OLED Display Refractive Index Layers Redirect Lateral Light
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices suffer from reduced light emission efficiency due to light emission in all directions, leading to increased power consumption and potential color mixture issues.
Innovation Solution
A display device structure incorporating a high refractive index portion, multiple low refractive index portions with inclined angles, and reflection layers on a thin film encapsulation layer to redirect lateral light emission towards the front, utilizing materials like molybdenum, aluminum, and silver for enhanced reflectance, and a circular polarization plate to prevent external light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light is emitted in all directions from the OLED, then the display device achieves omnidirectional light emission, but light emission efficiency is reduced and power consumption increases
Solution Approach 1:
The encapsulation layer is segmented into multiple regions with different refractive indices: a first region with refractive index 1.5-1.7, a second region with refractive index 1.3-1.5, and a third region with refractive index 1.5-1.7. This segmentation creates distinct optical zones that control light propagation paths, redirecting lateral light emissions toward the front direction while maintaining omnidirectional emission capability
Solution Approach 2:
Different regions of the encapsulation layer are assigned different local optical properties (refractive indices) to perform specific functions: the first region captures lateral light, the second region acts as a low refractive index layer to enhance total internal reflection, and the third region redirects light forward. This local quality differentiation resolves the contradiction by optimizing light emission efficiency in specific directions while preserving overall omnidirectional emission
2Adaptability or versatility
If light is emitted in all directions from the OLED, then the display device achieves omnidirectional light emission, but power consumption increases
Solution Approach 1:
The encapsulation layer is divided into functional segments with different refractive indices that optimize light extraction efficiency. By segmenting the structure into regions with refractive indices of 1.5-1.7, 1.3-1.5, and 1.5-1.7, the design enhances light emission in the front direction where it is most useful, reducing energy waste in less useful directions and thereby lowering power consumption while maintaining omnidirectional emission capability
Solution Approach 2:
The refractive index parameter is changed across different regions of the encapsulation layer to optimize light emission efficiency. By varying the refractive index from 1.3-1.5 in the second region to 1.5-1.7 in the first and third regions, the structure enhances total internal reflection and light extraction in the front direction, improving energy utilization efficiency while preserving omnidirectional emission
3Adaptability or versatility
If light is emitted in all directions from the OLED, then the display device achieves omnidirectional light emission, but color mixture occurs
Solution Approach 1:
The encapsulation layer is segmented into three distinct regions with different refractive indices positioned at specific locations relative to the pixel electrode. This spatial segmentation creates separate optical pathways that guide light from different emission zones, preventing color mixture by ensuring that light from adjacent pixels follows distinct paths to the viewer
Solution Approach 2:
Different local regions of the encapsulation layer are assigned specific refractive index values (1.5-1.7 for first and third regions, 1.3-1.5 for second region) to control light propagation locally. This local quality control ensures that light emissions maintain their color integrity by preventing cross-contamination between adjacent pixel colors through optimized refraction and total internal reflection at region boundaries
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
Improves light emission efficiency by redirecting lateral light emission towards the front, reducing power consumption and minimizing color mixture, thereby enhancing display quality.
Implementation Method 1
a high refractive index portion overlapping, on a plane, at least a portion of the first electrode on the thin film encapsulation layer; a first low refractive index portion overlapping, on a plane, the pixel defining layer on the thin film encapsulation layer
Implementation Method 2
including a first inclined portion forming a first angle with the thin film encapsulation layer; including a second inclined portion forming a second angle with the thin film encapsulation layer
Implementation Method 3
a first reflection layer disposed, on a plane, between the first low refractive index portion and the second low refractive index portion
Data Source
AI summary
A display device includes a first substrate, an organic light emitting element on the first substrate and including a first electrode, an organic light emitting layer, and a second electrode, a pixel defining layer surrounding the first electrode, a thin film encapsulation layer, and a capping layer on the thin film encapsulation layer. The capping layer may include two reflective interfaces adjacent the light emission or pixel area spaced apart from one another in a plane view. The reflective interfaces may include a boundary between high and low refractive index materials and/or a reflective layer.