DECROUPET DANIEL (BE)
JACOBS NADIA (BE)
DECROUPET DANIEL (BE)
| US20030184221A1 | 2003-10-02 | |||
| DE19628119A1 | 1998-01-29 | |||
| EP1641054A2 | 2006-03-29 | |||
| US20040188690A1 | 2004-09-30 | |||
| EP1562206A2 | 2005-08-10 |
| CLAIMS
1. An organic electroactive photonic device comprising a substrate, a first electrode, a second electrode and an organic film disposed between the first and the second electrode, characterised in that the first electrode includes at least one material selected from the group consisting of antimony-doped tin oxide, fluorine- doped tin oxide, aluminium-doped zinc oxide, fluorine-doped zinc oxide and zinc- tin oxide.
2. A device according to claim 1, characterised in that it comprises an encapsulating material on its side opposite to the substrate.
3. A device according to claim 1 or claim 2, characterised in that the first electrode is positioned between the organic film and the substrate.
4. A device according to claim 2, characterised in that the first electrode is positioned between the organic film and the encapsulating material.
5. A device according to claim 3, characterised in that an additional layer is positioned between the substrate and the first electrode.
6. A device according to claim 4, characterised in that an additional layer is positioned between the encapsulating material and the first electrode.
7. A device according to claim 5 or claim 6, characterised in that the additional layer is selected from the group consisting of iridescence-reducing layers and barrier layers adapted to reduce alkali migration.
8. A device according to any one of claims 5, 6 or 7, characterised in that the additional layer comprises a least one material selected from the group consisting of SiO 2 and SiO x .
9. A device according to any one of claims 5, 6 or 7, characterised in that the additional layer comprises a first sublayer consisting essentially of SnO 2 and a second sublayer consisting essentially of SiO 2 .
10. A device according to any preceding claim, characterised in that the first electrode has a thickness in the range 100 to 500 nm.
11. A device according to any preceding claim, characterised in that the additional layer has a thickness in the range 5 to 100 nm.
12. A device according to any preceding claim, characterised in that the substrate and the encapsulating material are selected from the group comprising glass and plastic.
13. A device according to any preceding claim, characterised in that it comprises, in order, a glass sheet, a layer comprising SiO x , a layer comprising fluorine-doped tin oxide, an organic film and a second electrode.
14. A device according to any one of claims 1 to 12, characterised in that it comprises, in order, a glass sheet, a layer comprising SiO x , a layer comprising antimony-doped tin oxide, an organic film and a second electrode.
15. A device according to any preceding claim, characterised in that it is a light-emitting device.
16. A device according to any of claims 1 to 14, characterised in that it is a light-absorbing device.
17. A method of manufacturing an organic electroactive photonic device comprising the following sequential steps: a) taking a glass substrate having a pyrolytically deposited electrically conductive coating deposited over one of its surfaces, the pyrolytically deposited electrically conductive coating being adapted to serve as the first electrode in the device and comprising at least one material selected from the group consisting of antimony- doped tin oxide, fluorine-doped tin oxide, aluminium-doped zinc oxide, fluorine- doped zinc oxide and zinc-tin oxide; b) depositing an organic film on the glass sheet over the pyrolytically deposited electrically conductive coating; c) arranging a conductive coating adapted to serve as the second electrode in the device over the light emitting film. |
Organic electroactive photonic device
This invention relates to electroluminescent devices and particularly to devices which include an active layer comprising organic and/or organometallic compounds so that the device can emit light, for example organic light-emitting diodes. Organic light-emitting devices may be used, for example, in flat panel display technologies (television sets, computer terminals...) or as lighting means. This invention also relates to devices including an active layer comprising organic and/or organometallic compounds, which can absorb light, for example, a solar cell. Both types of devices, which can emit light or which can absorb light, are herein gathered under the term "organic electroactive photonic devices"
