EP2912707A1

EP2912707A1 - Lighting module with optimised contacting

Info

Publication number: EP2912707A1
Application number: EP13785416.2A
Authority: EP
Inventors: Jörg AMELUNG; Michael Eritt; Christian Kirchhof
Original assignee: Tridonic GmbH and Co KG
Current assignee: Tridonic GmbH and Co KG
Priority date: 2012-10-29
Filing date: 2013-10-29
Publication date: 2015-09-02
Also published as: CN104919616B; US20150287944A1; DE102012219712A1; CN104919616A; WO2014067919A1; US9349973B2

Abstract

The invention relates to a lighting module or an organic solar cell, comprising two plate-type electrodes (12, 13) and an active material (14) located between the two electrodes (12, 13). In said module, one of the two electrodes (12, 13) consists of a transparent material and is provided with a grid structure with at least one metallic conductor track (11) running on the surface or in the material of the electrode (12), only some sections of the conductor track (11) being connected to the electrode material.

Description

Light module with optimized contacting

The present invention relates to a lighting module according to the preamble of

Claim 1, which comprises two plate-shaped electrodes and an active material arranged between the two electrodes. In particular, the lighting module may be an OLED (Organic Light Emitting Diode) structure or a QLED (Quantum-dot Light Emitting Diode) structure. Furthermore, the present invention relates to a so-called organic solar cell.

The development of novel light sources, which due to their improved

The ability to replace classic light sources such as incandescent or fluorescent lamps has made significant progress lately. In addition to conventional semiconductor light-emitting diodes (LEDs), which are essentially point-shaped light sources, in particular OLEDs or QLEDs have also become the focus of attention since new types of surface light elements can be realized on the basis of such structures. As a flat luminaire with a moderate luminance compared to a classic LED, an OLED or QLED is ideally suited for producing flat, diffuse surfaces

Light sources. The applications for such light sources are extremely diverse, which is why there has been a strong development in recent years in this field. Due to its structure, an OLED or QLED has the properties of a so-called Lambert view radiator with a constant luminance at any beam angles. Accordingly, it is particularly suitable for forming large-area light sources.

Organic light-emitting diodes, like organic solar cells, are so-called thin-film components. In this case, very thin layers are usually arranged on a glass substrate, the so-called substrate, whereby the individual layers may be only a few nanometers thick. In the case of an organic LED, for example, two electrode layers are provided, between which one or more layers of organic material are arranged. When a voltage is applied between the two electrode layers, the organic material emits Light, which is then to be radiated across the surface of the array. Inevitably, this means that one of the two electrode layers, usually the one which is arranged on the glass carrier, must be transparent. To form such a transparent electrode, a transparent conductive oxide (TCO), for example indium tin oxide (ITO), is usually used.

Structures of this type constitute so-called current-driven components, that is, light is generated by applying a voltage to the two electrode layers in the organic material. Accordingly, in order to achieve uniform and efficient light output, homogeneous current distribution over the entire area of the element is desirable. However, this poses a problem insofar as the above-mentioned materials for realizing transparent electrodes are basically conducting, but have a relatively low conductivity. This leads to the fact that only through the use of appropriate materials only a very limited homogeneity in the flow of current and thus in generating the light can be achieved.

In order to improve the poor conductivity of the transparent electrode, an additional structured metal layer is usually applied to the transparent electrode. As a rule, this layer consists of a plurality of tracks, which form a so-called grid structure and have a significantly higher conductivity than the material of the transparent electrode. As a result, the flow of current across the surface can be improved because the metal tracks act as a bypass for the flow of current. In this case, this metal layer or grid structure is contacted on the longitudinal or front side of the arrangement so that current can be introduced into the electrode layer over the entire length of the structure. In this case, an electrical balance of the current flow forms, which, however, is not linear over the entire area. Instead, areas with elevated form

Current density, which in turn counteracts the homogenization of the light output, since an increased current density is synonymous with a locally increased light production.

A comparable problem also arises with the already mentioned organic solar cells. Also in this case, organic material is between two

arranged plate-shaped electrode layers, wherein this organic material now converts incident light into charge carriers, which ultimately cause a current flow between the two electrodes. Again, at least one electrode must be translucent and accordingly again consists of the above-mentioned materials which have a relatively low conductivity. Accordingly, grid structures are also used in such organic solar cells, which, however, up to now have only limited homogeneity

Effect current flow over the entire area.

