WO2005117158A1

WO2005117158A1 - Light-emitting diode and method for the production of a light-emitting diode

Info

Publication number: WO2005117158A1
Application number: PCT/EP2004/005432
Authority: WO
Inventors: Jörg AMELUNG; Karl Leo
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2004-05-19
Filing date: 2004-05-19
Publication date: 2005-12-08
Also published as: DE112004002833A5

Abstract

A light-emitting diode comprising a substrate (1), a multi-layer arrangement which is disposed on the substrate (1) and wherein a recess is formed, in addition to an organic light emitting layer (91, 111, 131) which is arranged in the recess. The multi-layer arrangement comprises a contact layer (21, 31, 41) which extends as far as or into the recess and which is connected to the OLED (91, 111, 131) in an electrically conductive manner.

Description

Light emitting diode and method for producing a light emitting diode

description

The present invention relates to a light-emitting diode and a method for producing a light-emitting diode, and in particular to light-emitting diodes with organic light emission layers.

Displays or displays or even color displays or color displays are increasingly being used to improve communication between people and machines. The displays are replacing the monitors used until a few years ago in so-called desktop applications, but are also increasingly being used in portable devices, such as. B. mobile phones or PDAs. The displays are based on a formation of LEDs arranged in a matrix. Due to the increasing mass use of displays, there is a need to simplify the process for producing light-emitting diodes, which form the basis of the displays.

At the same time, there is a demand on the displays to produce ever higher-resolution images, which means that more and more pixels are concentrated on a certain area. Thus, of course, the LEDs used in the displays also have the requirement to have a smaller area or to be able to accommodate them on a smaller area.

Organic light-emitting diodes are a special form of light-emitting diodes. One possible way of production is based on the use of polymers. These are often applied as solutions. The structuring is carried out using a printing process such as an ink jet. This organic light emitting diodes are characterized by a short lifespan.

Another previous possibility of producing organic light-emitting diodes is based on the use of vapor-deposited materials. The disadvantage here, however, is that three sub-pixels for the colors yellow, red and blue are required for a color display. The area of a subpixel is less than 33% of the area of an overall pixel. In order to achieve the same luminance, a higher current density is required, which in turn leads to a shorter service life.

At the same time, shadow masks are used to manufacture light-emitting diodes based on vapor-deposited materials. However, these shadow masks are unfavorable for the production of displays with larger dimensions, since they tend to warp. In addition, after a short period of use, the masks become clogged with dyes, which precludes an economical industrial manufacturing process. At the same time, the inaccuracy in the geometric arrangement of the shadow masks limits the resolution behavior of the displays produced with them.

One possibility of producing light-emitting diodes on the basis of vapor-deposited materials, the sub-pixel area of the colors red, yellow and blue being equal to the area of the entire pixel, is to stack the organic light-emitting diodes on top of one another. However, there are only unsuitable contacts in exemplary embodiments according to the prior art for use in high-resolution displays.

Stacked organic light-emitting diodes and, in particular, a corresponding voltage supply for these stacked organic light-emitting diodes are explained in ÜS005917280A. DE 102 15 210 AI relates to the use of doped transport layers in light-emitting diodes with organic light-emitting layers.

No. 5,917,280 A explains an arrangement of stacked OLEDs and how the potentials for controlling the light-emitting layers are to be set.

The present invention has for its object to provide a light emitting diode and a method for producing a light emitting diode, wherein the light emitting diode can be contacted better and manufactured more easily.

This object is achieved by a light-emitting diode according to claim 1 and a method according to claim 20.

The present invention provides a light-emitting diode with the following features: a substrate, a multilayer arrangement which is arranged on the substrate and in which a recess is formed, and an organic light emission layer which is arranged in the recess, the multilayer arrangement having a contact layer which extends up to or into the recess and is electrically conductively connected to the OLED or optical light-emitting diode.

The main idea of the present invention is to form recesses in a multilayer arrangement arranged on a substrate, which comprises a contact layer, so that the contact layer extends as far as or into the recess. In a subsequent vapor deposition process with an organic light emission layer in order to form the organic light emission layer, this is simultaneously connected in an electrically conductive manner to the contact layer, the borders of the recesses functioning as a mask. An advantage of the present invention is that a shadow mask is no longer required to produce an array of light-emitting diodes, but the application such. B. Evaporation can take place over the entire area, since the multilayer arrangement functions as a shadow mask.

Because the contact layer is part of the multilayer arrangement arranged on the substrate, the manufacturing process for a light-emitting diode is simplified.

At the same time, the invention enables a plurality of OLEDs of different primary colors to be layered on top of one another in a recess, as a result of which the resolution of a display formed from these OLEDs is increased.

Another advantage of the present invention is that by concentrating a large number of pixels on a predetermined area, good material utilization can be achieved.

The saving of the shadow mask critical for the manufacturing process enables an increase in the yield of the manufactured light-emitting diodes and thus an improved economy of the manufacturing process.

