Red Light TADF Material for OLED Efficiency

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Solution Overview

Problem

Conventional red light OLEDs face limitations due to low internal quantum efficiency in fluorescent materials and the need for precious metals in phosphorescent materials, with few effective thermally activated delayed fluorescence (TADF) materials available for red light emission.

Innovation Solution

A red light thermally activated delayed fluorescence material is developed, comprising an electron donor and acceptor portion with specific substituents, and a method for preparing it using palladium acetate and tri-tert-butylphosphine tetrafluoroborate, allowing for efficient red light emission by facilitating reverse intersystem crossing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If fluorescent materials are used in OLEDs, then the device structure is simple and processing is easy, but the internal quantum efficiency can only reach 25% due to the 1:3 ratio of singlet to triplet excitons

Engineering Contradiction:

Improveease of manufactureVSAvoidinternal quantum efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent changes the energy parameters of the material system by designing TADF materials with specific singlet-triplet energy gaps and reverse intersystem crossing rates, enabling efficient triplet exciton utilization while maintaining simple device structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material strategy by combining electron donor and acceptor units with specific substituents (isobutyl, methoxyl, or dimethylamino groups) to create TADF materials that achieve both high efficiency and red light emission

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If heavy metal complex phosphorescent materials are used, then both singlet and triplet excitons can be utilized achieving 100% internal quantum efficiency, but precious metals such as Ir and Pt are required

Engineering Contradiction:

Improveinternal quantum efficiencyVSAvoidprecious metal content

Core Design Contradiction:

Loss of energyVSQuantity of substance

Solution Approach 1:

The patent replaces expensive precious metal complexes with organic TADF materials that achieve similar high efficiency through molecular design, eliminating the need for Ir and Pt while maintaining 100% internal quantum efficiency

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the heavy metal spin-orbit interaction mechanism with an organic reverse intersystem crossing mechanism, replacing the need for precious metals while achieving the same functional outcome of utilizing both singlet and triplet excitons

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Illumination intensity

If red light phosphorescent heavy metal materials are used, then high efficiency red light emission can be achieved, but the material availability is limited and requires breakthrough

Engineering Contradiction:

Improvered light emission efficiencyVSAvoidmaterial availability

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The patent adjusts the molecular parameters by introducing specific substituents (isobutyl, methoxyl, dimethylamino groups) to tune the HOMO-LUMO gap and singlet-triplet energy difference, enabling red light emission with efficient TADF characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent divides the TADF material into distinct electron donor and acceptor portions with specific functional groups, allowing independent optimization of each unit to achieve both red light emission and high efficiency

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 material achieves high luminescent efficiency and is used in OLED devices with maximum brightness and current efficiency ranging from 1300 to 1800 cd/m2 and 25 to 35 cd/A, respectively, overcoming the limitations of previous technologies.

Implementation Method 1

a fast reverse intersystem crossing constant (kRISC) and a high photoluminescence quantum yield (PLQY) are necessary for the preparation of high efficiency OLEDs

Methodology Applied

Scientific EffectReverse intersystem crossing:

Implementation Method 2

an organic light emitting diode (OLED) device having a high efficiency

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS11326096B2Red light thermally activated delayed fluorescence material, method for preparing the same, and organic light emitting diode device

Publication Date: 2022.05.10 WUHAN CHINA STAR OPTOELECTRONICS SEMICONDUCTOR DISPLAY TECHNOLOGY CO LTD

AI summary

A red light thermally activated delayed fluorescence material, a method for preparing the same, and an organic light emitting diode (OLED) device are provided. The OLED device has a luminescent material layer containing the red light thermally activated delayed fluorescence material. The red light thermally activated delayed fluorescence material has a specific molecular structure. The OLED device has a maximum brightness ranging from 1300 to 1800 cd/m2 and a maximum current efficiency ranging from 25 to 35 cd/A.