FR3036853A1 - METHOD FOR PRODUCING AN ORGANIC ELECTROLUMINESCENT DIODE - Google Patents

Abstract

The present invention relates to a method for producing an organic electroluminescent diode comprising: a step of forming a stack of layers on a substrate (50), a step of forming a protective layer (400), said step being configured so that the protective layer (400) covers at least part of the protruding portion (150, 250), a step of forming, through the protective layer (400), an access (501, 502) to the protruding portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200), a step of forming a metal layer (701, 702) filling at least one of the access (501, 502) to the protruding portion (150, 250) so that the metal layer (701, 702) is electrically continuous with the protruding portion (150, 250) of the at least one among the first electrode (100) and the second electrode (200).

Description

FIELD OF THE INVENTION The present invention relates to the field of lighting and in particular the use of organic light-emitting diodes which, when powered by an electric current, emit their own light. The present invention receives for advantageous application a method of producing such an organic light-emitting diode. BACKGROUND ART The light-emitting diode, better known by the acronym LED in English for "Light Emitting Diode", is a semiconductor with physical properties such that the light-emitting diode has the ability to directly convert electricity into light, while being unparalleled in terms of energy efficiency. Light-emitting diode illumination allows a homogeneous distribution of the light beam; this lighting is particularly close to the light of day.

It is these advantageous characteristics that have attracted designers to take an increasing interest in light-emitting diodes for automotive applications, for example, or in the field of lighting. These light sources also represent excellent opportunities for "designers". For example, it is possible to combine several diodes in order to create different shapes, luminance sets (the organic-type light-emitting diodes having, for example, a lower luminous radiation than that of the other diodes) and thus to obtain original visual effects. . Nevertheless, current technologies have limitations. Organic light-emitting diodes in particular have a constraining manufacturing process because of the high sensitivity to water and air of the organic layer, thereby requiring protection by encapsulation of this layer. On the other hand, arrangements must be made to avoid short circuits; the production of organic light-emitting diode-type light sources in large size requires, for example, a separation of two electrodes.

Currently, the organic layers are thermally deposited through a common stencil and serve in other words to separate the anode and the cathode. However, one of the disadvantages is that the organic layer is not fully protected by the cathode and, therefore, is therefore particularly sensitive to degradation as well as oxidation. In terms of manufacturing method, the positioning of the various layers forming the diode requires a particular machining of the stencils used during masking steps.

A solution for protecting the organic layers in particular is to deposit a protective layer so as to encapsulate the stack of layers (anode, organic layer, cathode) forming the organic light-emitting diode. To do this, it has been demonstrated that the technique of deposition of atomic monolayers (ALD in English for "Atomic Layer Deposition") makes it possible to produce a protective layer, preferably formed of a material chosen from aluminum (Al 2 O 3), silicon dioxide (SiO 2) or titanium dioxide (TiO 2), of excellent quality, typically between 10 and 100 nanometers thick. Nevertheless, one of the drawbacks of the ALD deposition technique is the difficulty of performing a masking step making it possible to save the electrical contacts (typically electrode contact pickups: anode and cathode) of the organic light-emitting diodes. Indeed, the contact resumptions are not bright and serve for the external electrical connection to the organic light emitting diode 15; they should not therefore be covered by a protective layer; said protective layer being electrically insulating. Given the constraints related to the manufacturing process of light emitting diodes, the present invention provides a simplified and less expensive method, allowing the realization of contact resumption for an organic light-emitting diode preserving good encapsulation of the organic layer in particular, while promoting a better luminous homogeneity of said organic electroluminescent diode.

SUMMARY OF THE INVENTION The present invention relates to a method of producing an organic electroluminescent diode comprising a step of forming a stack of layers on a substrate; said stack comprising, successively and in order, a first electrode deposited on the substrate, an organic layer deposited in contact with at least a portion of the first electrode, a second electrode deposited in contact with at least a portion of the organic layer; the at least one of the first electrode and the second electrode comprising an overflowing portion not covered either by the organic layer or by the other of the first electrode and the second electrode.

