WO2009001241A1

WO2009001241A1 - Organic functional device and method of manufacturing same

Info

Publication number: WO2009001241A1
Application number: PCT/IB2008/052285
Authority: WO
Inventors: Edward W. A. Young
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-06-25
Filing date: 2008-06-10
Publication date: 2008-12-31
Also published as: TW200919794A

Abstract

An organic functional device (20;60) comprising a substrate (2) having a first electrode layer (4) and a plurality of mutually spaced apart shunting structures (7a-e), each being in direct electrical contact with the first electrode layer (4); an organic functional layer (5) provided on top of the first electrode layer (4); a second electrode layer (6) arranged on top of the organic functional layer (5); and a lid (10) attached to the substrate (2) to enclose the organic functional layer (5) between the lid and the substrate. The organic functional device (20;60) further comprises a plurality of insulating spacer structures (21a-e), each being arranged between the lid (10) and the substrate (2) in a position corresponding to a corresponding one of the shunting structures (7a-e).

Description

Organic functional device and method of manufacturing same

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an organic functional device, such as an organic light-emitting diode (OLED), and a method of manufacturing such an organic functional device.

TECHNICAL BACKGROUND

Common to all organic functional devices, such as organic light emitting diodes (OLEDs), organic solar cells, organic photovoltaic elements, organic photo diodes, organic photosensors etc., is that an organic functional layer is sandwiched between, and interacts with, a pair of electrode layers. In an OLED, the application of a voltage between the electrode layers results in emission of light by the organic functional layer, and in an organic solar cell, absorption of light by the organic functional layer leads to the creation of a voltage between the electrode layers.

Organic functional devices are typically formed on a substrate and subsequently encapsulated by means of a lid to prevent ambient substances, such as water and oxygen, from reaching the functional layers (the electrode layers and the organic functional layer) of the device.

The lid may be arranged in such a way that there is a space or gap between the functional layers and the lid. This space may, for example, be filled with an inert gas, such as nitrogen.

A problem with these packages is the mechanical stability. Pressure differences in the surrounding environment may give rise to substantial deformations in the package. In particular in large devices, the pressure can be so high that the lid actually touches the functional layers of the device. This may cause at least partial failure of the device. Damage can be caused by direct contact between the lid and the functional layers or by particles sandwiched between the lid and the functional layers.

An alternative way of packaging the organic functional device is to attach the lid to the substrate in such a way that the space between the functional layers and the lid is filled with glue. In this method, the glue prevents the lid from touching the functional layers. However, it is difficult to control the thickness of the glue during manufacturing. Capillary forces will try to minimize the thickness of the glue and there still is a risk of direct contact between the lid and the functional layers at specific spots. Again, particles might get sandwiched between the lid and the functional layers and cause damage to the device.

SUMMARY OF THE INVENTION

In view of the above-mentioned and other drawbacks of the prior art, a general object of the present invention is to provide an improved organic functional device having, in particular, an improved robustness.

According to a first aspect of the present invention, these and other objects are achieved through a method of manufacturing an organic functional device, comprising the steps of: providing a substrate having a first electrode layer and a plurality of mutually spaced apart shunting structures, each being in direct electrical contact with the first electrode layer; providing an insulating spacer structure on top of each of the shunting structures; forming an organic functional layer on top of the first electrode layer; forming a second electrode layer on top of the organic functional layer; and attaching a lid to the substrate to enclose the organic functional layer between the lid and the substrate. Examples of organic functional devices include organic light-emitting diodes

(OLEDs), organic photocells, organic photovoltaic elements, organic photodiodes and organic photosensors.

By the term "electrode layer" should be understood an electrically conductive layer which could be transparent or non-transparent to light. The "organic functional layer" may consist of many different organic layers with different functions (such as hole injection, hole transport, hole blocking, excitation blocking, electron blocking, electron transport, electron injection or light emitting, light absorbing layers, or mixtures thereof), but may also include metal-organic materials like triplet emitters or inorganic materials such as dielectric, semi-conducting or metallic quantum dots or nano-particles.

The "shunting structures" are conductive structures which are provided in direct electrical contact with the first electrode layer in order to make the voltage distribution across the first electrode layer more homogeneous during operation of the organic functional device. The shunting structures may, for example, be applied in the form of metallic strips which may form a grid. The shunting structures should have a high electrical conductivity as compared to the first electrode layer.

Such shunting structures, or "shunts", are typically employed for large area devices and/or when the first electrode layer is formed from a transparent conductive layer. Transparent conductive layers generally have such a low conductance that the voltage across the organic functional layer (between the first and second electrode layers) becomes position- dependent in the absence of shunting structures. The spacing between adjacent shunting structures is typically in the range of millimeters.

