Organic light-emitting diode and method for producing an organic light-emitting diode

Abstract

Organic light-emitting diode (1) with - a substrate (2) with a substrate top (20), - an electrically conductive grid structure (8) on the substrate top surface (20) to a current distribution, - an electrically conductive particle layer (3) applied to the substrate surface (20) and in which the lattice structure (8) is embedded, such that the particle layer (3) completely or partially covers the lattice structure (8) on side surfaces oriented transversely to the substrate surface (20), - an organic layer sequence (4) located directly on the particle layer (3), and - a cover electrode (5) which is attached to the organic layer sequence (4), wherein - the particle layer (3) contains scattering particles (31) with a first mean diameter and electrically conductive conducting particles (32) with a smaller, second mean diameter and is free of a matrix material, - the scattering particles (31) together with the guide particles (32) are densely packed in the particle layer (3), - the particle layer (3) together with the lattice structure (8) form a substrate electrode (38) for the organic layer sequence (4), and - the grid structure (8) seen in top view of the substrate top (20) has a plurality of honeycombs, such that a material of the grid structure (8) completely encloses the honeycombs all around, with an interior of the honeycombs being free of the material of the grid structure (8).

Description

[0001] An organic light-emitting diode (OLED) is described. Furthermore, a method for manufacturing an organic light-emitting diode is described.

[0002] The following publications concern organic light-emitting diodes: DE 10 2015 104 793 A1, US 2014 / 0 008 620 A1, DE 10 2013 005 763 A1, DE 10 2005 002 837 A1, US 2011 / 0 001 153 A1.

[0003] One problem to be solved is to specify an organic light-emitting diode that efficiently emits homogeneous light over a larger area.

[0004] This problem is solved, among other things, by an organic light-emitting diode and by a method with the features of the independent claims. Preferred embodiments are the subject of the dependent claims.

[0005] According to at least one embodiment, the organic light-emitting diode (OLED) is configured to generate visible light. For example, the OLED emits blue, green, yellow, orange, or red light. It is also possible for the OLED to emit mixed-color light, particularly white light, during its intended use.

[0006] The organic light-emitting diode (OLED) comprises a substrate. The substrate has a substrate surface. The substrate can be the mechanically load-bearing and stabilizing component of the OLED. The substrate can be mechanically rigid or mechanically flexible and thus bendable.

[0007] An electrically conductive grid structure is located on the top surface of the substrate. This grid structure is designed to ensure current spreading and a uniform lateral current distribution across the substrate. The grid structure, viewed from above, consists of numerous honeycombs, with the grid material completely enclosing each honeycomb, while the interior of each honeycomb remains free of the grid material. The grid structure can be applied directly to the top surface. Alternatively, an additional layer can be placed between the substrate and the grid structure, particularly to improve adhesion of the grid structure to the substrate. Such a grid structure is also known as a busbar.

[0008] The light-emitting diode includes a particle layer. The particle layer is electrically conductive, at least in one direction perpendicular to the substrate surface, preferably in both directions perpendicular and parallel to the substrate surface.

[0009] The particle layer is located, in particular, directly on the substrate surface. In other words, a material from the particle layer then contacts the substrate surface and a material from the substrate. Preferably, the particle layer and the substrate surface are in contact over their entire area.

[0010] The lattice structure is embedded in the particle layer. This means that the particle layer completely or partially covers the lattice structure on side surfaces oriented transversely to the substrate surface. In the direction parallel to the substrate surface, the particle layer is directly adjacent to the lattice structure.

[0011] An organic layer sequence is applied to the particle layer. Preferably, the organic layer sequence is located directly on the particle layer. The organic layer sequence includes at least one layer based on at least one organic material and configured to generate radiation, in particular light. The organic layer sequence may include further layers such as charge carrier injection layers, charge carrier transport layers, charge carrier barrier layers, and / or charge carrier generation layers.

[0012] The organic light-emitting diode (OLED) includes a cover electrode. The cover electrode is attached to the organic layer sequence. That is, the cover electrode is located on the side of the organic layer sequence facing away from the substrate. It is possible that the cover electrode is located directly on the organic layer sequence.

[0013] The particle layer contains scattering particles. These scattering particles are designed to scatter light. In particular, the scattering particles scatter the light generated in the organic layer sequence during the intended use of the organic light-emitting diode (OLED). The scattering particles enable increased light extraction efficiency from the OLED. Therefore, the particle layer can be considered a light-scattering layer. The particle layer thus performs two main functions simultaneously: light scattering and electrical conduction.

