OLED Substrate Curvature for Light Extraction
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Solution Overview
Problem
Existing OLED lighting devices fabricated on flexible plastic substrates face challenges such as maintaining flatness during fabrication, rough surfaces causing shorting, and suboptimal light extraction due to planar surfaces.
Innovation Solution
A method involving a mold with topographical features to create substrates with curvatures on both sides, using volume-reducing materials to form specific curvatures, and applying planarization or metallization to enhance light extraction, allowing for the fabrication of OLEDs with improved light outcoupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible plastic substrate is used for OLED fabrication, then the device flexibility and refractive index are improved, but the substrate flatness and surface quality deteriorate
Solution Approach 1:
The patent applies curvature to the substrate surface by forming spherical microlens arrays directly on the flexible plastic substrate. This transforms the flat surface into a curved one with controlled topography, improving light extraction efficiency while maintaining the inherent flexibility of the plastic material. The spherical features are formed through a two-step process: first creating hemispherical protrusions on the mold, then casting the substrate material to replicate these features.
2Ease of manufacture
If a planar substrate surface is used, then the fabrication process is simplified, but the light extraction efficiency deteriorates
Solution Approach 1:
The patent introduces spherical microlens features on the substrate surface to improve light extraction. These curved features modify the optical path of generated light, reducing waveguide modes and increasing outcoupling efficiency. The spherical geometry is achieved through mold casting, where hemispherical features are formed on the mold surface and replicated in the substrate material.
Solution Approach 2:
The patent changes the surface topology parameter from flat to curved by forming microlens arrays. This parameter change affects the optical properties of the substrate, specifically improving light extraction efficiency by modifying the refractive index distribution and creating optical focusing effects that enhance outcoupling.
3Productivity
If the substrate surface is left as-is from molding, then the fabrication process is shortened, but the surface roughness causes shorting
Solution Approach 1:
The patent performs preliminary planarization by applying a planarization layer to the molded substrate surface before depositing the OLED functional layers. This preliminary action removes surface roughness and prevents shorting, ensuring device reliability while maintaining the beneficial curved features for light extraction. The planarization layer is applied conformally to preserve the underlying microlens topology.
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 approach results in OLEDs with enhanced light extraction efficiency and a smoother surface, overcoming the challenges of handling flexible substrates and improving the refractive index for better performance.
Implementation Method 1
using volume-reducing materials to form specific curvatures
Implementation Method 2
improving the refractive index for better performance
Implementation Method 3
applying planarization or metallization to enhance light extraction
Data Source
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AI summary
A method of fabricating a substrate for an organic light emitting device (OLED), by applying a volume-reducing substrate material onto a mold with topographical features that generates a smooth but non-flat surface on both sides of the substrate which can enhance light extraction of OLEDs that are built on top of the substrate. The resulting substrate includes surface features on a first substrate surface complementary to the surface features of a mold, such as spherical lens features, and surface features on a second substrate surface, such as dimple features, complementary to the curvature of the spherical lens features on the first substrate surface.