Luminescent material, method for producing luminescent material, and radiation-emitting component

Abstract

A luminescent material is presented. The light-emitting material has: a host material containing an oxide; an activator element having a rare earth element with a first valence; and a rare earth element having a second valence, wherein the second valence is greater than the first valence. The invention further relates to a method for producing the luminescent material and to a radiation-emitting component.

Description

Technical Field

[0001] The invention provides a luminescent material, a method for producing a luminescent material, and a radiation-emitting component. Summary of the invention

[0002] It is an object of at least one embodiment to specify a luminescent material with improved properties. It is an object of at least one further embodiment to specify a method for producing a luminescent material with improved properties. It is an object of at least one further embodiment to specify a radiation-emitting device with improved properties. These objects are achieved by luminescent materials, methods and radiation-emitting devices according to the independent claims.

[0003] A luminescent material is provided. According to at least one embodiment, the luminescent material comprises: a host material comprising an oxide; an activator element comprising a rare earth element with a first valence; and a rare earth element with a second valence, wherein the second valence is greater than the first valence.

[0004] That is, the luminescent materials described herein contain the same rare earth element having two different valencies, a first valency and a second valency.

[0005] Here and hereinafter, the term "luminescent material" is understood to mean a wavelength conversion material or, for short, a conversion material, i.e. a material which is configured to absorb and emit electromagnetic radiation. In particular, the luminescent material absorbs electromagnetic radiation which has a different wavelength maximum than the electromagnetic radiation emitted by the luminescent material. For example, the luminescent material absorbs radiation which has a wavelength maximum as an emission maximum at a smaller wavelength and thus emits radiation with an emission maximum shifted towards the red. Pure scattering or pure absorption is not understood to have a wavelength conversion effect in the present case.

[0006] Here and hereinafter, the term "host material" is understood to mean a crystalline material, such as a ceramic material, into which a rare earth element is introduced. Thus, the luminescent material is, for example, a ceramic material. The host material in particular forms a host lattice, which is composed of three-dimensional unit cells that are usually repeated periodically. In other words, a unit cell is the smallest repeating unit of the host lattice of a crystal. The element contained in the host material, the rare earth element with a first valence and the rare earth element with a second valence each occupy a fixed position in the unit cell, the so-called point position.

[0007] Currently, the term "valence" with respect to a particular element refers to how many elements with a single opposite charge are needed in a compound to achieve charge balance. Therefore, the term "valence" includes the charge number of an element. Here and in the following, a first valence and a second valence are understood to be two valences that are different from each other. For example, the first valence is 3 and the second valence is 4. Therefore, rare earth elements can be present in trivalent and tetravalent forms in luminescent materials. In particular, trivalent rare earth elements carry three positive charges, while tetravalent rare earth elements carry four positive charges.

[0008] Rare earth elements with a first valence have the function of activator elements in the luminescent material. As long as electromagnetic radiation in a first wavelength range can be absorbed by the luminescent material, the activator element changes the electronic structure of the host material. The so-called primary radiation can excite electron transitions in the luminescent material, which can be transferred back to the ground state under the condition of emitting electromagnetic radiation in a second wavelength range (also called secondary radiation). The activator element introduced into the host material is therefore responsible for the wavelength-converting properties of the luminescent material. The secondary radiation has, in particular, a wavelength in the visible spectrum.

[0009] Some of the rare earth elements are present in oxidized form, i.e. with a second, higher valence. Rare earth elements with a second valence do not, in particular, have the function of activator elements or do not bring about the conversion of primary radiation into secondary radiation in the visible spectral range of electromagnetic radiation. Here and hereinafter, in order to distinguish between rare earth elements with a first valence and rare earth elements with a second valence, only rare earth elements with a first valence are referred to as activator elements.

[0010] Rare earth elements currently include chemical elements of the third subgroup of the periodic table of elements and the lanthanides. Rare earth elements are currently typically selected from scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

[0011] The inventors have recognized that due to the presence of a rare earth element with a second valence, which rare earth element, in particular in comparison with a rare earth element with a first valence, is not an activator element or causes secondary radiation outside the visible spectral range, which secondary radiation can reduce the quantum efficiency of the luminescent material and thus reduce the brightness of the electromagnetic radiation emitted by the device containing the luminescent material. Therefore, when the ratio of the rare earth element with a first valence and the rare earth element with a second valence is appropriately changed, the brightness of a radiation-emitting device, such as an LED (LED: Light Emitting Diode), which is equipped with a luminescent material and is required for an application can be adjusted steplessly.

[0012] In so-called modular platforms for LEDs, the individual components are replaceable. The aim is to provide a modular component into which as many different LED derivatives as possible can be installed, including different colors, different white color coordinates and in particular different brightnesses. The different brightnesses have hitherto been achieved in particular by different chip sizes and chip types in order to cover a large brightness bandwidth. The special design of the chips and the possibly small individual volumes of the individual derivatives have the result that a complex chip portfolio has to be prepared in order for the modular platform to remain usable, in particular over long periods of time, for example longer than 10 years, which is important in particular in the automotive sector. This results in additional chip costs of two to three times that of standard chips.