Advantageously, the method comprises a step of forming a protective layer, said step being configured so that the protective layer covers at least part of the protruding part, a formation step, through the layer protection, access to the protruding part of the at least one of the first electrode and the second electrode, a step of forming a metal layer at least partially filling the access to the overflow part so the metal layer is in electrical continuity with the protruding portion of the at least one of the first electrode and the second electrode.

The present invention also relates to an organic electroluminescent diode comprising a stack of layers on a substrate; said stack comprising, successively and in order, a first electrode deposited on the substrate, an organic layer deposited in contact with at least a portion of the first electrode, a second electrode deposited in contact with at least a portion of the organic layer; the at least one of the first electrode and the second electrode comprising an overflowing portion not covered either by the organic layer or by the other of the first electrode and the second electrode. Advantageously, the diode comprises a protective layer, said protective layer covering at least partly the projecting portion. The diode includes, through the protective layer, access to the protruding portion of the at least one of the first electrode and the second electrode. The diode also comprises a metal layer at least partially filling the access to the protruding portion so that the metal layer is in electrical continuity with the protruding portion of the at least one of the first electrode and the second electrode.

Thus, the technical effect of the present invention is to provide a thin-film encapsulation solution of the organic light-emitting diode, a guarantee of reliability concerning the electrical conductivity from the electrodes of the diode, as well as luminous homogeneity. of said diode, while ensuring the protection of the organic layer especially during the formation of contact resumption. In this way, the layers present in the organic light-emitting device, known to be particularly sensitive to water and oxygen, are protected by the means used.

BRIEF INTRODUCTION OF THE FIGURES Other characteristics, objects and advantages of the present invention will appear on reading the detailed description which follows, with reference to the accompanying drawings, given by way of nonlimiting example, and in which: FIG. 1 illustrates a schematic view in longitudinal section of a stack on a substrate of different layers forming an organic light-emitting diode; said stack being covered with a protective layer. FIG. 2 illustrates a schematic view in longitudinal section of a stack on a substrate of different layers forming an organic light-emitting diode, after the formation of an access, by laser ablation, to at least one of the electrodes through the protective layer. FIG. 3A illustrates a schematic view in longitudinal section of said stack following total ablation; metal contacts being made at each of the electrodes forming the diode. FIG. 3B illustrates a schematic view in longitudinal section of said stack, following a partial ablation. For the sake of clarity, the elements in the figures are not represented to scale.

DETAILED DESCRIPTION It is pointed out that in the context of the present invention, the term "on" does not necessarily mean "in contact with". Thus, for example, the deposition of a layer on another layer does not necessarily mean that the two layers 25 are in direct contact with one another, but that means that one of the layers at least partially covers the other being either directly in contact with it, or being separated from it by a film, yet another layer or another element. It is also specified that a layer may comprise a plurality of layers. On the other hand, the term "layer" does not necessarily mean a full plate distribution on the substrate. Before entering into detail of preferred embodiments of the invention with reference to the drawings in particular, other optional features of the invention, which can be implemented in combination in any combination or alternatively, are The formation of the access to the projecting portion comprises a localized fusion of the protective layer material and the material of at least a portion of the projecting portion of the at least one of the first electrode and the second electrode.

According to one embodiment, the melting is carried out over the entire thickness of the protruding portion of the at least one of the first electrode and the second electrode, so as to reach the substrate. The melting is performed to form an electrically conductive portion, at least on the edges of the access to the protruding portion of the at least one of the first electrode and the second electrode. The formation of the metal layer is carried out so that the metal layer covers at least partly the electrically conductive portion. The formation of access to the protruding portion includes etching of at least the laser ablation protection layer. The step of forming the stack of layers is carried out so that the other one of the first electrode and the second electrode comprises a projecting portion not covering either the first electrode or the organic layer.

The formation of the protective layer is carried out so that the protective layer is electrically insulating. The formation of the protective layer comprises an atomic layer deposition. The formation of the metal layer comprises thermal evaporation or sputtering. A portion, advantageously electrically conductive, is formed, at least on the edges of the access to the projecting portion of the at least one of the first electrode and the second electrode. The electrically conductive portion comprises an alloy of the material forming the protective layer and the material forming the protruding portion of the at least one of the first electrode and the second electrode. The concentration of the material of the protective layer in the electrically conductive portion is less than 50%. The metal layer covers at least part of the electrically conductive portion.

