OPTOELECTRONIC COMPONENT WITH A LUMINESCENT CONVERSION LAYER

Abstract

Optoelectronic component (10), comprising - at least one light-emitting semiconductor layer sequence (2), and - at least one luminescence conversion layer (3) comprising a transparent conductive oxide and at least one dopant for the formation of luminescence centers; wherein the luminescence conversion layer (3) has several sublayers (3a, 3b, 3c) arranged alternately in a layer stack, with a transparent barrier layer (6) arranged between each of the sublayers.

Description

[0001] The invention relates to an optoelectronic component comprising at least one light-emitting semiconductor layer sequence and at least one luminescence conversion layer.

[0002] The optoelectronic component can in particular be a multi-colored LED display in which at least one of the several colors is generated by means of the luminescence conversion layer.

[0003] The publication DE 10 2009 051 748 A1 specifies a method for manufacturing a radiation-emitting semiconductor device in which a conversion element is applied to a light-emitting diode chip with a radiation emission surface and in which the conversion element is at least partially removed by means of laser radiation.

[0004] The publication DE 10 2012 101 920 A1 relates to an optoelectronic component comprising a sequence of layers with an active area that emits primary electromagnetic radiation and a conversion material that is arranged in the beam path of the primary electromagnetic radiation and at least partially converts the primary electromagnetic radiation into secondary electromagnetic radiation.

[0005] The publication DE 10 2018 104 993 A1 describes a component with a semiconductor body and a converter layer, in which the converter layer has phosphor particles and an electrically conductive matrix material (3M), wherein the phosphor particles are embedded in the matrix material.

[0006] One problem to be solved is to specify an optoelectronic component in which at least part of the emitted radiation is converted to another wavelength by means of a luminescence conversion layer, wherein the luminescence conversion layer is simultaneously characterized by advantageous electrical properties.

[0007] This problem is solved by an optoelectronic component according to the independent claim. Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0008] According to at least one embodiment, the optoelectronic device comprises at least one light-emitting semiconductor layer sequence and at least one luminescence conversion layer containing a transparent conductive oxide and at least one dopant for forming luminescence centers. The luminescence conversion layer is capable of converting all or part of the primary radiation emitted by the light-emitting semiconductor layer sequence into secondary radiation with a wavelength different from the primary radiation.

[0009] The light-emitting semiconductor layer sequence comprises, for example, a p-type semiconductor region, an n-type semiconductor region, and an active layer located between the p-type and n-type semiconductor regions. The p-type semiconductor region, the n-type semiconductor region, and the active layer can each comprise one or more semiconductor layers. The p-type semiconductor region contains one or more p-doped semiconductor layers, and the n-doped semiconductor region contains one or more n-doped semiconductor layers. It is also possible that the p-type and / or the n-type semiconductor region contain one or more undoped semiconductor layers. The light-emitting semiconductor layer sequence of the optoelectronic device is, in particular, a light-emitting diode (LED) layer sequence.

[0010] The light-emitting semiconductor layer sequence of the optoelectronic device is preferably based on a III-V compound semiconductor material, in particular on a nitride, phosphide, or arsenide compound semiconductor material. For example, the light-emitting semiconductor layer sequence can be in y Al y Ga 1-x-y N, In x Al y Ga 1-x-y P or In x Al y Ga 1-x-y The formulas contain elements such as 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and x + y ≤ 1. The III-V compound semiconductor material does not necessarily have to have a mathematically exact composition according to one of the formulas above. Rather, it can contain one or more dopants as well as additional components. For the sake of simplicity, however, the formulas above only include the essential components of the crystal lattice, even though some of these may be replaced by small amounts of other substances.

[0011] The luminescence conversion layer can be arranged, in particular, in one of the emission directions of the light-emitting semiconductor layer sequence and is preferably arranged directly on the light-emitting semiconductor layer sequence. Alternatively, a further transparent conductive oxide layer can be arranged between the light-emitting semiconductor layer sequence and the luminescence conversion layer. The luminescence conversion layer comprises a transparent conductive oxide that acts as a matrix material for the at least one dopant. The dopant of the transparent conductive oxide forms luminescence centers that are suitable for wavelength conversion of the radiation emitted by the light-emitting semiconductor layer sequence.In particular, the luminescence centers may be suitable for converting emitted primary radiation of a smaller wavelength, such as UV light, blue light or green light, into secondary radiation of a larger wavelength, such as red light.

[0012] The use of a transparent conductive oxide as a matrix material for the at least one dopant forming the luminescence centers has the advantage that the luminescence conversion layer is not only suitable for radiation conversion but also exhibits advantageous electrical properties, particularly its electrical conductivity. The luminescence conversion layer made of the transparent conductive oxide can be advantageously deposited at comparatively low process temperatures, for example, by sputtering. In particular, it is possible to deposit the luminescence conversion layer directly onto the light-emitting semiconductor layer sequence without damaging the light-emitting semiconductor layer sequence.

