Optoelectronic component

Abstract

The invention relates to an optoelectronic component, which, in at least one embodiment, comprises an optoelectronic semiconductor chip having an emission side and a conversion element on the emission side. The conversion element is configured for conversion of a primary beam emitted by the semiconductor chip in operation as intended. The conversion element is divided into at least one first layer and one second layer. The first layer is arranged between the second layer and the emission side. The first layer comprises a first matrix material having fluorescent particles introduced therein. The second layer comprises a second matrix material having fluorescent particles introduced therein. The first matrix material of the first layer has a higher index of refraction than the second matrix material of the second layer.

Claims

1. An optoelectronic component, comprising: an optoelectronic semiconductor chip with an emission side; a conversion element on the emission side, wherein the conversion element is configured for converting a primary radiation emitted by the semiconductor chip in operation as intended, the conversion element is divided into at least a first layer and a second layer, the first layer is arranged between the second layer and the emission side, the first layer comprises a first matrix material with phosphor incorporated therein, the second layer comprises a second matrix material with phosphors incorporated therein, and the first matrix material of the first layer has a higher refractive index than the second matrix material of the second layer.

2. The optoelectronic component as claimed in claim 1, wherein the refractive index of the first matrix material is lower than a refractive index of the semiconductor material of the semiconductor chip.

3. The optoelectronic component as claimed in claim 1, wherein a radiation-permeable optical element is arranged on the conversion element, a refractive index of the optical element is not higher than the refractive index of the second matrix material.

4. The optoelectronic component as claimed in claim 1, wherein the first and/or the second matrix material is based on a silazane or siloxane or silicone.

5. The optoelectronic component as claimed in claim 1, wherein the first layer comprises phosphors of a first phosphor, a refractive index difference between the first fluorescent and the first matrix material is no greater than 1.0.

6. The optoelectronic component as claimed in claim 1, wherein the first layer and the second layer comprise phosphors particles from the same first phosphor.

7. The optoelectronic component as claimed in claim 1, wherein the first layer and the second layer each comprise a mixture of phosphors of different phosphors, the mixtures of phosphors in the first layer and the second layer being equal within the production tolerances.

8. The optoelectronic component as claimed in claim 1, wherein the first layer comprises phosphors of a first phosphor, the second layer comprises phosphors of a second phosphor, the second phosphor is different from the first phosphor.

9. The optoelectronic component as claimed in claim 8, wherein the first and the second phosphor are designed in such a way that during the conversion of the primary radiation emitted by the semiconductor chip in operation, the first phosphor causes a greater Stokes shift than the second phosphor.

10. The optoelectronic component as claimed in claim 8, wherein the first phosphor has a higher refractive index than the second phosphor.

11. The optoelectronic component as claimed in claim 8, wherein a refractive index difference between the first phosphor and the first matrix material is less than a refractive index difference between the first phosphor and the second matrix material.

12. The optoelectronic component as claimed in claim 8, wherein the first phosphor is a nitride-based fluorescent, the second phosphor is a garnet-based fluorescent.

13. The optoelectronic component as claimed in claim 1, wherein the first layer and/or the second layer have a thickness of at least half the wavelength of the primary radiation.

14. The optoelectronic component as claimed in claim 1, wherein the first matrix material has a refractive index of at least 1.5.

15. The optoelectronic component as claimed in claim 1, wherein the semiconductor chip generates primary radiation in the blue spectral range and/or in the UV range in the intended operation, in the intended operation the conversion element converts the primary radiation partially or completely into radiation in the green and/or red spectral range.

16. The optoelectronic component as claimed in claim 1, wherein the conversion element comprises at least one additional layer on one side of the second layer facing away from the semiconductor chip, the additional layer comprises a matrix material with phosphors embedded therein, the matrix material of the additional layer has a lower refractive index than the second matrix material of the second layer.