Another advantage of the present invention is that a light emission layer can cover the entire recess and thus covers the area of an entire pixel. Due to the good use of space, a lower current density is required, which results in a longer lifespan for the LED.

Another advantage of the present invention results from the fact that an OLED using the entire superpixel area, a superpixel preferably comprising 3 subpixels, results in a good aspect ratio, which has a positive effect on the contrast of a display constructed from the light-emitting diodes of the present invention. Therefore, since the contact layer of the light-emitting diode of the present invention in the multilayer arrangement can be isolated well from a contact layer of an adjacent light-emitting diode, the crosstalk between two neighboring pixels is reduced.

Furthermore, the multilayer arrangement can be manufactured inexpensively by conventional semiconductor manufacturing processes, so that an array can be formed, for example, from a wafer.

Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Show it:

FIG. 1 a shows a sectional view of a light-emitting diode with three light emission layers, which emits light away from the substrate above according to an embodiment of the present invention;

Fig. Lb is a schematic plan view of the light emitting diode of Fig. La;

2 shows a sectional view of a light-emitting diode that emits the light downward through the substrate according to an exemplary embodiment of the present invention;

3 shows a sectional view of a light-emitting diode which emits light both upwards away from the substrate and downwards through the substrate according to an exemplary embodiment of the present invention;

4 is a sectional view of an alternative embodiment of a light emitting diode according to the present invention that emits light upward; 5 shows a sectional view of a light-emitting diode with three light emission layers and insulation edges according to an exemplary embodiment of the present invention;

Figure 6 shows an array comprising a plurality of light emitting diodes in accordance with the present invention; and

Fig. 7 is a flowchart of a manufacturing method of a light emitting diode according to the present invention.

1 a shows a structure in the case of a light-emitting diode in accordance with an exemplary embodiment of the present invention, the light-emitting diode essentially comprising a substrate 1, a multilayer arrangement 3 which is arranged on the substrate 1, and an OLED which is in a recess 5 of the multilayer arrangement 3 is formed, composed.

According to the present exemplary embodiment, the multilayer arrangement 3 comprises four metal levels 3a, 3b, 3c and 3d, which are separated from one another by insulation layers 51, 61 and 71 and are closed off by an insulation layer 81. The layer sequence of the insulation layers 51-81 is structured to form the recess 5. The lowermost metal level 3a is formed on the substrate 1 and is structured to form a lower electrode 16 and conductor tracks 18 and 20. The lower electrode 16 is structured such that it extends into the multilayer arrangement 3 over the entire cross section of the recess 5 and a little further. The lower electrode 16 is preferably designed as a conductor track over an OLED stack arranged in a row if it is part of an active matrix display, the latter Execution is explained in detail later. The metal planes 3b-3d lying above are structured to form contact layers 21, 31 and 41, respectively. In particular, the contact layers 21, 31 and 41 are formed such that they laterally completely surround the recess 5 and extend a little from the arrangement 3 into the recess 5 in order to protrude into the same.

Vias are provided to connect the contact layers 21, 31 and 41 to one of the conductor tracks 18 and 20 in the metal plane 3a on the substrate 1, only one contact layer 21 with the conductor track 18 in the sectional view of FIG connecting via 6 and a via 11 connecting conductor track 20 to contact layer 31 are shown.

The OLED in the recess 5 is formed by a layer stack within the recess 5. This layer stack comprises an organic light emission layer 91 extending laterally over the entire cross section of the recess 5, an electrode layer 101 arranged thereon, a further organic light emission layer 111 arranged on the electrode layer 101, an electrode layer 121 arranged on the further light emission layer 111, and finally one organic light emission layer 131 arranged on the electrode layer 121, on which in turn an electrode layer 141 is arranged. All layers 91-141 of the OLED extend over the entire cross section of the recess 5 in the order mentioned. Along the layer stacking or thickness direction, the electrode layers 101, 121 and 141 are such as to the contact layers 21, 31 and 41, which yes are in the recess 5 extend into, aligned so that the electrode layer 101 is contacted by the contact layer 21, the electrode layer 121, by the contact layer 31 and the electrode layer 141 by the contact layer 41 or adjoin one another, while the organic light emission layers 91, 111 and 131 in the thickness direction between the metal levels 3a - 3d are arranged.

FIG. 1b shows a top view of the light-emitting diode from FIG. La, but all the layers 91-141 forming the OLED in the recess 5 have not been shown for better illustration.

As can be seen in FIG. 1b, the cross section of the recess 5 in the exemplary embodiment has a rectangular outline 191, although other shapes would also be possible. Within the recess 5, the uppermost of the contact layers 21, 31 and 41 protruding into the recess 5, namely the contact layer 41, can also be seen, which also has a rectangular outline 201 which is somewhat smaller than the outline 191 of the recess 5, as it is is defined by the insulation layers 51-81.

In addition to the conductor tracks 18, 20, which have already been shown in FIG. 1 a, a conductor track 19 is also shown in this FIG. 1 b, which likewise runs in the level 3 a of the multilayer structure 3 like the conductor tracks 18 and 20, and does not include the latter cuts. In addition, a via 16 connecting the conductor track 19 with the electrode 41 is also shown in FIG. 1b.

