Five-Coordinate Metal Complex Host for OLED Durability

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Solution Overview

Problem

Phosphorescent organic electroluminescent devices face challenges with durability and low luminous efficiency, despite advancements in using phosphorescent materials and host materials like Balq2, which do not meet the demands for high luminance and long-term reliability.

Innovation Solution

The use of a five-coordinate metal complex as the host material in combination with an Ir complex having specific partial structures in the light emitting layer enhances both the durability and luminous efficiency of the organic electroluminescent device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If phosphorescent materials are used to improve luminous efficiency, then the utilization of triplet excitons increases, but device durability deteriorates

Engineering Contradiction:

Improveluminous efficiencyVSAvoiddevice durability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The invention changes the chemical composition parameters of the light emitting layer by incorporating specific host materials (carbazole derivatives with electron-accepting groups) and controlling the ratio of phosphorescent dopant to host material. This optimization allows efficient triplet exciton utilization while maintaining material stability and device durability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses composite material systems combining host materials (carbazole derivatives), phosphorescent dopants (iridium complexes), and electron-accepting groups. This composite approach enables synergistic effects where the host material provides structural stability and the phosphorescent dopant enables efficient triplet exciton utilization, resolving the contradiction between durability and luminous efficiency.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If conventional host materials like CBP are used, then the device structure is simple, but durability is insufficient

Engineering Contradiction:

Improvehost material structureVSAvoiddevice durability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention modifies the molecular structure parameters of host materials by introducing electron-accepting groups (cyano, carbonyl, or nitro groups) into carbazole derivative frameworks. This structural modification enhances the electron-accepting capability and stability of the host material, thereby improving device durability while maintaining structural simplicity.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If fluorescent light emission is utilized, then the device construction is simple, but only 25% of excitons can be effectively applied resulting in low luminous efficiency

Engineering Contradiction:

Improvelight emission mechanismVSAvoidluminous efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The invention introduces phosphorescent dopant materials (iridium complexes) as intermediaries that facilitate triplet exciton utilization. These dopants act as mediators that accept energy from the host material and emit light through phosphorescence, enabling efficient utilization of both singlet and triplet excitons while maintaining relatively simple device construction.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 improves the durability and luminous efficiency of the organic electroluminescent device, making it suitable for applications such as full-color displays and backlights, with enhanced performance over previous devices.

Implementation Method 1

organic electroluminescent devices utilizing phosphorescence with a phenylpyridine complex of iridium

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Implementation Method 2

a host material for undergoing energy transfer of triplet exciton energy into a light emitting material

Methodology Applied

Scientific EffectEnergy transfer:

Implementation Method 3

an organic electroluminescent device is constructed of a light emitting layer and a pair of counter electrodes having therebetween the light emitting layer

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS7618717B2Light emitting device

Publication Date: 2009.11.17 UDC IRELAND

AI summary

To provide an organic electroluminescent device having excellent durability and having high luminous efficiency and luminance, which can be effectively utilized for surface light sources such as full color displays, backlights, and illuminating light sources and light source arrays such as printers, the organic electroluminescent device includes at least one organic compound layer containing a light emitting layer between a pair of electrodes, wherein the light emitting layer contains a host material and a phosphorescent material; the host material is a five-coordinate metal complex; and the phosphorescent material is at least one Ir complex having a specific partial structure.