The present invention is based upon the realization that an organic functional device can be made more robust, substantially without any sacrifice in respect of the performance of the device, by providing spacer structures on top of shunting structures formed on the first electrode layer. As stated above, shunting structures are generally employed when the first electrode layer is transparent and/or for large-area devices. Consequently, the shunting structures are often already present in organic functional devices that would benefit from spacer structures protecting the organic functional layer of the organic functional device from mechanical interaction with the lid. Furthermore, the shunting structures are often robust and not easily damaged, which makes them a good base for the spacer structures. Moreover, in optical organic functional devices, which emit or receive light, the portions of the organic functional layer corresponding to the shunting structures generally do not significantly contribute to the function of the device, since these portions are shielded by the non-transparent shunting structures. Therefore, these portions of the organic functional layer need not be protected to the same degree as portions of the organic functional layer located between adjacent shunting structures. Consequently, according to an embodiment of the invention, the organic functional layer may be formed on top of the spacer structure, which facilitates production of the organic functional device.

Accordingly, by virtue of the present invention, the desired robustness can be achieved practically without adding process steps or sacrificing anything in terms of performance of the organic functional device.

The spacer structures may be provided on top of the second electrode layer or, preferably, between the first electrode layer and the organic functional layer.

When provided between the first electrode layer and the organic functional layer, the spacer structures should preferably have a smooth structure without any discontinuities or steps, in order to facilitate formation of a continuous organic layer and second electrode layer thereon. In particular, the contact angle between the first electrode layer and the spacer structure may advantageously be below 60°.

With this configuration, there may still be mechanical contact between the lid and the functional layers (the second electrode layer and the organic functional layer) of the organic functional device, but this contact takes place in areas which are shielded by the shunting structures and thus do not actively contribute to the function of the device.

Furthermore, when positioned between the first and second electrode layers, the spacer structures prevent electrical short circuits between these layers as a result of mechanical contact between the lid and the functional layers. The spacer structures may be formed using any one of a number of techniques.

For example, screen printing or photolithography using a sufficiently thick (>30 μm) resist layer may be utilized.

Alternatively, hot-melt inkjet printing (also sometimes referred to as "solid inkjet") can be applied. When using hot-melt inkjet printing, printed patterns should be well defined and structures should have a suitable height, such as between 30 and 70 μm, and smooth, shallow edges having a contact angle to the surface on which the spacer structures are printed of about 60° or less.

In applications where light should be received and/or emitted by the organic functional layer, the substrate and the first electrode layer and/or the lid and the second electrode layer should be optically transparent, that is, at least partly permit passage of light. In this case, the substrate and/or the lid may be made of glass or a transparent polymer, and the first and/or second electrode layer(s) may, for example, be manufactured of any material which is inherently conductive and transparent or, alternatively, of a sufficiently thin metal layer, which could be provided in combination with a transparent conductive or non-conductive layer.

The method according to the invention is especially useful in the production of large-area organic functional devices, such as OLED-lighting devices and organic solar cells etc. According to a second aspect of the present invention, the above-mentioned and other objects are achieved through an organic functional device comprising: a substrate having a first electrode layer and a plurality of mutually spaced apart shunting structures, each being in direct electrical contact with the first electrode layer; an organic functional layer provided on top of the first electrode layer; a second electrode layer arranged on top of the organic functional layer; and a lid attached to the substrate to enclose the organic functional layer between the lid and the substrate, the organic functional device further comprising a plurality of insulating spacer structures, each being arranged between the lid and the substrate in a position corresponding to a corresponding one of the shunting structures.

Features and advantages of this second aspect of the present invention are largely analogous to those described above in connection with the first aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention, wherein:

Fig 1 schematically shows pressure-induced deformation of an organic functional device according to the prior art;

Fig 2 schematically shows an organic functional device according to an embodiment of the present invention, when subjected to the same conditions as in Fig 1;

Fig 3 is a flow chart schematically illustrating a method of manufacturing the organic functional device in Fig 2; Figs 4a-d schematically illustrate the states of the organic functional device, following the corresponding method steps;

Fig 5 schematically shows an exemplary method of providing the spacer structures in the organic functional device in Fig 2; and

Fig 6 is a sectional view of another embodiment of the organic functional device according to the present invention in which the lid is supported by the spacer structures and the space between the substrate and the lid is filled up with a filling substance.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the following description, the present invention is mainly described with reference to an OLED-based light emitting panel. It should be noted that this by no means limits the scope of the invention, which is equally applicable to many other organic functional devices, such as organic solar cells or organic photodiodes.

