Multi-Device OLED Current Distribution via Inter Electrode Connectors
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Solution Overview
Problem
Existing multi-device OLEDs face limitations in device size due to poor conductivity of transparent electrodes, inhomogeneous light emission, and restricted light-emitting area caused by asymmetric contacting and the need for contact pads.
Innovation Solution
A multi-device OLED design featuring a device layer stack with a bottom electrode, top electrode, inter electrodes, and active layers, where current distribution means, such as current distribution layers and electrical connectors, supply current directly to exposed contact regions through openings in the stack, eliminating the need for additional contact pads and enhancing lateral conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent electrodes are used for inter electrode and anode, then device transparency and light emission are enabled, but lateral conductivity is poor which limits device size to maximum of about 5 cm by 5 cm
Solution Approach 1:
A highly conductive metal foil (aluminum or silver) is introduced as an intermediary layer between the transparent inter electrode and the active layers. This metal foil acts as a mediator that provides excellent lateral conductivity while allowing the transparent inter electrode to maintain its light-emitting function. The metal foil is positioned such that it does not block the light emission path, thus resolving the contradiction between transparency and conductivity.
Solution Approach 2:
The solution moves from a two-dimensional planar contact pad structure to a three-dimensional stacked structure with the metal foil positioned in a intermediate layer. This dimensional change allows the conductive path to be established without occupying the light-emitting area, effectively increasing the usable device size beyond the 5 cm by 5 cm limitation.
2Reliability
If contact pads are added for asymmetric contacting of inter electrode and cathode, then electrical connection is improved, but light-emitting area is reduced due to occupation of substrate area
Solution Approach 1:
The contact pads are relocated from the two-dimensional substrate plane to a three-dimensional stacked structure. The metal foil layer provides the electrical connection function previously requiring large contact pads, while these connections are made in a different spatial dimension (through the stack rather than on the substrate surface), thus preserving the light-emitting area.
Solution Approach 2:
The metal foil serves multiple functions simultaneously: it provides lateral conductivity for the inter electrode, acts as a reflective layer to enhance light extraction, and serves as a structural support layer. This multi-functionality eliminates the need for separate dedicated contact pad structures, maximizing the light-emitting area.
3Illumination intensity
If transparent conductor is used for conductive regions, then device transparency is maintained, but conductivity is poor which limits current distribution
Solution Approach 1:
The electrode structure uses a composite of transparent conductive material (such as ITO or PEDOT:PSS) and highly conductive metal foil. The transparent layer provides optical functionality while the metal foil provides electrical functionality. This composite structure combines the advantages of both materials to achieve both transparency and high conductivity for effective current distribution.
Solution Approach 2:
The electrode system is segmented into multiple functional layers: the transparent conductive layer for optical purposes and the metal foil layer for electrical purposes. This segmentation allows each layer to be optimized for its specific function without compromising the other, enabling both transparency and high current distribution capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design allows for homogeneous brightness distribution and removes size restrictions, enabling larger device applications with an uninterrupted light-emitting area suitable for decorative lighting and signage.
Implementation Method 1
current distribution means, such as current distribution layers and electrical connectors, supply current directly to exposed contact regions through openings in the stack, eliminating the need for additional contact pads and enhancing lateral conductivity
Implementation Method 2
The colour of the emitted light is largely determined by the composition of the active layer, which can comprise various organic polymers such as polyfluorenes chosen for their specific chemical structure that allows the colour of the emitted light to be determined
Data Source
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Figure 2
Figure 3A~3D
AI summary
The invention describes a multi-device OLED (1) comprising a device layer stack (100) comprising a bottom electrode (11), a top electrode (14), at least one inter electrode (13) and plurality of active layers (120, 121), wherein the bottom electrode (11) is applied to a substrate (10), and each active layer (120, 121) is enclosed between two electrodes (11, 13, 14); a current distribution means (500) comprising a current distribution layer (51, 53, 54) for each electrode (11, 13, 14) of the device layer stack (100); a plurality of openings (110, 130) extending from the top electrode (14) into the device layer stack (100), wherein each opening (110, 130) exposes a contact region (111, 131) of an electrode (11, 13); and a plurality of electrical connectors (41, 42), wherein an electrical connector (41, 42) extends into an opening (110, 130) to electrically connect the electrode (11, 13) exposed by that opening (110, 130) to the current distribution layer (53, 54) for that electrode (11, 13). The invention also describes a method of manufacturing such a multi-device OLED. The invention further describes a method of driving such a multi-device OLED, which method comprises applying a voltage across at least one pair (51, 53, 53, 54) of current distribution layers (51, 53, 54) of the current distribution means (500) to stimulate the corresponding active layer (120, 121) of a device of the multi-device OLED (1).