The present invention is therefore the task of proposing an improvement for the previously known solutions, with which a further improved homogenization of Stromfius can be achieved across the surface of such a light module or an organic solar cell away.

The object is achieved by a light-emitting module or an organic solar cell having the features of claim 1. Advantageous developments of the invention are the subject of the dependent claims.

The solution according to the invention is based on the idea of configuring the interconnects forming the grid in such a way or to couple them to the material of the transparent electrode that these interconnects only partially with the

Electrode material are connected. In other words, the printed conductors are separated from the electrode material over certain sections, with the result that the imbalances resulting from the coupling of the current in the previously known solutions can be avoided. The solution according to the invention is characterized in particular by the fact that the previously known

Technologies for creating QLEDs or OLEDs or organic ones

Solar cells can be used and an optimized, so more uniform flow of current can be achieved without high overhead. According to the invention, therefore, a light module or an organic solar cell is proposed which has two plate-shaped electrodes and an active material arranged between the electrodes. One of the two electrodes consists of a transparent material and is in addition to a

Grid structure provided, which has at least one metallic trace, the the surface or in the material of the transparent electrode.

According to the invention the conductor is only partially with the

Electrode material connected. According to an advantageous development, provision can be made in particular for the conductor track of the grid structure to extend from a lateral connection region of the electrode into a more central region, wherein the section of the conductor track closer to the connection region is separated from the electrode material. Alternatively or additionally, also the end portion of the conductor of the

Separate electrode material so that a compound is present only in a central region of the conductor. Preferably, the grid has a plurality of tracks, which may be e.g. are arranged like a grid and extend in parallel lines over the surface of the light module or the organic solar cell away. The separating of the conductor tracks from the electrode material over certain sections can be carried out in particular by making cuts in the

plate-shaped electrode material can be made. This can be done in a simple way by means of a laser or also in a conventional manner, e.g. done lithographically, so that the effort to implement the inventive solution is extremely low.

As already mentioned, the luminous module according to the invention can be an organic LED or a QLED. The coupling according to the invention between the grid structure and the transparent electrode, however, has an advantageous effect, as already mentioned, also in the case of organic solar cells.

The invention will be explained in more detail with reference to the accompanying drawings. 1 and 2 are schematic representations of an OLED structure known from the prior art without a metal grid; FIG. 3 is a plan view of an OLED structure known from the prior art in which a metal grid is used to improve the flow of current;

Figure 4 shows a first variant according to the invention for sections

Coupling between transparent electrode and metal grid;

FIG. 5 shows a second variant according to the invention; FIG. 6 shows a third variant according to the invention;

FIGS. 7a and 7b show a first possibility for coupling in sections or

Separation of Metallgrid and electrode and Figures 8 a and 8 b, a second variant for coupling in sections or

Separating metal grid and electrode.

The problem underlying the invention will first be explained with reference to Figures 1 to 3. FIGS. 1 and 2 show a sectional illustration and a plan view of a conventional organic LED known from the prior art, in which case no additional metal grid is initially used to improve the uniform current flow.

1, the usual structure of an OLED or QLED is that on a carrier substrate 5, which is usually formed by a glass plate, a layer arrangement consisting of two electrodes 12 and 13 is arranged, wherein between the two electrodes 12, 13 an active material 14 is located. In the case of an OLED, this active material 14 consists of one or more layers of organic material, which are such that when a voltage is applied between the two electrodes 12 and 13, light is generated. This is usually via the lower electrode layer 12 and the

Carrier substrate 5 emitted, which means that the electrode 12 must be formed inevitably transparent. Accordingly, it usually consists of a transparent conductive oxide (TCO), which is usually indium tin oxide (ITO) is used.

