Organic Electroluminescent Element with Segmented Emission Layers

Solution Overview

Problem

Existing organic electroluminescence devices face challenges in adjusting chromaticity without compromising drive voltage, luminous efficiency, and lifetime, as changing film thickness or dopant concentration can lead to undesirable effects such as increased voltage, reduced efficiency, or shortened device lifespan.

Innovation Solution

An organic electroluminescence device with multiple emitting layers, including a first and second emitting layer, where the layers contain specific host and dopant materials, allowing for adjustable chromaticity by varying the luminous intensities of these layers without altering their thickness or dopant concentration, thereby shifting the recombination zone and optimizing electron and hole transport.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the film thickness of each emitting layer is decreased to adjust chromaticity, then the chromaticity can be changed, but the lifetime of the organic EL device is shortened

Engineering Contradiction:

Improvechromaticity adjustmentVSAvoiddevice lifetime

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The emitting unit is divided into multiple emitting layers (first emitting layer with first host material and first dopant material, second emitting layer with second host material and second dopant material). Each layer can independently emit light with different characteristics, allowing chromaticity adjustment by controlling the relative luminous intensities of each layer rather than changing film thickness.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If the film thickness of each emitting layer is increased to adjust chromaticity, then the chromaticity can be changed, but the drive voltage of the organic EL device is increased

Engineering Contradiction:

Improvechromaticity adjustmentVSAvoiddrive voltage

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The emitting unit is divided into multiple emitting layers (first emitting layer with first host material and first dopant material, second emitting layer with second host material and second dopant material). Each layer can independently emit light with different characteristics, allowing chromaticity adjustment by controlling the relative luminous intensities of each layer rather than changing film thickness.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If the dopant concentration is increased to adjust chromaticity, then the chromaticity can be changed, but concentration quenching occurs to reduce the luminous efficiency

Engineering Contradiction:

Improvechromaticity adjustmentVSAvoidluminous efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The emitting unit is divided into multiple emitting layers (first emitting layer with first host material and first dopant material, second emitting layer with second host material and second dopant material). Each layer can independently emit light with different characteristics, allowing chromaticity adjustment by controlling the relative luminous intensities of each layer rather than changing film thickness.

Inventive Principle:

Principle #1Segmentation

4Device complexity

If a single emitting layer is used, then the device structure is simple, but the chromaticity cannot be easily adjusted without compromising performance

Engineering Contradiction:

Improveemitting layer structureVSAvoidchromaticity adjustment capability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The emitting unit is divided into multiple emitting layers (first emitting layer with first host material and first dopant material, second emitting layer with second host material and second dopant material). Each layer can independently emit light with different characteristics, allowing chromaticity adjustment by controlling the relative luminous intensities of each layer rather than changing film thickness.

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

Enables flexible adjustment of chromaticity while maintaining low drive voltage and high luminous efficiency, improving the device's color reproduction and extending its lifespan by optimizing the recombination zone and carrier transport properties.

Implementation Method 1

When an electric field is applied on both electrodes, electrons are injected from the cathode while holes are injected from the anode. Further, the electrons are recombined with the holes in the emitting layer to generate an excited state. When the excited state is returned to a ground state, energy is emitted as light.

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS9647226B2Organic electroluminescent element

Publication Date: 2017.05.09 IDEMITSU KOSAN CO LTD

AI summary

An organic electroluminescence device according of the invention includes an anode, a cathode, and at least a first emitting layer and a second emitting layer interposed between the anode and the cathode. The first emitting layer includes a first host material and a first dopant material. The second emitting layer includes a second host material, a third host material and a second dopant material.