Top Emission OELD Pixel Shift for Aperture Ratio
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Solution Overview
Problem
The top emission type organic electroluminescent display (OELD) devices face limitations in maximizing aperture ratio due to the positioning of the drain contact hole, which affects the size of the emitting area and consequently the luminance and power consumption.
Innovation Solution
The OELD device is designed with a first and second pixel region, where the second pixel region is shifted relative to the first, allowing the second gate line to cross the second pixel region, and a bank is formed to surround the second pixel region, maximizing the area for the organic emitting layer and improving luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the drain contact hole is positioned in the conventional manner, then the device structure is simple, but the aperture ratio is reduced and luminance is limited
Solution Approach 1:
The pixel region is divided into a first pixel region containing the TFT and a second pixel region for light emission. This segmentation allows the emitting area to be separated from the transistor area, enabling the drain contact hole to be positioned in the first pixel region without reducing the aperture ratio of the second pixel region.
Solution Approach 2:
The patent introduces a spatial dimension by creating overlapping regions between the first and second pixel regions. The second pixel region is positioned to overlap with the first pixel region, allowing the emitting area to extend into the space above the TFT structure without increasing the planar footprint.
2Illumination intensity
If the emitting area is increased to improve luminance, then the aperture ratio is improved, but the drain contact hole positioning becomes more constrained
Solution Approach 1:
By segmenting the pixel region into functional zones (first pixel region for TFT, second pixel region for emission), the patent allows the drain contact hole to be positioned in the first region while the emitting area in the second region remains unconstrained, thus improving luminance without compromising ease of operation.
Solution Approach 2:
The bank structure serves as an intermediary element that defines the boundary of the second pixel region and provides a platform for forming the organic light-emitting layer. This intermediary structure enables the emitting area to be maximized while maintaining proper positioning of the drain contact hole in the first pixel region.
3Area of stationary object
If the second pixel region is shifted to maximize emitting area, then the aperture ratio is improved, but the gate line routing becomes more complex
Solution Approach 1:
The second gate line is designed to serve multiple functions: it acts as a gate electrode for the TFT in the first pixel region and simultaneously serves as a boundary definition and electrical connection element for the second pixel region. This multi-functionality reduces the need for additional structures and simplifies the overall gate line configuration.
Solution Approach 2:
The patent merges the gate line function with the pixel region boundary definition. The second gate line is positioned to coincide with the boundary of the second pixel region, combining the electrical function of gating with the structural function of defining the emitting area, thus reducing complexity despite the shifted configuration.
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 enhances the aperture ratio and luminance of the OELD device by maximizing the emitting area, regardless of the drain contact hole's position, thereby improving the overall performance and efficiency.
Implementation Method 1
an organic emitting layer in the second pixel region and on the first electrode; and a transparent second electrode on the organic emitting layer and the bank
Data Source
AI summary
An organic electroluminescent display (OELD) device includes a first substrate having a first unit pixel region including first and second pixel regions; first and second gate lines along a first direction; first and second data lines along a second direction; a switching TFT in the first pixel region; a driving TFT in the first pixel region; a passivation layer including a first contact hole exposing a portion of the driving TFT; a first electrode contacting the driving TFT through the first contact hole; a bank surrounding the second pixel region an organic emitting layer in the second pixel region; and a transparent second electrode on the organic emitting layer and the bank, wherein the second pixel region is a region shifted from the first pixel region such that the second gate line goes across the second pixel region.