Luminophore mixture, conversion element and optoelectronic component

Abstract

The invention relates to a luminophore mixture which comprises at least one quantum dot luminophore and at least one functional material, the functional material is formed such that it scatters electromagnetic radiation and/or has a high density.

Claims

1. A phosphor mixture, comprising: at least one quantum dot phosphor; at least one functional material; and at least on further phosphor; wherein the functional material comprises scattering particles configured to scatter electromagnetic radiation, the scattering particles having a diameter selected from a range of 0.5 μm to 5 μm, wherein the scattering particles include garnets, and/or wherein the functional material comprises second particles having a density of not less than 2 g/cm.sup.3, and having a second diameter of not less than 5 μm, wherein the second particles include garnets; and wherein the at least one quantum dot phosphor and the functional material are in a form of a mixture of particles embedded in a matrix; and wherein the further phosphor comprises a material selected from the group consisting of N(N.sub.aM.sub.1-a)SX.sub.2AX.sub.2NX.sub.6:D where N is at least one divalent metallic element, M is a divalent metallic element other than N, D comprises one, two or more elements from the group of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, alkali metals and Yb, SX comprises at least one tetravalent element, AX comprises at least one trivalent element, NX comprises at least one element selected from the group of N, O, F, Cl, the parameter a is between 0.6 and 1.0 inclusive, Sr.sub.xCa.sub.1-xAlSiN.sub.3:Eu where between 0.1% and 5% inclusive of the Sr—Ca lattice sites and/or of the Sr lattice sites and/or of the Ca lattice sites are replaced by Eu, (M).sub.2-2xEu.sub.2xSi.sub.5N.sub.8 with M=Sr, Ca and/or Ba and 0.001≤x≤0.2, beta-SiAlON Si.sub.6-xAl.sub.zO.sub.yN.sub.8-y:RE where 0<x≤4, 0<y≤4, 0<z<1 and RE contains one or more elements selected from rare earth metals, Y.sub.3(Al.sub.1-xGa.sub.x).sub.5O.sub.12:Ce where the proportion of Ga is 0.2<x≤0.6, (Gd,Y).sub.3(Al.sub.1-xGa.sub.x).sub.5O.sub.12:Ce having a cerium content of 1.5-5 mol and a gallium content x between 0 to 0.5, (Tb,Y).sub.3(Al.sub.1-xGa.sub.x).sub.5O.sub.12:Ce having a cerium content of 1.5-5 mol and a gallium content x between 0 to 0.5, Lu.sub.3(Al.sub.1-xGa.sub.x).sub.5O.sub.12:Ce having a cerium content of 0.5-5 mol % and a gallium content x between 0 to 0.5, (Lu,Y).sub.3(Al.sub.1-xGa.sub.x).sub.5O.sub.12:Ce having a cerium content of 0.5-5 mol % and a gallium content x between 0 to 0.5, and mixtures thereof.

2. The phosphor mixture as claimed in claim 1, wherein the scattering particles have a proportion in the phosphor mixture selected from a range of 1% to 5% by weight.

3. The phosphor mixture as claimed in claim 1, wherein the second particles have a proportion in the phosphor mixture of not more than 50% by weight.

4. The phosphor mixture as claimed in claim 1, wherein the scattering particles are configured to convert electromagnetic radiation of a first wavelength range at least partly to electromagnetic radiation of a second wavelength range.

5. The phosphor mixture as claimed in claim 4, wherein the electromagnetic radiation of the second wavelength range are selected from a red spectral region and/or from a green spectral region.

6. The phosphor mixture as claimed in claim 1, wherein the at least one quantum dot phosphor is selected from a group consisting of CdSe, CdS, CdTe, InP, InAs, Cl(Z)S, AlS, Zn.sub.3N.sub.2, Si, ZnSe, ZnO and GaN.

7. The phosphor mixture as claimed in claim 1, wherein the at least one further phosphor is present in the phosphor mixture with a proportion of 20% to 30% by weight.

8. The phosphor mixture as claimed in claim 1, wherein the at least one quantum dot phosphor and the functional material arranged as particles in the matrix in two different, adjoining regions.

9. The phosphor mixture as claimed in claim 8, wherein a region of the adjoining regions comprising the quantum dot phosphor is free of further phosphors.

