Heteroleptic Iridium Complexes for OLED Efficiency

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Solution Overview

Problem

There is a need for novel emitters for electroluminescent devices that can efficiently produce high-quality light, particularly for applications like OLEDs, which require materials that can emit saturated colors and have deep LUMOs for effective electron trapping and high luminescent efficiency.

Innovation Solution

The development of heteroleptic tris-cyclometalated iridium (III) complexes with deep LUMOs, represented by the compound structure (LA)nIr(LB)3-n, which can be used as emissive dopants in OLEDs to enhance light emission efficiency and produce high-efficiency OLED devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional emissive materials are used in OLEDs, then the device structure is simpler, but the luminescent efficiency and color saturation are insufficient

Engineering Contradiction:

Improvedevice structure simplicityVSAvoidluminescent efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent employs heteroleptic iridium(III) complexes comprising cyclometalating ligands and ancillary ligands as composite emissive materials. These complexes combine multiple ligand types with specific electronic properties to achieve deep LUMO levels and high phosphorescent quantum yields, resolving the contradiction between structural simplicity and luminescent efficiency through molecular-level composite design

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent systematically modifies molecular parameters of the iridium complexes, including ligand substitution patterns, aromatic ring substitutions, and heteroatom incorporation, to optimize LUMO depth and phosphorescent emission properties. These parameter changes enable achievement of saturated colors and high efficiency simultaneously

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If materials with shallow LUMO levels are used, then electron injection is easier, but electron trapping efficiency and luminescent performance deteriorate

Engineering Contradiction:

Improveelectron injection easeVSAvoidelectron trapping efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent achieves deep LUMO levels (below -2.5 eV) through specific ligand design including electron-withdrawing groups and extended aromatic systems on the cyclometalating and ancillary ligands. This parameter optimization enables simultaneous achievement of adequate electron injection and superior electron trapping efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The iridium(III) complex acts as an intermediary species that facilitates efficient electron trapping and energy transfer to the emitter. The complex's deep LUMO level serves as an electron acceptor while its phosphorescent state serves as an energy source, mediating between electron injection and light emission processes

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If fluorescent emitters are used in OLEDs, then the device structure is simpler, but the maximum luminescent efficiency is limited to 25%

Engineering Contradiction:

Improveemissive mechanism simplicityVSAvoidmaximum luminescent efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent exploits the spin-state transition from singlet to triplet excitons through phosphorescent emission. By utilizing heavy atom effects in iridium(III) complexes, the system accesses the triplet state manifold, enabling utilization of both singlet and triplet excitons for light emission and achieving internal quantum efficiencies exceeding 25%

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The patent replaces fluorescent emission mechanism with phosphorescent emission mechanism. This substitution enables utilization of triplet excitons that are otherwise non-emissive in fluorescent systems, thereby doubling the potential luminescent efficiency through access to additional quantum mechanical pathways

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

These complexes enable the production of OLEDs with improved luminescent efficiency by effectively trapping electrons and emitting light through phosphorescence, leading to enhanced performance and efficiency in electroluminescent devices.

Implementation Method 1

deep LUMOs for effective electron trapping

Methodology Applied

Scientific EffectElectron trapping:

Implementation Method 2

emitting light through phosphorescence

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentUS12048237B2Organic electroluminescent materials and devices

Publication Date: 2024.07.23 UNIVERSAL DISPLAY CORP

AI summary

The present invention includes a new series of heteroleptic iridium complexes that demonstrate high efficiency in OLED device.