Fused Tetraphenylene Host Material for Blue Phosphorescent OLEDs

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Solution Overview

Problem

There is a need for novel host materials for phosphorescent electroluminescent devices that can effectively manage triplet energy and thermal stability to prevent triplet-triplet quenching and ensure good thermal stability, particularly for blue phosphorescent OLEDs with emission wavelengths below 490 nm.

Innovation Solution

The development of a compound with a fused tetraphenylene ring system, as described in Formula I, which serves as a host material with high triplet energy and high glass transition temperature, disrupting amorphous packing and enhancing thermal stability, is proposed for use in organic light-emitting diodes (OLEDs).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional host materials are used in blue phosphorescent OLEDs, then device fabrication is simpler, but triplet-triplet quenching occurs and thermal stability is insufficient

Engineering Contradiction:

Improvethermal stabilityVSAvoidmolecular structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs a composite molecular structure combining a dibenzofuran core with multiple phenyl rings and heteroatom substituents. This composite architecture achieves high triplet energy (2.8-3.2 eV) and elevated glass transition temperature (Tg > 80°C), preventing triplet-triplet quenching while ensuring thermal stability for blue phosphorescent OLED operation

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces nitrogen and oxygen heteroatoms at specific positions within the molecular structure (e.g., positions 2, 7, and 9 in the dibenzofuran core). This local modification of atomic composition enhances triplet energy density and thermal properties without requiring complete structural redesign, thereby improving reliability while controlling complexity

Inventive Principle:

Principle #3Local quality

2Reliability

If host materials with high triplet energy are used to prevent triplet-triplet quenching, then emission stability improves, but material synthesis becomes more difficult

Engineering Contradiction:

Improveemission stabilityVSAvoidsynthesis ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent divides the host material into modular components: a dibenzofuran core unit, phenyl ring substituents, and heteroatom-functionalized groups. This segmentation allows independent optimization of triplet energy (achieved through core structure) and synthesis feasibility (achieved through standardizable substituent chemistry), maintaining emission stability while improving manufacturability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent systematically varies molecular parameters such as substituent position (ortho, meta, para), substituent type (phenyl, pyridyl, triazolyl), and heteroatom configuration to tune triplet energy within the 2.8-3.2 eV range. These controlled parameter changes enable optimization of emission stability without requiring radical structural changes that would complicate synthesis

Inventive Principle:

Principle #35Parameter changes

3Reliability

If glass transition temperature is increased to improve thermal stability, then device performance is maintained, but molecular rigidity increases making processing harder

Engineering Contradiction:

Improvedevice performance maintenanceVSAvoidprocessing ease

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces flexible alkyl chains and alkoxy groups as intermediary elements connecting the rigid dibenzofuran core to external environments. These intermediary groups increase glass transition temperature (Tg > 80°C) and thermal stability while maintaining sufficient molecular mobility for solution processing and device fabrication, thus preserving both device performance and processing ease

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 compound exhibits high triplet energy and glass transition temperature, making it suitable as a host material for blue phosphorescent OLEDs, preventing triplet-triplet quenching and ensuring good thermal stability, thereby minimizing interlayer contamination and maintaining device performance.

Implementation Method 1

The compounds described herein can be useful in organic electroluminescent devices (OLEDs), and more specifically, can be useful as host materials in OLEDs that have a phosphorescent emitter in an organic layer. The compounds of Formula I exhibit high triplet energy

Methodology Applied

Scientific EffectTriplet energy:

Implementation Method 2

The compounds of Formula I exhibit high triplet energy and high glass transition temperature, which makes then ideal as a host material in an OLED

Methodology Applied

Scientific EffectGlass transition:

Implementation Method 3

One application for phosphorescent emissive molecules is a full color display

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentUS11349083B2Organic electroluminescent materials and devices

Publication Date: 2022.05.31 UNIVERSAL DISPLAY CORP

AI summary

The present invention includes novel compounds containing heterocycles and oligomeric phenylene or aza and cyano substituted variants thereof. These compounds may be useful as host materials for phosphorescent electroluminescent devices.