Auxiliary Electrodes for Uniform Brightness in Large OLEDs
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Solution Overview
Problem
Organic light emitting devices with large areas face challenges in achieving uniform brightness due to voltage drop, which occurs because the current density decreases as distance from the electrode pad increases, leading to uneven brightness across the device.
Innovation Solution
The substrate is divided into multiple driving regions with auxiliary electrodes connecting the electrode pad to the central portions of each region, ensuring uniform current distribution by maintaining the same length and distance between auxiliary electrodes and the electrode pad, and using a dielectric to connect the transparent electrode to the auxiliary electrodes through contact holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electrode pad is used to power a large-area transparent electrode, then the device structure is simple, but voltage drop occurs causing non-uniform brightness
Solution Approach 1:
The transparent electrode is divided into multiple light emitting regions, and auxiliary electrodes are introduced to divide the current distribution zones. This segmentation allows current to be supplied from multiple points (electrode pad and auxiliary electrodes) rather than a single point, reducing the current density gradient and voltage drop across the large-area electrode, thereby achieving uniform brightness.
2Illumination intensity
If auxiliary electrodes are added to reduce voltage drop, then brightness uniformity improves, but device complexity increases
Solution Approach 1:
The auxiliary electrodes are strategically positioned at specific locations (central portions of light emitting regions) rather than uniformly distributed. This local quality approach ensures that current is supplied to areas where it is most needed to maintain uniform brightness, while minimizing the number of auxiliary electrodes required and reducing overall device complexity.
3Manufacturing precision
If the transparent electrode is divided into multiple driving regions, then voltage drop is prevented and current distribution is uniform, but the manufacturing process becomes more complex
Solution Approach 1:
The auxiliary electrodes have asymmetric designs including bent portions that allow them to connect to the electrode pad while reaching the central portions of light emitting regions. This asymmetric configuration enables current distribution uniformity across the device while maintaining manufacturability through standardized bending patterns and connection geometries.
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 approach prevents voltage drop and ensures uniform current application across the device, resulting in consistent brightness across the entire light emitting area, effectively addressing the issue of uneven brightness in large-area organic light emitting devices.
Implementation Method 1
a plurality of auxiliary electrodes each having an end connected to the electrode pad and the other end connected to a central portion of each of the driving regions; and a transparent electrode disposed on the auxiliary electrodes over the light emitting part
Implementation Method 2
using a dielectric to connect the transparent electrode to the auxiliary electrodes through contact holes
Data Source
AI summary
According to the present invention, an electro-optic device comprises: a substrate which is split into a light emitting unit and a non-light emitting unit, wherein said light emitting unit is divided into a plurality of driving regions; an electrode pad which is formed in the non-light emitting unit of the substrate; and an electrode unit which comprises a plurality of supplementary electrodes each of which has one end connected to the electrode pad and has the other end connected to the centers of each of the plurality of driving regions, and transparent electrodes formed on the upper sides of the plurality of supplementary electrodes in the light emitting unit, wherein the area of each of the plurality of driving regions is set to an area in which no voltage drop occurs, and the plurality of supplementary electrodes are manufactured in the same length. Thus, according to the present invention, if power is supplied to each one end of the plurality of supplementary electrodes by using the electrode pad, the power is transmitted, at the same time, to the other ends of each of the plurality of supplementary electrodes. Therefore, the power is simultaneously supplied to each center of the plurality of driving regions regardless of the distance between the electrode pad and the driving regions. Further, as mentioned above, a voltage drop phenomenon is prevented since the light emitting unit is divided into the plurality of driving regions in which no voltage drop occurs. That is to say, uniform currents can flow on the front side of each driving region irrespective of the distance between the supplementary electrodes and the driving regions. Consequently, a large-scaled organic light emitting device which can show uniform brightness properties in the overall light emitting unit can be manufactured.