Optoelectronic component and method for producing an optoelectronic component

Abstract

An optoelectronic component and a method for producing an optoelectronic component are disclosed. In an embodiment an optoelectronic component includes a semiconductor chip including a plurality of pixels, each pixel configured to emit electromagnetic primary radiation from a radiation exit surface and conversion layers located on at least a part of the radiation exit surfaces, wherein the conversion layers comprise a crosslinked matrix having a three-dimensional siloxane-based network and at least one phosphor embedded in the matrix, and wherein the conversion layers have a thickness of ≤30 μm.

Claims

1. An optoelectronic component comprising: a semiconductor chip comprising: a plurality of pixels, each pixel configured to emit electromagnetic primary radiation from a radiation exit surface; and conversion layers located directly on at least a part of the radiation exit surfaces, each conversion layer having a size conforming to a cross-section of one pixel, wherein the conversion layers comprise a crosslinked matrix having a three-dimensional siloxane-based network and at least one phosphor embedded in the matrix, wherein the conversion layers have a thickness of ≤3 μm, wherein the crosslinked matrix is made from a precursor material comprising a precursor having a structure chosen from one of the generic formulae: ##STR00008## wherein R.sup.1 and R.sup.2 are—independently from each other—selected from the group consisting of alkyl, alkoxy, aryl, aryloxy, alkenyl, substituted alkyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted alkenyl and combinations thereof, wherein R.sup.11, R.sup.12 and R.sup.13 are—independently from each other—selected from the group consisting of H, alkyl, alkoxy, aryl, aryloxy, alkenyl, substituted alkyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted alkenyl, and combinations thereof, wherein R.sup.3 and R.sup.4 are—independently from each other—selected from the group consisting of alkoxy, vinyl, hydroxyl, carboxylic acid, ester, H, alkyl, aryl, substituted alkoxy, substituted carboxylic acid, substituted ester, substituted vinyl, substituted alkyl, substituted aryl, and combinations thereof, wherein R.sup.1 and R.sup.2 and R.sup.11, R.sup.12 and R.sup.13 comprise an alkoxy content being in a range between 10 wt % and 50 wt % of the total formula, wherein the conversion layers comprise a top surface facing away from the semiconductor chip and a bottom surface facing the semiconductor chip, the top and/or the bottom surface being structured, and wherein the structured surfaces comprises a random roughness.

2. The optoelectronic component according to claim 1, wherein the pixels comprise a pixel-to-pixel period of ≤125 μm.

3. The optoelectronic component according to claim 1, wherein the crosslinked matrix comprises an organic content of less than 40 wt % of the conversion layers.

4. The optoelectronic component according to claim 1, wherein the crosslinked matrix comprises an organic content of less than or equal to 20 wt % of the conversion layers.

5. The optoelectronic component according to claim 1, wherein the precursor material further comprises at least one additive that is selected from the group consisting of catalysts, nanoparticles, metal-organic compounds, organic molecules, organic polymers, inorganic polymers, and combinations thereof.

6. The optoelectronic component according to claim 1, wherein the precursor material further comprises fumed silica, and wherein a content of the fumed silica is in a range of 5 wt % to 40 wt %.

7. The optoelectronic component according to claim 1, wherein the precursor material further comprises a D-unit type bonding, and wherein a content of the D-unit bonding is between 0 mol % and 30 mol % of all siloxane units.

8. The optoelectronic component according to claim 1, wherein the precursor material has a molecular weight of less than 3000 g/mol.

9. The optoelectronic component according to claim 1, wherein the three-dimensional siloxane-based network has the generic formula: ##STR00009## wherein each R is—independently from each other—selected from the group consisting of the groups for R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.11, R.sup.12, and R.sup.13, and any combination thereof, and dangling bonds are—independently from each other—representative of a continuation of the network or one of the groups for R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.11, R.sup.12, and R.sup.13.

