Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/805—Electrodes
  • H10K50/81—Anodes
  • H10K50/816—Multilayers, e.g. transparent multilayers
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/805—Electrodes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/805—Electrodes
  • H10K50/81—Anodes
  • H10K50/813—Anodes characterised by their shape
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/805—Electrodes
  • H10K50/81—Anodes
  • H10K50/814—Anodes combined with auxiliary electrodes, e.g. ITO layer combined with metal lines
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
  • H10K50/856—Arrangements for extracting light from the devices comprising reflective means

Definitions

• the present invention relates to a supported electrode for use, preferably as anode, in an organic light-emitting diode.
• An organic light-emitting diode is an opto-electronic device comprising two electrodes, at least one of which is transparent to visible light, and a stack of thin layers comprising at least one light-emitting layer. (EL layer).
• This light-emitting layer is sandwiched at least between, on the one hand, an electron injection or transport layer (EIL or ETL) located between the EL layer and the cathode and, on the other hand, a injection or hole transport layer (HIL or HTL) located between the EL layer and the anode.
• EIL or ETL electron injection or transport layer
• HIL or HTL injection or hole transport layer
• OLEDs having a transparent electrode support and a transparent electrode in contact therewith are conventionally referred to as OLEDs that emit through the substrate or OLEDs that emit downward (bottom emitting OLED).
• the transparent electrode is typically the anode.
• OLEDs with an opaque electrode support are called OLEDs (top emitting OLED), the emission then being through the transparent electrode which is not in contact with the support, usually the cathode.
• OLED directly depends on the potential difference between the anode and the cathode.
• a known way to limit this ohmic drop is the reduction of the resistance per square (RD OUR S , of the English sheet resistance) of the electrodes, typically by increasing their thickness.
• RD OUR S resistance per square
• Such an increase in the thickness of the electrodes poses significant problems when it comes to transparent electrodes. Indeed, the materials used for these electrodes, for example ⁇ (Indium Tin Oxide), have insufficient light transmission and a prohibitive cost that make thicknesses greater than 500 nm are very uninteresting. In practice, the ITO layers do not exceed about 150 nm.
• the present invention is based on the surprising discovery that the decrease in the opening rate of a transparent electrode does not lead to not necessarily a reduction in the amount of light extracted from the EL layer, via the HTL or ETL layer, and the transparent layer of the electrode, to the glass support and, finally, the air.
• the stack of HTL / EL / ETL layers has a high refractive index, close to 1.8, while the refractive index of the transparent support, when it is made of ordinary glass, is about 1 , 5, and that of the air equal to 1.
• the total internal reflection of the light at different interfaces makes the OLED is a waveguide in which a very large part of the light is reflected a large number of times and ends up being absorbed.
• diffusing elements microparticles, nanoparticles, micropores or nanopores .
• These diffusing elements may be incorporated in the substrate or in the electrode or they may be inserted between the electrode and the substrate in the form of an additional diffusing layer, as described for example in international application WO2009 / 116531.
• ⁇ 2 90 °
• the grazing rays are all the less likely to reach the electrode / substrate interface as the height of the metal strands is high.
• the subject of the present invention is therefore an OLED-transparent composite electrode comprising, on a transparent substrate, an electrode layer formed by a continuous metal network, of regular or irregular grid type, incorporated in a transparent conductive layer, and in which the average size of the "meshes" (in English mesh) non-metallized is reduced compared to composite electrodes known hitherto.
• the subject of the present invention is an organic electroluminescent diode electrode comprising
• a transparent or translucent layer having a refractive index between 1.6 and 2.4, preferably between 1.75 and 2.05, and a resistivity greater than that of the continuous network of metallic lines and less than 10 4 ⁇ -cm, preferably less than 10 3 ⁇ -cm, said layer completely covering the network of metallic lines and the non-metallized domains, the continuous network of metal lines (b) and the transparent or translucent layer (c) together forming a composite layer called an electrode layer.
• the subject of the invention is also an OLED containing such an electrode, this electrode being preferably the anode, and the OLED preferably being an OLED emitting through the substrate.
• the non-conductive substrate used in the present invention may be any inorganic or organic glass substrate conventionally used in the field of OLEDs. It can also be a sheet or a flexible plastic film.
• transparent or translucent substrate is meant a substrate having a light transmission (T L ) of the light (determined according to standard NF EN 410) of at least 85%. It is generally flat and flat substrates, possibly polished, having two main surfaces and a slice. The thickness of the substrate is preferably between 0.05 and 5 mm.