17. An optoelectronic component, comprising: an optoelectronic semiconductor chip with an emission side; a conversion element on the emission side, wherein the conversion element is configured for converting a primary radiation emitted by the semiconductor chip in operation as intended, the conversion element is divided into at least a first layer and a second layer, the first layer is arranged between the second layer and the emission side, the first layer comprises a first matrix material with phosphor particles incorporated therein, the second layer comprises a second matrix material with phosphor particles incorporated therein, the first matrix material of the first layer has a higher refractive index than the second matrix material of the second layer, the maximum thickness of the first and second layer is 100 μm or 50 μm, and the proportion by mass of phosphor particles in the first and second layer is at least 30%.

Description

(1) In the drawings:

(2) FIG. 1 shows an exemplary embodiment of an optoelectronic component in a cross-sectional view,

(3) FIG. 2 shows a detail from the exemplary embodiment of FIG. 1,

(4) FIGS. 3A to 3E show different positions in an exemplary embodiment of a method for producing an optoelectronic component.

(5) FIG. 1 shows an exemplary embodiment of an optoelectronic component 100 in a cross-sectional view. The optoelectronic component 100 comprises a semiconductor chip 1, for example an AlInGaN semiconductor chip, on a substrate 5. The semiconductor chip 1 is a thin-film chip, for example, in which the growth substrate has been removed. The substrate 5 is a ceramic substrate, for example.

(6) The semiconductor chip 1 is connected in an electrically conductive manner to electrical contact elements 61, 62 by means of contact wires 63. The contact elements 61, 62 are exposed on a rear side of the substrate 5 on the opposite side to the semiconductor chip 1. In this case, the optoelectronic component 100 is therefore a surface-mountable optoelectronic component.

(7) The semiconductor chip 1 emits primary radiation, in particular radiation in the blue spectral range or in the UV range, in the intended operation. The semiconductor chip 1 comprises an emission side 10, via which, for example, at least 50% of the radiation extracted from the semiconductor chip 1 is emitted during the intended operation. Lateral surfaces of the semiconductor chip 1 running at right angles to the emission side 10 are covered with a reflecting material 4. For example, the reflecting material 4 is a white silicone, for example a silicone doped with TiO.sub.2 particles.

(8) A conversion element 2 is applied to the emission surface 10 and to parts of the reflecting material 4. The conversion element 2 completely covers the emission side 10 of the semiconductor chip. Furthermore, the conversion element 2 is designed to be simply contiguous. The conversion element 2 is used for the partial or complete conversion of the primary radiation emitted by the semiconductor chip 1 in the intended operation. For example, in operation, the conversion element 2 converts the primary radiation partially or completely into light in the yellow to green and/or orange to red spectral range. The radiation emitted from the conversion element 2 is preferably white light.

(9) The semiconductor chip 1 and the conversion element 2 are covered with an optical element 3. In this case, the optical element 3 is a lens, for example a silicone lens.

(10) In FIG. 2, the excerpt outlined with a dashed box in FIG. 1 is shown enlarged. It is apparent that the conversion element 2 consists of two layers 21, 22. The first layer 21 comprises a first matrix material 210 with phosphors 211 embedded therein. The second layer 22 comprises a second matrix material 220 with phosphors 221 embedded therein. The first layer 21 and the second layer 22 are in direct contact with each other and are separated from each other by an interface.

(11) The phosphors 211 of the first layer 21 are preferably a mixture of phosphors of different phosphors. The same preferably applies to the phosphors 221 of the second layer 22. The mixtures of phosphors used in the first layer 21 and the second layer 22 are, for example, equal within the scope of the manufacturing tolerance.

(12) The first matrix material of 210 has a higher refractive index than the second matrix material 220. This reduces the total internal reflection at the emission surface 10 for primary radiation coming from the semiconductor chip 1, compared to the case in which the second matrix material 220 were to be used for the entire conversion element 2. On the other hand, the use of the second layer 22 with the second matrix material 220 with the lower refractive index is advantageous, because the light conversion produces heat, which is dissipated less well the farther away from the semiconductor chip 1 that the heat is generated. In other words, in the intended operation, the second layer 22 heats up to higher temperatures than the first layer 21. However, the second matrix material 220 with the lower refractive index is more temperature-stable than the first matrix material 210 with the higher refractive index.

(13) FIGS. 3A to 3E show different positions in a method for producing an optoelectronic component, in particular the optoelectronic component 100 of FIG. 1.