[0014] The particle layer comprises a large number of conductive particles. These conductive particles are electrically conductive. The electrical conductivity of the particle layer is largely determined and adjusted by these conductive particles. The number of conductive particles exceeds the number of scattering particles, for example, by a factor of at least 10 or 10⁻⁶. 3 or 10 5 .

[0015] The scattering particles have a first mean diameter, and the guide particles have a second mean diameter. The second mean diameter is smaller than the first mean diameter. Preferably, the guide particles are so-called nanoparticles, i.e., particles with a mean diameter of at most 100 nm. More preferably, the scattering particles are microparticles, i.e., particles with a mean diameter between 0.1 µm and 10 µm inclusive. The mean diameter is defined in particular as the diameter d. 50understood in Q0.

[0016] The scattering particles are densely packed together with the guide particles in the particle layer. Densely packed preferably means that the packing density and volume filling are on the order of the closest possible packing of spheres of equal size. For example, the volume filling of the particle layer by the scattering particles together with the guide particles is at least 67%, 70%, 75%, 80%, 85%, 90%, or 95%. A packing density above that of the closest possible packing of spheres of equal size can be achieved by having the scattering particles and the guide particles have different mean diameters.

[0017] According to at least one embodiment, the volume fraction of the scattered particles in the particle layer is at most 50% or 30% or 15% or 10% or 8%.

[0018] The lattice structure, together with the particle layer, forms a substrate electrode for the organic layer sequence. This means that the organic layer sequence is supplied with current via the substrate electrode, together with the cover electrode. The organic layer sequence preferably borders directly on the substrate electrode and / or the cover electrode across its entire surface.

[0019] The organic light-emitting diode (OLED) comprises a substrate with a substrate surface, an electrically conductive grid structure for current distribution, and an electrically conductive particle layer deposited on the substrate surface. The grid structure is embedded within the particle layer. An organic sequence of layers for generating radiation is located directly on the particle layer. A cover electrode is mounted on the organic layer sequence. The particle layer consists of scattering particles with a first, medium diameter and electrically conductive guide particles with a smaller, second, medium diameter. The scattering particles and guide particles are densely packed within the particle layer. The particle layer, together with the grid structure, forms a substrate electrode for the organic layer sequence.

[0020] To achieve efficient light extraction from an organic light-emitting diode (OLED), particle layers are typically used. These particle layers are usually composed of scattering particles embedded in an electrically insulating matrix, which is typically made of glass or a polymer. Such a particle layer, which is electrically insulating overall, is generally located between a substrate and an anode. However, the fabrication of such particle layers is relatively expensive. Furthermore, these particle layers often exhibit relatively low electrical conductivity, which limits the maximum achievable size of an organic light-emitting diode.

[0021] The electrically conductive particle layer described here, in combination with the grid structure, makes it possible either to completely eliminate the need for a separate anode or to arrange the particle layer directly on the side of the anode facing away from the substrate. This simplifies the fabrication of the particle layer, particularly with regard to the fabrication of the anode, and simultaneously enables the efficient and homogeneous emission of large-area organic light-emitting diodes.

[0022] According to at least one embodiment, the particle layer and the lattice structure are flush with each other in the direction away from the substrate surface. Thus, the lattice structure and the particle layer together can form a flat surface on which the organic layer sequence is applied. In this case, the organic layer sequence can contact both the lattice structure and the particle layer. Current is preferably injected into the organic layer sequence only via the particle layer and not via the lattice structure. In other words, an electric current is distributed across the lattice structure, locally injected into the particle layer, and then conducted from the particle layer into the organic layer sequence.

[0023] According to at least one embodiment, the particle layer extends beyond the lattice structure in a direction away from the substrate surface. The particle layer may completely or only partially cover the lattice structure. Alternatively, the lattice structure may be free of the particle layer on a side facing away from the substrate.

[0024] According to at least one embodiment, the particle layer above the lattice structure forms a flat, continuous surface. The organic layer sequence is applied directly to this surface. In this case, the organic layer sequence is spaced apart from the lattice structure.