Fig. Lb shows a series of hidden edges, which are drawn with dashed lines. In addition, the edges 21, 31, 41 are drawn apart for better representation. poses, although in reality they lie directly one above the other and therefore also hide each other.

Now that the structure of the OLED has been described above, its mode of operation and advantages are described below. The contact layers 41, 31, 21 each protrude into the electrode layers in order to achieve a uniform separation of the organic layers 101, 121, 141.

The first insulation layer 51 electrically separates the first contact layer 21 from the substrate 1. The second insulation layer 61 insulates the third contact layer 31 from the second contact layer 21, while the third insulation layer 71 is responsible for the insulation of the fourth contact layer 41 from the third contact layer 31. The fourth insulation layer 81 is responsible for the electrical shielding of the third contact layer 41 from the surroundings of the light-emitting diode.

The charge carriers of the first electrode layer 16 and the second electrode layer 101 recombine when a voltage is applied between them in the first OLED layer 91. A result of this recombination process is the light beam 151, which is red, for example.

The same applies to the charge carriers from the second electrode layer 101 and the third electrode layer 121, which recombine in the second OLED layer 111. This produces the light beam 161, which is green, for example.

The charge carriers from the third electrode layer 121 and the fourth electrode layer 141 recombine in the third OLED layer 131 and produce the light beam 171, which is blue here, for example. The arrangement of the OLED layers is advantageously carried out so that the light beam, which is composed of photons with the lowest energy, passes through most layers, while the light beam, which is composed of photons with the highest energy, passes through the fewest layers with it Photoemission no other colors are generated. Therefore, in the light-emitting diode according to an exemplary embodiment of the present invention, there is a sequence of the first OLED layer 91, which generates red light with the lowest photon energy, then the second OLED layer 111, which generates green light with medium photon energy, and finally the third OLED Layer 131 that produces blue light from the highest photon energy. Thus, the blue light beam 171, which is composed of photons of the highest energy, passes through the least number of layers.

The primary colors red, green and blue are generated in the OLED layers 91, 111, 131. A suitable mixture of light from these three color components can be used to create any color in the visible spectrum.

The electrodes 101, 121, 141 are transparent so that the light beams generated in the OLED layers 91, 111, 131 can penetrate them in the desired direction of radiation.

The edges of the recess 191 serve to limit the surfaces of the OLED layers 91, 111, 131, for example, as a result of which the shadow masks, which are particularly critical in the production of larger displays with a large number of light-emitting diodes, can be replaced ,

A way of setting potentials which are applied to the conductor tracks 18, 19, 20 and to the electrode layer 16 for controlling the light emission layers 91, 111, 131 is explained in US Pat. No. 5,917,280 A. A possible realization of the electrode layers as transport layers is described in DE 10215210 AI, which has also already been mentioned in the introduction to the description of the present application.

The OLED of FIGS. 1 a and 1 b could be part of an active matrix display. Then only one contact layer 21, 31, 41 or electrode 16 of a row of OLEDs could be controlled by a common interconnect in plane 3a on the substrate. Accordingly, all pixels can be controlled, so that suitable voltages drop across the organic layers, so that the desired color mixture results.

2 shows a further light-emitting diode according to an exemplary embodiment of the present invention. The difference from the light-emitting diode, which is constructed in accordance with the exemplary embodiment of the present invention shown in FIG. 2, compared to the light-emitting diode shown in FIG. 1 a, is that the light beams 151, 161, 171 are emitted through the substrate 1.

For this purpose, the substrate 1 is made translucent at least partially in the area in which the light rays 151, 161, 171 pass through the substrate 1, while the substrate 1 in FIG. 1 a is opaque. Another difference is that the fourth electrode layer 141 in the light-emitting diode in FIG. 2 is made opaque, while the fourth electrode layer 141 in the light-emitting diode in FIG. 1 a is made translucent. The above-mentioned design differences of the substrates 1 and the fourth electrode layer 141 result in the different radiation direction of the light beams 151, 161, 171.

Another difference is that the OLED layers 91, 111, 131 in the light-emitting diode shown in FIG. 2 are advantageously in the reverse order are arranged as in Fig. la. For example, the first OLED layer 91 in FIG. 2 is made of the same material as the third OLED layer 131 in FIG. In the light emitting diode shown in FIG. 2, the first OLED layer 91 generates the blue light beam 171, while in the light emitting diode shown in FIG. 1 a, the third OLED layer 131 generates the blue light beam 171. The same relationships also apply to the red light beam 151 and the green light beam 161 and the other OLED layers. The reason for the reverse arrangement of the light beams is again based on the fact that in these two exemplary embodiments it is advantageous if the light beam with the photons of higher energy passes through a smaller number of layers than the light beam with the photons of lower energy.

