OLED Microlens Array for Light Extraction
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Solution Overview
Problem
Organic Light Emitting Diodes (OLEDs) face significant light loss due to total internal reflection, resulting in low external efficiency, particularly in pixelated displays where surface texturing degrades optical quality and causes blur effects, with only about 20% of generated photons being extracted.
Innovation Solution
A light extraction structure featuring an array of high refractive index lenses applied between the active region and the encapsulation layer, combined with a planarization layer, enhances light extraction efficiency while preserving optical quality, using nanocomposites with inorganic nanocrystals dispersed in polymeric materials for improved refractive index and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If surface texturing is applied to the substrate to reduce total internal reflection, then light extraction efficiency is improved, but optical quality of pixels is degraded causing blur effects
Solution Approach 1:
The invention divides the light extraction function into two separate components: a planar pixel-defining layer that maintains optical quality and a microlens array layer that enhances light extraction. Each layer performs its specific function independently, avoiding the blur effects caused by surface texturing while achieving high extraction efficiency through the microlens structure.
Solution Approach 2:
The invention transitions from two-dimensional surface texturing to three-dimensional microlens structures. The microlenses are positioned at specific heights above the pixel array, creating a vertical dimension that allows light extraction enhancement without compromising the lateral optical quality of individual pixels.
2Loss of energy
If high refractive index materials are used to improve light extraction, then external efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The invention optimizes the refractive index parameters of the microlens material and surrounding layers to maximize light extraction efficiency. By carefully selecting materials with appropriate refractive indices and adjusting the numerical aperture of the microlenses, high external efficiency is achieved through parameter optimization rather than complex structural designs.
Solution Approach 2:
The invention uses spherical or hemispherical microlens shapes to simplify manufacturing while achieving superior light extraction compared to flat surfaces. The curved geometry of the microlenses naturally focuses and redirects light, providing high extraction efficiency with a relatively simple fabrication process using standard photolithography and reflow techniques.
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 significantly increases light extraction efficiency, achieving high refractive indices and optical transmittance, and maintains optical quality, with films demonstrating stability at elevated temperatures and reduced surface roughness.
Implementation Method 1
A light extraction structure may comprise an array of lenses or sets of lenses, each of the lens or set of lenses covers at least one pixel... each of the lens or set of lenses is applied between the active region of a light emitting device and the encapsulation layer
Implementation Method 2
Due to the specific device structures of LEDs and OLEDs, significant portion of the light generated inside the active region is totally reflected at various interfaces and is 'trapped' inside the device
Implementation Method 3
using nanocomposites with inorganic nanocrystals dispersed in polymeric materials for improved refractive index and transparency
Implementation Method 4
A light extraction structure may comprise an array of lenses or sets of lenses, each of the lens or set of lenses is applied between the active region of a light emitting device and the encapsulation layer... using nanocomposites with inorganic nanocrystals dispersed in polymeric materials
Data Source
AI summary
This presently disclosed technology relates to Organic Light Emitting Diodes (OLEDs), more particularly it relates to OLED display extraction and nanocomposite formulations that can be used for the light extraction structure. The OLEDs comprise, in order, an encapsulation layer or a substrate layer, an array of lenses, and an array of light emitting pixels at least partially covered by said array of lenses, wherein at least one of the lenses covers at least one of the pixel, and said lenses comprises a material with higher refractive index than the encapsulation layer or substrate layer.