• refractive index in the present application is meant the refractive index of the material determined at a wavelength of 550 nm.
• Certain anisotropic materials serving as transparent substrates may have more than one refractive index.
• at least one of the refractive indices of the anisotropic substrate has a value of between 1.3 and 1.6 at 550 nm.
• at least one non-zero component of the electromagnetic radiation of the OLED will be emitted along the axis having an index of refraction between 1.3 and 1.6.
• the continuous network of metal lines is generally deposited on only one of the main surfaces of the substrate. This main surface is covered in one or more areas of the continuous network of metal lines. When it is a single area, it can cover the entire main surface of the substrate or only a part of this surface. It may indeed be interesting to leave free, for example, a peripheral zone of this surface. It is important to note that the area of the zone or areas covered by the continuous network of metal lines will be used in the present reference value application, for example for the definition and calculation of the opening ratio or weight of the metal network.
• the metal or metal alloy forming the continuous network of metal lines (b) preferably has an electrical conductivity of between 6 ⁇ 10 6 m.sup.- 1 and 6.3 ⁇ 10.sup.- 7 m.sup.- 1 , this latter value corresponding to the electrical conductivity of silver, superior to that of all other metals.
• the metal or metal alloy is preferably selected from the group consisting of silver, copper, aluminum, gold, and alloys based thereon.
• Silver is the most preferred metallic material because it has both the best possible electrical conductivity and a higher reflection coefficient than all other metals. However, it is a metal considerably more expensive than aluminum and copper.
• the continuous network of metal lines is therefore formed of a network based on aluminum and / or copper plated silver.
• Silver plating may be by simple electrochemical methods and well known in the art.
• Such a composite network of copper or silver-plated aluminum has the reflection coefficient of silver and a cost close to that of the underlying metal (Al or Cu).
• the geometry of the continuous network of metal lines is of great importance. It is characterized by the following parameters:
• the average equivalent diameter (D) of the unmetallized domains is the average of all the equivalent diameters of the nonmetallized domains, also called “openings", determined by image analysis on an electron microscope or optical.
• the equivalent diameter of a non-metallized domain is the diameter of a circle of the same area as the non-metallized domain.
• the opening ratio (T) is the ratio of the non-metallized surface to the total area (non-metallized surface + metallized surface) of the zone covered by the continuous network of metal lines. This opening rate is measured, as the average equivalent diameter, by image analysis.
• the light transmission is the ratio of the light flux transmitted by a material to the incident light flux.
• the light transmission depends, among other things, on the absorption coefficient and the thickness of the material considered.
• the light transmission (T L ) is always significantly lower than the opening ratio. Indeed, absorption and reflection of light by the continuous network of metal lines (b) are added absorption and reflection of light by the layer (c).
• a composite electrode consisting of a metal network having an opening ratio of 70%, which is filled and covered with a transparent layer (c) having (in the absence of the network (b)) a light transmission of 80% will globally have a T L of about 56%.
• the average width L of the metal lines is obtained by calculation from the two experimental quantities defined above (D and T), assimilating the continuous network to a regular metal grid having square openings of side e to the formula:
• D being the average equivalent diameter of the continuous network of metal lines.
• the average equivalent diameter D of the continuous network of metal lines of the electrode of the present invention is between 0.1 and 7.0 ⁇ , preferably between 0.3 and 4.0 ⁇ , more preferably between 0.4 and 3.0 ⁇ and ideally between 0.5 and 2.0 ⁇ .
• the continuous network of metal lines must of course be such that the distribution of the equivalent diameters of the non-metallized domains is relatively narrow. This is a prerequisite for a good homogeneity of lighting.
• the electrode is preferably free of unmetallized domains visible to the naked eye, as this visibility would be felt by the viewer as a defect. More particularly, the cumulative area of the non-metallized domains having an equivalent diameter greater than 15 ⁇ m preferably does not exceed 5%, in particular not 2% and ideally not 1% of the total area over which the continuous network of metallic lines.
• the opening rate of the continuous network of metal lines may in principle be between relatively wide limits, for example between 20% and 80% of the area covered by said network, the Applicant has observed that it is more advantageous to use opening rates of the electrode layer of between 30 and 70%, preferably between 30% and 60%, and even between 35% and less than 50%.
• the present invention is based on the principle of the reorientation of the glowing light rays emitted by the EL layer and striking the network of metal lines.
• this reorientation to be effective, it must result in a reduction in the angle of incidence of the light beam when the latter, after having been reflected for example by the counter-electrode, returns to strike the substrate / interface again. electrode layer.