[0013] The dopant, which forms the luminescence centers, ensures that the transparent conductive oxide of the luminescence conversion layer itself becomes a phosphor. The luminescence conversion layer, which contains a transparent conductive oxide with at least one dopant for forming luminescence centers, is not a mixture or composite of conventional photoluminescent phosphor particles or powders and conductive material or binders. Rather, the luminescence conversion layer is advantageously based on an inherently conductive photoluminescent phosphor material, which is preferably applied as a thin film. In particular, the luminescence conversion layer can be produced using a vacuum deposition process. Conductivity and homogeneity can be controlled more effectively in this way than, for example, in sol-gel processes.The luminescence conversion layer can also be advantageously grown on very small structures such as LED pixels.

[0014] According to a preferred embodiment, the transparent conductive oxide is ZnO, IZO, Ga₂O₃, or IGZO. According to another embodiment, the transparent conductive oxide is In₂O₃, SnO₂, IMO, or ITO. It is also conceivable to use derivatives or modifications of the aforementioned materials. The dopant of the transparent conductive oxide is advantageously a rare earth material, preferably Eu, Er, Tb, or Ce. These dopants are suitable for forming luminescent centers in a transparent oxide.

[0015] According to at least one embodiment, the luminescence conversion layer contains at least one additional dopant. This additional dopant is specifically intended to selectively adjust the luminescence and / or electrical properties of the luminescence conversion layer. The additional dopant can be a non-rare earth material. For example, the transparent conductive oxide can be co-doped with Na, K, or Li to modify its luminescence properties.

[0016] According to at least one embodiment, the additional dopant is Ga, Al, K, Na, or Li. This additional dopant can be used to create n-type doping of the transparent conductive oxide. For example, Ga and Al are suitable for creating n-type doping in ZnO.

[0017] According to at least one embodiment, the luminescence conversion layer contains ZnO:Eu, ZnO:Eu, Ga or ZnO:Eu, Al. These materials advantageously enable the conversion of UV light, blue light or green light into red light.

[0018] According to at least one embodiment, the at least one luminescence conversion layer is electrically conductive and arranged between a first electrode and a second electrode of the light-emitting semiconductor layer sequence. In particular, it can be provided that the luminescence conversion layer carries the operating current of the light-emitting semiconductor layer sequence. In this embodiment, the luminescence conversion layer can advantageously function simultaneously as a luminescence conversion layer and as a current-carrying or current-expansion layer for the light-emitting semiconductor layer sequence. This simplifies the manufacturing process for the optoelectronic component.

[0019] According to at least one embodiment, the luminescence conversion layer comprises several sublayers arranged in a layer stack, the sublayers being separated from one another by at least one transparent barrier layer. This allows the optical and / or electrical properties of the luminescence conversion layer to be selectively adjusted. The layer stack can, in particular, contain alternating sublayers of the luminescence conversion layer and barrier layers. Specifically, the barrier layers manage or confine charge carriers within the sublayers of the luminescence conversion layer or modify the excitation or light extraction, thereby advantageously increasing efficiency. The at least one transparent barrier layer is, for example, a transparent oxide layer or nitride layer.

[0020] Preferably, the at least one transparent barrier layer is between 1 nm and 200 nm thick, particularly preferably between 5 nm and 30 nm. In this case, the barrier layers are comparatively thin. Such thin layers are sufficient to induce charge carrier confinement, thereby increasing the efficiency of the luminescence conversion in the sublayers. The multiple sublayers of the luminescence conversion layer are, for example, between 10 nm and 10 µm thick, preferably between 50 nm and 1 µm.

[0021] In a preferred embodiment, the at least one transparent barrier layer is a transparent conductive oxide layer. In this embodiment, both the sublayers of the luminescence conversion layer and the at least one barrier layer are electrically conductive. In particular, the layer stack containing the sublayers of the luminescence conversion layer and the at least one barrier layer is electrically conductive as a whole and can therefore advantageously function as a current-carrying or current-expansion layer.

[0022] According to at least one embodiment of the optoelectronic device, the light-emitting semiconductor layer sequence emits UV radiation, blue light, or green light, with the luminescence conversion layer converting the emitted light into longer-wavelength light, for example, red light. In this embodiment, the luminescence conversion layer can, in particular, comprise ZnO:Eu or ZnO:Eu,X, i.e., europium-doped zinc oxide, optionally doped with one or more further dopants X. A further dopant X can, for example, be Ga or Al. In another embodiment, the luminescence conversion layer can comprise ZnO:Ce,X, with the further dopant X being, for example, Li, Ga, or Al.