In Fig 1 , an OLED 1 according to the prior art is shown in order to illustrate the robustness problem solved through the present invention. Referring to Fig 1, the prior art OLED 1 comprises a transparent substrate 2 having a functional organic stack 3 formed thereon. The functional organic stack 3 comprises a first transparent electrode layer 4 (an anode layer), an electroluminescent layer (EL-layer) 5, and a second electrode layer (a cathode layer) 6. With a spacing D, which is generally a few mm, shunting structures in the form of metal leads 7a-e are provided on top of the first electrode layer 4 in order to improve the uniformity of the voltage across the first electrode layer 4, and thereby improve the uniformity of the current distribution across the device. The current here referred to is the current flowing through the organic functional layer, between the first and second electrode layers. Each of the shunting structures 7a-e is typically electrically isolated from the EL-layer 5 by means of a thin (typically 1 - 2 μm thick) insulating layer 8.

The functional organic stack 3 is enclosed by a protective lid 10, and the cavity 11 thus formed is often filled with an inert gas, such as nitrogen. When a force F is applied to the protective lid 10, the lid is deformed and makes contact with the functional organic stack 3. Through this contact, the organic functional stack 3 can be damaged, which may lead to reduced performance or complete malfunction of the OLED 1.

With reference to Fig 2, schematically showing an OLED 20 according to an embodiment of the present invention, the increased robustness obtained through the present invention will now be described. In the OLED 20 in Fig 2, each of the shunting structures 7a-e is covered by an insulating spacer structure 21a-e. Each spacer structure 21a-e has a height h which is sufficient to prevent the lid 10 from touching the organic functional stack 3 at positions between the spacer structures 21a-e when the lid 10 is deformed by an external force F as indicated in Fig 2. In order to satisfy this condition, the height h of the spacer structures 21a-e should advantageously be related to the distance D between the spacer structures (in this case the same as between the shunting structures 7a-e) in such a way that h/D > 30/1000. Furthermore, as is illustrated in Fig 2, the spacer structures 21a-e should preferably be formed such that a contact angle θ_c between the first electrode layer and the spacer structures 21a-e is smaller than 60°, thereby ensuring the formation of a continuous second electrode layer 6.

Through the configuration illustrated in Fig 2, the application of a force F on the lid 10 will, except in the event of an extreme situation, only lead to pressure being applied to the EL-layer 5 on top of spacer structures 21a-e. In these portions, the EL-layer is electrically isolated from the first electrode layer 4, and is therefore not "active". Consequently, the function of the OLED 1 will generally not be affected when portions of the EL-layer 5 corresponding to spacer structures 21a-e are damaged.

It should be noted that although the lid 10 shown in Fig 2 is spaced apart from the spacer structures (21a-e), the lid 10 may just as well be in contact with, and rest on, the spacer structures (21 a-e) .

In the following, a method of manufacturing the OLED of Fig 2 will be described with reference to Fig 3 and Figs 4a-d.

Referring first to Fig 3 and Fig 4a, a substrate 2 having a first electrode layer 4 and a plurality of shunt lines 7a-e formed thereon is provided in a first step 31. In a second step 32, insulating spacer structures 21 a-e are provided on top of the shunt lines 7a-e. This is illustrated in Fig 4b. As is also illustrated in Fig 4b, each insulating spacer structure should be formed in such a way that the contact angle θ_c between the spacer structure 21e and the first electrode layer 4 is sufficiently small to ensure that the subsequently applied layers (especially the second electrode layer 6) can follow the contour continuously, without being interrupted. In order to accomplish this, the contact angle θ_c should, as mentioned above in connection with Fig 2, preferably be below 60°. The contact angle θ_c is generally determined by the properties (for example the surface energy) of the surface 6 on which the spacer material is applied, and the properties of the spacer material itself, as well as the method of application. In Fig 5, a preferred method of applying spacer structures 21a-b is schematically illustrated.

Fig 5 illustrates the application of the spacer structures 21a-b on top of previously formed shunt structures 7a-b by means of hot-melt inkjet printing. As is very schematically shown in Fig 5, an inkjet printhead 50 moves along a shunt structure 7b while firing droplets 51a-b of a melted polymer material. Of course, the printhead 50 may alternatively be stationary while the substrate 2 is movable. The properties of the printed polymer material, as well as the printing parameters (temperature, droplet size, time of flight etc) determine, together with the properties of the surface on which the droplets 51a-b are printed, the final dimensions of the spacer structures 21a-b. Returning now to the flow chart in Fig 3 and Fig 4c, the method proceeds to step 33 in which the organic functional layer 5 and the second electrode layer 6 are formed on top of the first electrode layer 4 and the spacer structures 21 a-e.

The organic functional layer 5 may generally comprise several organic layers. In case the organic functional device 20 is a polymer light-emitting diode (LED), the organic functional layer 5 essentially comprises a two-layer stack of a hole conductor layer and a light emitting polymer layer and may further include several additional layers such as an evaporated organic hole-blocking layer on the light emitting polymer.