• the continuous metal network comprises only parallel surfaces and surfaces perpendicular to the substrate / electrode layer interface
• such a reorientation would not take place and the light beam would return with the same angle of incidence on the substrate / layer surface, as shown in FIG. 1.
• the surfaces of the continuous metal network should ideally have near-angle surfaces 45 ° with respect to the plane of the substrate and the electrodes.
• the continuous network of metal lines of the electrode of the present invention is therefore substantially free of parallel surfaces or perpendicular to the plane of the interface between the electrode layer (c) and the substrate (a). This technical characteristic does not of course concern the contact surface between the network and the substrate but only the contact surface between the metal network (b) and the layer (c).
• a cross section of such an electrode according to the invention is shown in FIG.
• the continuous network of metal lines (b) is advantageously free in a large proportion, that is to say more than 30%, preferably more than 50% and even more preferably greater than 80%, of parallel surfaces or perpendicular to the plane of the interface between the electrode layer and the substrate.
• At least 20%, preferably at least 40%, more preferably at least 60% of the surface of the continuous network of metal lines have an angle of between 15 and 75 °, of preferably between 25 and 65 ° and in particular between 33 ° and 57 ° relative to the plane of the substrate and the electrode, these percentages and these angles concerning the network interface (b) / layer (c).
• These angles can be evaluated as the slopes of tangents to the metal lattice on a transverse profile: They can be determined by scanning electron microscopy (SEM) or transmission (TEM), followed by image analysis, a cross section of the electrode, obtained for example by open fracture at low temperature or cutting.
• the metal lines In order for the continuous metal network to prevent grazing light rays from striking the non-metallized areas, the metal lines must have a certain height. This height is preferably at least one third of the width L of the metal lines and preferably between L / 2 and L / 1.5.
• the mass per unit area of the continuous network of metal lines (b) is preferably between 4 and 1000 ⁇ g / cm 2 of electrode, in particular between 20 and 600 ⁇ g / cm 2 of electrode, and ideally between 50 and 300 ⁇ g / cm 2 of electrode.
• the "openings" of the continuous network of metal lines are filled with a transparent or translucent electroconductive material. This material has a refractive index of between 1.70 and 2.40, preferably between 1.75 and 2.05, in particular between 1.80 and 1.98, and a resistivity greater than that of the continuous network of metallic lines. and less than 10 4 ⁇ -cm.
• This layer not only fills the voids left by the metal network but completely covers the latter.
• this layer (c) of planarization is as rough as possible.
• this layer is a metal oxide, its roughness RMS is preferably less than 5 nm, in particular less than 3 nm.
• this transparent or translucent layer (c) any transparent or translucent conductive material having a sufficiently high refractive index, close to the average index of the HTL / EL / ITL stack, and a conductivity less than that of the metal network.
• transparent conductive oxides such as aluminum-doped zinc oxide (AZO), indium-doped tin oxide (ITO), aluminum oxide, and aluminum oxide.
• AZO aluminum-doped zinc oxide
• ITO indium-doped tin oxide
• SnZnO indium-doped tin oxide
• Sn0 2 tin dioxide
• These materials advantageously have a much lower absorption coefficient than the organic materials forming the stack HTL / EL / ITL, preferably an absorption coefficient of less than 0.005, in particular less than 0.0005.
• the transparent conductive oxide is not ⁇ , it may be necessary to cover the layer (c) with a thin additional layer having an output work greater than that of the layer (c), for example a layer of ITO of Mo0 3 , W0 3 or V 2 0 5 .
• Deposition techniques for such oxides such as sputtering, magnetron deposition, sol-gel processes or pyrolysis, generally do not result in sufficiently smooth layers for application as an OLED electrode. . It will therefore generally be necessary to proceed, after deposition, to a polishing step.
• PEDOT poly (3,4-ethylenedioxythiophene)
• PEDOT poly (3,4-ethylenedioxythiophene)
• PEDOT poly (3,4-ethylenedioxythiophene)
• a high index oxide such as titanium oxide.
• the possibility of depositing this polymer in liquid form indeed makes it possible to obtain layers (c) of sufficient surface smoothness, which could make the polishing step superfluous.
• the present invention also encompasses embodiments where layer (c) not only functions as anode, but also the role of hole transport layer (HTL), ie embodiments where the electrode does not include not a separate electrode layer and HTL layer.
