TADF OLED Emitters With Small ΔEST for Rare-Metal-Free Efficiency

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Solution Overview

Problem

Existing organic light-emitting elements rely on phosphorescent materials containing rare and expensive metals, and there is a need for a more efficient and cost-effective alternative that can harness both singlet and triplet excitons to achieve high electroluminescent efficiency.

Innovation Solution

The use of benzobisoxazole, benzobisthiazole, and benzobisimidazole compounds with a small energy gap between S1 and T1 states to enable thermally activated delayed fluorescence (TADF), allowing for up-conversion of triplet excitons to singlet excitons, thereby enhancing exciton formation efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If phosphorescent materials containing rare metals (Ir or Pt) are used, then electroluminescent efficiency is improved by harvesting triplet excitons, but cost increases and resource sustainability deteriorates

Engineering Contradiction:

Improveelectroluminescent efficiencyVSAvoiduse of rare metals

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent extracts and eliminates the rare metal components (Ir, Pt) from the phosphorescent material system by developing a purely organic TADF emitter that achieves comparable or superior electroluminescent efficiency through a different mechanism (reverse intersystem crossing) that does not require heavy metals

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the fundamental parameter of exciton harvesting mechanism from phosphorescence (requiring triplet state emission with heavy metal assistance) to thermally activated delayed fluorescence (utilizing reverse intersystem crossing from triplet to singlet state), thereby achieving high efficiency without rare metals

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional fluorescent materials are used, then material simplicity is maintained, but electroluminescent efficiency deteriorates due to utilization of only 25% of excitons

Engineering Contradiction:

Improvematerial structureVSAvoidelectroluminescent efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent changes the energy gap parameter (ΔEST between S1 and T1 states) to be sufficiently small, enabling thermally activated reverse intersystem crossing from triplet to singlet state, thereby allowing fluorescent materials to harvest both singlet and triplet excitons for a maximum of 100% internal quantum efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic thermal activation that enables the system to overcome the energy gap between S1 and T1 states at operating temperatures, allowing bidirectional intersystem crossing and enabling the fluorescent emitter to utilize both singlet and triplet excitons dynamically

Inventive Principle:

Principle #15Dynamics

3Productivity

If phosphorescent materials are used to harvest triplet excitons, then electroluminescent efficiency is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improveexciton utilization efficiencyVSAvoidmanufacturing complexity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive, resource-limited phosphorescent materials containing rare metals with inexpensive, readily available organic compounds that can be synthesized through standard organic chemistry processes, thereby dramatically reducing manufacturing cost and complexity

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 compounds achieve external quantum efficiencies of over 5% and reduced efficiency roll-off at high luminance, providing a cost-effective and efficient alternative to traditional phosphorescent materials.

Implementation Method 1

thermally activated delayed fluorescence (TADF) emitters and/or hosts of formula (I), which have a sufficiently small energy gap between S1 and T1 (ΔEST) to enable up-conversion of the triplet exciton from T1 to S1

Methodology Applied

Scientific EffectReverse intersystem crossing:

Implementation Method 2

thermally activated delayed fluorescence (TADF) as a third generation luminescent material

Methodology Applied

Scientific EffectThermally activated delayed fluorescence:

Data Source

PatentUS12622170B2Fluorescent organic light emitting elements having high efficiency

Publication Date: 2026.05.05 UDC IRELAND

AI summary

The present invention relates to organic light emitting elements, comprising thermally activated delayed fluorescence (TADF) emitters and/or hosts of formulawhich have a sufficiently small energy gap between S1 and T1 (ΔEST) to enable up-conversion of the triplet exciton from T1 to S1. The organic light emitting elements show high electroluminescent efficiency.