Display Device Multi-Layer Electrode Light Extraction
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Solution Overview
Problem
Conventional display devices suffer from reduced light efficiency due to light emitted from the organic light emitting layer being lost at the bank layer, and external light reflection degrades visibility and contrast ratio, while the active layer of the thin film transistor is exposed to light and vulnerable to laser damage during repair.
Innovation Solution
A multi-layer structure is implemented with a first electrode made of transparent conductive material and a reflection layer on the bank layer, reducing the distance between the organic light emitting layer and the side reflection layer to enhance light extraction efficiency, protecting the active layer, and minimizing damage from laser beams by positioning clock lines on different layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-layer electrode structure is used, then the device structure is simple, but light extraction efficiency is reduced due to light being lost at the bank layer
Solution Approach 1:
The electrode structure is segmented into multiple functional layers: a first electrode layer (transparent conductive material) positioned closer to the organic light emitting layer for light extraction, and a second electrode layer (reflective material) positioned at the bank layer area to reflect stray light. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between structural simplicity and light extraction efficiency.
Solution Approach 2:
The solution transitions from a single-layer to a multi-layer structure in the vertical dimension, adding depth to the electrode configuration. The first electrode is positioned at a first vertical position closer to the organic light emitting layer, while the second electrode is positioned at a second vertical position at the bank layer area, creating a three-dimensional electrode architecture that improves light extraction without excessive complexity.
2Loss of energy
If the bank layer is positioned close to the organic light emitting layer, then light extraction is improved, but the active layer of the thin film transistor is exposed to light and vulnerable to damage
Solution Approach 1:
The electrode structure implements local quality by having different materials and positions at different locations: the first electrode (transparent) is positioned closer to the organic light emitting layer in the emission area to maximize light extraction, while the second electrode (reflective) is positioned at the bank layer area to block and reflect light away from the active layer, providing location-specific optical control.
Solution Approach 2:
The first electrode layer acts as an intermediary between the organic light emitting layer and the external environment, allowing light to pass through while the second electrode layer serves as an intermediary to reflect and redirect light away from sensitive areas. These intermediary layers mediate the interaction between light and different structural components, protecting the active layer while maintaining extraction efficiency.
3Loss of energy
If a multi-layer electrode structure is implemented, then light extraction efficiency is enhanced and active layer is protected, but device complexity increases
Solution Approach 1:
The multi-layer electrode structure achieves multi-functionality: the first electrode layer serves as both a transparent conductive element for electrical function and a light extraction interface, while the second electrode layer serves as both a reflective element for optical function and a structural component at the bank layer. This multi-functionality justifies the increased structural complexity by delivering multiple benefits simultaneously.
4Ease of manufacture
If clock lines are formed in the same layer, then the routing is simple, but the area required in the bezel area is increased
Solution Approach 1:
Clock lines are routed in different vertical layers rather than being confined to a single planar layer. This three-dimensional routing approach allows clock lines to overlap in the vertical dimension, reducing their horizontal footprint in the bezel area while maintaining routing simplicity through standardized multi-layer interconnect processes.
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
The solution enhances light extraction efficiency, protects the active layer from light exposure, reduces progressive dark spot defects, and minimizes the area required for clock lines in the bezel, thereby improving display performance and reliability.
Implementation Method 1
a reflection layer disposed on the first electrode on the inclined surface of the recess and including a metal or metal alloy
Data Source
AI summary
Embodiments of the disclosure relate to a display device. Specifically, there may be provided a display device capable of enhancing light extraction efficiency by reducing the distance between the organic light emitting layer and the side reflection layer by comprising a substrate including a plurality of subpixels, an overcoat layer disposed on the substrate and having a recess positioned between the subpixels, a first electrode disposed to cover an upper surface of the overcoat layer and an inclined surface of the recess and including a transparent conductive material, a reflection layer disposed on the first electrode on the inclined surface of the recess and including a metal or metal alloy, and a bank layer positioned in the recess and disposed on the reflection layer.