[0013] It has not been possible to generate different brightnesses of LEDs by means of chip types without either changing the operating current or the suitability, shape or function of the chip. Such changes are made, for example, via narrower light emission paths or via black materials in the light emission paths, such as soot particles. However, just soot particles also change the external optical impression, which is usually not desirable.

[0014] The methods known so far for grading the brightness of LEDs are carried out, for example, by adjustment via different chip sizes. Additional dimming is also known, for example by means of a special design of the soldering pads. These methods lead to high production costs, since the design of the LEDs required for different brightnesses is only required in small quantities, and the production costs of individual LED chips are therefore very high.

[0015] Furthermore, it is possible in principle to introduce additional non-conversion materials into the LED, which absorb radiation but have no quantum efficiency, in order to keep the influence on the color of the emitted radiation as small as possible. However, this results in the following problem: the original conversion material and the additional non-conversion material without quantum efficiency do not have exactly the same excitation optimum due to their different compositions. As a result, the LED with the additional non-conversion material has a different total absorption, which in turn leads to a complex adjustment of the color coordinates of the emitted radiation by adjusting the conversion material mixture. Therefore, it has not been possible to establish and guarantee a reproducible, reduced quantum efficiency of the converter, since this can only be achieved by introducing foreign elements, which bring about undesirable absorption and this leads to a change in the emission color.

[0016] On the contrary, with the aid of the luminescent material described here, the brightness of the radiation emitted by a radiation-emitting device, such as an LED, can be adjusted reproducibly, because at a constant high absorption, i.e. at a high efficiency, the position of the absorption maximum is maintained and at the same time a reduced quantum efficiency can be ensured. As a result, the emission color of the radiation-emitting device is not affected and the required brightness can be adjusted steplessly. Since the composition of the luminescent material is in principle constant and only a part of the rare earth elements has a changed valence, only the brightness of the emitted radiation can be adjusted while maintaining the properties of the luminescent material. Therefore, there is no need to adjust the luminescent material mixture in a complex manner to adjust the exact color coordinates when the brightness remains constant. The external visual impression of the device containing the luminescent material remains unchanged, which is not the case when, for example, soot particles or pigments are used.

[0017] This brings numerous advantages in application. For example, the luminescent material described here can be used alone or in a mixture with a basic luminescent material, which differs from the luminescent material only in that it does not contain a rare earth element with a second valence. As a result, the brightness of a component containing a luminescent material, such as an LED, can be adjusted flexibly and seamlessly, wherein the color coordinate, for example the white color coordinate, remains unchanged. As a result, the expenditure for color coordinate control is also reduced or avoided, because, apart from the brightness, all properties of the luminescent material, in particular the position of the absorption maximum, remain unchanged compared to the basic luminescent material.

[0018] Therefore, by seamlessly adjusting the brightness, for example, there is no need for components of different sizes and types, such as LED chips, which reduces the complexity of the component product portfolio, especially in the case of long-term availability, such as in automotive products. This coordination of the product portfolio can also further save costs, because only a large number of one component type or a small number of component types need to be provided.

[0019] According to at least one embodiment, the host material is garnet. With garnet as host material, when appropriately doped with activator elements, luminescent materials with high quantum efficiencies, for example, of more than 95%, can be provided. Here and hereinafter, garnet is understood to be an oxide, which can be obtained, for example, by the general formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 = , where 0≤x≤1. Depending on the type of garnet, the elements listed in the first bracket can be present in the garnet alone or in combination with one another. A specific example of garnet is, for example, a garnet of the general formula Y 3 Al 5 O 12 Yttrium aluminum garnet (YAG), and the general formula Lu3 Al 5 O 12 Lutetium aluminum garnet (LuAG).

[0020] Here and hereinafter, luminescent materials or host materials are described according to general formulas. The elements listed in the general formulas are present here in charged form. Thus, here and hereinafter, the elements and / or atoms related to the general formulas of the luminescent materials or host materials refer to ions in the form of cations and anions, even if not explicitly stated. This also applies to the element symbols if the charge numbers are not indicated for the sake of overview.

[0021] In a given general formula, it is feasible that the luminescent material or host material has other elements, for example, in the form of impurities. Generally speaking, the impurities have a maximum of 5 mol%, in particular a maximum of 1 mol%, and preferably a maximum of 0.1 mol%.

[0022] According to at least one further embodiment, the rare earth element is cerium (Ce). Thus, when Ce with a first valence exists, Ce can exist as an activator element in the luminescent material. If Ce with a second valence exists, then Ce exists as a non-activator element or at least causes secondary radiation outside the visible spectral range. Ce as an activator element, in particular in combination with garnet as the main lattice, causes a stable luminescent material with high quantum efficiency.

[0023] According to at least one further embodiment, the first valence is three and the second valence is four. Thus, Ce exists in the luminescent material as Ce 3+ and as Ce 4+ exists. Thus, Ce with the lower first valence 3+ exists as an activator element.

