Sub-Electrode Microlens Array for OLED Light Outcoupling

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Solution Overview

Problem

Conventional OLEDs suffer from 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 without introducing problematic thicker organic layers.

Innovation Solution

Incorporating a sub-electrode microlens array (SEMLA) embedded within the substrate, which redirects trapped light toward the substrate, combined with a distributed Bragg reflector and Purcell Factor enhancement layer to optimize light outcoupling and emission profile.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional OLED structure is used, then device simplicity is maintained, but light outcoupling efficiency is low due to trapped light in surface plasmon and waveguide modes

Engineering Contradiction:

Improvedevice simplicityVSAvoidlight outcoupling efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

A sub-electrode microlens array (SEMLA) is introduced as an intermediary component between the substrate and the electrode to redirect trapped light modes. The microlens array acts as a mediator that converts surface plasmon and waveguide modes into extractable light, improving outcoupling efficiency without requiring changes to the organic emissive layers

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent introduces optical microcavities and microlens structures that add dimensional complexity to the device architecture. By creating cavity resonances and using three-dimensional microlens arrays, the system transforms trapped two-dimensional light modes into extractable light paths, achieving enhanced outcoupling while maintaining thin-film device characteristics

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Loss of energy

If thicker organic layers are used to improve light extraction, then light outcoupling efficiency increases, but device complexity and fabrication difficulty increase

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidorganic layer thickness

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

Instead of modifying the organic emissive layers, the patent uses a sub-electrode microlens array as an intermediary optical element to improve light extraction. This approach avoids increasing organic layer thickness while achieving enhanced outcoupling efficiency through optical mode conversion at the electrode-substrate interface

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If sub-electrode microlens array is embedded in substrate, then light outcoupling efficiency improves to about 40%, but manufacturing precision requirements increase

Engineering Contradiction:

Improvelight outcoupling efficiencyVSAvoidmicrolens array embedding precision

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The microlens array is segmented into individual microlens elements that can be independently fabricated and positioned. This segmentation allows for modular manufacturing approaches, where precision requirements are distributed across multiple smaller elements rather than requiring monolithic precision, facilitating integration into existing OLED fabrication processes

Inventive Principle:

Principle #1Segmentation

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 achieves a maximum outcoupling efficiency of about 40% and a near Lambertian angular emission profile, significantly improving light extraction efficiency while maintaining device design flexibility and cost-effectiveness.

Implementation Method 1

Incorporating a sub-electrode microlens array (SEMLA) embedded within the substrate, which redirects trapped light toward the substrate

Methodology Applied

Scientific EffectLight redirection: Refraction

Implementation Method 2

combined with a distributed Bragg reflector and Purcell Factor enhancement layer to optimize light outcoupling and emission profile

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 3

Purcell-Effect-Enhanced Organic Light Emitting Diodes with Sub-Electrode Microlens Array

Methodology Applied

Scientific EffectPurcell effect:

Data Source

PatentUS20230092459A1Purcell-Effect-Enhanced Organic Light Emitting Diodes with Sub-Electrode Microlens Array

Publication Date: 2023.03.23 THE RGT UNIV OF MICHIGAN

AI summary

An organic light emitting device (OLED) comprises a substrate layer, a sub-electrode microlens array (SEMLA) at least partially embedded in the substrate layer comprising a plurality of microlenses, a first electrode layer over the substrate layer, a light emitting layer over the first electrode layer, and a second electrode layer over the light emitting layer. The device can further include a distributed Bragg reflector (DBR) layer between the substrate and first electrode layers and/or a Purcell Factor (PF) enhancement layer over the second electrode layer, comprising at least one layer pair including a silver mirror electrode and a metal-dielectric layer. Related methods are also disclosed.