OLED Edge Light Emission via Segmented Electrodes
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Solution Overview
Problem
Organic light emitting diodes (OLEDs) experience a rapid decrease in luminance over time due to increased electrical resistance in the light emitting layer, leading to 'tail drop' where light emission is concentrated at the edges, reducing the device's lifespan.
Innovation Solution
The OLED is designed with an anode and cathode in a striped pattern, allowing for separate light emission areas during initial and final usage stages, with the cathode formed in a striped pattern to maintain luminance by redirecting current flow around deteriorated regions, thereby extending the device's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light emitting layer is made of polymeric material dissolved in solvent, then the initial light emission is uniform and efficient, but the resistance increases over time causing rapid luminance drop (tail drop)
Solution Approach 1:
The electrode (anode or cathode) is divided into multiple separate stripes rather than a continuous structure. This segmentation creates multiple independent light emission regions, allowing current to flow through different paths and preventing the formation of a single high-resistance bottleneck that causes tail drop.
Solution Approach 2:
Different regions of the light emitting layer are utilized at different stages of device operation. During initial operation, central regions emit light; as resistance increases in the center, current automatically redirects to edge regions where resistance is lower, maintaining overall luminance stability.
2Power
If current flows through the light emitting layer along the shortest path, then light emission is concentrated at the center, but resistance increases at the center causing edge light emission and reduced overall luminance
Solution Approach 1:
The electrode is segmented into multiple stripes separated by pattern distances, creating multiple current paths through the light emitting layer. This prevents current concentration at a single central point and distributes current flow more evenly across the device area.
Solution Approach 2:
The invention transitions from centralized light emission (one-dimensional concentration) to distributed light emission across multiple stripes (two-dimensional distribution). The striped pattern creates a spatial distribution of light emission regions that maintains overall luminance as the device ages.
3Ease of manufacture
If the electrode is formed as a continuous layer, then the manufacturing process is simple, but the light emission area is limited and lifespan is reduced due to resistance increase
Solution Approach 1:
The continuous electrode layer is divided into multiple striped segments with specific pattern distances between them. This segmentation increases the effective light emission area and creates multiple current paths, extending device lifespan while maintaining compatibility with standard coating manufacturing processes.
Solution Approach 2:
The electrode geometry parameters are changed from a continuous uniform structure to a striped pattern with specific widths and spacing. This parameter change optimizes both light emission area and current distribution, extending device operational life without fundamentally changing the manufacturing approach.
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 prevents rapid luminance drops and maintains sufficient light emission throughout the OLED's lifespan by utilizing edge light emission, increasing the usable light emission area during the final stages and preventing 'tail drop', thus extending the device's operational life.
Implementation Method 1
When a current flows through the organic light emitting diode, the light emitting part is excited by combining holes with electrons (i.e., electric coupling), so that energy is emitted in the form of light.
Implementation Method 2
When the light emitting layer deteriorates over time, the property of the dissolved polymeric material is changed and the polymeric material no longer remains dissolved and produces an insoluble layer.
Data Source
AI summary
An organic light emitting diode that uses edge light emission and has a long lifespan. An anode and a cathode are spaced by a pattern distance and they are located at the upper and lower portions of the light emitting part respectively. The organic light emitting diode uses a separate light emission area of the light emitting part for each of the initial and the final usage stages so that a tail drop of the luminance is prevented and the lifespan of the diode is increased.