV-visible radiation and suppress the red glow effect. Furthermore, the volume encapsulation 21 can be applied to the semiconductor chip 10 and cured therein inexpensively and easily using conventional encapsulation methods.

[0080] Figure 2 shows the optoelectronic component 100, in which the filter element 20 in the form of a plate 22 is arranged directly on the semiconductor chip 10. The plate 22 is produced outside the component 100, i.e. the starting material in the form of the plate 22 is cast and cured and then placed on the semiconductor chip 10. The fixing on the semiconductor chip 10 can also be effected by means of an adhesive layer (not explicitly shown here). In this exemplary embodiment, the plate 22 is arranged directly on the semiconductor chip 10, but a spaced arrangement is also conceivable. The arrangement of the filter element 20 in the form of a plate 22 on the semiconductor chip can be advantageous for the thermomechanical behavior of the

[0081] component 100 .

[0082] Encapsulating resin 40, which encloses semiconductor chip 10 and the die 22 arranged thereon, may also be present in the housing 30. Alternatively, it is also possible for semiconductor chip 10 and die 22 to be arranged in the housing 30 without further encapsulation.

[0083] The potting resin 40 can be, for example, a silicone.

[0084] Figure 3 shows the optoelectronic component 100, in which the filter element 20 in the form of a lens 23 is applied to the housing 30. Here, too, fixing can be achieved by means of an adhesive layer (not shown here). In this exemplary embodiment, the lens 23 is arranged on the housing edge 30, but it could also be arranged on the semiconductor chip 10 or a frame. Furthermore, a potting resin 40 as described above, or a cavity, can be present in the housing 30 between the semiconductor chip 10 and the lens.

[0085] In addition to the filter function, the formation as a lens 23 can also cause increased radiation extraction from the component 100 if it is designed as an emitting component.

[0086] Furthermore, the filter element 20 formed as a lens 23 is produced outside the component 100 by pouring the starting material for the mixture into a mold having lens-shaped depressions 51. There, the material is hardened, and after a rotation of the mold

[0087] 50 is removed from the mold. The finished lens 23 can then be placed on the housing edge, for example.

[0088] Such a procedure is also shown in Figure 4. The mold 50 has a plurality of recesses 51, which are filled with the starting material. After curing, the finished lenses 23 are formed in the recesses 51. The entire mold 50 can now be turned over, the lenses 23 removed from the mold and further processed. Thus, the method can produce a plurality of lenses simultaneously.

[0089] A process as shown in Figure 4 can also be carried out analogously for the production of filter elements 20 in the form of platelets 22, except that the depressions

[0090] 51 then have the shape of the platelets. Alternatively, a large platelet of the desired thickness can be produced and, after completion, cut to the desired lateral size. In this way, a large number of platelets 22 can also be produced simultaneously.

[0091] Transmission measurements show that the filter element 20 described here reliably blocks UV-visible radiation, while it has a certain transmission for IR radiation with higher wavelengths. Figure 5 shows the solubility behavior of a commercially available dye system, which is used in polar

[0092] Solvents are soluble (in this example 2-ethylhexanol) in the polysiloxane (SL) described here in comparison to conventional silicone with a high refractive index (VL1) and conventional silicone with a low refractive index (VL2). It can be clearly seen that the dye system dissolves well in the polysiloxane and good mixing is achievable, whereas in the comparative examples VL1 and VL2 hardly any mixing can be observed, which is due to the insolubility of the dye system in the silicones.

[0093] The features and exemplary embodiments described in conjunction with the figures can be combined with one another according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in conjunction with the figures can alternatively or additionally comprise further features according to the description in the general part.

[0094] The invention is not limited to the embodiments by the description thereof. Rather, the invention encompasses every novel feature and every combination of features, including in particular every combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or embodiments. This patent application claims priority from German patent application 102023134624.5, the disclosure of which is hereby incorporated by reference.

[0095] Reference symbol list

[0096] 10 semiconductor chips

[0097] 20 filter element 21 volume potting

[0098] 22 tiles

[0099] 23 lens

[0100] 30 housings

[0101] 40 Casting resin 50 Mold

[0102] 51 Deepening

[0103] 100 Optoelectronic component

[0104] VL1 comparison example

[0105] VL2 comparison example SL from example example

Claims

Patent claims 1. Filter element which has a transmission of less than 10% for electromagnetic radiation with wavelengths of up to 750 nm and a transmission of more than 10% for electromagnetic radiation with wavelengths of greater than 850 nm, wherein the filter element comprises a mixture containing at least one dye and a polysiloxane in which Si atoms are linked to one another only via one O atom each.

2. Filter element according to the preceding claim, wherein in the polysiloxane each Si atom is linked to at least 2.5 O atoms. 3 . Filter element according to one of the preceding claims, wherein the mixture contains at least two different dyes.

4. Filter element according to one of the preceding claims, wherein the at least one dye is soluble in polar solvents.

5. Filter element according to one of the preceding claims, wherein the at least one dye absorbs electromagnetic radiation with wavelengths of up to 750 nm. 6 . Optoelectronic component comprising a semiconductor chip configured to emit or detect electromagnetic radiation in a wavelength range from 780 nm to 3000 nm, and a filter element according to the preceding claims, which in the beam path of the optoelectronic component.

7. Optoelectronic component according to the preceding claim, wherein the filter element is a volume encapsulation which encloses free outer surfaces of the semiconductor chip.

8. Optoelectronic component according to the preceding claim, wherein the volume encapsulation has a thickness selected from the range 100 pm to 700 pm.

9. Optoelectronic component according to claim 6, wherein the filter element is a lens which is arranged directly or at a distance on the semiconductor chip.

10. Optoelectronic component according to claim 6, wherein the filter element is a plate which is arranged directly or at a distance from the semiconductor chip.

11. Optoelectronic component according to one of claims 6 to 10, which is a micro-LED.

12. A method for producing a filter element which has a transmission of less than 10% for electromagnetic radiation with wavelengths of up to 750 nm and a transmission of more than 10% for electromagnetic radiation with wavelengths of greater than 850 nm, comprising the steps of: Providing a dye solution containing at least one dye dissolved in an alcohol, adding a precursor material for a polysiloxane in which Si atoms are linked to one another only via one O atom each are, to produce a homogeneous starting mixture, Pouring and curing the homogeneous starting mixture.

13. A process for producing a filter element according to the preceding claim, wherein the starting material of the polysiloxane has at least three reactive leaving groups.

14. A process for producing a filter element according to one of claims 12 or 13, wherein the at least one dye is soluble in polar solvents.

15. A method for producing a filter element according to any one of claims 12 to 14, wherein the curing is carried out at a temperature selected from the range 120°C to 220°C.

16. A method for producing a filter element according to any one of claims 12 to 15, wherein the step of adding a starting material is carried out with mixing and degassing.

17. A method for producing a filter element according to one of claims 12 to 16, wherein the casting comprises shaping the homogeneous starting mixture as a volume casting.

18. A method for producing a filter element according to any one of claims 12 to 16, wherein the casting comprises shaping the homogeneous starting mixture into a lens. 19 . A method for producing a filter element according to one of claims 12 to 16 , wherein the casting comprises a Formation of the homogeneous starting mixture as platelets includes . 20 . Method for producing an optoelectronic component with the steps Providing a semiconductor chip which is configured to emit or detect electromagnetic radiation in a wavelength range from 780 nm to 3000 nm, producing a filter element on the semiconductor chip using a method according to one of claims 12 to 19, or producing a filter element using a method according to one of claims 12 to 19 and arranging the filter element on the semiconductor chip.

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