10. A conversion element including the phosphor mixture as claimed in claim 1.

11. An optoelectronic component, comprising: at least one radiation-emitting semiconductor chip that emits electromagnetic radiation of a first wavelength range, and the phosphor mixture as claimed in claim 1.

12. The optoelectronic component as claimed in claim 11, wherein the phosphor mixture is present in a conversion element disposed on the semiconductor chip.

13. The optoelectronic component as claimed in claim 11, wherein the phosphor mixture is in an encapsulating arrangement on the semiconductor chip.

14. An optoelectronic component, comprising: at least one radiation-emitting semiconductor chip that emits electromagnetic radiation of a first wavelength range, and a phosphor mixture comprising at least one quantum dot phosphor, at least one functional material and at least one further phosphor different from the quantum dot phosphor; wherein the functional material comprises scattering particles configured to scatter electromagnetic radiation, the scattering particles having a diameter selected from a range of 0.5 μm to 5 μm, wherein the scattering particles include garnets, and/or wherein the functional material comprises second particles having a density of not less than 2 g/cm3, and having a second diameter of not less than 5 μm, wherein the second particles include garnets; wherein the at least one quantum dot phosphor and the functional material are in a form of a mixture of particles embedded in a matrix; wherein the quantum dot phosphor and the further phosphor are arranged in a first layer; wherein the functional material is arranged in a second layer such that the quantum dot phosphor and the functional material are spatially separated; and wherein the second layer forms a radiation exit surface of the optoelectronic component.

15. An optoelectronic component, comprising: at least one radiation-emitting semiconductor chip that emits electromagnetic radiation of a first wavelength range, and a phosphor mixture comprising at least one quantum dot phosphor, at least one functional material and at least one further phosphor different from the quantum dot phosphor; wherein the functional material comprises scattering particles configured to scatter electromagnetic radiation, the scattering particles having a diameter selected from a range of 0.5 μm to 5 μm, wherein the scattering particles include garnets, and/or wherein the functional material comprises second particles having a density of not less than 2 g/cm3, and having a second diameter of not less than 5 μm, wherein the second particles include garnets; wherein the at least one quantum dot phosphor and the functional material are in a form of a mixture of particles embedded in a matrix; wherein the further phosphor is arranged in a first layer; wherein the quantum dot phosphor and the functional material are arranged in a second layer; wherein the first layer and the second layer are spatially separated; wherein the second layer forms a radiation exit surface of the optoelectronic component; and wherein the first layer is arranged between the radiation-emitting semiconductor chip and the second layer.

Description

(1) Further advantageous embodiments and developments of the invention are apparent from the working examples described hereinafter in conjunction with the figures.

(2) FIGS. 1 to 4 show, in a schematic section view, phosphor mixtures according to working examples.

(3) FIGS. 5 to 8 show, in a schematic section view, optoelectronic components according to working examples.

(4) Elements that are the same, are of the same type or have the same effect are given the same reference numerals in the figures. The figures and the size ratios of the elements shown in the figures relative to one another should not be considered to be to scale. Instead, individual elements, especially layer thicknesses, may be shown in exaggerated size for better representation and/or for better understanding.

(5) FIG. 1 shows the schematic side view of a phosphor mixture 1 in a working example. The phosphor mixture 1 contains a matrix 50 in which particles of quantum dot phosphors 20 and particles of a functional material are disposed. In this working example, the functional material takes the form of scattering particles 31. These increase scatter in the phosphor mixture 1, which reduces the free path length of the light through the phosphor mixture 1 and enables a higher conversion by the quantum dot phosphors 20 present. The proportion of quantum dot phosphors 20 in the phosphor mixture 1 is about 1% by weight, and that of the scattering particles 31 is 1% to 5% by weight. The matrix 50 may, for example, be a silicone matrix. But a matrix of glasses is also conceivable. The quantum dot phosphor 20 may contain or consist of, for example, CdSe, CdS or CdTe. The scattering particles 31 include a material that is, for example, aluminum oxide, titanium dioxide, oxides of the rare earths, garnets or specialty glasses. The diameter of the scattering particles 31 is between 0.5 μm and 5 μm.

