Optoelectronic device and method of producing an optoelectronic device

Abstract

An optoelectronic device and a method of producing an optoelectronic device are disclosed. In an embodiment an optoelectronic device includes components including an active layer stack, a housing and electrical contacts and at least one protective layer on a surface of at least one of the components, wherein the at least one protective layer includes a cross-linked material with a three-dimensional polysiloxane-based network.

Claims

1. An optoelectronic device comprising: components including an active layer stack, a housing and electrical contacts; and at least one protective layer on a surface of at least one of the components, wherein the at least one protective layer comprises a cross-linked material with a three-dimensional polysiloxane-based network, wherein the cross-linked material with the three-dimensional polysiloxane-based network is made from a liquid precursor material comprising the following structure: ##STR00007## wherein R.sup.1 is an alkyl group, wherein R.sup.2, R.sup.3 and R.sup.4 are, independently of one another, an alkyl or an aryl group and n+m=1, and wherein a viscosity of the liquid precursor material is between 1 mPa.Math.s and 150 mPa.Math.s inclusive.

2. The optoelectronic device according to claim 1, wherein the at least one protective layer is free of a converter material.

3. The optoelectronic device according to claim 1, wherein 0.50≤n≤1 and 0≤m≤0.50.

4. The optoelectronic device according to claim 1, wherein the liquid precursor material comprises a methoxy methyl siloxane.

5. The optoelectronic device according to claim 1, wherein the at least one protective layer is arranged on a surface of the housing and is in direct mechanical contact with the surface of the housing.

6. The optoelectronic device according to claim 5, wherein the surface of the housing comprises silver.

7. The optoelectronic device according to claim 1, wherein the at least one protective layer comprises traces of titanium, zirconium or tin.

8. The optoelectronic device according to claim 1, wherein the at least one protective layer has a layer thickness of 0.5 μm to 50 μm.

9. The optoelectronic device according to claim 1, wherein the liquid precursor material comprises a methoxy methyl phenyl siloxane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Advantageous embodiments and developments of the optoelectronic device and the method of producing an optoelectronic device will become apparent from the exemplary embodiments described below in association with the figures.

(2) In the figures:

(3) FIGS. 1 to 4 show schematic illustrations of an optoelectronic device according to different embodiments;

(4) FIG. 5 shows thermogravimetric analysis profiles of a comparative silicone material and a polysiloxane material according to an exemplary embodiment; and

(5) FIG. 6 shows exemplary silver surfaces with and without a protective layer.

(6) In the exemplary embodiments and figures, similar or similarly acting constituent parts are provided with the same reference symbols. The elements illustrated in the figures and their size relationships among one another should not be regarded as true to scale. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and/or for the sake of better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(7) The optoelectronic devices 1 in FIGS. 1 and 2 each comprise an active layer stack 2 which is configured to emit electromagnetic radiation. The active layer stack 2 is contacted with electrical contacts 3, 4. In particular, the electrical contacts 3, 4 have at least a metallic surface, preferably made of silver. For example, the electrical contacts 3, 4 are part of a lead frame. For stabilization and protection, the active layer stack 2 can be arranged in the recess 6 of a housing 5. At least one surface of the housing may be a reflective surface 8 as shown, for example, in FIG. 2. In particular, the reflective surfaces 8 are metallic, preferably made of silver.

(8) A protective layer 7 can be arranged on selectively predetermined surfaces, for example, the surfaces of the electrical contacts 3, 4 (FIG. 1). Alternatively, the protective layer 7 can be arranged on all exposed surfaces of the components protecting the surfaces of the electrical contacts 3, 4 as well as the reflective surface 8 of the housing 5 (FIG. 2).

(9) In addition, the recess 6 of the housing 5 can be filled with an encapsulation 9 (not shown here) for further protection and stabilization. The encapsulation 9 can at least partially, preferably completely, surround the components of the optoelectronic devices 1. The encapsulation 9 is, for example, made of silicone or epoxy resin.

(10) The optoelectronic devices 1 in FIGS. 3 and 4 each further comprise a conversion element 10. The conversion element 10 is arranged above the active layer stack 2 in such a way that the radiation emitted from the active layer stack 2 passes through at least a part of the conversion element 10. The conversion element 10 can be in direct contact to the active layer stack 2 or the conversion element 10 and the active layer stack 2 can be spaced apart (not shown here). That is to say that other layers or spaces can be located between the active layer stack 2 and the conversion element 10.

(11) The conversion element 10 is configured to convert the wavelength of the electromagnetic radiation emitted from the active layer stack 2. In particular, the conversion element 10 absorbs the incident electromagnetic radiation and reemits electromagnetic radiation with a different, preferably longer, wavelength.

(12) The protective layer 7 can again be arranged on selectively predetermined surfaces, for example, the reflective silver surfaces 8 of the housing 5 (FIG. 3). Alternatively, the protective layer 7 can be arranged on all exposed surfaces of the components prior to encapsulating the optoelectronic devices 1 (FIG. 4).

(13) A protective layer 7 with a cross-linked material with a polysiloxane-based network can be produced according to the following exemplary embodiment:

(14) A methoxy methyl siloxane with n=1, m=0, R.sup.1=R.sup.2=methyl and a methoxy content in the order of 30-40 wt % is chosen as the liquid precursor material. The liquid siloxane precursor material can be a mixture of different molecular weight species all fulfilling the structural requirement listed in the previous sentence and therefore leading to a viscosity in the range of 1-50 mPa.Math.s, preferably in the range of 2-40 mPa.Math.s. Just prior to application, 0.5-5.0 wt % of titanium n-butoxide is added to the liquid siloxane precursor material. The precursor/hardener mixture is applied, either selectively on the exposed electrical contacts 3, 4 (FIG. 1), on the exposed reflective silver surfaces 8 of the housing 5 (FIG. 3) or on all of the exposed surfaces (FIGS. 2 and 4). The liquid siloxane precursor material is then allowed to react to form the highly cross-linked polysiloxane layer 7. The thickness of the layer can be around 1 μm. Once the curing is complete, the remainder of the optoelectronic device fabrication steps, if any, is carried out.

(15) FIG. 5 shows a thermogravimetric analysis profile of a comparative methyl-based silicone (5-2), a D-unit based component cured by addition reactions, in comparison to a polysiloxane (5-1) according to one embodiment, i.e., a moisture cured T-unit based component. The y-axis shows the weight W in %, the x-axis shows the temperature T in ° C. The standard silicon reference 5-2 loses almost 60% of its weight indicating a large organic content. In contrast, the polysiloxane material 5-1 loses less than 20% of its weight indicating a significantly lower organic content. The significantly lower organic content leads to an enhanced thermal stability and impermeability of the protective layer 7 in comparison to analogous materials based on standard optical silicones.

(16) FIG. 5 shows two silver mirrors that were exposed to H.sub.2S gas at 100° C. for a week. The mirror S1 was not coated with a protective layer, while the mirror S2 was coated with a thin transparent layer of the cross-linked polysiloxane-based material as a protective layer. The silver of the mirror S1 reacted with the H.sub.2S gas and formed gray/black silver sulfide ii that is detrimental to the reflectivity of the silver mirror. Due to the transparent protective layer, the reflectivity of the mirror S2 remains intact.

(17) The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.