OLED Emissive Layer with Secondary NIR Emitter Sensitization

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Solution Overview

Problem

Conventional OLEDs face limitations in achieving efficient near-infrared (NIR) emission due to long excited state lifetimes and lower emission quantum yields, particularly when using phosphorescent or fluorescent emitters.

Innovation Solution

Incorporating a secondary NIR emitter, such as a lanthanide complex or organic fluorophore, into a phosphorescent OLED structure where the primary phosphorescent emitter acts as a sensitizer, enabling energy transfer through Dexter or Forster mechanisms to enhance efficiency and emission properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If phosphorescent emitters are used for NIR emission, then device efficiency is improved, but excited state lifetime becomes too long causing non-radiative decay

Engineering Contradiction:

Improvedevice efficiencyVSAvoidexcited state lifetime

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of moving object

Solution Approach 1:

The patent introduces a secondary NIR emitter as an intermediary that receives energy from the phosphorescent emitter via Dexter or Forster energy transfer mechanisms. This intermediary then emits NIR light with shorter excited state lifetime, effectively mediating between the phosphorescent emitter's efficiency advantage and the need for shorter lifetime to reduce non-radiative decay

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the emission mechanism parameter by transitioning from direct phosphorescent emission to energy transfer followed by secondary emission. This parameter change allows the system to maintain high efficiency while achieving shorter effective excited state lifetime through the secondary emitter's faster decay characteristics

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If phosphorescent emitters are used for NIR emission, then device efficiency is improved, but emission quantum yield decreases

Engineering Contradiction:

Improvedevice efficiencyVSAvoidemission quantum yield

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The secondary emitter acts as an intermediary that converts the phosphorescent emitter's energy with high efficiency while providing superior emission quantum yield for NIR. This intermediary approach allows the system to capture the efficiency benefit from phosphorescence while achieving the quantum yield advantage from the secondary emitter's radiative properties

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite emissive system combining phosphorescent emitter and secondary NIR emitter materials. This composite approach leverages the complementary strengths of both materials - the phosphorescent emitter's efficiency in energy capture and the secondary emitter's superior NIR emission quantum yield

Inventive Principle:

Principle #40Composite materials

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

This configuration improves device efficiency by leveraging shorter excited state lifetimes and higher emission quantum yields of secondary emitters, specifically benefiting NIR emission by reducing non-radiative decay and increasing radiative efficiency.

Implementation Method 1

enabling energy transfer through Dexter or Forster mechanisms to enhance efficiency and emission properties

Methodology Applied

Scientific EffectDexter energy transfer:

Implementation Method 2

enabling energy transfer through Dexter or Forster mechanisms to enhance efficiency and emission properties

Methodology Applied

Scientific EffectForster energy transfer:

Implementation Method 3

Incorporating a secondary NIR emitter, such as a lanthanide complex or organic fluorophore, into a phosphorescent OLED structure where the primary phosphorescent emitter acts as a sensitizer

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentUS11910702B2Organic electroluminescent devices

Publication Date: 2024.02.20 UNIVERSAL DISPLAY CORP

AI summary

An OLED structure including a first organic layer disposed between the anode and the cathode is disclosed. The first organic layer includes a primary phosphorescent emitter and a first host, and where one of the following conditions is true: (1) the first organic layer further includes a secondary emitter; or (2) the OLED further includes a second organic layer disposed between the anode and the cathode, wherein the second organic layer includes a secondary emitter. The phosphorescent emitter has a peak emission wavelength λmax that is ≥600 nm and ≤750 nm, the secondary emitter has a peak emission wavelength λmax that is ≥750 nm, and the first host has a lowest excited state triplet energy T1 that is at least 0.1 eV higher than that of the primary phosphorescent emitter.