Organic light emitting devices

Details Organic light emitting devices Organic light emitting devices

2001-06-22

2003-04-15

Philogene, Haissa (Department: 2821)

Electric lamp and discharge devices: systems

Plural power supplies

Plural cathode and/or anode load device

C315S169100, C313S506000, C257S040000

Reexamination Certificate

active

06548961

ABSTRACT:

FIELD OF INVENTION
The present invention relates to organic light emitting devices for display applications and to methods for fabricating such devices.
BACKGROUND
Organic light-emitting devices (OLEDs) are typically manufactured as a sequence of layers deposited on top of each other to form a layer structure. The layer structure typically comprises a first electrode on a supporting substrate and one or more organic layers disposed between the first electrode and a second electrode. Light output is generated by charge injection into the organic material via the electrodes. The organic material emits photons on excitation by the injected charge. At least one of the electrodes is typically formed from a light transmissive material such as Indium Tin Oxide (ITO) or a thin metal to permit passage of light out of the device. Light transmissive materials should be understood to include both transparent and semi-transparent materials.
If the OLED is driven by a thin film transistor (TFT) array, then part of the light emitted from the organic material can be shadowed by the TFT array. The ratio of area occupied by the TFT array to the light emissive area of the display is generally referred to as the aperture ratio. Clearly, it would be desirable to maximize the aperture ratio in the interests of optimizing the brightness of the display/efficiency. However, the higher the resolution of the display, the smaller the aperture ratio.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is now provided a method of making a light-emitting device comprising: forming a first component having a light-transmissive first substrate, the forming of the first component comprising locating a light transmissive first electrode layer on the first substrate, locating an organic layer on the first electrode, and locating a second electrode layer on the organic layer; forming a second component having a second substrate, the forming of the second component comprising locating driver array circuitry on the second substrate; joining the first component and the second component with the second electrode of the first component facing the driver array of the second component; and, forming an electrical contact between one of the first and second electrode layers of the first component and the driver array circuitry of the second component.
Spacers are preferably located between the first component and the second component. At least one of the spacers may be formed on the driver array of the second component. Equally however, at least one of the spacers may be formed on the first electrode layer of the first component. The or each spacer formed on the first electrode layer may be partially covered by the organic layer. Similarly, the or each spacer formed on the first electrode layer may be partially covered by the second electrode layer. At least one of the spacers may be formed on the second electrode layer of the first component. The spacers may be electrically conductive to form an electrical contact between one of the first and second electrode layers of the first component and the driver array circuitry of the second component. Alternatively, the spacers may be electrically insulating, particularly when they are located on the first electrode layer beneath the organic layer and the second electrode layer. The first component and the second component are preferably joined by forming a peripheral seal between the first component and the second component and creating a vacuum within the peripheral seal.
Viewing the present invention from another aspect, there is now provided a light-emitting device comprising: a first component having a light-transmissive first substrate, a light-transmissive first electrode layer on the first substrate, an organic layer on the first electrode layer, and a second electrode layer on the organic layer; a second component having a second substrate and driver array circuitry on the second substrate; means for joining the first component and the second component with the second electrode of the first component facing the conductive layer of the second component; and, an electrical contact for electrically connecting one of the first and second electrode layers of the first component and the driver array circuitry of the second component
The device preferably comprises spacers distributed between the first component and the second component. At least one of the spacers is preferably integral to the first component. The, or each, spacer of the first component may be disposed on the first electrode layer. The, or each, spacer of the first component may be partially covered by the organic layer. Likewise, the, or each, spacer of the first component may be partially covered by the second electrode. Alternatively, the, or each, spacer of the first component may be disposed on the second electrode. At least one of the spacers may be integral to the second component. The first component may comprise a plurality of organic layers disposed between the first electrode and the second electrode. The joining means preferably comprises a peripheral seal between the first component and the second component, and a vacuum is disposed within the peripheral seal.
In a preferred embodiment of the present invention to be described shortly, there is provided an OLED having a TFT driver array for large area display applications and a method for making the same. The example of an OLED described herein comprises two components. The first component has a light transmissive substrate carrying an organic layer. A light transmissvie first electrode layer is disposed between the organic layer and substrate. A second electrode layer is disposed on the surface of the organic layer remote from the substrate. The second electrode layer comprises a thin semitransparent metal electrode layer (<20 nm) in intimate electrical contact with an underlying organic layer to provide uniform charge injection in the interests of optimizing display output. The metal layer can be formed from any metal or combination of metals. The second component carries a TFT driver array. The first and second components are superimposed on each other with contacts the TFT array of the of the second component overlying and in electrical contact with contacts to the second electrode of the first component. Light generated in the organic layer is emitted via the first electrode and the substrate of the first component. Thus, the light output from the OLED is not obstructed by the TFT array. The aperture ratio of the display can thus be up to one hundred per cent. Another advantage is that, by forming the OLED in multiple components, each component can be optimized separately in terms of, for example, transparency, conductivity, low damage, injection efficiency, processing speed. Spacers are preferably provided between the first and second components to reduce the risk of mechanical damage when the first and second components of the OLED are brought together. Additionally, the spacers improve the mechanical stability of the OLED.


REFERENCES:
patent: 5929474 (1999-07-01), Huang et al.
patent: 6316786 (2001-11-01), Mueller et al.
patent: 6322712 (2001-11-01), Hanson et al.
patent: 6370019 (2002-04-01), Matthies et al.

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