Heterocyclic Host Material for OLEDs

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Solution Overview

Problem

Light-emitting elements with dibenzo[f,h]quinoxaline rings have a planar structure, leading to short lifetimes due to easy crystallization and decreased triplet excitation energy when a hole-transport skeleton is directly bonded, resulting in low efficiency and short lifespan.

Innovation Solution

A heterocyclic compound with a dibenzo[f,h]quinoxaline ring bonded through an arylene group to a hole-transport skeleton, preventing crystallization and maintaining high triplet excitation energy, used as a host material in light-emitting layers for phosphorescent compounds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a hole-transport skeleton is directly bonded to the dibenzo[f,h]quinoxaline ring, then the compound has enhanced hole transport capability, but the triplet excitation energy decreases and the compound becomes prone to crystallization

Engineering Contradiction:

Improvehole transport capabilityVSAvoidtriplet excitation energy

Core Design Contradiction:

Ease of operationVSDuration of action of moving object

Solution Approach 1:

The patent introduces a phenylene group as an intermediary segment between the dibenzo[f,h]quinoxaline ring and the hole-transport skeleton. This segmentation prevents direct bonding while maintaining the hole transport capability through the phenylene bridge, thereby preserving the triplet excitation energy of the dibenzo[f,h]quinoxaline core.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The phenylene group acts as an intermediary between the dibenzo[f,h]quinoxaline ring and the hole-transport skeleton. This mediator prevents the direct interaction that would otherwise reduce triplet excitation energy, while still allowing effective hole transport through the phenylene-heterocyclic system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If a hole-transport skeleton is directly bonded to the dibenzo[f,h]quinoxaline ring, then the compound has enhanced hole transport capability, but the compound is prone to crystallization leading to short device lifetime

Engineering Contradiction:

Improvehole transport capabilityVSAvoiddevice lifetime

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

By segmenting the molecular structure with a phenylene group, the patent prevents direct bonding between the dibenzo[f,h]quinoxaline ring and hole-transport skeleton, thereby reducing molecular planarity and crystallization tendency while maintaining hole transport functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The phenylene group serves as an intermediary that disrupts the direct π-π stacking interactions between dibenzo[f,h]quinoxaline rings and hole-transport skeletons, reducing crystallization propensity and improving device lifetime while preserving hole transport capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If phosphorescent compound is dispersed in host material matrix, then concentration quenching is suppressed, but the internal quantum efficiency is limited by singlet-triplet ratio

Engineering Contradiction:

Improveemission efficiencyVSAvoidinternal quantum efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent modifies the host material's triplet excitation energy parameter by using dibenzo[f,h]quinoxaline derivatives with high triplet energy levels. This parameter change enables efficient triplet energy transfer to phosphorescent guests, overcoming the theoretical 25% efficiency limit of fluorescent systems and achieving near-100% internal quantum efficiency through phosphorescence.

Inventive Principle:

Principle #35Parameter changes

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 compound extends the lifetime of light-emitting elements, enhances current efficiency, and reduces driving voltage, while maintaining high triplet excitation energy, achieving low power consumption in light-emitting devices.

Implementation Method 1

preventing crystallization and maintaining high triplet excitation energy

Methodology Applied

Scientific EffectCrystallization prevention: Crystallisation

Implementation Method 2

emission from the triplet excited state (T*) is called phosphorescence

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Implementation Method 3

since intersystem crossing (i.e. transition from a singlet excited state to a triplet excited state) easily occurs in a phosphorescent compound

Methodology Applied

Scientific EffectIntersystem crossing:

Data Source

PatentUS9960368B2Heterocyclic compound

Publication Date: 2018.05.01 SEMICON ENERGY LAB CO LTD

AI summary

Provided is a novel heterocyclic compound which can be used for a light-emitting element, as a host material of a light-emitting layer in which a light-emitting substance is dispersed. A heterocyclic compound represented by a general formula (G1) is provided. In the formula, A represents any of a substituted or unsubstituted dibenzothiophenyl group, a substituted or unsubstituted dibenzofuranyl group, and a substituted or unsubstituted carbazolyl group, R11 to R19 separately represent any of hydrogen, an alkyl group having 1 to 4 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 13 carbon atoms, and Ar represents a substituted or unsubstituted arylene group having 6 to 13 carbon atoms.