Organic electroluminescent devices (OLEDs) generally comprise a substrate, an electrode disposed over the substrate for supplying charge of a first polarity, an electrode disposed at the other side of the device for supplying charge of a second polarity opposite to said first polarity, an organic light-emitting layer disposed between the electrodes, and an encapsulating material disposed over the whole device. In one arrangement the substrate and the electrode of the first polarity are transparent to allow light emitted by the organic light-emitting layer to pass therethrough. Such an arrangement is known as a bottom-emitting device. In another arrangement the electrode of the second polarity and the encapsulating material are transparent so as to allow light emitted from the organic light-emitting layer to pass therethrough. Such an arrangement is known as a top-emitting device. In still another embodiment, both electrodes and substrate and encapsulating material are transparent and light is emitted through both sides of the device. Variations of the above-described structures are known. For example, the electrode adjacent the substrate may be the anode and the other electrode may be the cathode. Alternatively, the electrode adjacent the substrate may be the cathode and the other
electrode may be the anode. Further layers may be provided between the electrodes and the organic light-emitting layer in order to aid charge injection and transport, for example a hole transporting layer and/or an electron transporting layer and/or doped layers; charge blocking layers may also be introduced to confine the charges within the device. Generally the anode is made of a thin transparent layer of indium tin oxide (ITO), having a high work function (above 4.0 eV).
Whereas indium tin oxide is the most widely used electrode material in
OLEDs, indium is and is becoming more and more scarce and consequently ITO layers are very expensive. Additionally, although ITO provides only one part of an overall OLED system, its lack of availability could potentially jeopardise the commercial exploitation of OLED systems.
Furthermore, a portion of the light emitted by the organic light-emitting material in the organic light-emitting layer does not escape from the device. The light may be lost within the device by scattering, internal reflection, absorption and/or the like. This results in a reduction in the efficiency of the device.
One aim of the present invention is to provide an OLED device that is not dependent upon the use and availability of ITO. Another aim of the present invention is to reduce the amount of light lost within an OLED device.
According to a first aspect, the present invention provides an organic electroactive photonic device according to claim 1. This device may be light-emitting or light-absorbing. Although the hereinafter description will primarily discuss organic light-emitting devices, it is also applicable to light-absorbing devices like solar cells or photovoltaic cells.
One electrode of the device may include at least one material selected from the group consisting of antimony-doped tin oxide, fluorine-doped tin oxide, aluminium-doped zinc oxide, fluorine-doped zinc oxide and zinc-tin oxide.
Those materials may offer electrodes at least as efficient as ITO electrodes but with greater availability and/or at a lower cost.
Furthermore, use of an electrode according to the present invention may allow exit of a greater proportion of light out of the OLED. It is believed that this could be due to the texture of such layer forming the electrode, in particular its roughness (especially at nanometric scale) avoiding too much scattering and/or reflection of the light emitted by the organic light-emitting layer.
Additionally, materials for use as electrode according to the present invention offer work function values between 4.2 and 5 eV, i.e. similar to ITO work function. Antimony-doped tin oxide, fluorine-doped tin oxide may advantageously show work function values of around 4.9 eV, which may be even better than ITO (ITO generally shows values of between 4.5 and 4.8 eV).
Devices according to the present invention may have a substrate made of glass (for example a glass sheet or a sheet of float glass), or plastic materials (for example organic glass, polycarbonates), or polymer films (for example, PVB, PET, EVA). They may comprise, in a preferred manner, an encapsulating material, which may protect the whole device from diffusion into the device of atmosphere gases and moisture. This material may be selected amongst the same range of materials convenient for the substrate. Preferably, a film of PET or a sheet of glass may form the encapsulating material.
The electrode according to the present invention may be positioned between the organic film and the substrate or between the organic film and the encapsulating material.
Advantageously the electrode according to the present invention may have a thickness of at least 100 nm, preferably at least 250 nm and more preferably at least 300 nm. Its thickness may preferably be not more than 600 nm, not more than 500 nm, not more than 450 nm and more preferably not more than 400 nm.