[0023] According to at least one embodiment, the optoelectronic device is a multicolor LED display comprising a plurality of pixels. Each pixel has a light-emitting semiconductor layer sequence. The pixels are designed to generate light of a first color and at least one other color, with the luminescence conversion layer being arranged at least on the pixels that generate the light of the first color. In particular, the light emitted by the light-emitting semiconductor layer sequence of the first pixels can be converted into the light of the first color by means of the luminescence conversion layer. The light of the at least one other color can, for example, be generated directly by the light-emitting semiconductor layer sequence; that is, it can be the primary radiation of the light-emitting semiconductor layer sequence.It is possible that, in addition to the light of the first color, the light of at least one other color is also generated by luminescence conversion.

[0024] According to at least one embodiment, the light-emitting semiconductor layer sequences of the pixels are based on the same semiconductor material. "Based on the same semiconductor material" can, in particular, mean that the light-emitting semiconductor layer sequences of the pixels of the first color and of the at least one second color are each based on a nitride compound semiconductor material. In particular, the light-emitting semiconductor layer sequences, especially their active layers, can each be based on a nitride compound semiconductor material. x Al y Ga 1-x-yThe light-emitting semiconductor layer sequences can advantageously be grown on the same growth substrate. Separate growth of light-emitting semiconductor layer sequences of different material systems on different growth substrates and subsequent transfer to a common support substrate can be advantageously avoided.

[0025] According to at least one embodiment, the first color generated by the luminescence conversion layer is red. For example, the multicolor LED display is an RGB display in which a first group of pixels emits red light, a second group of pixels green light, and a third group of pixels blue light.

[0026] According to at least one embodiment, the at least one light-emitting semiconductor layer sequence and / or the at least one luminescence conversion layer are surrounded laterally by an opaque layer. This is particularly advantageous when the optoelectronic component is designed as a multicolor LED display, in order to prevent optical crosstalk between adjacent pixels.

[0027] The optoelectronic component is particularly suitable for use in LED displays or can itself be an LED display. The LED display is specifically a multicolor LED display, for example, an RGB LED display. In particular, the optoelectronic component can be used in small displays such as those found in smartphones, watches, or head-up displays.

[0028] The invention is described below with reference to exemplary embodiments in connection with the Fig. 1 to 11 explained in more detail.

[0029] They show: Fig. 1A to 1E each show a schematic representation of a cross-section through an example of the optoelectronic component, Fig. 2A to 2C each show a schematic representation of a cross-section through an optoelectronic component according to further examples, Fig. 3A a schematic representation of a cross-section through an example of the luminescence conversion layer, Fig. 3B a schematic representation of a cross-section through another example of the luminescence conversion layer, Fig. 4 a schematic representation of a cross-section through an optoelectronic component according to another example, Fig. 5 a schematic representation of a cross-section through an optoelectronic component according to another example, Fig. 6 a schematic representation of a cross-section through an optoelectronic component according to another example, Fig. 7 a schematic representation of a cross-section through an optoelectronic component according to another example, Fig. 8 a schematic representation of a cross-section through an optoelectronic component according to another example, Fig. 9 a schematic representation of a cross-section through an optoelectronic component according to another example, Fig. 10 a schematic representation of a cross-section through an optoelectronic component according to another example, and Fig. 11 a schematic representation of a cross-section through an optoelectronic component according to another example.

[0030] Identical or similarly functioning components are marked with the same reference symbols in the figures. The depicted components and their relative sizes are not to be considered to scale.

[0031] In Fig. Figure 1A shows a first example of the optoelectronic device 10. The optoelectronic device 10 has a light-emitting semiconductor layer sequence 2 arranged on a substrate 1. The light-emitting semiconductor layer sequence 2 is, in particular, a light-emitting diode layer sequence. The light-emitting semiconductor layer sequence 2 can have several sublayers, which are arranged in the Fig. 1 and are not shown individually in the following figures for the sake of simplicity. In particular, the light-emitting semiconductor layer sequence 2 can have an n-type semiconductor region, a p-type semiconductor region, and an active layer arranged between the n-type semiconductor region and the p-type semiconductor region. The n-type semiconductor region, the p-type semiconductor region, and the active layer can each be formed from several layers. The light-emitting semiconductor layer sequence 2 can, for example, emit UV light, blue light, and / or green light. In this embodiment, the light-emitting semiconductor layer sequence 2 is, for example, a semiconductor layer sequence based on a nitride compound semiconductor, which in particular comprises semiconductor layers with the composition In x Al y Ga 1-x-y N, with 0 ≤ x ≤ 1, 0 ≤ y ≤ 1 and x + y ≤ 1.