(6) In one working example, scattering particles 31 used in the phosphor mixture 1 are 5% by weight of aluminum oxide with a specific density of about 2 g/cm.sup.3 and a size of 0.5 to 5 μm. It is thus possible to increase the conversion of electromagnetic radiation of a first wavelength to radiation of a second wavelength by up to 50% by means of the quantum dot phosphors 20. When the phosphor mixture 1 is used in an optoelectronic component, for example a warm white LED, it is thus possible, given the same content of quantum dot phosphors 20 and hence the same content of cadmium, to obtain more converted light from the quantum dot phosphors 20 and hence to increase the efficiency of the white LED by 2% to 5%. The quantum dot phosphor 20 may especially be a red-emitting quantum dot phosphor.

(7) FIG. 2 shows a phosphor mixture 1 in which the scattering particles 31 are replaced by high-density particles 32 that are embedded in the matrix 50 as functional material together with the quantum dot phosphor 20. The high-density particles 32 may likewise contain or consist of, for example, particles of aluminum oxide, titanium dioxide, garnets, oxides of the rare earths or specialty glasses. If the high-density particles 32 are designed to have high scatter, the proportion thereof in the phosphor mixture 1 is 1% to 3% by weight; if they are designed to have zero or low scatter, the proportion thereof is less than 50% by weight. The diameter of the high-density particles 32 is 0.5 to 5 μm when they are designed to have high scatter, otherwise not less than 5 μm. More particularly, the diameter is not less than 10 μm. The density of the high-density particles 32 is not less than 2 g/cm.sup.3, preferably not less than 5 g/cm.sup.3. The high-density particles 32 increase the weight of the phosphor mixture 1, which means that, given the same proportion by weight, a greater number of quantum dot phosphors 20 may be present in the phosphor mixture 1. Thus, more quantum dot phosphors 20 are available in the phosphor mixture 1 and can lead to an efficiency gain.

(8) Normally, scattering materials in a phosphor mixture are optimized such that a high scattering effect is achieved with little scattering material. If larger particles having a diameter of ≥5 μm, preferably ≥10 μm, are utilized, this enables introduction of distinctly more heavy scattering material owing to their reduced scatter. If the high-density particles 32 introduced into the phosphor mixture 1 are, for example, 10% by weight of aluminum oxide, the density of the phosphor mixture 1 is increased by 4% to 5%. It is thus possible to introduce 4% to 5% more quantum dot phosphors 20 without exceeding the limits for the cadmium content. The amount of high-density particles 32 introduced is limited only for process-related reasons since too high a concentration would make the material too viscous for casting.

(9) If the aluminum oxide in the above example is replaced by a garnet, for example undoped LuAG with a specific density of 6.7 g/cm.sup.3, it is possible to introduce 8% to 15% more quantum dot phosphors 20 and hence to correspondingly increase the efficiency.

(10) FIG. 3 shows a further working example of a phosphor mixture 1. Compared to the phosphor mixture 1 as shown in FIG. 1, the scattering particles 31 are replaced by scattering converting particles 33 that are present in the matrix 50 as functional material together with the quantum dot phosphor 20. These particles 33 have essentially the same properties with regard to particle diameter and content in the phosphor mixture 1 as the scattering particles 31, except that they additionally have wavelength-converting properties. Examples of such particles 33 are LuAG and LuAGaG. Thus, the scattering converting particles 33 also lead to elevated efficiency, as already elucidated in relation to the scattering particles 31. The scattering converting particles 33 are fine-grain phosphor particles having diameters of 0.5 to 5 μm, which, by contrast with phosphors that are normally used with a grain size of more than 15 μm, are introduced into the phosphor mixture 1.

(11) The examples of FIGS. 1 to 3 may also be present in combination in a phosphor mixture 1 (not shown here). This means that, as well as the quantum dot phosphor 20, functional material may be present in the phosphor mixture 1, comprising scattering particles 31, high-density particles 32 and scattering converting particles 33. Also conceivable as functional material are combinations of scattering particles 31 and high-density particles 32, of scattering particles 31 and scattering converting particles 33, and of high-density particles 32 and scattering converting particles 33.

(12) FIG. 4 shows, in a schematic side view, a phosphor mixture 1 which, as well as the quantum dot phosphor 20 and the functional material (scattering particles 31 are shown here by way of example), also contains at least one further phosphor 40. This may be designed, for example, to be red-emitting or green-emitting. In this working example, the quantum dot phosphors 20, the functional material and the further phosphor 40 are mixed in particle form in the matrix 50. In order to further increase the efficiency of the quantum dot phosphor 20, a particularly heavy, i.e. dense, phosphor 40 may be used as further phosphor 40. A suitable example for this purpose is LuAGaG with a specific density of about 7 g/cm.sup.3 in place of LuAG with a specific of 6.7 g/cm.sup.3. The proportion of the further phosphor 40 in the phosphor mixture 1 is between 20% and 30% by weight.

