Light Emitting Display Device Shared Contact Hole Structure
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Solution Overview
Problem
The challenge in organic light emitting display devices is the shortening of the organic light emitting layer's lifetime and the occurrence of turn-on defects due to the reduction in emissive area ratio, caused by the limitations in contact hole size and the step change in height between the anode electrode and the source or drain electrode, leading to disconnection and reduced luminance.
Innovation Solution
The implementation of a shared contact hole structure that allows multiple pixels to share a contact hole, forming a reverse taper shape to expose the side surface of the drain electrode, preventing disconnection and ensuring uniform deposition of the organic light emitting layer, thereby maintaining emissive area and preventing turn-on defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size is reduced to achieve high resolution, then the resolution is improved, but the emissive area ratio is decreased
Solution Approach 1:
Multiple pixels share a common contact hole structure, merging what would traditionally be separate contact holes into a shared infrastructure. This reduces the total non-emissive area while maintaining electrical connection for each pixel, thereby improving the emissive area ratio despite reduced pixel dimensions.
Solution Approach 2:
The shared contact hole structure serves multiple pixels simultaneously, making it a multi-functional element. This single structure performs the electrical connection function for N pixels, reducing redundant non-emissive areas and improving the overall emissive area ratio in high-resolution displays.
2Length of moving object
If the contact hole size is reduced to accommodate smaller pixels, then the pixel size is decreased, but the organic light emitting layer deposition becomes non-uniform
Solution Approach 1:
The contact hole structure extends into the third dimension with a reverse taper shape, creating a stepped configuration that provides adequate surface area for uniform organic light emitting layer deposition while maintaining a small top opening size compatible with high-resolution pixels.
Solution Approach 2:
The contact hole geometry is changed from a simple cylindrical shape to a reverse taper shape with specific dimensional parameters. The top opening diameter is smaller than the bottom diameter, creating a stepped structure that optimizes both the top opening size for pixel integration and the bottom surface area for uniform layer deposition.
3Ease of manufacture
If the contact hole is formed through photo process with size limitations, then the manufacturing process is simplified, but the contact hole cannot be formed to have less than a certain size
Solution Approach 1:
The contact hole structure utilizes vertical dimensionality with reverse taper shaping, allowing the top opening to be smaller than what conventional photo processes can directly form, while the larger bottom diameter compensates for the deposition area requirements. This dimensional transformation enables smaller effective contact hole sizes without sacrificing manufacturing feasibility.
4Reliability
If the anode electrode is formed on the source or drain electrode with step change in height, then the electrical connection is established, but the anode electrode can be disconnected at the side surface
Solution Approach 1:
The reverse taper shaped contact hole creates a stepped structure that transforms the height difference into a multi-level configuration. The anode electrode can be formed on different levels (top surface and side surface), creating multiple connection paths that enhance connection strength and prevent disconnection despite the inherent step change in height.
Solution Approach 2:
The reverse taper shape creates an asymmetric geometry where the top opening is smaller than the bottom diameter. This asymmetry allows the anode electrode to make contact at multiple locations (top surface and inclined side surface), distributing the electrical connection stress and preventing disconnection at any single point.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
Disclosed are a light emitting display device and a method of manufacturing the same, which prevent the lifetime of a light emitting layer from being shortened and prevent occurrence of a turn-on defect. The light emitting display device includes a plurality of pixels each including a transistor (210) having a gate electrode (212), an active layer (211) overlapping the gate electrode, a source electrode (213) connected to one side of the active layer, and a drain electrode (214) connected to another side of the active layer. The pixels further include a light emitting device (260) having a first electrode (261), a light emitting layer (262) disposed on the first electrode, and a second electrode (263) disposed on the light emitting layer. The light emitting display device includes a contact hole (CTS), and the first electrodes (261) of at least two of the plurality of pixels are electrically connected to side surfaces of respective source electrodes (213) or to side surfaces of respective drain electrodes (214) in the contact hole (CTS).