[0032] It is possible that substrate 1 is a growth substrate on which the light-emitting semiconductor layer sequence 2 has been epitaxially grown. Alternatively, it is also possible that substrate 1 is a support substrate onto which the light-emitting semiconductor layer sequence 2 has been transferred from a growth substrate. Substrate 1 can comprise at least one electrode for electrically contacting the light-emitting semiconductor layer sequence 2 and / or an electrical circuit for operating the at least one light-emitting semiconductor layer sequence 2. In particular, the optoelectronic device 10 can be a multi-pixel LED display, wherein a control circuit for the pixels can be at least partially integrated into substrate 1.

[0033] In the optoelectronic device 10, a luminescence conversion layer 3 is arranged in one emission direction of the light-emitting semiconductor layer sequence 2. The luminescence conversion layer can, in particular, be directly adjacent to the light-emitting semiconductor layer sequence 2. The luminescence conversion layer 3 is suitable for converting primary radiation emitted by the light-emitting semiconductor layer sequence 2, either completely or at least partially, into secondary radiation with a different wavelength. In particular, the luminescence conversion layer 3 can be designed to convert primary radiation of a shorter wavelength into secondary radiation of a longer wavelength. For example, the light-emitting semiconductor layer sequence 2 can emit UV light, blue light, or green light as primary radiation, and the luminescence conversion layer 3 can generate red light as secondary radiation.

[0034] The luminescence conversion layer 3 comprises a transparent conductive oxide and at least one dopant for the formation of luminescence centers. The transparent conductive oxide can be, for example, ZnO, In₂O₃, IZO, Ga₂O₃, IGZO, SnO₂, or ITO. These transparent conductive oxides are particularly advantageous because the layer can be produced at relatively low process temperatures in the range of approximately 300 °C to 550 °C. This temperature range is compatible with LED manufacturing.

[0035] The at least one dopant is preferably an element from the rare earth group. Preferred dopants are Eu, Er, Tb, and Ce. The luminescence conversion layer 3 can additionally contain at least one further dopant, which can be used to selectively adjust the electrical properties and / or the luminescence properties (efficiency, lifetime of excited states). The further dopant can be an element that does not belong to the rare earth group. For example, the further dopant can be Ga or Al. The addition of Ga or Al can, in particular, achieve n-type doping of the transparent conductive oxide. Alternatively, it is also conceivable to provide the transparent conductive oxide with a p-type dopant or to use an intrinsic transparent conductive oxide.

[0036] Particularly preferred is the transparent conductive oxide ZnO doped with Eu or Ce and optionally with one or more further dopants X. A transparent conductive oxide with the composition ZnO:Eu or ZnO:Eu,X, where X is, for example, Ga, Al, Na, K or Li, is particularly suitable for converting UV light, blue light or green light into red or green light.

[0037] The luminescence conversion layer 3 can be deposited directly onto the light-emitting semiconductor layer sequence 2, for example, using a vacuum coating process such as sputtering. A key advantage of this method is that sputtering allows for fabrication at a comparatively low temperature, thus preventing damage to the existing light-emitting semiconductor layer sequence 2 during the deposition of the luminescence conversion layer 3. Alternative coating processes for fabricating the luminescence conversion layer 3 include electron beam evaporation, MOCVD, ALCVD, sol-gel processes, printing processes, and spin coating. Alternatively, the luminescence conversion layer can be fabricated by producing and depositing nanoparticles. It is also possible to subject the luminescence conversion layer 3 to a heat treatment after deposition.

[0038] As an alternative to directly applying the luminescence conversion layer 3 to the light-emitting semiconductor layer sequence, it can also be produced separately on a support substrate and subsequently transferred to the light-emitting semiconductor layer sequence 2.

[0039] In the optoelectronic component 10, an optional cover layer 4 can be arranged above the luminescence conversion layer 3. The cover layer 4 can, for example, be an encapsulation layer to protect the optoelectronic component 10. It is also possible that the cover layer 4 has an optical function, for example as a color filter, for contrast enhancement, or for suppressing optical crosstalk. It is also possible that the cover layer 4 contains one or more electrodes and / or electrical circuit elements for the optoelectronic component 10.

[0040] In the illustrated example, the light-emitting semiconductor layer sequence 2 and the luminescence conversion layer 3 are each surrounded laterally by an opaque layer 5. The opaque layer 5 prevents the emitted primary and / or secondary radiation from escaping laterally from the optoelectronic device 10. This is particularly advantageous in optoelectronic devices that have several light-emitting semiconductor layer sequences 2 and / or luminescence conversion layers 3 arranged side by side, for example in LED displays with a large number of adjacent pixels.

