OLED Pixel Edge Reflectors for Light Extraction
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Solution Overview
Problem
Achieving high efficiency in organic light-emitting diode (OLED) displays is challenging due to the trade-off between on-axis and off-axis viewing quality, where improved on-axis efficiency often results in worse off-axis color variation.
Innovation Solution
Incorporating a reflector at the edge of OLED pixels to reflect waveguided light out of the display, which can be formed from metal, high-refractive-index and low-refractive-index material interfaces, or light-reflecting particles within the pixel definition layer, to increase extraction efficiency and mitigate cavity effects at wide viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If on-axis efficiency is improved, then light extraction efficiency increases, but off-axis color variation worsens
Solution Approach 1:
The patent segments the light extraction function by introducing a reflector structure that separates on-axis and off-axis light paths. The reflector is positioned to selectively redirect waveguided light at different angles, allowing on-axis light to pass through while reflecting off-axis light to improve color consistency across viewing angles.
Solution Approach 2:
The reflector acts as an intermediary element between the organic light-emitting layers and the external environment. It mediates the extraction of waveguided light by providing a controlled reflection interface that manages both on-axis efficiency and off-axis color variation through its specific positioning and optical properties.
2Use of energy by moving object
If waveguided light is extracted to improve efficiency, then overall extraction efficiency increases, but device complexity increases
Solution Approach 1:
The reflector structure serves multiple functions simultaneously: it extracts waveguided light to improve efficiency, maintains color consistency at off-axis angles, and can be integrated with existing pixel definition layers. The patent describes implementations where the reflector replaces or works with the pixel definition layer, reducing the need for separate components.
Solution Approach 2:
The patent explores different configurations of the reflector including varying materials (metal, dielectric, hybrid), positions (at different depths within the pixel structure), and geometries (continuous vs. patterned). These parameter changes allow optimization of extraction efficiency while managing structural complexity through material and design selection.
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 reflector enhances overall light extraction efficiency and reduces off-axis color variation, improving viewing quality by recycling waveguide mode light and providing a broader spectrum with less color variation at wide angles.
Implementation Method 1
A reflector may be placed at the edge of the organic layers to reflect the waveguided light out of the display
Implementation Method 2
The reflector may be formed from one or more interfaces between high-refractive-index material and low-refractive-index material
Data Source
AI summary
A display may have an array of pixels formed from organic light-emitting diodes and thin-film transistor circuitry. Each pixel may include organic layers interposed between an anode and a cathode. The organic layers may emit out-coupled light that escapes the display and waveguided light that is waveguided within the organic layers. A reflector may be placed at the edge of the organic layers to reflect the waveguided light out of the display. The reflector may be located within a pixel definition layer and may be formed from metal or may be formed from one or more interfaces between high-refractive-index material and low-refractive-index material. The reflector may be formed from an extended portion of the pixel anode. The reflector may be formed from light-reflecting particles that are suspended in the pixel definition layer.