Bottom-Emission OLED Pixel Electrode Structure for Light Efficiency
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Solution Overview
Problem
Bottom emission type OLED displays suffer from reduced light emitting efficiency due to light absorption and color coordinate distortion by the insulating and organic layers, which hinder the effective emission of light to the outside.
Innovation Solution
The design includes a thin film transistor with a drain electrode and an ohmic contact layer on an insulating substrate, a pixel electrode with a two-layer structure, and a common reflective metal electrode, where the organic emission layer is positioned to minimize light loss and distortion, with the pixel electrode having a lower resistance and direct contact with the substrate to enhance light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light is emitted from the emission layer through the insulating substrate, then the display can be viewed from the bottom side, but light absorption and color distortion occur due to the insulating layer and organic layer
Solution Approach 1:
The patent extracts the light emission function from the traditional top-emission structure by creating a bottom-emission structure where light is emitted from the emission layer through the insulating substrate. This extraction allows light to exit from the bottom side, avoiding the light absorption and color distortion that occur when light passes through the insulating layer and organic layer in conventional top-emission structures.
Solution Approach 2:
The patent inverts the traditional emission direction by making the display bottom-emission instead of top-emission. In conventional OLED displays, light is emitted from the top side; this patent reverses the structure so that light is generated in the emission layer and exits through the bottom insulating substrate, thereby avoiding the harmful effects of light passing through the insulating layer and organic layer.
2Illumination intensity
If the pixel electrode is positioned to minimize light loss, then light emitting efficiency improves, but the electrode structure becomes more complex with multiple parts and contact holes
Solution Approach 1:
The pixel electrode is segmented into multiple parts: a first part in direct contact with the insulating substrate, a second part connected to the first part, and a third part connected to the drain electrode through the contact hole. This segmentation allows the electrode to be positioned optimally for light transmission while maintaining electrical connectivity, resolving the conflict between light efficiency and structural simplicity.
Solution Approach 2:
The patent introduces an intermediary ohmic contact layer between the drain electrode and the insulating substrate. This intermediary layer facilitates both electrical connection and optimal positioning of the pixel electrode structure, enabling the electrode to be placed in the most favorable position for light transmission while maintaining proper electrical connectivity through the contact hole.
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 improves light emitting efficiency by reducing light absorption and distortion, allowing for more effective light emission from the organic layer without passing through the insulating layer, thereby enhancing the display's brightness and color accuracy.
Implementation Method 1
a common electrode disposed on the organic layer
Data Source
AI summary
A display device includes; an insulating substrate, a thin film transistor disposed on the insulating substrate and which comprises a drain electrode, a wall disposed on the thin film transistor and which includes an opening and a contact hole which exposes the drain electrode, a pixel electrode connected to the drain electrode through the contact hole and which comprises a first part in direct contact with the insulating substrate and a second part connected to the first part, an organic layer disposed on the pixel electrode and which comprises an organic emission layer, and a common electrode disposed on the organic layer.