[0024] According to the composition of the garnet in the case of about 460 nm, the garnet luminescent material with Ce 3+ as an activator element can have a quantum efficiency higher than 95% and a reflection of less than 10% in the blue spectral range of electromagnetic radiation. The activator element Ce 3+ is activated by photons, in particular blue photons, and shows the transition of 4f1-5d0 <-> 4f0-5d1. In the relaxation of this transition, light in the visible spectral range is usually released. For example, if YAG is used as the garnet, then in the doped system YAG:Ce 3+ emission in the yellow spectral range is released, and the yellow spectral range has a peak maximum in the range of 540 nm to 580 nm and a half-value width in the range of 110 nm to 130 nm.

[0025] Compared with Ce 3+ Compared with the basic luminescent materials, Ce 4+ Additional introduction or Ce 3+ Partially converted to Ce 4+ There is no change in the emission in the visible spectral range, however the high absorption and the position of the absorption maximum in the blue spectral range remain unchanged. 3+ The color coordinates of a radiation-emitting device comprising the luminescent material described herein are not changed compared to a luminescent material containing Ce in a conventional manner. For example, the white color coordinates of an LED are not affected by the Ce in the luminescent material. 4+ In addition, with the presence of Ce in the luminescent material 4+ As the Ce content increases, the absorption in the UV range, i.e. in the range of 300 nm to 400 nm, increases. Increased absorption in the UV range results in the absorption of the short-wave portion of the primary radiation, which does not contribute to the brightness but accelerates the aging of encapsulation materials such as silicone or epoxy resins. Therefore, by placing Ce 3+ Partially replaced by Ce 4 + , for example by adding Ce 3+ Oxidation to form Ce 4+ , while maintaining high absorption and the precise position of the absorption maximum, the quantum efficiency or quantum yield of the luminescent material can be arbitrarily adjusted to a value without Ce 4+ The proportion is between 0% and 100%, in particular between 20% and 100%, for example between 50% and 100%, of the quantum efficiency of the reference luminescent material (base luminescent material). Furthermore, the lifetime of a component containing the luminescent material can also be increased.

[0026] According to at least one further embodiment, the luminescent material has the general formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , where 0≤x≤1 and 0<y<1. Therefore, the host material is a material having the general formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 Garnet, the activator element, i.e. the rare earth element with the first valence is Ce 3+ , and the rare earth element with the second valence is Ce 4+ .

[0027] According to at least one embodiment, the luminescent material has no divalent codopant, in particular no Mg 2+ Here and hereinafter, a codopant is to be understood as an element which is additionally introduced into the host material in addition to the activator element or the rare earth element having a second valency.

[0028] According to at least one further embodiment, the luminescent material has an absorption region with an absorption maximum, wherein the position of the absorption maximum is substantially identical to the position of the absorption maximum of a basic luminescent material, wherein the basic luminescent material differs from the luminescent material only in that the basic luminescent material does not have a rare earth element with a second valence.

[0029] Here and hereinafter, “substantially identical” shall mean that the two dimensions to be compared are exactly identical and differ only within the scope of measurement inaccuracies or only to an extent that is imperceptible to an external observer. This also includes deviations of up to 5%, in particular up to 2%, for example up to 1%.

[0030] Here and hereinafter, a base phosphor is to be understood as a composition which differs from the phosphor described here only in that it contains no rare earth element having a second valency.

[0031] That is, the basic luminescent material does not have a reduced quantum efficiency as the luminescent material described here, because in the basic luminescent material, the activator element is not partially replaced by the rare earth element with the second valence. The higher the proportion of the rare earth element with the second valence and the lower the proportion of the activator element, the lower the quantum efficiency of the luminescent material. For example, if the luminescent material has the formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , then the basic luminescent materials are (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce 3+ However, since the other compositions of the phosphor and the base phosphor are identical, the position of the absorption maximum remains unchanged, whereby the color coordinate of the phosphor determined, for example, by means of fluorescence spectroscopy remains unaffected.

[0032] According to at least one embodiment, the absorption range of the luminescent material is at least in the UV wavelength range to the blue wavelength range of the electromagnetic spectrum. Therefore, the absorption range of the luminescent material is in the range of 300nm to 500nm. The position of the absorption maximum can be, for example, in the range of 440n to 470nm.

[0033] According to at least one further embodiment, the quantum efficiency of the luminescent material is reduced compared to the quantum efficiency of the basic luminescent material, wherein the basic luminescent material differs from the luminescent material only in that the basic luminescent material does not contain a rare earth element with a second valence. That is, the basic luminescent material does not have a reduced quantum efficiency as the luminescent material described here. The higher the proportion of the rare earth element with a second valence in the luminescent material and the lower the proportion of the activator element, the lower the quantum efficiency of the luminescent material. For example, if the luminescent material has the formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , then the basic luminescent materials are (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce 3+ .

[0034] According to at least one further embodiment, the electromagnetic radiation emitted by the luminescent material has a dominant wavelength that is substantially the same as a dominant wavelength of a base luminescent material, wherein the base luminescent material differs from the luminescent material only in that the base luminescent material does not have a rare earth element with a second valence. For example, if the luminescent material has the formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , then the basic luminescent materials are (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce 3+ .

[0035] In order to determine the dominant wavelength of the electromagnetic radiation emitted by the luminescent material, a straight line is drawn from the white point through the color coordinates of the electromagnetic radiation in the CIE standard diagram. The intersection of this straight line with the spectral color lines delimiting the CIE standard diagram represents the dominant wavelength of the electromagnetic radiation. In general, the dominant wavelength is different from the wavelength of the emission maximum.

