Organometallic Compound for OLED Emission Layer

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Solution Overview

Problem

Organic light-emitting devices (OLEDs) face challenges in achieving high luminescent efficiency and lifespan due to issues with excimer and exciplex formation, which affect color purity and device stability, particularly in the emission layer where host materials may not adequately suppress these formations.

Innovation Solution

An organometallic compound represented by Formula 1, which includes a metal atom bonded to boron or nitrogen, is introduced in the emission layer, enhancing metal-ligand charge transfer and structural durability, thereby improving luminescent efficiency and lifespan by suppressing excimer and exciplex formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional host materials are used in the emission layer, then device structure is simple, but excimer and exciplex formation occurs leading to reduced color purity and luminescent efficiency

Engineering Contradiction:

Improveemission layer structureVSAvoidcolor purity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent introduces a host-guest complex system where the host material serves as an intermediary between the excitation source and the guest emitter. The host material absorbs excitation energy and transfers it to the guest, preventing direct excitation of the guest that would lead to excimer formation. This intermediary mechanism maintains color purity while enabling efficient energy transfer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The emission layer employs a composite system consisting of host materials and guest materials with specifically designed molecular structures. The host-guest complex forms a composite material where the host provides structural stability and the guest provides emission properties, achieving both structural simplicity and high color purity through material composition rather than structural complexity.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If conventional host materials are used in the emission layer, then device fabrication is easier, but luminescent efficiency and lifespan are reduced due to excimer formation

Engineering Contradiction:

Improveemission layer fabricationVSAvoiddevice lifespan

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent modifies molecular parameters of the host and guest materials, specifically designing molecular weights, steric hindrance, and structural rigidity parameters. These parameter changes prevent excimer formation by maintaining appropriate intermolecular distances while preserving ease of fabrication through solution processing. The optimized molecular parameters enable both manufacturability and enhanced device lifespan.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If excimer formation is allowed in the emission layer, then device structure remains simple, but energy loss increases reducing luminescent efficiency

Engineering Contradiction:

Improveemission layer structureVSAvoidluminescent efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The host material is designed to preemptively intercept excitation energy before it can lead to excimer formation. The host molecules are positioned and structured to prevent the close contact between guest molecules that would necessitate excimer formation, thereby preventing energy loss pathways before they occur. This preliminary anti-action maintains simple device structure while eliminating energy loss.

Inventive Principle:

Principle #9Preliminary anti-action

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 organometallic compound improves the luminescent efficiency and lifespan of OLEDs by reducing excimer and exciplex formation, leading to enhanced color purity and stability of the organic light-emitting device.

Implementation Method 1

enhancing metal-ligand charge transfer

Methodology Applied

Scientific EffectMetal-ligand charge transfer:

Implementation Method 2

suppressing excimer and exciplex formation

Methodology Applied

Scientific EffectExcimer formation suppression:

Implementation Method 3

suppressing excimer and exciplex formation

Methodology Applied

Scientific EffectExciplex formation suppression:

Implementation Method 4

Organic light-emitting devices (OLEDs) are self-emitting devices

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS11316117B2Organometallic compound and organic light-emitting device including the same

Publication Date: 2022.04.26 SAMSUNG DISPLAY CO LTD

AI summary

An organic light-emitting device includes an organometallic compound represented by M1(L1)n1(L2)n2, wherein L1 is a ligand represented by Formula 1-1:In Formula 1-1, *1 to *4 indicate a binding site to M1, and Z11 and Z12 are respectively boron (B) and nitrogen (N), or N and B. When M1 binds to an α-position of the B or N atom, metal-ligand charge transfer in the complex may be improved. An OLED including the organometallic compound may have a long lifespan and improved luminescent efficiency and colorimetric purity.