Multifunctional Electrode Leakage Current Control in OLED Displays
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Solution Overview
Problem
In organic electroluminescent displays, leakage currents between adjacent pixels cause unintended light emission and chromaticity changes, making gamma correction difficult, especially when a full-color pixel is driven with a low current and displayed in a single color.
Innovation Solution
A display device with a multifunctional electrode that overlaps and contacts pixel electrodes and a common electrode, set to a potential closer to the common electrode than the pixel electrodes during image display, effectively releases leakage currents and functions as both a transmission and reception electrode group during touch sensing periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a continuous carrier injection and transport layer is used across all pixels, then device complexity is reduced and manufacturing is simplified, but leakage current occurs between adjacent pixels causing unintended light emission and chromaticity changes
Solution Approach 1:
The patent divides the continuous carrier injection and transport layer into pixel-specific segments. Each pixel has its own carrier injection layer and transport layer that are electrically isolated from adjacent pixels through insulating layers, preventing leakage current while maintaining the benefits of a layered structure.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between adjacent pixel electrodes and their respective carrier transport layers. This insulating layer acts as a barrier that prevents charge carriers from leaking into adjacent pixels, thereby eliminating the harmful effect while allowing the continuous layer structure to be maintained for manufacturing simplicity.
2Adaptability or versatility
If the multifunctional electrode is set to pixel electrode potential during image display, then touch sensing capability is maintained, but leakage current is not effectively released to adjacent pixels
Solution Approach 1:
The patent implements dynamic potential switching for the multifunctional electrode. During image display periods, the electrode potential is adjusted to prevent leakage current to adjacent pixels, while during touch sensing periods, it switches to a potential that enables touch detection. This dynamic adjustment allows the electrode to serve multiple functions at different times.
Solution Approach 2:
The patent employs periodic switching between different operational modes for the multifunctional electrode. The electrode alternates between image display mode (where it prevents leakage current) and touch sensing mode (where it detects touch input), with the switching occurring at regular intervals synchronized with the display refresh rate and touch sensing cycles.
3Manufacturing precision
If the number of pixels is increased to improve resolution, then display quality improves, but adjacent pixels come closer increasing leakage current risk
Solution Approach 1:
The patent segments the carrier transport function into pixel-specific layers with insulating barriers between them. This segmentation allows pixels to be placed closer together for higher resolution while the insulating layers prevent electrical interaction and leakage current between adjacent pixels, thus maintaining both high pixel density and low leakage current.
Solution Approach 2:
The patent introduces insulating layers as intermediary barriers between closely spaced pixel electrodes and carrier transport layers. These insulating layers enable higher pixel density by preventing charge carrier leakage into adjacent pixels, thereby allowing increased manufacturing precision and pixel density without suffering from the harmful effects of leakage current.
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 configuration prevents leakage currents from reaching adjacent pixels, allowing for effective utilization and reducing unintended light emission, while also enabling touch sensing functionality.
Implementation Method 1
the multifunctional electrode is set to a potential closer to that of the common electrode than the plurality of pixel electrodes in an image display period, and thus leakage current to an adjacent pixel can be released
Implementation Method 2
an organic electroluminescent display having a layer (for example, a carrier injection and transport layer) that is continuous to all pixels even if a light emitting layer is separated for each pixel
Data Source
AI summary
A display device includes an electroluminescent layer laminated on pixel electrodes and a multifunctional electrode and a common electrode laminated on the electroluminescent layer. The electroluminescent layer includes a lower common layer that continuously overlaps and contacts the pixel electrodes and the multifunctional electrode and light emitting layers separated from each other corresponding to each of the pixel electrodes on the lower common layer. The multifunctional electrode includes portions each passing between a pair of adjacent pixel electrodes of the pixel electrodes, and is set to a potential closer to that of the common electrode than the pixel electrodes in an image display period, and at least a part of the multifunctional electrode functions as at least one electrode group of a transmission electrode group and a reception electrode group in a touch sensing period.