[0025] According to at least one embodiment, the particle layer and the lattice structure have the same or approximately the same thickness. For example, the thicknesses are the same with a tolerance of at most 30%, 20%, or 10%, based on the thickness of the lattice structure. In the case that the particle layer extends beyond the lattice structure, the particle layer above the lattice structure is then comparatively thin.

[0026] According to at least one embodiment, the coverage of the substrate surface by the grid structure is at least 3%, 10%, or 20%. Alternatively or additionally, the coverage is at most 60%, 30%, 25%, or 15%. This means that a relatively large proportion of the substrate surface is covered by the grid structure.

[0027] According to at least one embodiment, the lattice structure comprises or consists of one or more metal layers. For example, the lattice structure comprises three metal layers, in particular two adhesion-promoting layers and one current-conducting layer.

[0028] According to at least one embodiment, the grid structure has ribs that border the meshes. The mean line width of the grid structure and / or the mean width of the ribs, particularly when viewed from above on the substrate surface, is preferably at least 1 µm, 2 µm, 5 µm, 10 µm, or 20 µm and / or at most 200 µm, 120 µm, 70 µm, 40 µm, or 15 µm. In particular, the ribs are so narrow that they are not visible to the naked eye during the intended use of the organic light-emitting diode.

[0029] According to at least one embodiment, the mean mesh size of the grid structure is at least 0.1 mm, 0.5 mm, or 0.8 mm. Alternatively or additionally, the mean mesh size is at most 5 mm, 3 mm, 1.5 mm, or 1 mm. The mean mesh size is, in particular, the mean diameter of the meshes as seen from a top view of the substrate surface.

[0030] According to at least one embodiment, the lattice structure has a thickness of at least 100 nm, 200 nm, 300 nm, or 500 nm. Alternatively or additionally, the thickness of the lattice structure is at most 10 µm, 5 µm, 1 µm, or 0.4 µm. Preferably, the thickness of the particle layer is of a similar nature.

[0031] According to at least one embodiment, the grid structure, viewed from above, is formed by a triangular, square, pentagonal, hexagonal, or octagonal pattern. In other words, the meshes are designed as triangles, squares, pentagons, hexagons, and / or octagons. The patterns and the meshes are preferably arranged regularly.

[0032] Alternatively, the grid structure can also be irregular and / or statistically distributed and / or randomly designed. It can consist of a triangular, square, pentagonal, hexagonal, or octagonal basic pattern that is modified and / or altered.

[0033] According to at least one embodiment, the struts of the grid structure are rectangular in cross-section. Alternatively, the struts may taper in cross-section towards the substrate surface. In this case, the struts are approximately triangular, trapezoidal, semicircular, hyperbolic, and / or parabolic in cross-section.

[0034] According to at least one embodiment, the surface conductivity of the substrate electrode is at least 1 mS·□, 0.1 S·□, 1 S·□, or 4 S·□. Alternatively or additionally, the surface conductivity is at most 100 S·□, 20 S·□, or 10 S·□. The nominal conductivity is preferably constant or approximately constant across the entire substrate electrode.

[0035] According to at least one embodiment, the luminescent area of ​​the organic light-emitting diode is comparatively large. In particular, the luminescent area is a continuous surface that is not functionally subdivided into smaller units. Specifically, the luminescent area is at least 0.01 × 0.01 m². 2 or 0.05 × 0.05 m 2 or 0.1 × 0.1 m 2 and / or at most 1 × 1 m 2 or 0.7 × 0.7 m 2 or 0.3 × 0.3 m 2 .

[0036] According to at least one embodiment, the scattering particles and the conducting particles are made of different materials. In particular, the difference between the refractive indices of the materials of the scattering particles and the conducting particles is at least 0.1, 0.2, or 0.3. The refractive indices preferably refer to a wavelength of maximum intensity of the radiation produced by the light-emitting diode in its intended use and to room temperature.

[0037] According to at least one embodiment, the mean diameters of the guide particles and the scattering particles differ by at least a factor of 1.5, 2, 3, 5, or 10. Preferably, the guide particles, and alternatively or additionally the scattering particles, exhibit a relatively large diameter distribution. This can mean that at most 50% or 65% of the guide particles have a diameter that lies between 50% and 150% of the mean diameter of the respective particles. A particularly dense packing in the particle layer can be achieved through a relatively large diameter distribution, especially of the guide particles.

