Sub-electrode Microlens Array for OLED Light Extraction

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Solution Overview

Problem

Conventional OLEDs have low optical outcoupling efficiency due to light being trapped in surface plasmon modes and waveguide modes, with existing techniques failing to significantly improve light extraction efficiency.

Innovation Solution

Incorporating a high refractive index sub-electrode microlens array (SEMLA) between the OLED substrates and transparent electrodes, which redirects light confined in organic and electrode layers toward the substrate, allowing for enhanced light extraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional OLED structures are used, then device simplicity is maintained, but light extraction efficiency remains low due to light being trapped in surface plasmon modes and waveguide modes

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoiddevice structure

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

A microlens array is introduced as an intermediary component between the OLED substrate and the transparent electrode. This microlens array acts as a mediator that redirects light confined in waveguide modes and surface plasmon modes toward the substrate, thereby enhancing light extraction efficiency without fundamentally altering the OLED's core structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The microlens array divides the light extraction function into multiple discrete lens elements arranged in an array. Each microlens individually redirects light from specific regions, collectively improving overall light extraction efficiency while maintaining a manageable and fabricable structure

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If light extraction efficiency is increased using conventional techniques, then more light is extracted, but image sharpness and spectral integrity are compromised

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidimage sharpness

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The microlens array provides localized light redirection at specific positions across the OLED surface. Each microlens is positioned and sized to redirect light from its corresponding region, maintaining spatial resolution and image sharpness while improving overall light extraction efficiency. This localised approach prevents the blurring that can occur with global light extraction enhancement techniques

Inventive Principle:

Principle #3Local quality

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 SEMLA achieves light extraction efficiencies of up to 70% for green PHOLEDs and 50% for white PHOLEDs, significantly surpassing conventional techniques, with no perceptible impact on image sharpness and maintaining spectral integrity, making it suitable for display and illumination applications.

Implementation Method 1

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11362311B2Sub-electrode microlens array for organic light emitting devices

Publication Date: 2022.06.14 THE RGT UNIV OF MICHIGAN

AI summary

Substrates are disclosed that include an embedded or partially-embedded microlens array. Devices are disclosed that include an OLED disposed over a substrate having an embedded or partially embedded micro lens array. Devices as disclosed herein redirect up to 100% of the light that otherwise would be confined in organic and electrode layers toward the substrate and thus provide improved light extraction and device efficiency.