10. The optoelectronic component according to claim 1, wherein the at least one phosphor is selected from the group consisting of: (RE.sub.1−xCe.sub.x).sub.3(Al.sub.1−yA′.sub.y).sub.5O.sub.12 with 0<x≤0.1 and 0≤y≤1, (RE.sub.1−xCe.sub.x).sub.3(Al.sub.5−2yMg.sub.ySi.sub.y)O.sub.12 with 0<x≤0.1 and 0≤y≤2, (RE.sub.1−xCe.sub.x).sub.3Al.sub.5−ySi.sub.yO.sub.12−yN.sub.y with 0<x≤0.1 and 0≤y≤0.5, (RE.sub.1−xCe.sub.x).sub.2CaMg.sub.2Si.sub.3O.sub.12:Ce.sup.3+ with 0<x≤0.1, (AE.sub.1−xEu.sub.x).sub.2Si.sub.5N.sub.8 with 0<x≤0.1, (AE.sub.1−xEu.sub.x)AlSiN.sub.3 with 0<x≤0.1, (AE.sub.1−xEu.sub.x).sub.2Al.sub.2Si.sub.2N.sub.6 with 0<x≤0.1, (Sr.sub.1−xEu.sub.x)LiAl.sub.3N.sub.4 with 0<x≤0.1, (AE.sub.1−xEu.sub.x).sub.3Ga.sub.3N.sub.5 with 0<x≤0.1, (AE.sub.1−xEu.sub.x)Si.sub.2O.sub.2N.sub.2 with 0<x≤0.1, (AE.sub.xEu.sub.y)Si.sub.12−2x−3yAl.sub.2x+3yO.sub.yN.sub.16−y with 0.2≤x≤2.2 and 0<y≤0.1, (AE.sub.1−xEu.sub.x).sub.2SiO.sub.4 with 0<x≤0.1, (AE.sub.1−xEu.sub.x).sub.3Si.sub.2O.sub.5 with 0<x≤0.1, K.sub.2(Si.sub.1−x−yTi.sub.yMn.sub.x)F.sub.6 with 0<x≤0.2 and 0<y≤1−x, (AE.sub.1−xEu.sub.x).sub.5(PO.sub.4).sub.3Cl with 0<x≤0.2, (AE.sub.1−xEu.sub.x)Al.sub.10O.sub.17 with 0<x≤0.2, (Y.sub.1−x−yGd.sub.xCe.sub.y).sub.3Al.sub.5O.sub.12 with 0≤x≤0.2 and 0<y≤0.05, and combinations thereof, wherein RE is one or more of Y, Lu, Tb or Gd, wherein AE is one or more of Mg, Ca, Sr, or Ba, and wherein A′ is one or more of Sc or Ga.

11. The optoelectronic component according to claim 1, wherein the structured surface comprises a micro-lens, a micro-lens array, a micro-optic, a photonic crystal, a plasmonic array, a meta lens, aperiodic nanostructured arrays, a dielectric film, a stack of dielectric films, or a graded index anti-reflective coating.

12. The optoelectronic component according to claim 1, wherein the optoelectronic component is an LED or a laser diode.

13. A method for producing an optoelectronic component, the method comprising: providing a semiconductor chip with a plurality of pixels, each pixel configured to emit electromagnetic primary radiation from a radiation exit surface; preparing a starting mixture comprising at least one phosphor and a precursor material, wherein the precursor material comprises a precursor having a structure that is chosen from one of the generic formulae: ##STR00010## wherein R.sup.1 and R.sup.2 are—independently from each other—selected from the group consisting of alkyl, alkoxy, aryl, aryloxy, alkenyl, substituted alkyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted alkenyl, and combinations thereof, wherein R.sup.11, R.sup.12 and R.sup.13 are—independently from each other—chosen form the group consisting of H, alkyl, alkoxy, aryl, aryloxy, alkenyl, substituted alkyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted alkenyl, and combinations thereof, wherein R.sup.3 and R.sup.4 are—independently from each other—selected from the group consisting of alkoxy, vinyl, hydroxyl, carboxylic acid, ester, H, alkyl, aryl, substituted alkoxy, substituted carboxylic acid, substituted ester, substituted vinyl, substituted alkyl, substituted aryl, and combinations thereof, wherein n is chosen such that a viscosity of the precursor is in a range of 1 to 150 mPas, and wherein R.sup.1 and R.sup.2 and R.sup.11, R.sup.12 and R.sup.13 comprise an alkoxy content being in a range from 10 wt % to 50 wt %; applying the starting mixture directly on at least a part of the radiation exit surfaces of the pixels or on a temporary substrate; and curing the starting mixture to form a conversion layer on at least the part of the radiation exit surfaces, each conversion layer having a size conforming to a cross-section of one pixel, wherein the conversion layer comprises a crosslinked matrix having the phosphor dispersed in the matrix, wherein the conversion layer comprises a thickness of ≤30 μm, wherein the conversion layer comprises a top surface facing away from the semiconductor chip and a bottom surface facing the semiconductor chip, the top and/or the bottom surface being structured, and wherein the structured surfaces comprises a random roughness.

14. The method according to claim 13, further comprising adding to the starting mixture at least one additive, wherein the additive is selected from the group consisting of catalysts, nanoparticles, metal-organic compounds, organic molecules, organic polymers, inorganic polymers, and combinations thereof.