[0036] The unchanged dominant wavelength of the luminescent material compared to the basic luminescent material means that the color coordinates of the luminescent material, which can be determined, for example, by means of fluorescence spectroscopy, are not affected by the presence of rare earth elements with a first valency, such as Ce. 3+ Rare earth elements with a second valence such as Ce 4+ The impact of partial replacement.

[0037] According to at least one further embodiment, the electromagnetic radiation emitted by the luminescent material has a half-value width that is substantially the same as the half-value width of the base luminescent material, wherein the base luminescent material differs from the luminescent material only in that the base luminescent material does not have a rare earth element with a second valence. For example, if the luminescent material has the formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , then the basic luminescent materials are (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce 3+ The approximately constant half-value width is due to the approximately constant emission behavior of the luminescent material compared to the basic luminescent material.

[0038] According to at least one other embodiment, other specification parameters of the luminescent material are also substantially unchanged compared to the basic luminescent material as described above. Other specification parameters include, for example, particle size, morphology, scattering properties and body color of the luminescent material powder.

[0039] According to at least one further embodiment, the brightness of the luminescent material decreases as the proportion of the rare earth element with the second valence in the luminescent material increases. 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+For example, where 0 ≤ x ≤ 1 and 0 < y < 1, the brightness is thus higher when y is large than when y is small. Thus, the brightness of the luminescent material described herein can be adjusted steplessly.

[0040] A method for manufacturing a luminescent material is also proposed. The method is suitable for manufacturing the luminescent material as described herein. Thus, all features disclosed in connection with the luminescent material also apply to the method, and vice versa.

[0041] According to at least one embodiment, the method comprises the following steps:

[0042] - providing a base luminescent material having

[0043] - a host material containing oxides, and

[0044] - an activator element having a rare earth element with a first valence,

[0045] - oxidizing the base luminescent material to form a luminescent material having - a host material containing oxides,

[0046] - an activator element having a rare earth element with a first valence, and - a rare earth element with a second valence, where the second valence is greater than the first valence.

[0047] Thus, by means of the method, the base luminescent material is processed into a luminescent material having a reduced and steplessly adjustable quantum efficiency, in such a way that a part of the activator element is oxidized to form a rare earth element with a second valence. The more rare earth elements with a first valence are oxidized to rare earth elements with a second valence, the lower the quantum efficiency and thus the lower the brightness of the emitted radiation.

[0048] The manufacturing cost of the luminescent material is not significantly higher than that of the base luminescent material, and in particular does not require expensive raw materials such as gallium or scandium oxide, so that the production cost of the luminescent material and devices containing the luminescent material is not significantly increased. Thus, the luminescent material described herein can be manufactured and provided at low cost with a reproducible, reduced quantum efficiency.

[0049] The low-cost manufacture of the luminescent material is a simple post-treatment of the base luminescent material. Other costs can also be saved by means of the method, since no additional luminescent materials or other foreign elements without quantum efficiency are provided to reduce the brightness of the luminescent material, but rather different brightnesses of the resulting, refined luminescent material can be produced according to the application with the aid of the sole base luminescent material. That is, no additional costs are incurred to provide different luminescent materials and a new formulation is established therewith to adjust the color coordinates of the emitted radiation.

[0050] According to at least one embodiment, the oxidation is carried out by heating. According to at least one embodiment, the oxidation is carried out at a temperature in the range of 350° C. to 1400° C. (limit values ​​included), in particular in the range of 600° C. to 1200° C. (limit values ​​included), for example in the range of 600° C. to 1000° C. (limit values ​​included). Thus, the method can be carried out at moderate to high temperatures and the oxidation is carried out by post-sintering of the basic luminescent material to form the luminescent material. The higher the temperature is selected, the greater the oxidized Ce in the resulting luminescent material. 4+ The higher the proportion of , the lower its quantum efficiency. The resulting brightness of the emitted radiation can therefore be controlled in the method via the temperature.

[0051] According to at least one further embodiment, the oxidation is carried out in the presence of air or oxygen. Thus, the oxidation or post-sintering of the base luminescent material takes place under oxidizing conditions.

[0052] According to at least one embodiment, the oxidation is performed over a period of one hour to five hours inclusive, for example three hours.

[0053] According to at least one further embodiment, a basic luminescent material (Y, Lu, Gd, Tb) is provided 3 (Al 1-x ,Ga x ) 5 O 12 :Ce 3+ , where 0≤x≤1, and oxidize it to form a luminescent material (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , where 0≤x≤1 and 0 <y<1。

[0054] According to at least one embodiment, no divalent codopants, in particular no Mg, are used in the method. 2+ .

[0055] A radiation-emitting component is also provided. The radiation-emitting component is configured and arranged to contain the phosphor described herein. Therefore, all features disclosed in conjunction with the phosphor also apply to the radiation-emitting component, and vice versa.

[0056] According to at least one embodiment, a device emitting radiation includes - a semiconductor chip which emits electromagnetic radiation in a first wavelength range during operation, - a conversion element having a luminescent material described herein, the luminescent material converting the electromagnetic radiation in the first wavelength range into electromagnetic radiation in a second wavelength range, the second wavelength range being at least partially different from the first wavelength range.

