Azine Material for Organic EL Device Triplet Energy Management

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Solution Overview

Problem

Current organic electroluminescence devices face limitations in achieving long lifetimes due to differences in material selection and device design required for fluorescent and phosphorescent emission mechanisms, with phosphorescent devices having shorter lifetimes and requiring specific triplet energy management.

Innovation Solution

A material represented by formula (I) is introduced, featuring an azine ring with a cyano-substituted aromatic hydrocarbon or heterocyclic group, which is bonded to a central skeleton, enhancing the triplet energy and carrier balance, thereby improving the lifetime of organic electroluminescence devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a compound with larger energy gap is used in the light emitting layer to confine triplet energy, then triplet energy confinement is improved, but the driving voltage increases

Engineering Contradiction:

Improvetriplet energy confinementVSAvoiddriving voltage

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent modifies the energy gap parameter of the host material by introducing specific heterocyclic groups (triazine, pyrimidine, pyridine rings) to achieve optimal triplet energy confinement. This chemical structural modification allows tuning of the energy parameters to balance confinement efficiency and driving voltage requirements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material design by combining the host material with phosphorescent dopant materials in specific ratios. This composite approach allows the host to provide triplet energy confinement while the dopant enables efficient phosphorescence emission, resolving the contradiction between energy confinement and emission efficiency.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If an organic compound having a heteroatom is used instead of hydrocarbon compound, then triplet energy is increased, but the device lifetime is shortened

Engineering Contradiction:

Improvetriplet energyVSAvoiddevice lifetime

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

The patent applies local quality modification by introducing heteroatoms (nitrogen, oxygen) at specific positions within the molecular structure of the host material. This localized modification increases triplet energy at the molecular level while the overall molecular design maintains stability and longevity, resolving the contradiction between energy level and device lifetime.

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If phosphorescence emission mechanism is used instead of fluorescence, then internal quantum efficiency is increased to 100%, but device lifetime is reduced

Engineering Contradiction:

Improveinternal quantum efficiencyVSAvoiddevice lifetime

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

The patent introduces a carefully designed host material as an intermediary between the phosphorescent dopant and the electrodes. This host material mediates the triplet energy management and carrier transport, enabling high internal quantum efficiency through phosphorescence while the host's stable structure protects the dopant from degradation, thereby extending device lifetime.

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

The material extends the lifetime of organic electroluminescence devices by optimizing triplet energy management and carrier balance, leading to improved emission efficiency and device performance.

Implementation Method 1

a host material having triplet energy larger than that of the phosphorescent dopant material should be used in the light emitting layer

Methodology Applied

Scientific EffectTriplet energy transfer: Fluorescence

Implementation Method 2

since the phosphorescence utilizes the emission from triplet excitons, it has been known that the internal quantum efficiency of a phosphorescent organic EL device can be increased to 100% if the intersystem crossing occurs efficiently

Methodology Applied

Scientific EffectIntersystem crossing: Phosphorescence

Data Source

PatentUS9130174B2Material for organic electroluminescence device and organic electroluminescence device

Publication Date: 2015.09.08 IDEMITSU KOSAN CO LTD

AI summary

A material for organic EL device which includes a compound having a specific structure: an azine ring having a cyano-substituted aromatic hydrocarbon group, an azine ring having a cyano-substituted heterocyclic group, or an azine ring having a cyano group directly bonded to the azine ring. An organic electroluminescence device including an organic thin film layer between a cathode and an anode, wherein the organic thin film layer includes a light emitting layer and at least one layer containing the material for organic electroluminescence device, has a long lifetime.