The other of the first electrode and the second electrode comprises an overhanging part covering neither the first electrode nor the organic layer. The protective layer is made of an electrically insulating material.

The protective layer comprises a material selected from aluminum oxide, silicon oxide, titanium oxide. The at least one protruding portion of the at least one of the first electrode and the second electrode comprises a bilayer stack. At least one of the first metal layer and the second metal layer comprises a thickness greater than 100 nanometers. The protective layer comprises a thickness greater than 25 nanometers, preferably of the order of 50 nanometers. As indicated above, the following process aims to provide at least one organic light-emitting diode comprising a protective layer; said protective layer serving as a layer for encapsulating and protecting sensitive layers such as the organic layer. In a first step, illustrated in FIG. 1, a stack of 20 layers is formed on a substrate 50. Advantageously, the substrate 50 is a flat plate made of a transparent material. Optionally, the substrate 50 is made of glass. A first electrode 100 is preferably deposited on the substrate 50. An organic layer 300 is advantageously deposited so as to cover a portion 25 of the first electrode 100. Preferably, the first electrode 100 protrudes laterally from the organic layer 300. Advantageously the first electrode 100 has an overflowing portion 150 not covered by the organic layer 300. A second electrode 200 is deposited so as to at least partially cover the organic layer 300. According to a preferred embodiment, the second electrode 200 is extends beyond the organic layer 300 as shown in FIG. 1. The second electrode 200 protrudes laterally from the stack of layers. The protruding portion 150 of the first electrode 100 and the protruding portion 250 of the second electrode 200 are neither superimposed nor in contact. They may be located on opposite edges of the stack of layers.

Preferably, the first electrode 100 constitutes the anode. The first electrode 100 is typically made of a metallic material.

According to one embodiment where the emission of light is in the direction opposite to the substrate 50, the first electrode 100 is chosen from a reflective material (or even a semi-reflective material). The first electrode 100 may be, for example, aluminum.

According to a preferred embodiment where the emission of light is through the substrate 50, then the first electrode 100 is selected from a transparent material. Preferably, the first electrode 100 is composed of a layer 101 for example based on indium oxide doped with tin (Indium Tin Oxide, ITO). Particularly advantageously, the first electrode 100 comprises at least 10 on the projecting portion 150 an additional layer 102 deposited on the layer 101 previously formed. The additional layer 102 comprises for example a metallic material such as aluminum or silver or a magnesium / silver alloy. Optionally, the first electrode 100 is at least 85% transparent to allow light transmission. According to a preferred embodiment, the organic layer 300 is advantageously arranged to be inserted between the first electrode 100 and the second electrode 200. The organic layer 300 is advantageously composed of one or more sublayers. These sub-layers preferably comprise specific materials, making it possible to improve the injection of electrons and holes, and consequently to improve the efficiency of the light emission device. By way of example, the organic layer 300 may in particular comprise a hole injection layer, a hole transport layer, a light emission layer produced by the recombination of the holes and electrons, a layer of 25 electron transport and an electron injection layer. The second electrode 200 generally constitutes the cathode. Advantageously, the second electrode 200 is transparent. Optionally, it is semi-transparent. The second electrode 200 is typically made of a metallic material. The second electrode 200 may, for example, be of a material such as aluminum or silver or a magnesium / silver alloy. It is preferably deposited by thermal evaporation. The thicknesses of the first electrode 100, the organic layer 300 and the second electrode 200, are advantageously between 10 nanometers and 200 nanometers.

According to a preferred embodiment, the deposition conditions of the different layers are under a controlled atmosphere. The presence, in fact, of impurities depends on the atmosphere in which the structures are manufactured.