[0038] According to at least one embodiment, the substrate is homogeneously formed from a single material. In particular, the substrate is then an electrically insulating substrate. Specifically, in this case, the substrate surface is electrically insulating. In particular, it is possible that the substrate is free of scattering particles or scattering centers.

[0039] According to at least one embodiment, the particle layer of the light-emitting diode consists of scattering particles and conducting particles. This means that there is no matrix material in which the scattering and conducting particles are embedded. The term "consists" refers only to solids and liquids. It is therefore possible that evacuated cavities or small spaces filled with a gas exist between the particles of the particle layer. If gas-filled spaces are present, these spaces are preferably filled with an inert gas such as nitrogen or argon. In the case of such a gas, its pressure at room temperature is preferably not, or not significantly, above normal atmospheric pressure.

[0040] According to at least one embodiment, the mean diameter of the scattering particles is at least 50 nm, 100 nm, or 150 nm. Alternatively or additionally, this mean diameter is at most 2 µm, 1 µm, or 0.4 µm. Furthermore, the guide particles preferably have a mean diameter of at least 2 nm, 5 nm, or 10 nm and / or at most 100 nm, 50 nm, or 20 nm.

[0041] According to at least one embodiment, the scattering particles are made of an electrically insulating material. In particular, the scattering particles comprise or consist of one or more of the following materials: TiO2, Ta2O5, ZrO2, CrO2, AlN, SiO2

[0042] According to at least one embodiment, the scattering particles are also made of an electrically conductive material. In particular, the scattering particles are then made of a transparent conductive oxide, or TCO for short, with a relatively high optical refractive index.

[0043] According to at least one embodiment, the particle layer has two or more than two sublayers that differ from each other with respect to their optical properties. In particular, one of the sublayers is more strongly scattering of light than another sublayer.

[0044] According to at least one embodiment, the particle layer has a first sublayer located directly on the substrate surface. The first sublayer contains a higher concentration of scattering particles than a second sublayer of the particle layer, the second sublayer being located directly adjacent to the organic layer sequence. For example, the concentration of scattering particles in the sublayers differs by at least a factor of 2, 3, 5, or 10. In particular, it is possible that the second sublayer is free of scattering particles and / or consists solely of the guide particles.

[0045] In the first sublayer, the scattering particles are preferably homogeneously and statistically distributed. Alternatively, it is possible that the scattering particles, relative to the guide particles, are more heavily sedimented in the entire particle layer or in the first sublayer and show an increasing concentration towards the substrate surface.

[0046] According to at least one embodiment, the mean roughness of a main surface of the particle layer facing away from the substrate is at most 50 nm, 25 nm, 15 nm, or 10 nm. It is possible that the mean roughness, also known as R, a This is defined as a roughness that is less than 25% or 10% of the mean diameter of the scattering particles. In particular, the mean roughness is at most 50% or 100% of the mean diameter of the guide particles.

[0047] According to at least one embodiment, the substrate surface has an average roughness of at most 15 nm, 10 nm, or 5 nm. In particular, the average roughness of the main surface of the particle layer facing away from the substrate is at most 3, 2, or 1.5 times greater than the average roughness of the substrate surface.

[0048] According to at least one embodiment, the conductive particles are percolated within the particle layer. In other words, a continuous path, particularly for conducting electricity, is formed by the conductive particles in the particle layer. It is possible that only the conductive particles, and thus not the scattering particles, are percolated. This means that no continuous paths are formed by the scattering particles alone.

[0049] According to at least one embodiment, the light-emitting diode (LED) emits the light generated in the LED partially or completely through the particle layer and through the substrate during intended operation. It is possible that the LED emits light only from a single main surface where the substrate is located.

[0050] According to at least one embodiment, the volume fraction of the scattering particles in the particle layer is at least 1.5%, 3%, or 5%. Alternatively or additionally, this volume fraction is at most 20%, 15%, or 10%. Preferably, the volume fraction is between 5% and 10% inclusive.

[0051] According to at least one embodiment, the particle layer is free or substantially free of organic materials. This can mean that the particle layer consists of at least 90%, 95%, or 98% by mass of inorganic materials. In particular, the functionality of the particle layer, i.e., its scattering effect and electrical conductivity, is due exclusively to inorganic materials. The high proportion of inorganic materials is achieved, in particular, by the fact that the particle layer is free of a matrix material for the scattering particles or the conducting particles. The predominant use of inorganic materials results in increased service life and resistance to external environmental influences.