3 shows a further exemplary embodiment of a light-emitting diode in accordance with the present invention. The structure of the light-emitting diode shown in FIG. 3 differs from the structure of the light-emitting diode shown in FIG. 2 in that the fourth electrode layer 141 in FIG. 3 is translucent, while in FIG. 2 it is made opaque. This results in a radiation characteristic which differs from the light-emitting diode shown in FIG. 2 for the light-emitting diode shown in FIG. 3. The light beams 151, 161, 171 are now emitted in both directions, that is to say both through the substrate 1 and through the fourth electrode layer 141. Thus, in addition to the light-emitting diode of FIG. 2, the light-emitting diode in FIG. 3 also emits all three colors in the opposite direction through the fourth electrode layer 141.

4 shows a further exemplary embodiment of a light-emitting diode in accordance with the present invention. The light-emitting diode shown here differs from the exemplary embodiment shown in FIG. 1a in that the fourth insulation layer 81 from FIG. layer edge 204 is replaced, and the third contact layer 41 from FIG. la is omitted, and in that the fourth electrode layer 141 from FIG. la in FIG. 4 is replaced by the electrode track 208.

An arrangement shown in FIG. 4 is a light emitting diode which is part of a passive matrix display in which a color light emitting diode represents a pixel and the pixels are arranged in rows and columns. In the passive matrix display, the translucent electrode track 208 is connected to a plurality of light-emitting diodes which are arranged in a row or extends in a strip shape over a row of pixels or recesses. The electrode track 208 is connected to a plurality of light-emitting diodes and thus a plurality of third OLED layers 131. Thus, the plurality of light emitting diodes, which are arranged in a row, are connected to one another via the electrode track 208.

4 in the passive matrix array is activated by activating one of the columns 208 or rows 208 and activating the lower electrodes 16 which are connected by conductor tracks (not shown) on the substrate 1 in the direction perpendicular to the tracks 208 are connected in series, i.e. in rows or Column direction. Only the OLED stack, to which a high voltage is applied between the track 208 and the lower electrode, can be illuminated. The other control options for each OLED stack or pixel, namely the middle contact layers 21, 32, can be controlled individually via the conductor tracks 18, 20.

A decision as to whether or not the third OLED layer 131 is supplied with charge carriers is made solely by the voltage at the contact layer 31, which together with the electrode track 208 is responsible for the charge carrier supply of the third electrode layer 121. The contact layers 31 are in the series arranged light-emitting diodes, which are connected via the electrode track 208, are electrically separated from one another. Every third OLED layer 131 can thus be controlled separately by each light-emitting diode.

In other words, in the light-emitting diode shown in FIG. 4, the fourth electrode layer 141 from FIG. 1 a is implemented jointly over a plurality of light-emitting diodes arranged in the row. This arrangement is referred to as a passive matrix display.

Another difference between the exemplary embodiment of the light-emitting diode according to the present invention shown in FIG. 1a and the light-emitting diode according to the present invention shown in FIG. 4 is that the fourth insulation layer 81 is replaced by the insulation layer edge 204. The geometric design of the insulation edge 204 prevents the material which is deposited on the insulation layer edge 204 during the vapor deposition of the electrode web 208 from forming a common layer with the electrode web 208, which may even result in an electrically conductive connection to the electrode web 208 in the adjacent one Series could result.

5 shows a further exemplary embodiment of a light-emitting diode in accordance with the present invention. The light-emitting diode shown here differs from the exemplary embodiment in FIG. 1 a in that a first insulating layer 211 is applied to the first contact layer 21 and a second insulating layer 216 is applied to the second contact layer 31. The insulating layers 211, 216 extend beyond the contact layers 21, 31, both on the side facing away from the recess into the insulation layers 61, 71 and on the side facing the recess into the electrode layers 101, 121. The insulating layers 211, 216 prevent the material of the electrode layer 121 from forming a conductive connection between the contact layer 21 and the third electrode layer 121 during the manufacturing process, and thus a short circuit of the second OLED layer 111. This would destroy the LED. The same applies to the second insulating layer 216, which prevents the accidental formation of contact between the second contact layer 31 and the fourth electrode layer 141. The light-emitting diodes according to the exemplary embodiment of the present invention in FIG. 5 are thus more resistant to unwanted contacts in the manufacturing process, which leads to an increase in the yield.

6 shows an array consisting of light-emitting diodes or light-emitting diode stacks according to an exemplary embodiment of the present invention. An array 216, a multilayer structure 221 and recesses 191, which are arranged in columns and rows, can be seen. The multilayer structure 221 comprises the insulation layers, the contact layers and the contact holes, although the contact layers also extend into the recesses 191. The insulation layers, contact layers and the contact holes are not shown in this FIG. 6. The recesses 191 comprise the electrode layers, the OLED layers and parts of the contact layers which extend into the recess 191. The electrode layers, the OLED layers and the contact layers extending into the recesses 191 are also not shown in this FIG. 6.

