OLED Light Extraction Structure with Graded Refractive Indices
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Solution Overview
Problem
Conventional OLED displays have relatively low light extraction efficiency due to abrupt changes in refractive indices between film layers, leading to significant light reflection and reduced emission.
Innovation Solution
The implementation of light extraction structures with multiple layers having gradually decreasing refractive indices, where at least one surface includes straight lines in a cross-section perpendicular to the substrate, to minimize refractive index differences and enhance light convergence, thereby reducing reflection and increasing emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional OLED display structure with uniform film layers is used, then manufacturing process is simple, but light extraction efficiency is low due to abrupt refractive index changes
Solution Approach 1:
The light extraction structure is divided into multiple layers (first light extraction layer, second light extraction layer, third light extraction layer) with progressively decreasing refractive indices. This segmentation allows gradual transition of refractive index from the organic light-emitting unit to the external environment, reducing abrupt interface reflections and improving light extraction efficiency while maintaining manufacturing feasibility through layer-by-layer fabrication processes
Solution Approach 2:
Different regions of the light extraction structure have different refractive indices tailored to their specific functions. The first light extraction layer has higher refractive index for strong light convergence, while subsequent layers have progressively lower refractive indices for gradual index transition. This local quality differentiation optimizes light extraction at each interface while maintaining overall manufacturing simplicity
2Loss of energy
If multiple light extraction layers with gradually decreasing refractive indices are implemented, then light extraction efficiency is improved, but device structure becomes more complex
Solution Approach 1:
The complex light extraction function is segmented into multiple layers with progressively decreasing refractive indices. This segmentation achieves gradual refractive index transition to minimize reflection losses, while each layer can be fabricated using standard thin-film deposition techniques, thereby managing structural complexity through modular design
Solution Approach 2:
The light extraction structure employs composite material design with different materials having progressively decreasing refractive indices (first light extraction layer with highest index, second light extraction layer with intermediate index, third light extraction layer with lowest index). This composite approach achieves superior light extraction efficiency while maintaining compatibility with existing OLED manufacturing 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
This configuration reduces light reflection and enhances light extraction efficiency by allowing more light to be emitted outside the display panel, improving the overall performance of OLED displays.
Implementation Method 1
refractive indexes of the plurality of light extraction layers gradually decrease in a direction facing towards the first organic layer... reduces a refractive index difference of two adjacent film layers... an amount of light reflected back to the display panel is reduced, while an amount of light emitted to the outside of the display panel is increased
Data Source
AI summary
Provided are a display panel and a display device. The display panel includes a substrate, light-emitting units, a first organic layer, and light extraction structures located between the light-emitting units and the first organic layer. The first light extraction layer has a first central axis and is symmetrical about the first central axis, the second light extraction layer has a second central axis and is symmetrical about the second central axis, and the first central axis and the second central axis are perpendicular to the substrate. A surface of the second light extraction layer connecting the first light extraction layer is a first surface, a surface of the second light extraction layer facing away from the first light extraction layer is a second surface, and at least one of the first surface and the second surface comprises straight lines in a cross-section perpendicular to the substrate.