[0052] According to at least one embodiment, the thickness of the substrate electrode is constant, in particular with a tolerance of at most 50% or 25% or 10% of the mean diameter of the scattering particles.

[0053] According to at least one embodiment, the cover electrode is a metallic electrode. In particular, the cover electrode is designed as a metal mirror and has, for example, aluminum, silver and / or gold as its main component, or consists of a metal alloy of these or of the aforementioned materials.

[0054] According to at least one embodiment, the LED appears milky-cloudy and / or whitish to an observer when switched off. This color impression of the switched-off LED is caused in particular by the particle layer.

[0055] Furthermore, a method for producing an organic light-emitting diode (OLED) is disclosed. The method produces an OLED as described in connection with one or more of the embodiments mentioned above. Features of the method are therefore also disclosed for the OLED, and vice versa.

[0056] In at least one embodiment, the method comprises the following steps: A) Provide the substrate with the substrate top side down, B) Creating the lattice structure on the substrate surface, C) Producing a solution comprising or consisting of at least a solvent, the scattering particles and the guiding particles, D) Applying the solution to the substrate surface so that the lattice structure is embedded by the solution and the finished particle layer, E) Drying the solution by removing the solvent and thus forming the particle layer, and F) Applying the organic layer sequence to the particle layer.

[0057] With the exception of step C), which can also be performed before steps A) and B), the individual steps are preferably carried out in the specified order.

[0058] The solvent is, in particular, a solvent that evaporates without leaving a residue, for example, through an increase in temperature and / or a decrease in pressure. The solvent is formed, for example, by an alcohol, an alkane, an alkene, a benzene, an ether, a ketone, a lactone, a lactam, a nitrile, a sulfoxide, or a sulfone, or by mixtures thereof. Examples of such solvents include isopropanol, ethanol, acetone, 1-methoxy-2-propanol, or mixtures thereof.

[0059] According to at least one embodiment, the solution is applied via inkjet printing, slot dye deposition, screen printing, or squeegeeing. Such application methods make it possible to apply the particle layer locally and thus in a structured manner.

[0060] According to at least one embodiment, the lattice structure is applied using a printing process such as inkjet printing. This eliminates the need for subsequent removal of previously applied lattice material. Alternatively, the lattice structure is first applied over the entire surface, for example by vapor deposition, even in multiple layers, and then subsequently structured, for example, by photolithography.

[0061] The organic light-emitting diode (OLED) and the method described herein are explained in more detail below with reference to the drawing and exemplary embodiments. Identical reference symbols indicate identical elements in the individual figures. However, the figures are not to scale; rather, individual elements may be exaggerated for clarity.

[0062] They show: Fig. 1 a schematic sectional view and a schematic top view of an embodiment of an organic light-emitting diode described herein, Fig. 2 schematic sectional views of exemplary embodiments of substrate electrodes for the organic light-emitting diodes described here, Fig. 3 and Fig. 5 schematic sectional views of exemplary embodiments of the organic light-emitting diodes described here, Fig. 4 schematic sectional views of process steps of a process described here for the production of an organic light-emitting diode described here, and Fig. 6 and Fig. 7 schematic representations of the electrical surface conductivity of substrate electrodes for the organic light-emitting diodes described here.

[0063] In Fig. Figure 1 shows an embodiment of an organic light-emitting diode 1. The light-emitting diode 1 has a substrate 2 with a substrate surface 20. The translucent, electrically insulating substrate 2 comprises, for example, a glass base body onto which an electrically conductive grid structure 8 is directly applied.

[0064] Directly on the substrate surface 20 is a particle layer 3 in which the lattice structure 8 is arranged. The particle layer 3 extends beyond the lattice structure 8 in the direction away from the substrate surface 20. Furthermore, the lattice structure 8 is completely covered by the particle layer 3. The lattice structure 8 has a trapezoidal cross-section, see [reference]. Fig. 1A. Viewed from above, the grid structure 8 is designed as a regular, square grid, see Fig. 1B.

[0065] The particle layer 3 is composed of relatively large scattering particles 31, which are configured to scatter light. Furthermore, the particle layer 3 comprises a multitude of conducting particles 32, which are made of an electrically conductive and transparent material such as ITO. One example of the material used for the scattering particles 31 is electrically insulating titanium dioxide. Due to the difference in refractive index between the scattering particles 31 and the conducting particles 32, the scattering particles 31 act as light scatterers.