The structure of an organic solar cell is identical in principle. Also in this case, two electrodes are usually arranged on a transparent carrier substrate, between which organic material is located. In the case of a solar cell, the organic material is in particular two layers which form a so-called electron donor and an electron acceptor. When light enters this area, charge carriers are generated, which then provide a current flow between the two electrode layers. It is also necessary here for one of the two electrodes to be transparent or transparent for efficient light incidence, which in turn means that the abovementioned transparent conductive materials are used. A view of the underside of the OLED structure of FIG. 1 is shown in FIG. 2, the illustration of the carrier substrate being omitted here. Visible here is the two-dimensional transparent electrode layer 12, which electrically extends laterally over a contact 10 extending over the entire width of the structure

is connected. On the opposite side, the connection 13a for the electrode 13 is shown, which, however, has no further relevance to the present invention. Usually, the upper electrode 13 is made of a thin metal layer which, due to its high conductivity, poses no problems with regard to the uniformity of the current flow through the device over its surface.

If a voltage is applied in the arrangement according to FIG. 2 in order to achieve a flow of current through the organic material and to generate light accordingly, then due to the low conductivity of the material for the transparent electrode 12, there will not be a uniform flow of current across the surface. Instead, significantly higher current densities are present in the area near the terminal 10, whereas, on the other hand, virtually no current flows at the opposite end area of the arrangement. As a result, as seen across the surface of the light module uneven light is generated and emitted. From the prior art, therefore, the solution shown in Figure 3 is known to improve the Stromfius, in which the electrode 12 in addition to a

Grid structure is provided. In the illustrated embodiment, the

Grid structure only of a track 11, which is formed by a metallic conductor with high conductivity, which is directly connected to the lateral terminal 10 and conductively coupled to the electrode material along its length. The use of this grid structure results in better distribution of the current flow across the surface of the electrode 12. Since, however, the current is distributed over the entire length of the conductor path, the effect occurs here too that almost no or only a small current flow is present at the end region 1 1b of the conductor 11, whereas in turn higher currents occur directly at the contact 10 be present on the area I Ia. As before, therefore, no optimal uniform current distribution over the entire surface of the electrode 12 can be achieved, even if certain improvements, e.g. of the

Variant of Figures 1 and 2 are present, in which no Metallgrid is used.

With the solution according to the invention, the current distribution over the entire area is significantly improved. This is inventively achieved in that an electrical connection of the metal grid to the electrode material only

in sections. This idea will be explained below in principle first with reference to FIGS 4 to 6.

A first conceivable embodiment of the invention is shown in FIG. In this case, it is provided that the conductor track 11 of the metal grid is connected to the material of the electrode 12 only in a region 1 1b remote from the terminal 10. By contrast, the region I 1 a located in the vicinity of the connection 10 is separated from the electrode material, which is achieved by means of a separation 1 la or subdivision of the electrode material which will be described in more detail below. In this case, therefore, the conductor 11 is distributed to the surface of the electrode 12 with the aid of the grid current only in the more remote region 11b.

The effect of the grid is accordingly in the illustrated

Embodiment limited to the terminal 10 more remote areas of the electrode 12. The closer to the terminal 10 areas of Electrode 12, however, receive 10 directly via this connection. From the ratio of the length of the conductor 11 and the not directly coupled to the electrode 12 region 1 la then a corresponding adjustment can be made with respect to the action of the metal grid. It is thus possible to influence the luminance of the structure in a targeted manner, whereby in particular, of course, it is possible to compensate for inhomogeneities and to achieve homogeneous light output over the entire area.

A development of the idea of Figure 4 is shown in Figure 5, wherein like elements are provided with the same reference numerals. In this case, the final end portion 11 c of the conductor 11 is due to a separation or

Insulation 12c separated from the electrode material 12 so that only one

Connection between conductor 11 and electrode 12 in the central region I Ib is present. This example illustrates that there is the possibility of selectively linking between grid structure and only over specific sections

Make electrode material.

The coupling of the metal grid to the electrode 12 can be made arbitrarily complex to optimally adjust the current flow over the entire surface of the electrode 12 away. With the help of electrical calculations or simulations an optimal structure for each surface can be found, wherein a further conceivable possibility is shown in FIG. The grid in this case consists of a plurality of mutually parallel conductor tracks 11, which, however, are in turn coupled only in their remote from the terminal 10 lying areas with the electrode material. Such a grid is typically the optimal shape for a grid to cover over the entire area

to achieve a uniform flow of current. This is additionally optimized by the inventive only partial coupling between the grid structure and the electrode material.