[0041] In Fig. Figure 1B shows another example of the optoelectronic device 10. This example differs from the previous example in that the luminescence conversion layer 3 is also arranged laterally from the light-emitting semiconductor layer sequence 2. The light-emitting semiconductor layer sequence 2 is electrically isolated laterally from the luminescence conversion layer 3 by a passivation layer 13. This arrangement is particularly advantageous if the light-emitting semiconductor layer sequence 2 does not have a surface roughening, so that the vertical light extraction can be impaired by total internal reflection. This arrangement can also be advantageous for light-emitting semiconductor layer sequences 2 that form small LED pixels, e.g., with an edge length of no more than 15 µm, especially if the pixel pitch is comparatively large.In this case, light exiting laterally from the light-emitting semiconductor layer sequence 2 can also be utilized, thus increasing the area of ​​light conversion. Crosstalk to neighboring pixels can be further prevented by the addition of an opaque layer 5, which in this example borders the luminescence conversion layer 3.

[0042] In Fig. Figure 1C is another example of the optoelectronic device 10. This example differs from the previous example in that the light-emitting semiconductor layer sequence 2 has side faces that run obliquely to the substrate 1. In particular, the light-emitting semiconductor layer sequence 2 has a trapezoidal cross-section. This configuration can be advantageous for light extraction.

[0043] In Fig. Figure 1D shows another example of the optoelectronic device 10. This example differs from the previous example in that the luminescence conversion layer 3 is arranged exclusively laterally to the light-emitting semiconductor layer sequence 2. An opaque, in particular light-blocking, cover layer 4 is arranged on the light-emitting semiconductor layer sequence. In this case, the light is essentially coupled out of the light-emitting semiconductor layer sequence 2 only laterally. The light-blocking layer 5, arranged laterally to the luminescence conversion layer, can in particular be reflective and cause radiation to be coupled out of the luminescence conversion layer 3 upwards.

[0044] In Fig. Figure 1E is another example of the optoelectronic device 10. This example differs from the previous example in that the luminescence conversion layer 3 is formed both laterally and above the light-emitting semiconductor layer sequence 2. The cover layer 4 on the light-emitting semiconductor layer sequence can, in this case, be opaque, in particular non-transparent, or alternatively transparent. The non-transparent layer 5 is arranged laterally to the luminescence conversion layer 3 and can be configured as a reflector, in particular as a reflector with side faces inclined to the substrate 1. Furthermore, it is possible for the non-transparent layer 5 configured as a reflector to cover the substrate 1. In this way, the upward light emission is enhanced.

[0045] In Fig. 2A is another example of the optoelectronic device 10 shown, which differs in the arrangement of the luminescence conversion layer 3 relative to the light-emitting semiconductor layer sequence 2 from the example of the Fig. 1A differs. In this example, the luminescence conversion layer 3 is arranged between the substrate 1 and the light-emitting semiconductor layer sequence 2. This configuration is particularly possible if the light-emitting semiconductor layer sequence 2 is transparent to the secondary radiation generated by the luminescence conversion layer 3. The top layer 4 can advantageously have a color filter that is, for example, transparent to the secondary radiation and opaque to the primary radiation. A color filter in the top layer 4 can also be partially transparent to the primary radiation in order to generate, for example, mixed light with a component of the primary radiation and a component of the secondary radiation. With regard to further possible configurations, the second example corresponds to the example of Fig. 1A.

[0046] In Fig. Figure 2B shows another example of the optoelectronic device 10. This example differs from the previous example in that the luminescence conversion layer 3 is also arranged laterally to the light-emitting semiconductor layer sequence 2. The light-emitting semiconductor layer sequence 2 is electrically isolated laterally from the luminescence conversion layer 3 by a passivation layer 13. In this case, light emitted laterally from the light-emitting semiconductor layer sequence 2 can also be utilized, thus increasing the area of ​​light conversion. Crosstalk to neighboring pixels can be further prevented by the arrangement of an opaque layer 5, which in this example borders the luminescence conversion layer 3.

[0047] In Fig. 2C is another example of the optoelectronic device 10. This example differs from the previous example in that the light-emitting semiconductor layer sequence 2 has side faces that run obliquely to the substrate 1. In particular, the light-emitting semiconductor layer sequence 2 has a trapezoidal cross-section. This configuration can be advantageous for light extraction.

[0048] In the Fig. Figure 3A shows one possible embodiment of the luminescence conversion layer 3. In this example, the luminescence conversion layer 3 is a single layer comprising ZnO:Eu, Ga. Alternatively, the luminescence conversion layer 3 could comprise one of the other materials mentioned previously.

