Diffusion-limiting electroactive barrier layer for an optoelectronic component

Abstract

An optoelectronic component is provided having a cathode, an anode and a layer system between the cathode and the anode, the layer system includes electroactive layers, in particular charge-carrier injection and transport layers, and including an optically active layer, the charge-carrier injection and transport layers themselves being a diffusion barrier to water or oxygen.

Claims

1. An optoelectronic component (1) having a cathode (25) and an anode (27) and a layer system between the cathode (25) and the anode (27) comprising at least one electron injection layer (29) or electron extraction layer adjacent to the cathode, at least one electron transport layer (33), at least one optically active layer, at least one hole transport layer (35), at least one hole injection layer (31) or hole extraction layer adjacent to the anode, characterised in that the at least one electron injection layer (29) or electron extraction layer and the at least one hole injection layer (31) or hole extraction layer are diffusion-limiting to water and/or oxygen and having a water vapour transmission rate (WVTR) of less than 1 g/(m.sup.2*d) and an oxygen transmission rate (OTR) of less than 1 cm.sup.3/(m.sup.2*d) and the at least one electron transport layer (33) and the at least one hole transport layer (35) represent a diffusion barrier against water and/or oxygen and having a water vapour transmission rate (WVTR) of less than 0.1 g/(m.sup.2*d) and an oxygen transmission rate (OTR) of less than 0.1 cm.sup.3/(m.sup.2*d).

2. The optoelectronic component (1) according to claim 1, characterised in that a layer combination of a cathode (25), the at least one electron injection layer (29) or electron extraction layer and the at least one electron transport layer (33) has a water vapour transmission rate (WVTR) of less than 0.1 g/(m.sup.2*d) and an oxygen transmission rate (OTR) of less than 0.1 cm.sup.3/(m.sup.2*d) and/or a layer combination of an anode (27), the at least one hole injection layer (31) or hole extraction layer and the at least one electron transport layer (35) has a water vapour transmission rate (WVTR) of less than 0.1 g/(.sup.2*d) and an oxygen transmission rate (OTR) of less than 0.1 cm.sup.3/(m.sup.2*d).

3. An optoelectronic component (1) according to claim 1, characterised in that the at least one electron transport layer (33) and the at least one hole transport layer (35) have an oxygen transmission rate (OTR) of less than 1 cm.sup.3/(m.sup.2*d) and a water vapour transmission rate (WVTR) of less than 0.1 g/(m.sup.2*d).

4. An optoelectronic component (1) according to claim 1, characterised in that the at least one electrode transport layer (33) has an electron mobility between 10.sup.6 cm.sup.2/(V*s) and 100 cm.sup.2/(V*s) and and the at least one hole transport layer (35) has a hole mobility between 10.sup.6 cm.sup.2/(V*s) and 100 cm.sup.2/(V*s).

5. An optoelectronic component (1) according to claim 1, characterised in that the at least one electron transport layer (33) has a doped metal oxide.

6. An optoelectronic component (1) according to claim 1, characterised in that the at least one hole transport layer (35) has a doped metal thiocyanate.

7. An optoelectronic component (1) according to claim 1, characterised in that the at least one electron transport layer (33) has an overall layer thickness of 10-50 nm, and the at least one hole transport layer (35) has an overall layer thickness of 10-40 nm.

8. An optoelectronic component (1) according to claim 1, characterised in that the at least one electron injection layer (29) or electron extraction layer and the at least one hole injection layer (31) or hole extraction layer have an oxygen transmission rate (OTR) of less than 1 cm.sup.3/(m.sup.2*d) and a water vapour transmission rate (WVTR) of less than 1 g/(m.sup.2*d).

9. An optoelectronic component (1) according to claim 1, characterised in that the at least one electron injection layer (29) or electron extraction layer comprises dielectric polymers.

10. An optoelectronic component (1) according to claim 1, characterised in that the at least one hole injection layer (31) or hole extraction layer comprises dielectric polymers.