[0066] In the particle layer 3, the conductive particles 32 are densely packed together with the scattering particles 31, as is the case in all other embodiments. In particular, the particle layer 3 is free of a matrix material. Since the conductive particles 32 are percolated in the particle layer 3 and are made of an electrically conductive material, the particle layer 3 as a whole is electrically conductive. The thickness d of the particle layer 3 is, for example, between 300 nm and 800 nm, and in particular approximately 470 nm.

[0067] An organic layer sequence 4 is deposited directly onto the particle layer 3. The organic layer sequence 4 is shown in a highly simplified form. The organic layer sequence 4 includes at least one active zone for generating light. This light generated in the active zone 4 is scattered by the scattering particles 31, thereby increasing the light extraction efficiency from the light-emitting diode 1.

[0068] A cover electrode 5 is applied directly to the organic layer sequence 4. The cover electrode 5 is preferably a metal layer or a metal layer system. The cover electrode 5 acts as a reflector for the radiation generated in the organic layer sequence 4. Current is injected into the organic layer sequence 4 by means of the particle layer 3 and the cover electrode 5, both of which are made of inorganic materials.

[0069] The particle layer 3 together with the lattice structure 8 forms a substrate electrode 38. The lattice structure 8 causes a lateral current distribution across the substrate surface 20. Current is injected into the organic layer sequence 4 via the particle layer 3. Due to the lattice structure 8, which exhibits a comparatively high electrical conductivity, large-area light-emitting diodes 1 can be achieved. Furthermore, the thickness d of the substrate electrode 38 is relatively small due to the lattice structure 8, thus enabling high transparency of the substrate electrode 38.

[0070] The substrate electrode 38 can be electrically isolated via an electrical contact surface 9a. The same applies to the cover electrode 5 with regard to the electrical contact surface 9b. The contact surfaces 9a, 9b are preferably located outside the encapsulation layer 7.

[0071] Optionally, an encapsulation layer 7 is located on one side of the cover electrode 5 facing away from the substrate 2. Contrary to what is shown, the encapsulation layer 7 can also be composed of several sublayers. For the sake of simplicity, other components of the organic light-emitting diode 1, such as electrical connection areas, current distribution rails, mounting devices, or further encapsulation layers, are not shown.

[0072] In the Fig. Figures 2A to 2D schematically show further embodiments of the substrate electrode 38. The scattering particles 31 and the conducting particles 32 are only indicated. Fig. In cross-section, the lattice structure 8 in 2A is rectangular. Unlike in Fig. As shown in Figure 2A, the lattice structure 8 preferably does not extend beyond the particle layer 3, but rather is flush with the particle layer 3.

[0073] According to Fig. In section 2B, the lattice structure 8 is triangular in shape. Fig. Figure 2C shows that the lattice structure 8 is approximately parabolic in cross-section. In particular, lattice structures 8 such as those shown in Fig. The 2C images shown can be produced using an inkjet printing process. The lattice structures, as shown in Fig. 2A, shown, are produced, for example, via photolithography.

[0074] The lattice structure 8 can be seen Fig. The 2D structure, as well as all other embodiments, can be multilayered. A thicker conductive layer 82 is located between two adhesion-promoting layers 81, 83. The layers 81, 82, 83 are formed, for example, by Cr, Al, Cr or by Mo, Al, Mo, where the aluminum can also be replaced by silver. The layer thicknesses of the layers 81, 82, 83 are, for example, 100 nm, 500 nm, and 100 nm. The conductive layer 82 can also be thinner and, for example, have a thickness of only 300 nm.

[0075] Contrary to the representation in Fig. In 2D, the lattice structure 8 can also be formed by a single layer that includes or consists of, for example, aluminum, silver, copper and / or gold.

[0076] In the exemplary embodiment as in Fig. As can be seen in Figure 3, the particle layer 3 has two sublayers. The lattice structure 8 is shown for the sake of simplicity. Fig. 3 not drawn. The sublayers are in Fig. The layers are schematically separated by a dash-dot line. However, this separation into sublayers is fictitious and does not correspond to any real material boundary or seam within particle layer 3.