• HTL deposited during the realization of an OLED stack is indeed a material perfectly usable both as HTL and as anode because low conductivity is sufficient because of the proximity of the metal gate on which it is deposited. In this case, it may be necessary to position under the layer (c) a thin additional layer having a suitable output work, for example a layer of ITO, Mo0 3 , WO 3 or V 2 0 5 .
• the layer (c) of the electrode of the present invention may thus contain a certain fraction of particles or pores having a mean equivalent diameter of between 0.05 and 2 ⁇ , preferably between 0.1 and 0.5 ⁇ .
• the presence of such particles if it effectively helps the extraction of light, however, results in too high concentrations by some opacity of the layer. Due to the particular geometry of the composite electrode layer of the present invention, the problems of light extraction are largely solved and the presence of scattering particles or pores becomes less important or even superfluous.
• the layer (c) of the composite electrode layer therefore contains less than 1% by volume, preferably less than 0.8% by volume of pores or particles having a mean equivalent diameter of between 0.05 and 2 ⁇ . . It is preferably a transparent layer essentially free of such pores and diffusing particles having a mean equivalent diameter of between 0.05 and 2 ⁇ .
• the composite electrode layer of the present invention formed by the continuous network of metal lines (b) and the transparent or translucent layer (c) preferably has a total thickness of between 0.1 and 3 ⁇ , in particular between 0 , 2 and 1.0 ⁇ , and more preferably between 0.3 and 0.6 ⁇ .
• Its resistance per square (RD) is preferably the lowest possible and in particular less than 5 ⁇ / D, preferably between 0.05 and 2.0 ⁇ / D, in particular between 0.1 and 1 ⁇ / D.
• the electrode of the present invention can be used for the manufacture of OLEDs according to methods familiar to those skilled in the art using known steps and materials.
• the layers of the OLED HTL / EL / ITL stack of the present invention preferably have an average refractive index of between 1.7 and 2.1, i.e. an index close to that of the translucent or transparent layer (c) directly in contact with the stack.
• the supported electrode of the present invention may be manufactured for example as follows:
• a continuous aluminum or silver metal layer is deposited by magnetron cathode sputtering onto a mineral glass sheet in a thickness of about 300 nm.
• the aperture rate T measured by image analysis, is 48%.
• the width L of the metal lines of the grid is calculated as 0.76 ⁇ .
• the layer thus "perforated” is then subjected to a limited etching intended to texture the metal surface of the grid so as to increase the proportion of surfaces have an angle close to 45 ° relative to the plane of the electrode. Then deposited over the entire textured metal network a layer of AZO by sputtering in a thickness of the order of 500 nm. This layer is then polished so as to obtain a surface roughness of less than 2 nm.
• FIG. 1 represents a cross-sectional view of an OLED containing a comparative electrode
• FIG. 2 represents a cross-sectional view of an OLED containing an electrode according to the invention.
• FIG. 1 an OLED with a non-conducting support or substrate (1) carrying a composite anode consisting of a continuous network of metal lines (2) whose voids are filled by a transparent conductive oxide (3). .
• the composite anode is surmounted by a stack of HTL / EL / ETL layers (4) in contact with the cathode (5).
• the set of surfaces of the continuous network of metal lines (2) is either parallel or perpendicular to the anode / support interface (6).
• a radius R having a high angle of incidence ⁇ (greater than 57 °) is reflected by the interface (6), the surface of the continuous metal network (2), the cathode (5) and then again hit the interface (6) with an angle ⁇ 2 identical to ⁇ .
• FIG. 2 The components of the electrode according to the invention shown in FIG. 2 are the same as those of FIG. 1. The only difference lies in the fact that the surfaces of the metal network (2) are neither perpendicular nor parallel to the interface (6) between the electrode (3) and the support (1). The phenomenon of trapping the light beam is thus impossible.
• a radius R having a high angle of incidence ⁇ is reflected by the interface (6), the surface of the continuous metal network (2), the counter-electrode (cathode) (5) and then again hits the interface ( 6) with an angle ⁇ 2 smaller than ⁇ and sufficiently low to be refracted by the interface (6).

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• 2012
  • 2012-02-10 FR FR1251258A patent/FR2986909B1/fr not_active Expired - Fee Related
• 2013
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  • 2013-02-07 EP EP13706646.0A patent/EP2812932A1/fr not_active Withdrawn
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  • 2013-02-07 US US14/377,657 patent/US20150001520A1/en not_active Abandoned
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  • 2013-02-07 WO PCT/FR2013/050255 patent/WO2013117862A1/fr active Application Filing
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