[0057] The electromagnetic radiation in the first wavelength range constitutes the emission spectrum of the semiconductor chip and is also referred to as primary radiation.

[0058] The semiconductor chip is, for example, a light-emitting diode chip or a laser diode chip. Thus, the device can be a light-emitting diode (LED) or a laser. Preferably, the semiconductor chip has an epitaxially grown semiconductor chip layer sequence having an active region suitable for generating electromagnetic radiation. For this purpose, the active region has, for example, a pn junction, a double heterostructure, a single quantum well structure or a multiple quantum well structure.

[0059] The semiconductor chip can emit electromagnetic radiation from the ultraviolet spectral range and / or from the visible spectral range, in particular from the blue spectral range, during operation. Thus, the primary radiation has, for example, a wavelength in the range from 300 nm to 500 nm, in particular in the range from 400 nm to 460 nm.

[0060] The conversion element is in particular arranged on the radiation exit surface of the semiconductor chip and is, for example, in the ray path of the semiconductor chip such that at least a part of the radiation emitted by the semiconductor chip impinges on the conversion element.

[0061] The luminescent material in the conversion element converts the electromagnetic radiation in the first wavelength range into electromagnetic radiation in a second wavelength range. The electromagnetic radiation in the second wavelength range constitutes the emission spectrum of the luminescent material and is also referred to as secondary radiation.

[0062] The electromagnetic radiation in the second wavelength range is at least partially different from the first wavelength range. The luminescent material contained in or constituting the conversion element imparts the conversion element with the property of wavelength conversion. For example, the conversion element only partially converts the electromagnetic radiation of the semiconductor chip into electromagnetic radiation in the second wavelength range, while another part of the electromagnetic radiation of the semiconductor chip is transmitted by the conversion element. The device emitting radiation emits in this case a mixed light composed of electromagnetic radiation in the first wavelength range and electromagnetic radiation in the second wavelength range. The mixed light includes, for example, white light. If there is complete conversion of the primary radiation by the conversion element and / or no transmission of the primary radiation through the conversion element occurs, then this is referred to as full conversion. In this case, the device emitting radiation emits the secondary radiation emitted by the conversion element.

[0063] Due to the properties of the phosphor described here, the desired final brightness of the radiation-emitting component can be adjusted continuously while the brightness of the primary radiation emitted by the semiconductor chip remains constant, since the quantum efficiency of the phosphor can be adjusted as a function of the proportion of the rare earth element with the second valence. The color coordinate of the emitted total radiation remains constant in this case, without having to develop a new formulation of the phosphor mixture in order to adjust the color coordinate.

[0064] Thus, a broad spectrum of brightness can be provided by means of only one type and only one size of semiconductor chips and thus by means of only one type and only one size of radiation-emitting components. In particular, special chip types are required for specific applications, for example in the automotive sector, so that they can be purchased or produced in large quantities and the desired brightness can be set by means of matching luminescent materials with reproducible, reduced quantum efficiency. Thus, the additional costs that have hitherto been caused by the need for different chip types can be reduced. Thus, the chip product portfolio can be coordinated by using the luminescent materials described here, without changing the properties of the radiation-emitting components with respect to their specifications, in particular the emission color and the external visual impression. The external visual impression of the component, which is not changed by the introduction of the luminescent materials described here, cannot be achieved by means of soot particles or other pigments.

[0065] According to at least one embodiment, the conversion element contains only luminescent material. The luminescent material is therefore used as the only luminescent material in the conversion element. With the luminescent material described here, the desired brightness of the radiation-emitting component can be adjusted steplessly depending on the proportion of the rare earth element with the second valence.

[0066] According to at least one embodiment, the conversion element additionally comprises a base luminescent material, wherein the base luminescent material differs from the luminescent material only in that it does not contain a rare earth element with a second valence. The conversion element thus contains a mixture of an unrefined base luminescent material and a refined luminescent material with a reduced quantum efficiency, whereby a flexible and seamless adjustment of the brightness of the radiation-emitting component can be achieved. While maintaining the absorptivity of the base luminescent material and the position of the absorption maximum, the quantum efficiency can be set to between 50% and 100% of the quantum efficiency of the base luminescent material, depending on the selected luminescent material and the ratio between the base luminescent material and the luminescent material.

[0067] Regardless of whether the luminescent material is used alone or together with a basic luminescent material in the conversion element, the color coordinates of the basic luminescent material remain unchanged. In order for a radiation-emitting component containing the luminescent material and optionally the basic luminescent material to also have the same color coordinates as a radiation-emitting component in which only the basic luminescent material is present, the amount of luminescent material added and / or the mixing ratio between luminescent material and basic luminescent material can be adjusted accordingly.

[0068] According to at least one embodiment, the conversion element comprises (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ As the only luminescent material, where 0≤x≤1 and 0<y<1.

[0069] According to at least one further embodiment, the conversion element contains a luminescent material (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , where 0≤x≤1 and 0<y<1 and basic luminescent materials (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ , where 0≤x≤1 is a mixture.