[0077] The first sublayer, located directly on the substrate surface 20, contains both the scattering particles 31 and the guide particles 32. The second sublayer, located directly adjacent to the organic layer sequence 4, consists exclusively or predominantly of the guide particles 32. Since the guide particles 32 have a smaller average diameter, this division of the particle layer 3 into two sublayers results in a flatter, less rough main surface of the particle layer 3 adjacent to the organic layer sequence 4.

[0078] For example, the mean roughness of a main surface of the particle layer 3 on the organic layer sequence 4 is relatively low, at approximately 15 nm. In comparison, the roughness of the substrate surface 20 is in the range of 5 nm to 10 nm. In other words, despite the particle structure in the particle layer 3, the mean roughness at the surface where the organic layer sequence 4 is applied is not significantly increased. Materials of the organic layer sequence 4 preferentially penetrate the particle layer 3 only within the roughness of this main surface. The spaces between the guide particles 32 and / or the scattering particles 31 are preferably evacuated, but can also be filled with an inert gas.

[0079] In Fig. Figure 4 schematically depicts the process steps for the production of the organic light-emitting diode 1, whereby the grid structure 8 is again omitted for the sake of simplicity. Fig. 4A A solution 6 is applied to the top of the substrate 20.

[0080] Solution 6 comprises a solvent 60 or a mixture of several solvents. Scatter particles 31 and guide particles 32 are present in the solvent 60, preferably homogeneously distributed. To stabilize the particles 31 and 32 in the solvent 60 and to prevent agglomeration, particularly of the guide particles 32, the scatter particles 31 and / or the guide particles 32 can be provided with an organic coating. In the finished particle layer 3, this organic coating, which may optionally be present in all other embodiments as well, has no function. In particular, this organic coating does not act as a binder between the particles, nor as an electrically conductive medium, nor as a light-scattering component. Accordingly, organic materials constitute only a very small mass fraction in the finished particle layer.

[0081] In Fig. Figure 4B shows the resulting particle layer 3. The solvent 60 preferably evaporates completely and without residue, so that the densely packed particle layer 3 is formed.

[0082] In Fig. Figure 5 shows another embodiment of the organic light-emitting diode 1. The encapsulation layer 7 partially covers the contact surfaces 9a, 9b. In cross-section, the encapsulation layer 7 is U-shaped.

[0083] In Fig. 6 is a coverage C with respect to a surface conductivity σ, in Fig. 7 the surface conductivity σ against a mesh size E of the grid structure 8 plotted.

[0084] The surface conductivity σ increases approximately linearly at low coverage levels C. Preferred surface conductivities σ are achieved at coverage levels C of a few tens of percent. Preferably, the coverage level C is approximately 30%.

[0085] In the double-logarithmic representation of the Fig. Figure 7 shows that the surface conductivity σ depends on the mesh size E. Particularly preferred ranges for the mesh size E are in the range of 0.5 mm to 1 mm.

[0086] Depending on the size of the organic light-emitting diode 1, which can have edge lengths on the order of several decimeters, the desired surface conductivity σ can be specifically adjusted by the parameters mesh size E, thickness d of the substrate electrode 38, thickness of the grid structure 8 and materials of the substrate electrode 38, for example by means of the Fig. 6 and / or 7 to achieve high efficiency. Reference symbol list 1 organic light-emitting diode 2 Substrat 20 Substrate top 3 electrically conductive particle layer 31 scatter particles 32 electrically conductive conductive particles 38 Substrate electrode 4 organic layer sequence 5 Cover electrode 6 Solution 60 solvents 7 Encapsulation layer 8 Grid structure 81 first metal layer / adhesion layer 82 second metal layer / conducting layer 83 third metal layer / adhesion layer 9 electrical contact surfaces C Coverage rate in percent d thickness of the substrate electrode E Mesh size σ electrical surface conductivity in S·□