(13) The phosphor mixture 1 may be used in conversion elements that can be used as conversion laminas or else as encapsulation in optoelectronic components. It is possible in the phosphor mixture 1, for example, for one or more green phosphors to be present together with functional material in a matrix 50 in combination with one or more red phosphors as further phosphors 40, and red quantum dot phosphors 20 or green quantum dot phosphors 20.

(14) FIG. 5 shows, in a schematic section view, an optoelectronic component with a radiation-emitting semiconductor chip 60 which is preferably a light-emitting diode chip and emits radiation from an excitation spectrum of a first wavelength range. The semiconductor chip 60 is disposed in the recess of a component housing 70. The recess of the housing 70 is also filled with a phosphor mixture 1 in the form of an encapsulation for the semiconductor chip 60. The composition of the phosphor mixture 1 may be as described with regard to FIGS. 1 to 4. The component emits warm white electromagnetic radiation composed of converted radiation from the phosphor mixture 1 and unconverted radiation from the semiconductor chip 60.

(15) FIG. 6 shows, in a schematic section view, an alternative embodiment of the semiconductor component. Semiconductor chips 60 are disposed here on a substrate 90 that may be a printed circuit board. Semiconductor chips 60 are surrounded by a frame 80. The frame 80 is filled with a phosphor mixture 1, the composition of which may again be as described in one of the examples for FIGS. 1 to 4.

(16) FIG. 7 again shows, in a schematic section view, an optoelectronic component as already described for FIG. 5. The phosphor mixture 1 here has two regions, with the quantum dot phosphors 20 and a further phosphor 40 embedded in a matrix 50 in the lower region in an adjoining arrangement with the semiconductor chip 60. Scattering particles 31 are disposed as functional material in the adjoining region of the phosphor mixture 1 that does not directly adjoin the semiconductor chip 60. In the phosphor mixture 1, there is thus a spatial separation in the phosphor mixture 1 of scattering materials, in this case the scattering particles 31, and the phosphor layer containing the quantum dot phosphors 20 and the further phosphor 40. The region containing the scattering particles 31 can be cast more easily since only the scattering particles 31 contribute to the solids content. Thus, a higher concentration of the scattering particles 31 is also possible in this region. Additionally or alternatively, it is also possible for high-density particles 32 to be present in the region that contains the scattering particles 31 here and/or for scattering converting particles 33 to be present in the region containing the quantum dot phosphors 20 (not shown here).

(17) FIG. 8 shows, in a schematic section view, a further embodiment of the optoelectronic component. Here, a region of the phosphor mixture 1 containing phosphors 40, for example green phosphors, embedded in a matrix 50 is in an adjoining arrangement with the semiconductor chip 60. Positioned further removed from the semiconductor chip 60 is the region of the phosphor mixture 1 containing the quantum dot phosphors 20 and optionally further functional materials, here by way of example scattering particles 31. In this example, there is thus a spatial separation of phosphors 40 and quantum dot phosphors 20. The blue radiation emitted by the semiconductor chip 60 must thus first pass through the phosphors 40 before it hits the quantum dot phosphors 20. Thus, the flow density of the blue light at the quantum dot phosphors 20 is lowered, which increases the efficiency of the quantum dot phosphors 20. It is also possible for scattering converting particles 33 to be disposed in the region containing the phosphors 40 (not shown here).

(18) The invention is not limited to the working examples by the description with reference thereto. Instead, the invention includes every new feature and every combination of features, which especially includes any combination of features in the claims, even if this feature or this combination itself is not specified explicitly in the claims or working examples.

(19) This patent application claims the priority of German patent application 10 2017 129 917.3, the disclosure content of which is hereby incorporated by reference.

LIST OF REFERENCE NUMERALS

(20) 1 phosphor mixture 20 quantum dot phosphor 31 scattering particles 32 high-density particles 33 scattering converting particles 40 phosphor 50 matrix 60 semiconductor chip 70 housing 80 frame 90 substrate