The only partial coupling of the grid structure to the transparent electrode can be done in different ways. Below, two preferred variants will be explained for this purpose, which are characterized in that the associated costs are relatively low and in particular on existing technologies for producing OLEDs can be used. These variants differ primarily in the way in which the Metallgrid is integrated into the arrangement. During the manufacturing process, the transparent electrode 12 is usually first patterned, since it defines the later region of the luminous area of the OLED. Likewise, the metallizations for the contacts of the electrodes are structured. In the arrangement or production of Metallgrids exist in

Essentially two variants, wherein the conductor tracks of the grid are arranged either below the transparent layer or in the electrode material or above thereof.

In this case, FIG. 7a initially shows a variant in which the conductor track 11 is arranged above the electrode 12. In order to avoid local high current densities, in this case the printed conductor 11 is "passivated" by a non-conductive material 20. This non-conductive material 20 thus separates the printed conductor 11 from the surrounding organic material 14 or prevents direct contact between the printed conductor 11 and organic material 14, however, of course permits a connection between interconnect 11 and electrode 12. In the production, the conductor 11 and then the non-conductive material 20 are first applied to the electrode 12. Subsequently, the organic material 14 is applied.

In order to carry out a coupling only in sections between conductor 11 and electrode 12 according to the present invention, a separation of the electrode material must be made below the corresponding area only in those areas in which a direct connection between conductor 11 and electrode 12 is not desired. as shown in FIG. 7b. Such separations or cuts 40 can easily over

Etching or laser ablation or other suitable method can be made without this being associated with a lot of effort.

In a second variant, the conductor track is arranged below the transparent electrode 12 or, as shown in FIG. 8b, embedded in the latter. Usually, this is achieved by first of all on the glass substrate 5 shown in FIG Grid structure is arranged and then the material of the transparent electrode 12 is deposited. In order to achieve according to the invention only a partial coupling between grid structure or conductor 11 and electrode 12, cuts 40 are then introduced into the electrode material in the corresponding areas in this case, in order to achieve the desired division or separation. Subsequently, again a passivation of suitable, ie insulating material 20 in the area above the conductor 11 and the

Final application of the organic material 14. In both variants shown so the solution according to the invention can be realized very easily. In this case, it is advantageous that the section-wise coupling between the metal grid and the electrode material is achieved by very simple

Measures can be achieved and in particular the application of additional layers or the like is not required. Despite all this, very complex systems can be realized, which can be freely varied in their length, shape and position of structuring.

With the aid of the present invention, the efficiency of planar lighting modules, in particular of OLEDs or QLEDs, can therefore be increased significantly in a relatively simple manner. Also, organic solar cells can be improved in terms of their efficiency with the help of the sectional coupling between grid structure and electrode material.

Claims

claims

1. Light module or organic solar cell, comprising

two plate-shaped electrodes (12, 13) and an active material (14) arranged between the two electrodes (12, 13),

wherein one of the two electrodes (12, 13) consists of a transparent material and is provided with a grid structure which has at least one metallic conductor track (11) running on the surface or in the material of the electrode (12), characterized

that the conductor track (11) is only partially connected to the electrode material.

2. Light module or organic solar cell according to claim 1,

characterized,

in that the conductor track (11) of the grid structure extends from a lateral connection region (10) of the electrode (11) into a central region, wherein the said

Connection portion (10) closer portion (I Ia) of the conductor track (11) is separated from the electrode material.

3. Light module or organic solar cell according to claim 1 or 2,

characterized,

in that an end region (11c) of the conductor track (11) is separated from the electrode material.

4. Light module or organic solar cell according to one of the preceding sections, characterized

in that the separation between the conductor track (11) and the electrode material takes place through cuts in the electrode material.

5. Light module or organic solar cell according to one of the preceding sections, characterized that the grid structure has a plurality of mutually parallel conductor tracks (11).

6. Light module or organic solar cell according to one of the preceding claims, characterized

that the active material is an organic material.

7. lighting module according to claim 6,

characterized,

that it is an OLED or QLED.