OLED Phosphorescent Ligands with Cycloalkyl Linkages

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Solution Overview

Problem

Current organic light-emitting diodes (OLEDs) face challenges in achieving optimal emission line shape and external quantum efficiency due to limitations in phosphorescent emitter materials.

Innovation Solution

Development of novel ligands with an aryl group covalently bonded to a coordinating metal, featuring a cycloalkyl or substituted cycloalkyl linkage, which improves the emission line shape and external quantum efficiency of phosphorescent emitters in OLEDs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional phosphorescent emitter materials are used in OLEDs, then the device structure and material selection are straightforward, but the emission line shape and external quantum efficiency are suboptimal

Engineering Contradiction:

Improveemission line shapeVSAvoidligand structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent modifies the ligand structure by changing specific parameters: introducing cycloalkyl groups (R3) at defined positions on the phenyl ring, and adjusting substituent patterns (R1, R2, R4) on the bipyridine or phenanthroline ligands. These parameter changes in the molecular structure lead to improved emission line shape and external quantum efficiency without fundamentally changing the overall device architecture.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite ligand structures combining multiple functional groups: coordinating atoms (N or C from bipyridine/phenanthroline), cycloalkyl groups (R3), and various substituents (R1, R2, R4). This composite molecular design creates phosphorescent emitters with optimized photophysical properties, resolving the contradiction between performance and structural complexity.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional phosphorescent emitter materials are used in OLEDs, then the material synthesis and device fabrication are simpler, but the external quantum efficiency is suboptimal

Engineering Contradiction:

Improveexternal quantum efficiencyVSAvoidligand synthesis complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The ligand molecule is segmented into distinct functional regions: the coordinating bipyridine or phenanthroline core, the cycloalkyl substituent (R3) at specific positions, and additional substituents (R1, R2, R4) that can be independently optimized. This segmentation allows for modular synthesis approaches, improving external quantum efficiency while managing manufacturing complexity through systematic structure-activity relationship studies.

Inventive Principle:

Principle #1Segmentation

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 use of these novel ligands enhances the emission characteristics and efficiency of OLEDs, leading to improved performance in organic light-emitting devices.

Implementation Method 1

One application for phosphorescent emissive molecules is a full color display

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentUS11201298B2Organic electroluminescent materials and devices

Publication Date: 2021.12.14 UNIVERSAL DISPLAY CORP

AI summary

Ligands for metal complexes that are useful as phosphorescent emitters in OLEDs are disclosed. The ligands contain an aryl group covalently bonded to the coordinating metal. The aryl group has a cycloalkyl or a substituted cycloalkyl that is linked para to the linkage of the coordinating metal on that aryl group.