[0049] In the Fig. Figure 3B shows an advantageous embodiment of the luminescence conversion layer 3. In this example, the luminescence conversion layer 3 is not a single layer, but a layer stack. The layer stack comprises several sublayers 3a, 3b, 3c of the luminescence conversion layer, which, as in the previous examples, are each a transparent conductive oxide layer doped with at least one dopant to form luminescence centers and optionally one or more further dopants. A barrier layer 6 is arranged before and after each sublayer 3a, 3b, 3c. The barrier layers 6 can, for example, be oxide or nitride layers. Preferably, the transparent barrier layers 6 are thin layers, only between 1 nm and 200 nm thick, and particularly preferably between 5 nm and 30 nm thick.The barrier layers 6 can be used to optimize the luminescence properties, for example, through charge carrier management or inclusion in the sublayers 3a, 3b, 3c. Additionally or alternatively, other properties of the layers in the layer stack, such as layer thicknesses, charge carrier doping, band structure, or refractive indices, can be used to optimize the luminescence properties as well as the optical and / or electronic properties of the luminescence conversion layer 3.

[0050] Preferably, the barrier layers 6 are transparent conductive oxide layers. For example, the barrier layers contain ZnO:Ga or ITO. The layer stack of the luminescence conversion layer 3 can therefore be an alternating sequence of alternating transparent conductive oxide layers 3a, 3b, 3c with luminescence centers and further transparent conductive oxide layers that form the barrier layers 6.

[0051] In Fig. Figure 4 shows another example of the optoelectronic device 10. In this example, the luminescence conversion layer 3 is arranged between a first electrode 11 and a second electrode 12 of the optoelectronic device 10. This embodiment particularly utilizes the fact that the luminescence conversion layer 3 is electrically conductive. During operation of the optoelectronic device 10, the operating current of the light-emitting semiconductor layer sequence 2 flows through the luminescence conversion layer 3. In this case, the luminescence conversion layer 3 can advantageously have a dual function as both a luminescence conversion layer and a current expansion layer of the optoelectronic device 10. The luminescence conversion layer 3 comprises, for example, ZnO:Eu, Ga, X.

[0052] The Fig. Figure 5 shows a variation of the example of Fig. 4, in which a further transparent conductive oxide layer 7 is arranged between the luminescence conversion layer 3 and the light-emitting semiconductor layer sequence 2. This further transparent conductive oxide layer 7 can have a transparent conductive oxide without luminescence centers. The further transparent conductive oxide layer 7 can function as a current-expansion layer. As in the previous example, the luminescence conversion layer 3 is arranged between the first electrode 11 and the second electrode 12 of the optoelectronic device and is traversed by the operating current of the light-emitting semiconductor layer sequence 2. The luminescence conversion layer 3 has, for example, ZnO:Eu, Ga, and the further transparent conductive oxide layer 7 has ZnO:Ga or ITO.

[0053] The Fig. Figure 6 shows another variation of the example of Fig. 4, in which the additional transparent conductive oxide layer 7 is arranged between the luminescence conversion layer 3 and the second electrode 12. As in the previous example, the additional transparent conductive oxide layer 7 acts as a current-expansion layer of the optoelectronic device 10. The luminescence conversion layer 3 is arranged between the first electrode 11 and the second electrode 12 of the optoelectronic device and carries the operating current of the light-emitting semiconductor layer sequence 2.

[0054] In the further example of the Fig. 7 A layer stack is arranged between the light-emitting semiconductor layer sequence 2 and the second electrode 12 of the optoelectronic device 10, which forms a luminescence conversion layer 3 according to the example of the Fig. 3 forms. The layer stack contains alternating sublayers 3a, 3b, 3c of the luminescence conversion layer and transparent barrier layers 6 arranged between them, which have a transparent conductive oxide and are therefore electrically conductive. The sublayers 3a, 3b, 3c of the luminescence conversion layer 3 have, for example, ZnO:Eu, Ga and the transparent barrier layers ZnO:Ga or ITO.

[0055] In the examples of Fig. For simplicity, Figures 1 to 7 each represent an optoelectronic device with only one light-emitting semiconductor layer sequence 2. A luminescence conversion layer according to the principle proposed herein is particularly suitable for LED displays in which several pixels, each formed by a light-emitting semiconductor layer sequence, are arranged side by side. The optoelectronic device 10 can, in particular, be a multicolor LED display having a multitude of pixels, the pixels being designed to emit different colors. For example, the optoelectronic device can be an RGB display. In the case of a multicolor LED display, the luminescence conversion layer according to the principle proposed herein can be applied to at least the pixels of a first color.