Claims

[1] Organic light-emitting diode (1) with - a substrate (2) with a substrate top (20), - an electrically conductive grid structure (8) on the substrate top surface (20) to a current distribution, - an electrically conductive particle layer (3) applied to the substrate surface (20) and in which the lattice structure (8) is embedded, such that the particle layer (3) completely or partially covers the lattice structure (8) on side surfaces oriented transversely to the substrate surface (20), - an organic layer sequence (4) located directly on the particle layer (3), and - a cover electrode (5) which is attached to the organic layer sequence (4), wherein - the particle layer (3) contains scattering particles (31) with a first mean diameter and electrically conductive conducting particles (32) with a smaller, second mean diameter and is free of a matrix material, - the scattering particles (31) together with the guide particles (32) are densely packed in the particle layer (3), - the particle layer (3) together with the lattice structure (8) form a substrate electrode (38) for the organic layer sequence (4), and - the grid structure (8) seen in top view of the substrate top (20) has a plurality of honeycombs such that a material of the grid structure (8) completely encloses the honeycombs all around, with an interior of the honeycombs being free of the material of the grid structure (8). [2] Organic light-emitting diode (1) according to the preceding claim, wherein the lattice structure (8) and the particle layer (3) are flush with each other in the direction away from the substrate top surface (20), so that the lattice structure (8) and the particle layer (3) together form a flat surface on which the organic layer sequence (4) is applied. [3] Organic light-emitting diode (1) according to claim 1, wherein the particle layer (3) extends beyond and completely covers the lattice structure (8) in the direction away from the substrate top surface (20), such that the particle layer (3) forms a flat surface onto which the organic layer sequence (4) is applied. [4] Organic light-emitting diode (1) according to one of the preceding claims, wherein the particle layer (3) and the lattice structure (8) have the same thickness with a tolerance of at most 30% of the thickness of the lattice structure (8). [5] Organic light-emitting diode (1) according to any one of the preceding claims, where the degree of coverage of the substrate surface (20) by the grid structure (8) is between 3% and 30% inclusive, wherein the lattice structure (8) consists of one or more metal layers (81, 82, 83). [6] Organic light-emitting diode (1) according to any one of the preceding claims, where the lattice structure (8) has a mean line width between 10 µm and 200 µm inclusive, wherein a mean mesh size of the lattice structure (8) is between 0.1 mm and 3 mm inclusive and the thickness of the lattice structure (8) is at least 200 nm and at most 10 µm, and wherein the lattice structure (8) is formed by a regular triangular, square or hexagonal pattern. [7] Organic light-emitting diode (1) according to one of the preceding claims, wherein the struts of the grid structure (8) have a rectangular, triangular, trapezoidal or parabolic shape in cross-section. [8] Organic light-emitting diode (1) according to any one of the preceding claims, in which the grid structure (8) and the particle layer (3) are each applied directly to the substrate surface (20), wherein the particle layer (3) consists of the scattering particles (31) and the guide particles (32), and wherein the mean diameter of the scattering particles (31) is between 100 nm and 400 nm inclusive and the mean diameter of the guiding particles (32) is between 5 nm and 50 nm inclusive. [9] Organic light-emitting diode (1) according to one of the preceding claims, wherein the particle layer (3) in a first sublayer directly on the substrate top surface (20) has a higher concentration of the scattering particles (31) than in a second sublayer directly on the organic layer sequence (4), wherein the first and second sublayers are directly adjacent to each other and the concentrations of the scattering particles (31) differ from each other by at least a factor of 3, and wherein the scattering particles (31) are electrically insulating. [10] Organic light-emitting diode (1) according to any one of the preceding claims, wherein the guide particles (32), but not the scattering particles (31), are percolated in the particle layer (3), and wherein the light-emitting diode (1) emits light only through the particle layer (3) and the substrate (2) during normal operation. [11] Organic light-emitting diode (1) according to any one of the preceding claims, in which the particle layer (3) consists of at least 90% by mass of inorganic materials and is free of a matrix material for the scattering particles (31) or the guide particles (32), wherein the cover electrode (5) is applied directly to the organic layer sequence (4) and is a metal mirror, where the light-emitting diode (1) appears milky-cloudy and whitish to an observer when switched off due to the particle layer (3), and wherein the light-emitting diode (1) is configured to produce visible light during operation. [12] Method for producing an organic light-emitting diode (1) according to any one of the preceding claims comprising the steps: A) Providing the substrate (2) with the substrate top (20), B) Creating the lattice structure (8) on the substrate surface (8), C) Producing a solution (6) comprising at least a solvent (60), the scattering particles (31) and the guide particles (32), D) Applying the solution (6) to the substrate surface (20) so that the lattice structure (8) is embedded, E) Drying the solution (6) by removing the solvent (60) to the particle layer (3), and F) Applying the organic layer sequence (4) to the particle layer (3), wherein an organic light-emitting diode (1) is produced according to one of the preceding claims. [13] Method according to the preceding claim, in which the grid structure (8) is produced photolithographically, where the particle layer (3) is printed on.

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