When antimony-doped tin oxide is used in the electrode according to the present invention, the atomic ratio Sb/Sn in the antimony-doped tin oxide may preferably be in the range 0.01 to 0.20, preferably in the range 0.03 to 0.15, more preferably in the range 0.05 to 0.10. When fluorine-doped tin oxide is used in the electrode according to the present invention, the atomic ratio F/Sn in the fluorine- doped tin oxide may preferably be in the range 0.005 to 0.20, preferably in the range 0.01 to 0.10, more preferably in the range 0.01 to 0.05.
In a preferred embodiment, an additional layer is present between the electrode according to the present invention and the substrate, or the encapsulating material, depending whether this electrode is positioned between the organic film and the substrate or between the organic film and the encapsulating material. This additional layer may be an iridescence-reducing layer or a barrier layer adapted to inhibit, or at least reduce, alkali migration which may occur, for example, from a glass substrate towards the layer including antimony-doped tin oxide, fluorine-doped tin oxide, aluminium-doped zinc oxide, fluorine-doped zinc oxide or zinc-tin oxide. The additional layer may also be a haze-reducing layer or an anti-reflection layer. Such layers are known, for example, from EP275662, GB2302102, GB2248243, US4377613. The additional layer may comprise, for example, SiO 2 , SiO x , i.e. an
incompletely oxidised silicon oxide, or TiO 2 . It may be an oxidised aluminium/vanadium layer. Alternatively, the additional layer may be a bi-layer, i.e. comprise two sublayers. It may, for example, comprise a first sublayer of SnO 2 and a second, overlaying, sublayer of SiO 2 .
The additional layer may advantageously have a thickness of at least 5 nm, at least 10 nm, preferably at least 40 nm, at least 50 nm, more preferably at least 60 nm. Its thickness may preferably be not more than 100 nm, not more than 90 nm and more preferably not more than 80 nm.
The electrode according to the present invention and the additional layer may be deposited on the substrate or the encapsulating material by any known method, for example, chemical vapour deposition (CVD), spray, magnetron sputtering, etc. Pyrolytic coatings, particularly CVD films are preferred. The organic film comprises a light-emitting layer or a light-absorbing layer, and may comprise other layers like a hole transporting layer and/or an electron transporting layer and/or doped layers; charge blocking layers may also be introduced to confine the charges within the device. The light-emitting or light-absorbing layer may be formed by a combination of one or more organic materials which have the necessary light emission or absorption properties. The organic film may be formed, for example, by spin-coating, by evaporation or by printing. The organic film may have a thickness of around 100 nm.
The second electrode may comprise a conductive material having a low work function. It may have thicknesses in the range 400-600 nm. This electrode may comprise, for example, Ag/Mg alloys, Ag/Ba alloys, or Al/Li alloys. The second electrode may alternatively be transparent. When both electrodes are transparent light may be emitted through both sides of the device. In that case, the second
electrode may comprise an ITO layer in combination with a very thin (< 10 nm) layer of metal or alloy adjacent to the organic film, for example Ag or alloys cited hereinabove. It may also comprise a layer of a material as for the first electrode of this invention in combination with the same very thin (< 10 nm) layer of metal or alloy adjacent to the organic film. Here also an additional layer as defined herein may be present between the substrate or the encapsulating material and the second electrode.
Embodiments of the invention will now be further described, by way of example only.
Examples 1 to 9 show possible structures for OLEDs according to the present invention. The second column of each example gives the layers thicknesses.
Examples 1, 3, 4, 5, 7 and 9 are bottom-emitting devices. Example 2 is a top-emitting device. Examples 6 and 8 are fully transparent OLEDs: light is emitted through both sides of the device.
In each example, "glass" was a sheet of float glass around 4 mm thick and "PET film" was a sheet of PET of around 100 μm. Otherwise specified, the Ag/Mg alloy used as electrode was around 500 nm thick and the organic film, around 100 nm thick.
Example 1 Example 2
Exam le 3
Example 4
Example 5
Example 6
Exam le 7
Example 8
Example 9