[0056] In Fig. Figure 8 schematically shows a cross-sectional view of an optoelectronic device 10, which, by way of example, has two adjacent pixels 21, 22 for emitting different colors. The optoelectronic device 10 can have a large number of such pixels 21, 22, for example, at least 1000, at least 100,000, or even at least 1,000,000. The optoelectronic device 10 has several adjacent light-emitting semiconductor layer sequences 2, each of which is assigned to a pixel 21, 22 of the optoelectronic device 10. The luminescence conversion layer 3, which has a transparent conductive oxide with luminescence centers, is arranged at least over one pixel 21 of a first color. For example, the luminescence conversion layer 3 is a layer having ZnO:Eu,Ga. In this case, the Pixel 21 with the luminescence conversion layer 3 can, for example, be designed to emit red light.

[0057] In pixel 21 with the luminescence conversion layer 3, an additional transparent conductive oxide layer 7 is arranged as a current-expansion layer between the light-emitting semiconductor layer sequence 2 and the luminescence conversion layer 3. Alternatively, the layer structure of pixel 21 can be one of the other previously described configurations according to the Fig. The optoelectronic device 10 has at least one second pixel 22 that is not covered by a luminescence conversion layer 3. For example, in the second pixel 22, only the transparent conductive oxide layer 7 is arranged as a current-expansion layer on the light-emitting semiconductor layer sequence 2. In this case, the second pixel 22 emits the primary radiation of the light-emitting semiconductor layer sequence 2, for example, blue light or green light.

[0058] The optoelectronic component 10 can additionally have a plurality of further pixels 21 of the first color and further pixels 22 of the second color. Furthermore, the optoelectronic component 10 can have pixels of at least one further color. In particular, the optoelectronic component 10 can be a multicolor LED display, for example an RGB LED display.

[0059] The pixels 21, 22 of the optoelectronic device 10 are advantageously arranged on a common substrate 1, which can be a growth substrate for the light-emitting semiconductor layer sequences 2, for example, a sapphire substrate. Alternatively, the substrate 1 can be a support substrate onto which the light-emitting semiconductor layer sequences 2 have been transferred from a growth substrate. In one embodiment, a reflective and / or contrast-enhancing layer 8 is arranged below the substrate 1. An opaque layer 5 is preferably arranged between the pixels 21, 22 of the optoelectronic device 10.

[0060] Furthermore, it is possible that a cover layer 4 is arranged above pixels 21 and 22, which, for example, forms an encapsulation of the optoelectronic component. It is also possible that the cover layer 4 has an optical and / or electrical function. For example, the cover layer 4 can include at least one color filter or electrical circuit elements for controlling pixels 21 and 22.

[0061] In Fig. Figure 9 shows a further embodiment of the optoelectronic device 10 with multiple pixels 21, 22. This example differs from the previous example in that the luminescence conversion layer 3 and the additional transparent conductive oxide layer 7 of the at least one first pixel 21 are arranged between the substrate 1 and the light-emitting semiconductor layer sequence 2. Furthermore, in the at least one second pixel 22, which does not have a luminescence conversion layer, an additional conductive layer, for example a transparent conductive oxide layer 7, is arranged between the substrate 1 and the light-emitting semiconductor layer sequence 2.

[0062] The light-emitting semiconductor layer sequence 2 is contacted by means of a first electrode 11 and a second electrode 12, wherein in this example the first electrode 11 is arranged on the further transparent conductive oxide layer 7 and the second electrode is arranged on a top surface of the light-emitting semiconductor layer sequence. Additionally, a reflective and / or a contrast-enhancing layer 8, in particular a black matrix, can be arranged between the substrate 1 and the light-emitting semiconductor layer sequence 2. Since no luminescence conversion layer is arranged in the second pixel 22, a filler layer 9 can be provided to compensate for the height difference to the first pixel 21; this filler layer can, for example, be arranged between the substrate 1 and the reflective or contrast-enhancing layer 8.

[0063] A first color filter layer 41 for a first color can be arranged above the first pixel 21, and a second color filter or luminescence conversion layer 42 for a second color can be arranged above the second pixel 22. For example, the first color filter layer 41 can be designed to transmit the converted radiation from the first pixel, such as red light, and the second color filter or luminescence conversion layer 42 can be designed to filter out the primary radiation from the second pixel 22, such as blue or green light, or to generate the second color by luminescence conversion. An opaque layer 5 is advantageously arranged between the color filters 41 and 42, as well as between the pixels 21 and 22.

[0064] In Fig. 10 is a variation of the example of Fig. Figure 9 shows that this differs from the previous example in that the first pixel 21 and the second pixel 22 have the same layer structure. This simplifies the manufacturing process. In this example, the emission of light of different colors can be achieved by placing a first color filter layer 41 over the first pixel 21 for a first color and a second color filter or luminescence conversion layer 42 over the second pixel 22 for a second color. For example, the first color filter layer 41 can be designed to filter out the converted radiation from the first pixel, such as red light, and the second color filter or luminescence conversion layer 42 can be designed to filter out the primary radiation from the second pixel 22, such as blue or green light, or to generate the second color through luminescence conversion.An opaque layer 5 is advantageously arranged between the color filter or luminescence conversion layers 41, 42 and between the pixels 21, 22. The electrical contacting of the light-emitting semiconductor layer sequences 2 can be effected by a first electrode 21 and a second electrode 22, each of which is electrically connected to the transparent conductive oxide layer 7 and the top surface of the light-emitting semiconductor layer sequence 2.