As illustrated in FIG. 1, after the step of forming a stack of layers, a step of forming a protective layer 400 above said stack of layers follows. The protective layer 400 is preferably arranged so as to cover the entire stack of layers. The protective layer 400 has the advantage of being deposited by atomic layer deposition (ALD in English for "Atomic Layer Deposition"). Preferably, the protective layer 400 is formed so as to have a water vapor transmission rate (VVVTR) for the order of 10-4 g / m 2 / d. The protective layer 400 is advantageously formed of an electrically insulating material. It preferably comprises an inorganic material chosen, for example, from Alumina (Al 2 O 3), Aluminum Oxide (AlO), Silicon Dioxide (TiO 2), Titanium Oxide (TiO 2) or nitrate. Silicon (SiN), Zirconium oxide (ZrO 2), Hafnium oxide (HfO 2), tantalum oxide (Ta 2 O 5), or Nobium oxide (Nb 2 O 5), the oxide of Yttrium (Y 2 O 3), magnesium oxide (MgO), cerium oxide (CeO 2), Lanthanum oxide (La 2 O 3), Strontium titanate (SrTiO 3), Barium titanate (BaTiO 3), Zinc sulphide (ZnS), Selenium sulphide (ZnSe), Telluride zinc (ZnTe), Indium oxide (1n203), Tin dioxide (5nO2), Gallium oxide (Ga203), Nickel oxide (NiO).

Particularly advantageously, the protective layer 400 has a thickness to form a uniform and homogeneous coating on the stack of layers. According to a preferred embodiment, the protective layer 400 has a thickness of less than 100 nanometers and preferably of the order of 50 nanometers.

The protective layer 400 has the advantage of being formed in such a way as to perfectly follow the surface roughness of the stack of layers. The protective layer 400 further has the particularity of forming a coating on the stack of layers, and thereby isolating it electrically. On the other hand, the protective layer 400, thus arranged, acts particularly advantageously as a sealed protective barrier for the sensitive layers such as the first electrode 100, the organic layer 300 and the second electrode 200. The encapsulation (in particular of the organic layer 300) obtained is thus perfectly achieved. FIG. 2 illustrates the step of forming, through the protective layer 400, an access 501, 502 to the protruding portion 150, 250 of the first electrode 100 and / or the second electrode 200. Particularly advantageous, the formation of the access 501, 502 to the projecting portion 150, 250 of the at least one of the first electrode 100 and the second electrode 200 comprises an etching of at least the protective layer 400 by ablation. laser or laser irradiation. According to a non-limiting exemplary embodiment of the invention, an Nd: YAG type laser is used, with a wavelength of 1064 nanometers, a maximum pulse energy of 1 millijoule, a pulse duration of 100 ns, and a maximum repetition rate of 80 kHz.

The openings 501, 502, in the form of openings, have a preferential depth at least equal to the thickness of the protective layer 400. The ports 501, 502 preferably have a width of at least 10 microns. The accesses 501, 502 have the distinction of being separated by a distance of at least 100 microns. The accesses 501, 502 thus formed allow access to the first electrode 100 and / or the second electrode 200. The use of a laser has the advantage of forming patterns of different shapes in the protective layer 400. The pattern can be chosen from a round, oblong, square or rectangular shape. Particularly advantageously, laser ablation does not require a step of protecting the areas not exposed to the laser, and thus avoids the use of a complex process potentially incompatible with the manufacture of light-emitting diodes. Laser ablation removes locally the protective layer 400 to access the electrodes 100, 200 through the ports 501, 502. Advantageously, the laser ablation introduces a local heating on the protective layer 400 and on the one of the first electrode 100 and the second electrode 200. As discussed above, the laser ablation through at least the protective layer 400 causes a local melting of said protective layer 400 with one of the first electrode 100 and the second electrode 200. This fusion is at the origin of a deposit of a portion 601, 602, advantageously electrically conductive, at the edges of the accesses 501, 502 to the first and second electrodes 100, 200, on the surface of the protective layer 400. The set of portions 601, 602 created on the surface of the protective layer 400 corresponds to a zone which is altered by melting of the protective layer 400 situated on the edge of the protective layer 400. access 501, 502, spreading in a plane parallel to the substrate 10. A border is understood to mean a certain width on the contour of an access 501, 502.

These portions 601, 602 come from the localized fusion generating a mixture, in alloy form, of the material of the protective layer 400 and the material of at least a part of the protruding part 150, 250 of the first electrode 100. and / or the second electrode 200. The melting is performed so as to form a portion 601, 602 advantageously electrically conductive. The electrically conductive portion 601, 602 comprises an alloy between the material forming the protective layer 400 and the material forming the protruding portion 150, 250 of the at least one of the first electrode 100 and the second electrode 200. Advantageously, the concentration of the material of the protective layer 400 in the portion 601, 602 electrically conductive is less than 50%.