Due to a geometric structure of the array 216, the shadow masks and the evaporation of the OLED and electrode layer material can be carried out over the entire area, since when the electrode layers and the OLED layers are evaporated, the material can be deposited both on the multilayer structure 221 and in the recesses 191 without that this leads to crosstalk between the light emitting diodes, since the multi-layer structure not only serves to control but also to form tear-off edges.

FIG. 7 explains a manufacturing method of the light-emitting diode shown in FIG. 1 a according to an exemplary embodiment of the present invention. In a step 220, the substrate 1 is provided. The first metal level 3a is then applied and structured on the substrate 1 in a step 230, so that the first electrode layer 16 and the conductor tracks 18, 20 are formed.

In a step 240, the multilayer arrangement is then completed by successive application, so that the contact holes 6, 11, 181, the contact layers 21, 31, 41 and the insulation layers 51, 61, 71, 81 are formed. The layers 21 - 81 applied one after the other are either structured in the same way, ie always before the overlying layer is made, so that the arrangement 5 is formed, or the arrangement 5 is produced as a final step after formation of all layers. Steps 230, 240 are preferably carried out by means of lithographic methods, with a wafer being used as the substrate, as a result of which the production method is inexpensive and the use of a shadow mask becomes unnecessary, which in turn enables the production of larger dispalys.

The OLED layer 91 is then applied to the first electrode layer 16 in a step 250. The second electrode layer 101 is then applied in a step 260 by means of deposition over the entire surface. During steps 250 and 260, parts protruding into the recess, together with the multilayer arrangement, serve as separators, which enable tear edges or prevent layers 16, 101 from being formed continuously with those of neighboring pixels. Thereupon, in a process flow diagram in this exemplary embodiment for producing the light-emitting diode shown in FIG. 1 a, the process jumps back to step 250 in order to apply the second OLED layer 111 and in the subsequent step 260 the third electrode layer 121.

For the light-emitting diode shown in FIG. 1 a according to an exemplary embodiment of the present invention, the steps 250, 260 are then carried out a third time, the third OLED layer 131 and the fourth electrode layer 141 being applied. The manufacturing process of the light-emitting diode shown in FIG.

In the above exemplary embodiments of the present invention, the recesses 191 in which the OLED layers 91, 111, 131 and the electrode layers 16, 101, 121, 141 are introduced are rectangular. Alternatively, however, any geometric designs for a floor plan of the recesses 191 such as B. circles or ellipses.

The above exemplary embodiments each comprise three OLED layers 91, 111, 131, four electrode layers 16, 101, 121, 141, three contact holes 6, 11, 181 and three or four insulation layers. However, any number of OLED layers, electrode layers, contact holes and insulation layers can alternatively be implemented.

It is also not necessary that the OLED layers 91, 111, 131 and the electrode layers 16, 101, 121, 141 each fill the base area of the complete recess 191. Alternatives are also electrode layers or OLED layers which only fill part of the recess 191, the OLED layers or electrode layers then also being able to be electrically insulated from one another by an insulation layer. In the exemplary embodiments FIGS. 1 a to 7, light-emitting diodes with three primary colors red, green and blue are listed. Alternatives are also light-emitting diodes with any color distribution.

The contact layers 21, 31, 41 are geometrically identical, in the exemplary embodiments FIGS. 1 a to 7 and all extend into the electrode layers 101, 121, 141. The contact layers can also be of any desired design, have no symmetries and are non-symmetrical also do not extend into the electrode layers, but only adjoin them.

In the exemplary embodiments of the present invention, the light beams shown are perpendicular to the base surface of the substrate 1. However, it is pointed out that the radiation characteristic is such that the radiation takes place in a wide angular range of approximately 180 °. Alternatives are also oblique arrangements of the light-generating layers in the recess 5, the light-generating layers and a surface normal to the substrate 1 having an angle that deviates from 90 °.

In the above exemplary embodiments, the contact layers 21, 31, 41 are designed such that they completely surround the electrode layers. Alternatives are also arrangements in which the contact layers are not self-contained and are only arranged around part of the recess 191.

Also, in the exemplary embodiments of the light-emitting diodes according to the present invention, all contact layers 21, 31, 41 are connected to the substrate 1. Alternatives are also connections in the multilayer structure 221 or on the multilayer structure 221, so that one or a plurality of contact layers are also insulated from the substrate 1. In an exemplary embodiment according to the present invention in FIG. 4, the fourth electrode layer 141 from FIG. 1 a is designed as an electrode track 208, while the lower electrode is connected in series with those of pixels in the same column or row. This creates a passive matrix display. Of course, in the case of a passive matrix display, another combination, such as the second electrode layer 101 or the third electrode layer 121, can also be designed as an electrode track if the fourth electrode layer is not designed as an electrode track, and it applies that only two electrode layers of the OLED Stacks are designed as an electrode track.

Alternatively, a step is also possible for step 230 of the production method shown in FIG. 7, in which a metal level is introduced into a recess in the substrate 1. In addition, the sequence of steps can be varied in FIG. 7.

