OLED Performance Enhancement Layer Refractive Index Optimization

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Solution Overview

Problem

Existing organic electroluminescent devices face challenges with high concentrations of low refractive index materials, which improve light extraction efficiency but compromise charge transporting properties, leading to higher voltage, reduced efficiency, and lower operational stability and durability.

Innovation Solution

An organic electroluminescent device design incorporating a performance enhancement layer with a refractive index of ≤1.6, positioned between the electron transport layer and the second electrode, utilizing materials like silsesquioxanes, alkanes, and metal fluorides, to enhance light outcoupling efficiency while maintaining charge transport integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If high concentrations of low refractive index materials are incorporated into charge transport layers, then light extraction efficiency is improved, but charge transporting properties deteriorate resulting in higher voltage and reduced efficiency

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidcharge transporting properties

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The device is divided into functionally distinct layers: a first electron transport layer for charge transport and a separate performance enhancement layer for light extraction optimization. This segmentation allows each layer to be optimized for its specific function without compromise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device are assigned different material properties: the first electron transport layer uses materials optimized for charge transport, while the performance enhancement layer uses low refractive index materials optimized for light extraction. Each layer has localized quality tailored to its function.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If high concentrations of low refractive index materials are used, then light extraction efficiency increases, but operational stability and durability decrease

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidoperational stability and durability

Core Design Contradiction:

Illumination intensityVSDuration of action of stationary object

Solution Approach 1:

The device structure separates the electron transport function from the light extraction function into distinct layers, allowing the performance enhancement layer to contain high concentrations of low refractive index materials without compromising the stability of the charge transport layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first electron transport layer acts as an intermediary between the emission layer and the performance enhancement layer, protecting the device from the potential instability of high concentration low refractive index materials while still enabling their light extraction benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Illumination intensity

If low refractive index materials are incorporated into charge transport layers, then light extraction is improved, but device voltage increases

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoiddevice voltage

Core Design Contradiction:

Illumination intensityVSPower

Solution Approach 1:

The device is segmented into separate functional layers where charge transport and light extraction are handled by different layers, preventing the voltage increase associated with incorporating low refractive index materials into charge transport layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first electron transport layer maintains material properties optimized for charge transport with appropriate voltage characteristics, while the performance enhancement layer locally provides the low refractive index property for light extraction without affecting device voltage.

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 solution effectively increases light extraction efficiency while minimizing the adverse effects on charge transport properties, resulting in improved operational stability and durability of the OLED device.

Implementation Method 1

the performance enhancement layer having a refractive index of ≤1.6 at a wavelength of 1,200 nm

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11183649B2Organic electroluminescent device

Publication Date: 2021.11.23 NOVALED GMBH

AI summary

The present invention relates to an organic electroluminescent device comprising a first electrode, at least one second electrode, at least one emission layer and at least one electron transport region, wherein the emission layer and the electron transport region are arranged between the at least one second electrode and the first and the electron transport region is arranged between the emission layer and the at least one second electrode, wherein the at least one electron transport region comprises a first electron transport layer, the first electron transport layer preferably not comprising an n-type dopant; and a performance enhancement layer, the performance enhancement layer having a refractive index of ≤1.6 at a wavelength of 1,200 nm; wherein the first electron transport layer is arranged between the emission layer and the performance enhancement layer; and the performance enhancement layer is arranged between the first electron transport layer and the at least one second electrode.