[0070] In accordance with at least one embodiment, the ratio of phosphor to base phosphor in the conversion element is selected from the group consisting of 100:0, 80:20 and 60:40.

[0071] The luminescent material and optionally the basic luminescent material can be embedded in the matrix material. The luminescent material and optionally the basic luminescent material are then present in the form of particles. According to one embodiment, the matrix material is selected from polymers and glass. For example, polystyrene, polysiloxane, polysilazane, PMMA, polycarbonate, polyacrylate, polytetrafluoroethylene, polyethylene, silicone resin, silicone, epoxy resin and transparent synthetic rubber can be selected as polymers. For example, silicate, water glass, quartz glass, etc. can be selected as glass.

[0072] According to at least one embodiment, the conversion element is configured as a potting element. For this purpose, the luminescent material and optionally the basic luminescent material can be present in the form of being embedded in the matrix material. The potting element can be arranged, for example, in a recess of the housing and surround the semiconductor chip. According to one embodiment, the potting element is a volume potting part, in which the luminescent material and optionally the basic luminescent material are present in the form of being uniformly distributed in the matrix material. Alternatively, according to another embodiment, the luminescent material and optionally the basic luminescent material are present in the potting element in the form of a deposit. That is, there is a concentration gradient of the luminescent material and optionally a concentration gradient of the basic luminescent material in the matrix material within the potting element, wherein the concentration of the luminescent material and optionally the concentration of the basic luminescent material decreases as the distance from the semiconductor chip increases.

[0073] According to at least one embodiment, the conversion element is formed as a conversion layer. The conversion layer can be applied in direct or indirect contact with the semiconductor chip. In the case of indirect contact, the conversion layer can be applied to the semiconductor chip, in particular to its radiation exit surface, by means of an adhesive layer, for example, or a potting material can be present between the semiconductor chip and the conversion element.

[0074] According to another embodiment, the semiconductor chip, the optional converter element and the optional adhesive layer can be surrounded by a potting material. For example, the semiconductor chip, the converter element and the optional adhesive layer are then arranged in a recess of the housing, in which the potting material is also arranged.

[0075] The potting element can have a permeability for the primary radiation and / or the secondary radiation of at least 85%, preferably 95%. Furthermore, the potting element can include silicone or epoxy resin as a material, for example.

[0076] According to at least one embodiment, two or more phosphors described here with different compositions are present in the conversion element. In this case, the respectively associated base phosphors may also be present in the conversion element. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Further advantageous embodiments and developments of the phosphor, the component and the method result from the exemplary embodiments described below in conjunction with the figures.

[0078] Figure 1 A schematic sectional illustration of a radiation-emitting component according to one exemplary embodiment is shown.

[0079] 2 a and 2 b show schematic sectional views of a radiation-emitting component according to an exemplary embodiment.

[0080] Figure 3 Shown is a reflection spectrum of a luminescent material according to an embodiment.

[0081] Figure 4 Shown is a reflection spectrum of a luminescent material according to an embodiment.

[0082] Identical, similar or functional elements are provided with the same reference numerals in the drawings. The drawings and the size relationships of the elements shown in the drawings to one another are not to be regarded as being true to scale. Rather, individual elements, in particular layer thicknesses, may be shown exaggeratedly for better illustration and / or for better understanding. DETAILED DESCRIPTION

[0083] Figure 1 A schematic cross-sectional view of a radiation-emitting component according to an exemplary embodiment is shown. The radiation-emitting component 100 has a semiconductor chip 10. During operation, the semiconductor chip 10 emits electromagnetic radiation (primary radiation) in a first wavelength range that leaves a radiation exit surface 11. The semiconductor chip 10 has an epitaxially grown semiconductor layer sequence having an active region that is suitable for generating electromagnetic radiation. The primary radiation has, for example, a wavelength in the blue and / or ultraviolet range. The semiconductor chip 10 is in particular an LED chip.

[0084] Furthermore, the device has a conversion element 20. The conversion element 20 contains a matrix material in which a luminescent material 1, in particular particles of the luminescent material 1, is embedded, or the conversion element 20 has a ceramic formed by the luminescent material 1 or consists thereof. Alternatively, the conversion element 20 contains a matrix material in which a luminescent material 1 and a basic luminescent material 2, in particular particles of the luminescent material 1 or a basic luminescent material 2, are embedded, or the conversion element 20 has a ceramic formed by the luminescent material 1 and the basic luminescent material 2 or consists thereof.

[0085] The matrix material is selected from polymers such as polystyrene, polysiloxane, polysilazane, PMMA, polycarbonate, polyacrylate, polytetrafluoroethylene, polyethylene, silicones, silicones, epoxy resins and transparent synthetic rubbers and glasses such as silicates, water glass and quartz glass.

[0086] During operation, the luminescent material 1 and optionally the basic luminescent material 2 convert electromagnetic radiation in a first wavelength range into electromagnetic radiation in a second wavelength range (secondary radiation). Thus, in the case of incomplete conversion of the primary radiation by the conversion element, the device emits mixed light consisting of primary radiation and secondary radiation.

[0087] The conversion element 20 , which is designed here as a conversion layer, can either be applied directly on the semiconductor chip 10 or be fastened thereto, for example by means of an adhesive layer (not explicitly shown here).