In the above exemplary embodiments of the light-emitting diodes according to the present invention, the electrodes of a stacked OLED are contacted by vertically arranged contact electrodes, each color being contacted by the vertical application, in each case only by one contact electrode. In the exemplary embodiments according to the present invention, pixelation of a stacked OLED can be achieved in almost any resolution, so that color displays can be produced both for mini displays larger than 1 "diagonal" and for microdisplays. Furthermore, in the above exemplary embodiments according to the present invention, shadow mask structuring is no longer required, which therefore enables the above exemplary embodiments to be implemented with substrates of any size. The manufacturing method according to the exemplary embodiment of the present invention can therefore also be used in normal displays and large displays. As shown in the embodiments of the present invention, the aspect ratio, which is the ratio between active sub-pixel area and total pixel area are defined, greatly increased, which on the one hand leads to an extension of the service life of the OLEDs with the same view with a display brightness and furthermore enables an optimal color mixing in pixels. Furthermore, the pixels are dielectrically and optically isolated from one another, which reduces crosstalk of the pixels.

In addition, the electrodes 16, 101, 121, 141, which have so far been implemented consistently with inorganic layer systems, can optionally be replaced by organic conductive layers (doped layer systems), since the lateral connection resistance is greatly reduced by the arrangement. Another interesting application of the light-emitting diode described in the above exemplary embodiments is the use for lighting purposes in which white or specific color tones can be set. Compared to laterally structured OLEDs, better utilization of the area can be achieved here.

The above exemplary embodiments are an improved structuring option in a color display, an increase in the aspect ratio of the subpixels, an improvement in the color mixing in the display, an improvement in the service life of the display by in-situ structuring or completely in vacuum structuring, an increased material utilization in the manufacture of the display , a reduction in crosstalk between the pixels and a possibility of using organic electrode systems.

In the above exemplary embodiments of the present invention, a side view is shown in FIG. 1 a and a top view in FIG. 1 b. The starting electrode 16 is structured on the substrate 1. After deposition of an insulation layer 51, the first counter electrode 21 is applied in a structured manner, followed by a further insulation layer 61 with the next counter electrode 31 for the following color. The next insulation layer 71 with the following Electrode 41 is used to contact the last color. The structuring stack is completed by the insulation layer 81. The electrodes 21, 31, 41 are arranged overhanging within the pixel area of the recess 191 and form local tear-off edges in the subsequent organic stack deposition. The color electrodes are contacted on the side of the pixel area.

For a particularly favorable arrangement of the OLED stack for a top-emitting structure, the OLED structures are arranged such that the OLED with the emission with the smallest photon energy (red) as the lowest and the OLED with the highest photon energy (blue) as the top is applied. This minimizes the absorption in the layers above.

After the pixel electrodes have been manufactured, the organic light-emitting diodes are deposited over a large area. First, the organic matter of the first OLED (eg red) 91 is deposited, followed by the contacting of the lateral electrodes through the first contacting layer 101. This is followed directly by the organic matter of the second OLED (eg green) 111 with the subsequent contacting 121. The last organics 131 and the last electrode 141 complete the production.

Within an active matrix display, the side electrodes 21, 31, 41 are connected to the underlying circuit through contact holes. The stacked OLED is emitted away from a substrate.

Another arrangement according to the invention is shown in FIG. 2, where the stacked OLED is emitted by the substrate 1. Here, the electrode 141 is designed to be opaque. For a particularly favorable arrangement of the OLED stack for a substrate-emitting structure, the OLED structures are arranged in such a way that the OLED with the emission at the smallest photon energy (red) as the top one and the OLED with the highest photon energy (blue) is applied as the lowest. This minimizes the absorption in the respective layer.

3 shows a further exemplary embodiment according to the present invention, in which the electrode 141 is also designed to be translucent, and thus an emission takes place in both directions. In the switched-off state, the stacked diode is then transparent.

An arrangement explained in FIG. 4 according to an exemplary embodiment of the present invention shows the case where the application is used in passive matrix displays. The structuring of the electrodes 21, 31 takes place in the form of rows and columns, and the last side electrode 41 can be omitted in this exemplary embodiment and by a lateral structuring of the OLED electrode 141 and by an overhanging edge of the insulation layer 81, which here as insulating layer 204 is achieved.

A further modified arrangement in accordance with the exemplary embodiments of the present invention is explained in FIG. 5. In order to avoid contacting the underlying lateral electrodes 21, 31 during the deposition of the OLED electrodes 121, 141, additional overhanging insulating edges 211, 216 are inserted. This embodiment increases the process reliability of the arrangement and thus increases the yield.

A modification in the sense of the above exemplary embodiments of the present invention is the replacement of at least one of the OLED electrodes 101, 121, 141 by a conductive organic layer, since the arrangement of the electrodes means that the lateral contact resistance is so low that it can also be realized by organic layers can. This arrangement results in particular in simplifying the manufacture. The above exemplary embodiments show the manufacture and integration of a stacked organic light-emitting diode by structuring and contacting the stacked diodes by laterally stacked overhanging edges.