The surface roughness of the altered zone, ie the thickness of the electrically conductive portions 601, 602, depends mainly on the thickness of the protective layer 400. The portions 601, 602 observed in the altered zone have a height between 50 nm and 200 nm for a thickness of the protective layer of 50 nm and a thickness of ITO of 150 nm, and a minimum width of 10 micron. These portions 601, 602, due to the fusion of the protective layer 400 and the at least one of the first electrode 100 and the second electrode 200, by laser, appear on the edge of the etching. The term electrically conductive portion, a layer portion comprising a resistivity threshold of less than 10-3 Ohm.m.

FIGS. 3A and 3B illustrate the step of forming a metal layer 701, 702. FIG. 3A illustrates an embodiment where laser ablation is performed, in a total manner, so as to consume the entire thickness of the protruding portion 150, 250 of the first electrode 100 and / or the second electrode 200. In the preferred case where the protruding portion 150 of the first electrode 100 comprises an ITO / Aluminum bilayer stack, the resulting fusion of the laser irradiation is carried out over the entire thickness of the projecting portion 150, so as to reach the substrate 50. FIG. 3B illustrates a preferred embodiment where the laser ablation is carried out, in a partial manner, so as not to consume the entire thickness of the protruding portion 150, 250 of the projecting portion 150, 250 of the first electrode 100 and / or the second electrode 200. In the case of a total ablation, the area 3036853 11 etched (c that is, the access 501, 502) during the irradiation will be visible from the face of the substrate 50, opposite the face from which the layers forming the organic light-emitting diode are deposited. This can affect the aesthetics of the diode. Partial ablation is thus preferred without being however limiting of the present invention. The metal layer 701, 702 is made so as to fill at least part of the access 501, 502 to the projecting portion 150, 250 of at least one of the first electrode 100 and the second electrode 200 so that the metal layer 701, 702 is in electrical continuity with said protruding portion 150, 250. Advantageously, the first metal layer 701 is in direct contact with the protruding portion 150 of the first electrode 100, and the second metal layer 702 is in contact with the protruding portion 250 of the second electrode 200; so that the first metal layer 701 and the second metal layer 702 are in electrical continuity, respectively, with the first electrode 100 and the second electrode 200. Advantageously, the metal layer 701, 702 covers at least partly the portion 601, 602 electrically conductive. Preferably, the metal layer 701, 702 comprises a material selected from aluminum, titanium, copper, chromium, silver, zinc, nickel, gold, platinum, magnesium. The metal layer 700 is advantageously carried out by cathodic sputtering or by thermal evaporation. Vacuum deposition advantageously makes it possible to obtain a metal layer 701, 702 whose thickness is between a few nanometers and a few microns (for example, between 50 nanometers and 5 microns). In a particularly advantageous manner, the process according to the invention makes it possible to form a metal layer 701, 702 acting as a contact recovery for the first and second electrodes 100, 200, ie the anode and the cathode, without resorting to steps masking electrodes 100, 200. The metal layers 701, 702 are advantageously in electrical continuity with each of the electrodes 100, 200 of the diode. In a particularly advantageous manner, the protective layer 400 serves to serve as a layer for encapsulating sensitive layers such as the organic layer 300.

The present invention thus proposes a particularly simple and inexpensive method for obtaining an organic light emission device having increased reliability and luminous homogeneity; the sensitive layers of the diode 5 being protected from any damage that may occur during a conventional method of producing organic light-emitting diodes. On the other hand, the encapsulated device is advantageously compatible with industrial requirements, also for large areas.

The invention is not limited to the embodiments described above, but extends to all embodiments within its spirit.