11. An optoelectronic component (1) according to claim 1, characterised in that the at least one electron injection layer (29) or electron extraction layer has an overall layer thickness between 0.1 nm and 10 nm and the at least one hole injection layer or hole extraction layer has an overall layer thickness between 0.1 nm and 10 nm.

12. An optoelectronic component (1) according to claim 1, characterised in that the component (1) has at least two electron injection layers (29) or electron extraction layers, at least two electron transport layers (33), at least two hole transport layers (35) and at least two hole injection layers (31) or hole extraction layers, wherein the electron injection layers (29) or electron extraction layers and the electron transport layers (33) and the hole injection layers (31) or hole extraction layers and the hole transport layers (35) are arranged in an alternating arrangement.

13. An optoelectronic component (1) according to claim 1, characterised in that the anode (27) is at least one of metals, metal oxides, metal thiocyanates, metal nanowires, halogens and/or mixtures of these metals.

14. An optoelectronic component (1) according to claim 1, characterised in that the anode (27) has a layer thickness between 50 and 500 nm.

15. An optoelectronic component (1) according to claim 1, characterised in that the cathode (25) is at least one of metals, metal oxides, metal thiocyanates, metal nanowires and/or mixtures of these materials.

16. An optoelectronic component (1) according to claim 1, characterised in that the cathode (25) has a layer thickness between 50 nm and 500 nm.

17. An optoelectronic component (1) according to claim 1, characterised in that the optically active layer is an emitter layer (15).

18. An optoelectronic component (1) according to claim 1, characterised in that the optically active layer is an absorber layer with an absorption spectrum.

19. A method for producing an optoelectronic component (1) according to claim 1, characterised in that the electron injection layer (29), the electron transport layer (33), the optically active layer, the hole transport layer (35) and/or the hole injection layer (31) are applied with a wet chemical method and/or a thermal evaporation method.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 Schematic representation of the layer structure of a conventional optoelectronic component which is encapsulated by a barrier film.

(2) FIG. 2 Schematic zoom view of the layer structure of the barrier film for a conventional optical component.

(3) FIG. 3 Schematic representation of a preferred embodiment of the optoelectronic component according to the invention.

DETAILED DESCRIPTION OF THE FIGURES

(4) FIGS. 1 and 2 show the schematic structure of a conventional optoelectronic component 1 which is encapsulated by a barrier film 17. The layer structure for the represented component 1 is that of a light-emitting diode and is composed as follows. A cathode 3 serves to provide electrons, while the anode 5 provides holes as soon as a voltage is applied to these electrodes. The symbols + and each preferably show the voltage direction. The properties of the electron injection layer 7 and the hole injection layer 9 preferably allow for an efficient quantum mechanical tunnelling of the charge carriers to the transport layers. The electron transport layer 11 and the hole transport layer 13 are characterised by a high mobility for the charge carriers and ensure a targeted transport to the emitter layer 15. In the emitter layer 15, the charge carriers recombine to produce excitons and the emission of visible light 2. The penetration of water or oxygen into the emitter layer significantly reduces the efficiency coefficient and thus the lifespan. For this reason, in the prior art, the optoelectronic component 1 is encapsulated by a barrier film 17, which is intended to prevent penetration of water and oxygen. For this purpose, it is customary in the prior art to select an alternating layer structure in which diffusion-limiting layers 19 alternate with diffusion barriers or block layers 21. The diffusion barrier or block layer 21 should prevent the diffusion of molecules. However, there is also the possibility that molecules will diffuse through small defects. Due to the diffusion-limiting layers 19, the path length of the molecules is extended, so that they emerge again preferably through the defect in a diffusion barrier or block layer 21. Furthermore, in the prior the barrier film comprises a carrier substrate 23.