15. The method according to claim 13, wherein applying the starting mixture on at least the part of the radiation exit surfaces or on the temporary substrate comprises applying a method selected from the group consisting of screen printing, stencil printing, spray coating, and ink jetting.

16. The method according to claim 13, wherein curing takes place at room temperature or at elevated temperatures.

17. The method according to claim 13, wherein the starting mixture is applied on the temporary substrate, cured on the temporary substrate, and glued to the radiation exit surface of at least one of the pixels of the semiconducting chip, and wherein, after gluing, the temporary substrate is removed.

18. The method according to claim 13, wherein applying the starting mixture on at least the part of the radiation exit surfaces is repeated at least once.

19. An optoelectronic component comprising: a semiconductor chip comprising: a plurality of pixels, each pixel configured to emit electromagnetic primary radiation from a radiation exit surface; and conversion layers located directly on at least a part of the radiation exit surfaces, each conversion layer having a size conforming to a cross-section of one pixel, wherein the conversion layers comprise a crosslinked matrix having a three-dimensional siloxane-based network and at least one phosphor embedded in the matrix, wherein the conversion layers have a thickness of ≤30 μm, wherein the crosslinked matrix is made from a precursor material comprising a precursor having a structure chosen from one of the generic formulae: ##STR00011## wherein R.sup.1 and R.sup.2 are—independently from each other—selected from the group consisting of alkyl, alkoxy, aryl, aryloxy, alkenyl, substituted alkyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted alkenyl and combinations thereof, wherein R.sup.11, R.sup.12 and R.sup.13 are—independently from each other—selected from the group consisting of H, alkyl, alkoxy, aryl, aryloxy, alkenyl, substituted alkyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted alkenyl, and combinations thereof, wherein R.sup.3 and R.sup.4 are—independently from each other—selected from the group consisting of alkoxy, vinyl, hydroxyl, carboxylic acid, ester, H, alkyl, aryl, substituted alkoxy, substituted carboxylic acid, substituted ester, substituted vinyl, substituted alkyl, substituted aryl, and combinations thereof, wherein R.sup.1 and R.sup.2 and R.sup.11, R.sup.12 and R.sup.13 comprise an alkoxy content being in a range between 10 wt % and 50 wt % of the total formula, wherein the conversion layers comprise a top surface facing away from the semiconductor chip and a bottom surface facing the semiconductor chip, the top and/or the bottom surface being structured, and wherein the structured surface comprises a micro-lens, a micro-lens array, a micro-optic, a photonic crystal, a plasmonic array, a meta lens, aperiodic nanostructured arrays, a dielectric film, or a graded index anti-reflective coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional advantages, advantageous embodiments and developments are explained in the following in connection with the figures and examples.

(2) FIG. 1 shows a schematic cross-section of an optoelectronic component;

(3) FIG. 2 shows a schematic top view on an optoelectronic component; and

(4) FIG. 3 shows thermogravimetric analysis profiles of a comparative matrix material and matrix material of a conversion layer according to an exemplary embodiment.

(5) In the examples and figures, like parts are designated by like numerals. The depicted parts and their proportions are not to scale, rather some parts as, for example, layers, may be depicted exaggeratedly large in order to improve presentability.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(6) FIG. 1 shows a schematic cross-section of an optoelectronic component having a substrate 30, a semiconductor chip 20 being pixelated and conversion layers 10. The pixel-to-pixel period may be ≤125 μm. The size of a pixel may be in the range of 300 μm.

(7) The optoelectronic component may be an LED package or a laser diode-based light source. Not explicitly shown in FIG. 1 are the active layer sequence of the semiconductor chip 20 and additional elements like a housing or a reflective sealing material surrounding the semiconductor chip 20.

(8) The semiconductor chip emits a primary electromagnetic radiation, for example, in the near-UV to blue spectrum. Each pixel of the semiconductor chip 20 is individually controllable. The conversion layer 10 absorbs the primary electromagnetic radiation at least partially and converts it to a secondary radiation being different from the primary radiation. The emission of light of each pixel is composed of the combination of primary and secondary radiation.

(9) The wavelength of the secondary radiation depends on the phosphor or blend of phosphors embedded in the matrix of the conversion layer. Each conversion layer may have a different secondary radiation, i.e., the emission of light from each pixel may be different from other pixels.

(10) The conversion layers 10 are applied on the radiation exit surface of the pixels of the semiconductor chip, the radiation exit surface facing away from the substrate 30 on which the semiconductor chip 20 is applied. Not on all of the pixels of the semiconductor chip 20 are necessarily conversion layers 10 if partially no conversion is desired (not shown).