[0088] The semiconductor chip 10 together with the converter element 20 arranged thereon is arranged in a recess of a housing 30. The housing 30 has side surfaces inclined toward the semiconductor chip 10, which can be designed to be reflective. The semiconductor chip 10 and the converter element 20 can be surrounded by a potting member 40 in the housing 30, as shown here. However, the presence of the potting member 40 is not necessarily required. The potting member can be formed, for example, from silicone or epoxy resin and has a permeability to the electromagnetic radiation of the active region of at least 85%, preferably 95%.

[0089] Alternatively, the housing 30 can also have no side walls and thus no recesses and be designed as a carrier (not shown here).

[0090] FIG2a shows another embodiment of a radiation-emitting component. Figure 1 The embodiments of FIG. 1 apply to elements with the same reference numerals. In the present exemplary embodiment, the conversion element 20 is not arranged directly on the semiconductor chip 10, but is arranged at a distance therefrom on the side of the potting 40 facing away from the semiconductor chip 10. Here, too, the conversion element 20 is again formed as a conversion layer.

[0091] FIG2 b shows another embodiment of a radiation-emitting component. Figure 1 The same applies to the elements with the same reference numerals as in the embodiment of FIG. 2a. In the present embodiment, the conversion element 20 is designed as a potting element and is arranged in a recess of the housing 30. Here, the potting element surrounds the semiconductor chip 10. The potting element can be designed as a volume potting, in which the luminescent material 1 and optionally the basic luminescent material 2 are present in a uniformly distributed form in the matrix material. Alternatively, the luminescent material 1 and optionally the basic luminescent material 2 can be present in a deposited form. The concentration of the luminescent material 1 and optionally the basic luminescent material 2 in the matrix material is then high close to the semiconductor chip 10 and decreases as the distance from the semiconductor chip 10 increases.

[0092] exist Figure 1 The device shown in FIG. 2 is, for example, an LED. For the sake of overview, the Figure 1 and elements additionally present in FIG. 2 , such as electrical contacts.

[0093] The phosphor 1 described here and a method for producing the same are explained below with reference to exemplary embodiments.

[0094] As a starting material, a basic luminescent material B1 (YAG:Ce) according to an embodiment is provided. 3+ , with a Ce content of 2.0 mol% 3+ ) and B2(YAG:Ce 3+ , with a Ce content of 2.8 mol% 3+). These basic luminescent materials respectively contain oxide Y 3 Al 5 O 12 as an oxide or host material and contains the rare earth element Ce as an activator element having a first valence of 3+.

[0095] The basic phosphors B1 and B2 were subjected to post-sintering. For this purpose, they were heated in air at different temperatures for three hours and oxidized to form phosphor 1. Depending on the temperature applied, phosphors according to embodiments L1 to L4 were produced from basic phosphor B1 and phosphors L5 and L6 were produced from basic phosphor B2.

[0096] The following Tables 1 and 2 list the examples L1 to L6 and their corresponding production temperatures T, relative quantum efficiencies QE compared to the corresponding basic luminescent materials. rel , minimum reflection R at wavelengths of 450nm to 470nm 450-470 , relative brightness H rel As well as the half-value width FWHM and the main wavelength λ of the corresponding emission spectrum dom .

[0097]

[0098] Table 1

[0099]

[0100]

[0101] Table 2

[0102] The reflectance spectrum belongs to Figure 3 and Figure 4 Shown in. Figure 3 shows the reflection spectra of the basic luminescent material B1 and the luminescent materials L1 to L4, Figure 4 The reflection spectra of the base luminescent material B2 and the luminescent materials L5 and L6 are shown. Accordingly, the wavelength λ in nm is plotted against the reflectivity R in %.

[0103] It can be clearly seen that as the temperature increases during the oxidation of the basic luminescent material, the relative quantum efficiency and thus the relative brightness of the luminescent material decreases, which is attributed to the content of the activator element Ce. 3+ reduction, thereby reducing the Ce content in the corresponding luminescent material 4+ The content increased.

[0104] At the same time, the absorption behavior of the basic phosphor in the phosphor remains unchanged, which is particularly evident at wavelengths of 450 nm and 470 nm at the approximately constant minimum reflection R450-470. Figure 3 and Figure 4 In the spectrum of , this is seen at the complete overlap of the curves in the range between 450 nm and 470 nm.

[0105] Furthermore, the emission behavior of the phosphor produced also remains unchanged, which is evident in the approximately unchanged half-value width of the emission spectrum.

[0106] The dominant wavelength λ of the luminescent material is substantially the same as that of the corresponding elementary luminescent material. dom It is shown that the base phosphor can be oxidized to form the phosphor without a change in the color locus of the emitted radiation occurring.

[0107] The phosphors described here are therefore very suitable for use in components which are to be provided with different brightnesses.

[0108] Features and embodiments described in conjunction with the figures can be combined with one another according to further embodiments, even if not all combinations are explicitly described. Furthermore, the embodiments described in conjunction with the figures can alternatively or additionally have further features according to the description in the general part.