(5) FIG. 3 shows a schematic representation of a preferred embodiment of the optoelectronic component according to the invention. The layer structure for the optoelectronic component 1 represented is that of a light-emitting diode. The basic functions of the layers in the layer structure are the same as those for conventional optoelectronic components according to FIG. 1 or 2. A cathode 25 serves to provide electrons, while the anode 27 provides holes as soon as a voltage is applied to these electrodes. The symbols + and each preferably show the voltage direction. In addition, however, the cathode 25 and anode 27 have blocking properties against water and oxygen molecules, thus providing a diffusion barrier for the permeants.

(6) The electrical properties of the electron injection layer 29 and the hole injection layer 31 preferably allow for an efficient quantum mechanical tunnelling of the charge carriers to the transport layers. At the same time, the materials of the electron injection layer 29 and the hole injection layer 31 are selected such that they have diffusion-limiting effects on water and oxygen molecules, so that the diffusion length of the molecules in the respective layer is extended.

(7) The electron transport layer 33 and the hole transport layer 35 are characterised by a high mobility for the charge carriers and ensure a targeted transport to the emitter layer 15. In the emitter layer 15, the charge carriers recombine to produce excitons and the emission of visible light 2.

(8) However, in contrast to the prior art, the electron transport layer 33 and the hole transport layer 35 provide a diffusion barrier to water and oxygen. The layer structure according to the invention thus facilitates an alternating layer structure of diffusion-limiting layers and diffusion barriers in the same way as the barrier film from the prior art. However, according to the invention it has been found that electrically active layers (electron injection layer 29, hole injection layer 31, electron transport layer 33 and hole transport layer 35) and the electrodes (cathode 25 and anode 27) themselves can be used as diffusion-limiting layers and diffusion barriers. The electron transport layer 33, the hole transport layer 35, the cathode 25 and the anode 27 thus function as diffusion barriers which should reduce the diffusion of water or oxygen molecules. The electron injection layer 29 and hole injection layer 31 function as diffusion-limiting layers which extend the path lengths of the molecules and thus defects of the diffusion barriers can be compensated for. In the preferred embodiment, the layer combination of the cathode 25, diffusion-limiting electron injection layer 29 and electron transport layer as a diffusion barrier 33 has an OTR of less than 0.1 cm.sup.3/(m.sup.2*d), preferably less than 0.01 cm.sup.3/(m.sup.2*d) and a WVTR of less than 0.1 g/(m.sup.2*d), preferably less than 0.01 g/(m.sup.2*d). Likewise, the layer combination of the anode 27, diffusion-limiting hole injection layer 31 and hole transport layer as a diffusion barrier 35 has an OTR of less than 0.1 cm.sup.3/(m.sup.2*d), preferably less than 0.01 cm.sup.3/(m.sup.2*d) and a WVTR of less than 0.1 g/(m.sup.2*d), preferably less than 0.01 g/(m.sup.2*d).

(9) These parameters can prevent penetration of water and oxygen molecules into the emitter layer 15 and significantly increase the lifespan. Advantageously, this requires no complex and expensive barrier film which increases the overall thickness of the optoelectronic component 1.

(10) It should be noted that various alternatives to the described embodiments of the invention might be used to carry out the invention and to arrive at the solution according to the invention. The optoelectronic component according to the invention and the production thereof in the described method are not limited in their embodiments to the above-mentioned preferred embodiments. Rather, a variety of design variants is conceivable that may differ from the illustrated solution. The aim of the claims is to define the scope of protection for the invention. The scope of protection of the claims is directed to covering the optoelectronic component according to the invention and the manufacturing method thereof as well as equivalent embodiments thereof.

LIST OF REFERENCE NUMERALS

(11) 1 Optoelectronic component 2 Light 3 Cathode 5 Anode 7 Electron injection layer 9 Hole injection layer 11 Electron transport layer 13 Hole transport layer 15 Emitter layer 17 Barrier film 19 Diffusion-limiting layers 21 Diffusion barrier 23 Carrier substrate 25 Cathode as diffusion barrier 27 Anode as diffusion barrier 29 Diffusion-limiting electron injection layer 31 Diffusion-limiting hole injection layer 33 Electron transport layer as diffusion barrier 35 Hole transport layer as diffusion barrier