In case the organic functional device 20 is a small-molecule OLED, the organic functional layer 5 is generally formed as a more complex stack including a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, a hole blocking layer and an electron transporting layer, as well as an electron blocking layer or the like.

In a final step 34, a lid 10 is then attached to the substrate 2 to protect the organic functional device 20 from ambient substances, such as water and oxygen, as well as from mechanical damage. Through the spacer structures 21a-e, the OLED 20 has become more robust in respect of mechanical damage, as is schematically illustrated in Fig 2.

In Fig 2, an embodiment of the organic functional device according to the present invention is shown having a protective lid 10, between which lid and the second electrode layer 6, a cavity 11 is formed.

Fig 6 is a sectional view of another embodiment of the organic functional device according to the present invention in the form of a so-called direct seal package.

As is schematically illustrated in Fig 6, the organic functional device 60 illustrated therein differs from that illustrated in Fig 2 in that the protective lid 61 is attached to the substrate 2 and the various layers formed thereon (although not explicitly shown in Fig 6, the organic functional device 60 illustrated therein has the same or corresponding layers as the device 20 in Fig 2), including the spacer structures 21a-e, by means of a layer of glue 62. Through the provision of the spacer structures 21a-e, the glue layer 62 can be kept even and at a minimum thickness corresponding to the height h of the spacer structures 21a-e. As mentioned above in connection with Fig 2, the lid 61 of the organic functional device 60 in Fig 6 may advantageously rest on the spacer structures 21a-e, although this is not shown in Fig 6.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments. For example, the shunting structures need not be formed as parallel lines, but can have any configuration, such as a grid configuration with lines crossing each other and extending horizontally and vertically. Furthermore, although the above description mainly relates to organic functional displays based on relatively rigid substrates, the present invention is equally applicable to flexible organic functional devices, wherein the spacer structures improve the robustness of the organic functional device by preventing damage due to friction between the active portions (between the spacer structures) of the functional layers and the lid.

Claims

CLAIMS:

1. A method of manufacturing an organic functional device (20; 60), comprising the steps of: providing (31) a substrate (2) having a first electrode layer (4) and a plurality of mutually spaced apart shunting structures (7a-e), each being in direct electrical contact with said first electrode layer (4); providing (32) an insulating spacer structure (21a-e) on top of each of said shunting structures (7a-e); forming (33) an organic functional layer (5) on top of said first electrode layer

(4); - forming (33) a second electrode layer (6) on top of said organic functional layer (5); and attaching (34) a lid (10) to said substrate (2) to enclose said organic functional layer (5) between said lid (10) and said substrate (2).

2. A method according to claim 1, wherein said insulating spacer structure

(21a-e) is provided between said first electrode layer (4) and said organic functional layer (5).

3. A method according to claim 1 or 2, wherein said insulating spacer structure (21a-e) is formed by means of printing.

4. A method according to claim 3, wherein said insulating spacer structure (21a-e) is printed using hot-melt ink jet printing.

5. An organic functional device (20; 60) comprising: - a substrate (2) having a first electrode layer (4) and a plurality of mutually spaced apart shunting structures (7a-e), each being in direct electrical contact with said first electrode layer (4); an organic functional layer (5) provided on top of said first electrode layer (4); a second electrode layer (6) arranged on top of said organic functional layer (5); and a lid (10) attached to said substrate (2) to enclose said organic functional layer (5) between said lid and said substrate, characterized in that - said organic functional device (20; 60) further comprises a plurality of insulating spacer structures (21a-e), each being arranged between said lid (10) and said substrate (2) in a position corresponding to a corresponding one of said shunting structures (7a-e).

6. An organic functional device (20; 60) according to claim 5, wherein each of said insulating spacer structures (21a-e) is arranged between said first electrode layer (4) and said organic functional layer (5).

7. An organic functional device (20; 60) according to claim 5 or 6, wherein a ratio between a height (h) of said spacer structures (21a-e) and a distance (D) between adjacent spacer structures is larger than 0.03.

8. An organic functional device (20; 60) according to claim 7, wherein said height (h) of said spacer structures (21a-e) is larger than 10 μm.

9. An organic functional device (20; 60) according to any one of claims 5 to 8, wherein at least one of said spacer structures (21a-e) is in mechanical contact with said lid (10).

10. An organic functional device (20; 60) according to any one of claims 5 to 9, wherein said substrate (2) and said first electrode layer (4) are optically transparent.

11. An organic functional device (20; 60) according to any one of claims 5 to 10, wherein each of said spacer structures (21a-e) has a contact angle (θ_c) below 60° with respect to a surface on which said spacer structure is provided.

12. An organic functional device (20; 60) according to any one of claims 5 to 11, wherein said organic functional layer (5) comprises a light emitting layer.

13. An organic functional device (20; 60) according to any one of claims 5 to 11, wherein said organic functional layer (5) comprises a photovoltaic layer.