[0065] In Fig. 11 is a variation of the example of Fig.Figure 10 shows that this example differs from the previous example in the type of electrical contacting. In the example shown here, substrate 1 is a support substrate that provides electrical control for pixels 21 and 22. For example, substrate 1 can contain circuits based on thin-film transistors (TFTs). Alternatively, passive matrix elements can be arranged in substrate 1, which can be particularly advantageous for use in small displays. The light-emitting semiconductor layer sequences 2 are contacted from the side of substrate 1 by means of a first electrode 11 and a second electrode 12.

[0066] The invention is not limited by the description based on the exemplary embodiments. Reference symbol list 1 substrate 2 light-emitting semiconductor layer sequence 3 Luminescence conversion layer 3a Sublayer of the luminescence conversion layer 3b Sublayer of the luminescence conversion layer 3c sublayer of the luminescence conversion layer 4 Top layer 5 opaque layers 6 Barrier layer 7 transparent conductive oxide layer 8 reflective or contrast-enhancing layers 9 Filler layer 10 optoelectronic component 11 first electrode 12 second electrode 13 Passivation layer 21 first pixel 22 second pixel 41 first color filter layer 42 second color filter or luminescence conversion layer

Claims

[1] Optoelectronic component (10), comprising - at least one light-emitting semiconductor layer sequence (2), and - at least one luminescence conversion layer (3) comprising a transparent conductive oxide and at least one dopant for the formation of luminescence centers; wherein the luminescence conversion layer (3) has several sublayers (3a, 3b, 3c) arranged alternately in a layer stack, with a transparent barrier layer (6) arranged between each of the sublayers. [2] Optoelectronic device according to claim 1, wherein the transparent conductive oxide is ZnO. [3] Optoelectronic device according to claim 1, wherein the transparent conductive oxide is IZO, Ga2O3 or IGZO. [4] Optoelectronic device according to claim 1, wherein the transparent conductive oxide is In2O3, SnO2, IMO or ITO. [5] Optoelectronic device according to any of the preceding claims, wherein the dopant is Eu, Er, Tb or Ce. [6] Optoelectronic device according to one of the preceding claims, wherein the luminescence conversion layer (3) contains at least one further dopant. [7] Optoelectronic device according to claim 6, wherein the further dopant is Ga, Al, K, Na or Li. [8] Optoelectronic device according to any of the preceding claims, wherein the luminescence conversion layer (3) comprises ZnO:Eu, ZnO:Eu, Ga or ZnO:Eu, Al. [9] Optoelectronic device according to one of the preceding claims, wherein the at least one luminescence conversion layer (3) is electrically conductive and is arranged between a first electrode (11) and a second electrode (12) of the light-emitting semiconductor layer sequence (2). [10] Optoelectronic device according to one of the preceding claims, wherein the at least one transparent barrier layer (6) is between 1 nm and 200 nm thick. [11] Optoelectronic device according to one of the preceding claims, wherein the multiple sublayers (3a, 3b, 3c) are between 10 nm and 10 µm thick. [12] Optoelectronic device according to one of the preceding claims, wherein the at least one transparent barrier layer (6) is a transparent conductive oxide layer. [13] Optoelectronic device according to one of the preceding claims, wherein the at least one light-emitting semiconductor layer sequence (2) emits UV radiation, blue light or green light, and wherein the luminescence conversion layer (3) converts the emitted light into red light or green light. [14] Optoelectronic component according to any of the preceding claims, wherein the optoelectronic device (10) is a multicolor LED display having a plurality of pixels (21, 22) each having a light-emitting semiconductor layer sequence (2), wherein the pixels (21, 22) are provided for the emission of light of a first color and at least one further color, and wherein the luminescence conversion layer (3) is arranged at least on the pixels (21) of the first color. [15] Optoelectronic component according to claim 14, wherein the first color is red or green. [16] Optoelectronic device according to one of claims 14 or 15, wherein the light-emitting semiconductor layer sequences (2) of the pixels (21, 22) are based on the same semiconductor material. [17] Optoelectronic device according to one of the preceding claims, wherein the at least one light-emitting semiconductor layer sequence (2) and / or the at least one luminescence conversion layer (3) is surrounded laterally by an opaque layer (5).

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