Optically Reflective Concave Structure for OLED Out-Coupling

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Solution Overview

Problem

Typical organic light-emitting device (OLED) structures suffer from limited optical out-coupling efficiencies due to total internal reflection, confining a significant portion of internally generated light within the device, which hinders the achievement of high-efficiency displays or lighting applications.

Innovation Solution

The implementation of an electroluminescent device with an optically reflective concave structure and functional layers, where the optically reflective concave structure has a first surface, a second surface at an angle relative to the first surface, and a third surface parallel to the first surface, with a light emitting layer disposed over these surfaces, and a patterned interlayer to define electroluminescent areas, along with an index-matching material to reduce reflection losses and enhance light out-coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If typical OLED structures with flat surfaces are used, then device fabrication is simple, but optical out-coupling efficiency is limited to 20-25% due to total internal reflection

Engineering Contradiction:

Improvedevice fabrication simplicityVSAvoidoptical out-coupling efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent introduces a concave structure with curved surfaces into the OLED device. The concave shape modifies the optical path of emitted light, reducing total internal reflection at interfaces and enabling more light to escape the device. This curvature-based approach directly addresses the optical out-coupling limitation while maintaining compatibility with standard fabrication processes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent adds a third dimension by creating a concave depression in the device structure. Instead of relying solely on two-dimensional planar layers, the concave geometry introduces vertical depth variation that redirects light paths and improves out-coupling efficiency without significantly complicating the manufacturing process.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If higher refractive index materials are used in OLED layers, then internal quantum efficiency can reach nearly 100%, but total internal reflection at interfaces increases, confining light within the device

Engineering Contradiction:

Improveinternal quantum efficiencyVSAvoidlight confinement due to total internal reflection

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The concave structure modifies the interface geometry between layers with different refractive indices. By curving the interface, the critical angle for total internal reflection changes, allowing more light to escape even when high refractive index materials are used to achieve high internal quantum efficiency.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent converts the harmful effect of total internal reflection into a beneficial one by using the concave structure to redirect reflected light toward escape paths. The same refractive index differences that cause total internal reflection are now harnessed to redirect light in useful directions, improving overall light extraction efficiency.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 significantly enhances optical out-coupling efficiencies by re-directing and out-coupling trapped light, improving emission efficiency and reducing power consumption in OLED displays, while maintaining high contrast and resolution without degrading image quality.

Implementation Method 1

the optically reflective concave structure includes a first surface, a second surface that lies at an angle relative to the first surface, and a third surface parallel to the first surface, wherein at least the first and second surfaces of the optically reflective concave structure are optically reflective

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

an index-matching material to reduce reflection losses and enhance light out-coupling

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

one or more functional layers include a light emitting layer, disposed over the surfaces of the optically reflective concave structure, wherein at least one electroluminescent area of the light emitting layer is defined on the first surface

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS10483496B2Electroluminescent devices with improved optical out-coupling efficiencies

Publication Date: 2019.11.19 NAT TAIWAN UNIV

AI summary

An electroluminescent (EL) device is disclosed. An optically reflective concave structure includes a first surface and a second surface that lies at an angle relative to the first surface, wherein at least the first and second surfaces are optically reflective. One or more functional layers include a light emitting layer, disposed over the surfaces of the optically reflective concave structure, wherein at least one electroluminescent area of the light emitting layer is defined on the first surface. Especially, the ratio between the diameter of the first surface and the thickness of the one or more functional layers in the optically reflective concave structure is smaller than a constant value.