(11) According to an exemplary embodiment of the conversion layer a methoxymethyl polysiloxane is made or purchased as a precursor material. The methoxy content should be in the order of 10 to 50 wt %, preferably in the range of 15 to 45 wt %, even more preferably in the range of 30 to 40 wt %. The molecular weight should be such that the viscosity is in the range of 1 to 50 mPas, but preferably in the range of 2 to 40 mPas. Other polysiloxanes or polysilazanes with various substituents as mentioned above are possible as well.

(12) For a cool white application such as an automotive forward lighting, a YAG:Ce-type phosphor would be chosen as a down conversion material to be incorporated into the precursor material to prepare a starting mixture. For a warm-white, for example, a high CRI lighting application, the phosphor mixture could be a blend of cerium-activated, lutetium aluminum garnet (Lu.sub.1−xCe.sub.x)Al.sub.5O.sub.12, where 0<x≤0.2, and an europium-activated, calcium aluminum silicon nitride (Ca.sub.1−xEu.sub.x)AlSiN.sub.3 where 0<x≤0.2 may be provided as phosphor powders to be incorporated to the liquid precursor material. Generally, other phosphors or blends of phosphors as mentioned above are possible as well, depending on the application and color targets.

(13) The concentration, and ratio of the phosphors depends on the cerium and europium concentrations, the phosphors absorbances and quantum efficiencies, the target thickness of the conversion layer, the target color point of the optoelectronic component and if there are other scattering additives present. The ratio of garnet to nitride phosphor is typically within the range of 2.5:1 to 4.5:1.

(14) Further additives may be added to the starting mixture comprising the precursor and the phosphor blend or the phosphor blend. Depending on the viscosity a solvent may be added or fumed silica may be added if a thickening of the slurry is desired. Other additives may be added additionally or alternatively in order to change the refractive index or thermal conductivity. Further a hardener such as a titanium alkoxide may be added in the range of 0.5 wt % to 5 wt %.

(15) Regardless of the color target or phosphor composition, the slurry comprising the starting mixture is sprayed onto the pixelated semiconductor chip 20 where the phosphor concentration and layer thickness are chosen to hit the target color point, but the final thickness of the conversion layer must remain at or below the 30 μm height limit.

(16) Once sprayed on the pixels of the semiconductor chip 20, the starting mixture may be cured at room temperature or elevated temperatures to form a highly cross-linked matrix with the phosphors embedded therein. The curing can take place after the exposure to water or humidity. The spraying is performed separately, i.e., the pixels of the semiconductor chip 20 are provided with a conversion layer 10 separately from each other.

(17) The application of the starting material onto the pixels of the semiconductor chip 20 generally can be performed by methods like screen printing, stencil printing, spray coating or ink jetting.

(18) FIG. 2 refers to a top view of an optoelectronic component where the top surfaces of the conversion layers 10 are shown. One of the conversion layers 10 is applied onto a pixel of the semiconductor chip 20, wherein this central pixel is on. This pixel is indicated by hatches in FIG. 2. In this example, the semiconductor chip 20 comprises a 7×7 array of micro-pixels. Crosstalk among the pixels of the semiconductor chip is measured by how much light can be detected at neighboring pixels of the hatched pixel, i.e., the pixel that is on. Due to the conversion layer 10 of the optoelectronic component the desired value of crosstalk is accomplished, that is the brightness measured at a pixel with a distance of two pixels between this pixel and the hatched pixel is not greater than 200 times less than the brightness of the hatched pixel. This low crosstalk is realized by the low thickness of ≤30 μm of the conversion layer 10 as well as its direct application on the semiconductor chip 20.

(19) FIG. 3 shows a thermogravimetric analysis profile of a comparative methyl-based silicone (II) in comparison to a methyl-based polysiloxane (I). The x-axis shows the temperature T in ° C., The y-axis shows the weight W in percent. The standard silicone reference (II) loses almost 60% of its weight indicating a large organic content. In contrast, the polysiloxane material (I) loses less than 20% of its weight indicating a significantly lower organic content. This leads to the enhanced thermal stability of the conversion layer in comparison to analogous materials based on standard optical silicone matrixes.

(20) The scope of the application of the present disclosure is not limited to the examples given hereinabove. The present disclosure is embodied in each novel characteristic and each combination of characteristics, which particularly includes every combination of any features which are stated in the claims, even if this feature or this combination of features is not explicitly stated in the claims or in the examples.