In the above exemplary embodiments, the light is coupled out via a transparent cover electrode. In addition, as outlined in the above exemplary embodiments, the light can also be coupled out via a transparent substrate electrode. In addition, in the above exemplary embodiments, the light can be coupled out both via the transparent substrate electrode and via the transparent cover electrode.

Advantageous arrangements in the above exemplary embodiments show that the emission energy of the stacked light-emitting diodes away from the substrate becomes larger or smaller, depending on whether it is a top-emitting or a substrate-emitting light-emitting diode. It is also possible in the above exemplary embodiments to arrange the OLED with the lowest emission energy in the middle of the stacked light-emitting diode and the OLEDs with the higher emission energy on the outside.

In the above exemplary embodiments, the lateral electrodes 21, 31, 41 have direct contact with the substrate electronics. In the above method according to an exemplary embodiment of the present invention, the lateral electrodes 21, 31, 41 can be designed in the form of rows and columns. In addition, in the exemplary embodiments according to the present invention, an additional insulating layer 204 can be arranged above the lateral electrodes in FIGS. In addition, in the above exemplary embodiments according to the present invention, contacting of the lateral electrodes 21, 31, 41 can also be achieved by a conductive organic layer. The above exemplary embodiments have shown that the integration of stacked, vapor-deposited organic light-emitting diodes can take place by vertically arranged contacting of the electrodes. Thus, on the basis of organic light emitting diodes (OLEDs), novel flat displays with many advantages can be realized. This includes the large-scale deposition from various substrates, the self-illuminating properties that enable very thin displays, the high degree of independence from the viewing angle and the potentially high efficiency of such displays.

In order to be able to implement such displays, structuring in various emitting elements or so-called pixels is necessary. This applies in particular to full-color displays in which these pixels have to be realized in such a way that they emit in different colors. The structuring using shadow mask technology is no longer applicable to small pixels in mini or microdisplays. In the exemplary embodiments according to the present invention, a layer system comprising up to three differently colored OLEDs is integrated and contacted in a display in such a way that it can also be used in mini and microdisplays.

The possibilities for producing such structures depend very much on the materials used. On the one hand, organic light-emitting diodes based on polymers have been realized so far, which are usually applied from solutions. In this case, it is possible to structure the pixels using printing processes. For example, it could be shown that inkjet printing enables efficient pixelation. With this pixelation technology, the resolution limit is around 50 100 μm pixels. However, organic light-emitting diodes made of polymers also have disadvantages, such as the shorter lifespan in comparison to vapor-deposited organic light-emitting diodes. These printing techniques are not available for light-emitting diodes based on vapor-deposited materials. Furthermore, it is important for the quality of the OLEDs to carry out all structuring in a vacuum. For monochrome displays, it is possible to achieve structuring with tear-off edges in so-called passive matrix displays, ie with displays without their own control circuit on the pixels. For active matrix displays and especially for color displays, however, it is necessary to selectively implement the different colors. Traditionally, this has been achieved so far by dividing a pixel laterally into three subpixels for red, green and blue. In order to achieve a sufficient luminosity of the pixel, each sub-pixel must light up to three times the luminosity corresponding to the area fraction of a maximum of one third of the total pixel in order to present the observer with a corresponding luminance of the total pixel. In real cases, the area share of a subpixel is less than 33%. Due to the increased control, a higher current strength is required for each pixel, at the same time the life of the pixel is reduced.

The standard approach for structuring the vapor-deposited organic light-emitting diodes in the subpixels is based on the fact that the dyes are evaporated through a shadow mask. Such evaporation through a shadow mask was shown in principle on a laboratory scale. However, it is limited to displays with relatively small dimensions, since larger masks tend to warp. Such shadow masks also tend to clog and clog with dyes. This requires that the masks be cleaned frequently, which is a serious disadvantage in an industrial production process. Displays with subpixel sizes on a laboratory scale up to approx. 50 μm have already been presented, this method can no longer be used for smaller pixel sizes. Even with these pixel sizes for so-called mini displays (larger than 1 inch Diagonal), only a small area of the pixel can be used for the actual OLED, because due to the inaccuracy of the shadow mask, a distance between different colors has to be maintained in order to avoid overlapping of the subpixels.

In the case of even higher resolutions, approaches are known from the literature or from patents that use the implementation of white emitters, which are appropriately filtered by color filters. This can either be done by applying the filters to the substrate before the light-emitting diodes are deposited, in the case of light-emitting diodes which emit through the substrate, that is to say in the case of substrate emitters or after the light-emitting diodes have been deposited, in other words in the case of top emitters. However, the production of such structures with filters has the disadvantage, among other things, that considerable losses in efficiency are inevitable here. Furthermore, the color filters require further lateral structuring, which further reduces the area share of the differently colored displays. However, so far there is no method with which a colored structuring can be achieved at high resolutions for mini or microdisplays.