(14) In the position of FIG. 3A, the substrate 5 is shown with the semiconductor chip 1 mounted thereon and electrically connected.

(15) In the position of FIG. 3B, side faces of the semiconductor chip 1 are encapsulated with the reflecting material 4.

(16) In the position of FIG. 3C, the first layer 21 of the conversion element 2 is applied to the semiconductor chip 1. For example, the first matrix material 210 with phosphors 211 distributed therein has been applied by spraying.

(17) In the position of FIG. 3D, the second layer 22 of the conversion element 2 is applied. For example, the second matrix material 220 with incorporated phosphors 221 has again been sprayed on. The second layer 22 in this case has preferably been applied directly onto the first layer 21.

(18) FIG. 3E shows a position in which the semiconductor chip 1, together with the conversion element 2, is encapsulated or overmolded with an optical element 3, in this case a silicone lens 3.

(19) In the following, three more specific exemplary embodiments of the optoelectronic component 100 of FIG. 1 or the method according to FIGS. 3A to 3E are described.

(20) In a first exemplary embodiment, a silicone with a refractive index of 1.56 is used as the first matrix material 210. For the second matrix material 220, a silicone with a refractive index of 1.51 is used. The phosphors 211, 221 are, for example, phosphors of the same phosphor, such as a garnet. The optical element 3 is formed from a silicone with a refractive index of 1.50.

(21) In a second exemplary embodiment, the first matrix material is a silicone with a refractive index between 1.55 and 1.6 inclusive. Phosphors 211 of a first phosphor are distributed in the first matrix material 210. The first phosphor is a nitride-based fluorescent which converts the primary radiation of the semiconductor chip 1 into red light. The second matrix material 220 is a silicone with a refractive index between 1.50 and 1.54 inclusive. Phosphors 221 of a second phosphor are distributed in the second matrix material 220. The second phosphor is a garnet-based fluorescent, which converts the primary radiation into green light. The optical element 3 is again formed of a silicone with a refractive index of 1.50.

(22) In a third exemplary embodiment, the first matrix material 210 is a silicone with a refractive index between 1.5 and 1.60 inclusive. Phosphors 211 of a first and a second phosphor are distributed in the first matrix material 210. The first phosphor is a nitride-based fluorescent which converts the primary radiation into red light. The second phosphor is a garnet-based fluorescent which converts the primary radiation into green light. The second matrix material 220 is a silicone with a refractive index between 1.41 and 1.52 inclusive. In the second matrix material 220, phosphors 221 of a second, garnet-based phosphor are distributed, which converts the primary radiation into green light. The material of the optical element 3 is silicone having a refractive index between 1.41 and 1.48 inclusive.

(23) In order to test the performance of an optoelectronic component described here, the inventors have compared a component according to the invention with an alternative component. The component according to the invention comprised a conversion element with two layers, the first layer comprising a first matrix material with a refractive index of 1.55 and the second layer comprising a second matrix material with a refractive index of 1.51. This component according to the invention was compared with a first alternative component, in which the conversion element contained only one matrix material with a refractive index of 1.55, and with a second alternative component in which the conversion element contained only one matrix material with a refractive index of 1.51. The components were both operated at a current of 1500 mA at an ambient temperature of 125° C.

(24) The result of this test was that comparable luminous intensities were achieved with the first alternative component and the component according to the invention, while the luminous intensity of the second alternative component was significantly lower. On the other hand, the conversion elements of the component according to the invention and the second alternative component showed hardly any signs of aging even after an operating period of over 600 h, whereas the first alternative component showed significant changes in the chromaticity coordinate.

(25) The invention is not limited to the embodiments by the fact that the description is based on them. Rather, the invention comprises each new feature, as well as any combination of features, which includes in particular every combination of features in the patent claims, even if these features or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

LIST OF REFERENCE SIGNS

(26) 1 semiconductor chip 2 conversion element 3 optical element 4 reflective material 5 substrate 10 emission side 21 first layer 22 second layer 61 first contact element 62 second contact element 63 contact wire 100 optoelectronic component 210 first matrix material 211 phosphors 220 second matrix material 221 phosphors