Claims (19)

REVENDICATIONS1. A method of making an organic electroluminescent diode comprising: - a step of forming a stack of layers on a substrate (50); said stack comprising, successively and in order, a first electrode (100) deposited on the substrate (50), an organic layer (300) deposited in contact with at least a portion of the first electrode (100), a second electrode (200) deposited in contact with at least a portion of the organic layer (300); the at least one of the first electrode (100) and the second electrode (200) comprising an overflowing portion (150, 250) not covered either by the organic layer (300) or by the other of the first electrode ( 100) and the second electrode (200), characterized in that it comprises: - a step of forming a protective layer (400), said step being configured so that the protective layer (400) covers at least partly the protruding portion (150, 250); - a step of forming, through the protective layer (400), an access (501, 502) to the projecting portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200), - a step of forming a metal layer (701, 702) at least partially filling the access (501, 502) to the protruding (150, 250) so that the metal layer (701, 702) is electrically continuous with the overlying portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200). 2. Method according to the preceding claim wherein the formation of the access (501, 502) to the projecting portion (150, 250) comprises a localized melting of the material of the protective layer (400) and the material of at least a portion of the protruding portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200). 3. Method according to the preceding claim comprising a melting over the entire thickness of the protruding portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200), so as to reach the substrate (50). 4. Method according to any one of the two preceding claims wherein the melting is carried out so as to form a portion (601, 602) electrically conductive, at least on the edges of the access (501, 502) to the part protruding (150, 250) of the at least one of the first electrode (100) and the second electrode (200). 10 5. Method according to the preceding claim wherein the formation of the metal layer (701, 702) is formed so that the metal layer (701, 702) covers at least partly the portion (601, 602) electrically conductive. 6. A method according to any one of the preceding claims wherein the formation of the access (501, 502) to the protruding portion (150, 250) comprises etching of at least the protective layer (400) by ablation. laser. A method according to any one of the preceding claims wherein the step of forming the stack of layers is performed so that the other one of the first electrode (100) and the second electrode (200) comprises an overflowing portion (150, 250) covering neither the first electrode (100) nor the organic layer (300). The method of any of the preceding claims wherein the formation of the protective layer (400) is performed so that the protective layer (400) is electrically insulating. 9. A method according to any of the preceding claims wherein the formation of the protective layer (400) comprises an atomic layer deposition. The method of any of the preceding claims wherein the formation of the metal layer (701, 702) comprises thermal evaporation or sputtering. 35 An organic electroluminescent diode comprising: a stack of layers on a substrate (50); said stack comprising, successively and in order, a first electrode (100) deposited on the substrate (50), an organic layer (300) deposited in contact with at least a portion of the first electrode (100), a second electrode (200) deposited in contact with at least a portion of the organic layer (300); the at least one of the first electrode (100) and the second electrode (200) comprising an overflowing portion (150, 250) not covered either by the organic layer (300) or by the other of the first electrode ( 100) and the second electrode (200), characterized in that it comprises: a protective layer (400), said protective layer (400) covering at least in part the overflowing portion (150, 250), through of the protective layer (400), an access (501, 502) to the protruding portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200), a metallic layer (701, 702) at least partially filling the access (501, 502) to the protruding portion (150, 250) so that the metal layer (701, 702) is in electrical continuity with the overlying portion (150 250) of the at least one of the first electrode (100) and the second electrode (200). 12. Diode according to the preceding claim comprising a portion (601, 602) electrically conductive, at least on the edges of the access (501, 502) to the projecting portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200). 13. Diode according to the preceding claim wherein the portion (601, 602) electrically conductive comprises an alloy of the material forming the protective layer (400) and the material forming the overflowing portion (150, 250) of the at least 30 a among the first electrode (100) and the second electrode (200). 14. Diode according to any one of the two preceding claims wherein the concentration of the material of the protective layer (400) in the portion (601, 602) electrically conductive is less than 50%. 35 3036853 16 15. Diode according to any one of the three preceding claims wherein the metal layer (701, 702) covers at least part of the portion (601, 602) electrically conductive. 5 16. Diode according to any one of the five preceding claims wherein the other one of the first electrode (100) and the second electrode (200) comprises an overflowing portion (150, 250) not covering the first electrode (100), nor the organic layer (300). 10 17. Diode according to any one of the six preceding claims wherein the protective layer (400) is made of an electrically insulating material. 18. A diode according to any one of the preceding claims wherein the protective layer (400) comprises a material selected from aluminum oxide, silicon oxide, titanium oxide. 19. A diode according to any one of the preceding claims wherein the at least one protruding portion (150, 250) of the at least one of the first electrode (100) and the second electrode (200) comprises a stack bilayer.