[0109] The invention is not limited to this by the description based on the exemplary embodiments. Rather, the invention includes any novel features and any combination of features, which in particular includes any combination of features in the claims, even if the feature or the combination itself is not explicitly described in the claims or exemplary embodiments.

[0110] This patent application claims the priority of German application 102022126567.6, the disclosure content of which is incorporated herein by reference.

[0111] Reference numerals list

[0112] 1 Luminescent Materials

[0113] 2 Basic luminous materials

[0114] 10Semiconductor Chips

[0115] 11 Radiation exit surface

[0116] 20 conversion elements

[0117] 30 Shell

[0118] 40 potting parts

[0119] 100 radiation emitting devices

[0120] B1 Basic luminescent material according to one embodiment

[0121] B2 Basic luminescent material according to one embodiment

[0122] L1 Luminescent material according to one embodiment

[0123] L2 Luminescent material according to one embodiment

[0124] L3 Luminescent material according to one embodiment

[0125] L4 Luminescent material according to one embodiment

[0126] L5 Luminescent material according to one embodiment

[0127] L6 Luminescent material according to one embodiment

Claims

1. A luminescent material, the luminescent material having - a host material comprising an oxide, - an activator element having a rare earth element with a first valency, and - a rare earth element with a second valence, wherein the second valence is greater than the first valence, wherein the luminescent material has the general formula (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , where 0≤x≤1 and 0<y<1.

2. Luminescent material according to the preceding claim, wherein the host material is garnet.

3. The luminescent material according to any one of the preceding claims, wherein the rare earth element is Ce.

4. The luminescent material according to the previous item, wherein the first valence is 3 and the second valence is 4. 5 . The luminescent material as claimed in claim 1 , which has no divalent codopant.

6. A luminescent material according to any one of the preceding claims, wherein the luminescent material has an absorption range having an absorption maximum, wherein the absorption maximum has a position substantially identical to a position of an absorption maximum of a basic luminescent material, wherein the basic luminescent material differs from the luminescent material only in that the basic luminescent material does not have a rare earth element with the second valence. 7 . The phosphor according to claim 1 , wherein the absorption range of the phosphor lies at least in the UV wavelength range up to the blue wavelength range of the electromagnetic spectrum.

8. The luminescent material according to any of the preceding claims, wherein the luminescent material has a quantum efficiency that is reduced compared to the quantum efficiency of a basic luminescent material, wherein the basic luminescent material differs from the luminescent material only in that the basic luminescent material does not contain a rare earth element with the second valence.

9. A luminescent material according to any one of the preceding claims, wherein the electromagnetic radiation emitted by the luminescent material has a main wavelength, which is substantially the same as a main wavelength of a basic luminescent material, wherein the basic luminescent material differs from the luminescent material only in that the basic luminescent material does not contain a rare earth element with a second valence.

10. A luminescent material according to any of the preceding claims, wherein the electromagnetic radiation emitted by the luminescent material has a half-value width that is substantially the same as the half-value width of a basic luminescent material, wherein the basic luminescent material differs from the luminescent material only in that the basic luminescent material does not have a rare earth element with the second valence. 11 . The phosphor according to claim 1 , wherein the phosphor has a brightness which decreases as the proportion of the rare earth element having the second valence in the phosphor increases.

12. A method for producing a luminescent material, the method comprising the following steps: - providing a basic luminescent material, said basic luminescent material having - a host material comprising an oxide, and an activator element having a rare earth element with a first valency, - oxidizing the basic luminescent material into a luminescent material, the luminescent material having - said host material comprises an oxide, - the activator element, the activator element having a rare earth element with a first valence, and - a rare earth element with a second valence, wherein the second valence is greater than the first valence, wherein the luminescent material has the general formula: (Y,Lu,Gd,Tb) 3 (Al 1-x ,Ga x ) 5 A 12 :What y 3+ What 1-y 4+ , Where 0≤x≤1 and 0<y<1. 13 . The method according to claim 1 , wherein the oxidation is carried out at a temperature in the range of 350° C. to 1400° C. inclusive.

14. The method according to any one of claims 12 to 13, wherein the oxidation is carried out under air or oxygen and / or wherein the oxidation is carried out over a period of one hour to five hours, limit values ​​included.

15. The method according to any one of claims 12 to 14, wherein the basic luminescent material (Y, Lu, Gd, Tb) is provided 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ , wherein 0≤x≤1, and the basic luminescent material is oxidized into the luminescent material (Y, Lu, Gd, Tb) 3 (Al 1-x ,Ga x ) 5 O 12 :Ce y 3+ Ce 1-y 4+ , where 0≤x≤1 and 0<y<1.

16. The method according to any one of claims 12 to 15, wherein no divalent codopants are used.

17. A radiation emitting device, the radiation emitting device comprising: a semiconductor chip which, during operation, emits electromagnetic radiation in a first wavelength range, A conversion element comprising a luminescent material according to claim 1 , which converts electromagnetic radiation in the first wavelength range into electromagnetic radiation in a second wavelength range which partially differs from the first wavelength range. 18 . The radiation-emitting component as claimed in claim 1 , wherein the conversion element additionally comprises a base phosphor, wherein the base phosphor differs from the phosphor only in that it does not comprise a rare earth element having the second valency.

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