An alternative approach to the lateral structuring of the colored subpixels is the use of stacked OLEDs, the colored pixels being superimposed vertically, the colors below shining through the colors above, which is stated in the patent specification US 005917280 A. Such systems offer a much higher area percentage of a pixel per color and at the same time an optimal color mixture for the human eye. An arrangement according to the invention has so far been able to be integrated into a display, but it has not been possible to present it, since it was not possible to effectively contact the intermediate electrodes between the colors, which are arranged vertically. Furthermore, there were no OLED technologies available so far that would allow sufficient efficiency of the individual colors for stacked OLEDs. Such highly efficient inverted and transparent OLEDs are possible through the use of doped transport layers, as set out in published patent application DE 102 15 210 A1, which bears the title “Light-emitting component with organic layers”.

The subject of this invention is a possibility of integrating such stacked OLEDs in a display and to achieve the pixel contact. The process is also suitable for very high-resolution displays and any substrate sizes.

Claims

claims

1. LED with the following features: a substrate (1); a multilayer arrangement (221) which is arranged on the substrate (1) and in which a recess (191) is formed; and an organic light emission layer (91, 111, 131) disposed in the recess (191); the multilayer arrangement (221) having a contact layer (21, 31, 41) which extends as far as or into the recess (191) and is electrically conductively connected to the OLED (91, 111, 131).

2. Light-emitting diode according to claim 1, wherein the contact layer (21, 31, 41) is spaced from the substrate (1).

3. Light-emitting diode according to one of claims 1 or 2, wherein the contact layer (21, 31, 41) extends into the recess (191).

4. Light-emitting diode according to one of claims 1 to 3, in which a further organic light emission layer (91, 111, 141) is arranged in the recess (191).

5. Light-emitting diode according to claim 4, in which the further organic light emission layer (91, 111, 131) is designed to emit a different color from the organic light emission layer (91, 111, 131).

Light-emitting diode according to one of Claims 1 to 5, in which an insulating layer (211, 216) is arranged on a surface of the contact layer (21, 31) facing away from the substrate 1 and extends into the recess (191).

Light-emitting diode according to Claim 6, in which the insulation layer (211, 216) extends beyond the contact layer (21, 31) into the recess (191).

Light-emitting diode according to one of Claims 1 to 7, in which the substrate (1) is designed to transmit a light (151, 161, 171) emitted by the light-emitting layer (91, 111, 131).

9. Light-emitting diode according to one of claims 1 to 8, in which a lower electrode layer (16) is applied in the recess (191) on the substrate (1), the lower electrode layer (16) having a region which lies between the substrate 1 and the organic light emission layer (91) is arranged.

10. Light-emitting diode according to claim 9, wherein the lower electrode layer (16) is designed to transmit a light (151, 161, 171) emitted by the light emission layer (91).

11. Light-emitting diode according to claim 9 or 10, wherein the upper light-emitting layer is electrically connected between the lower electrode layer (16) and the contact layer (21, 31, 41).

12. Light-emitting diode according to one of claims 1 to 11, in which in the recess (191) an upper electrode layer (141) is applied to the organic light emission layer (131), which at least partially a surface of the organic facing away from the substrate (1) Light emission layer (131) covered.

13. The light-emitting diode according to claim 12, wherein the upper electrode layer (141) is designed to transmit a light (151, 161, 171) emitted by the light emission layer (131).

14. Light-emitting diode according to claim 12 or 13, wherein the upper electrode layer (141) is arranged in the recess so that the contact layer (41) is adjacent to the same.

15. Light-emitting diode according to one of claims 1 to 14, wherein the recess (191) has a blind hole which extends into the multilayer arrangement (221) to the substrate (1).

16. Light-emitting diode according to one of claims 1 to 15, in which the contact layer (21, 31, 41) is contacted with a conductor track on the substrate (1).

17. Array (221) which has a plurality of light-emitting diodes according to one of claims 1 to 16.

18. Array (221) according to claim 17, in which a first of the light-emitting diodes has a first contact layer (21, 31, 41) and a second of the light-emitting diodes has a second contact layer (21, 31, 41) and the first and second contact layers ( 21, 31, 41) are connected in an electrically conductive manner via a conductor track.

19. Wafer having a light emitting diode according to one of claims 1 to 16 or an array (216) according to claim 17 or 18.

20. Method for producing a light-emitting diode with the following steps:

Providing (220) a substrate (1); Arranging (230) a multilayer arrangement (221) on the substrate (1);

Forming a recess (191) in the multilayer arrangement (221); and

Arranging (250) an organic light emission layer (91, 111, 131) in the recess (191); wherein the step (240) of arranging the multilayer arrangement is carried out in such a way that the multilayer arrangement comprises a contact layer (21, 31, 41) which extends as far as or into the recess (191) and is connected to the OLED (91, 111, 131) is electrically conductively connected.

21. The method of claim 20, wherein the step of providing (220) the substrate (1) comprises providing a wafer, and the step of arranging (250) comprises a lithographic process.

22. The method according to any one of claims 21 or 22, wherein the step of arranging (250) the organic light emitting layer (91, 111, 131) comprises vapor deposition of organic material over the entire surface.