Organic Electroluminescent Device with Exciplex Host and TADF Auxiliary

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Solution Overview

Problem

Organic electroluminescent devices face issues with high driving voltage and low exciton utilization efficiency due to wide band gap host materials and Dexter energy transfer from host to luminescent dye molecules.

Innovation Solution

Incorporating a light-emitting layer with a host material exciplex formed by mixing an electron donor and acceptor material, along with a thermally activated delayed fluorescence (TADF) auxiliary host and fluorescent dye, to facilitate reverse intersystem crossing and Förster energy transfer, reducing triplet exciton loss and enhancing energy transfer efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a wide band gap host material is used, then device stability is improved, but driving voltage increases

Engineering Contradiction:

Improvedevice stabilityVSAvoiddriving voltage

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent uses a composite host system consisting of a wide band gap host material combined with a TADF auxiliary host material. This composite approach allows the system to maintain the stability benefits of the wide band gap material while the TADF component enables efficient triplet exciton utilization through reverse intersystem crossing, thereby reducing the energy barrier and lowering driving voltage requirements.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The TADF auxiliary host material acts as an intermediary between the wide band gap host material and the luminescent dye. It facilitates energy transfer by accepting triplet excitons from the host and transferring them to the dye through reverse intersystem crossing, enabling efficient energy utilization without requiring the wide band gap material to directly interact with the dye, thus reducing the energy barrier and driving voltage.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If Dexter energy transfer from host to luminescent dye is used, then energy transfer occurs, but triplet exciton utilization efficiency decreases

Engineering Contradiction:

Improveenergy transferVSAvoidtriplet exciton loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

Instead of using conventional Dexter energy transfer which directly transfers triplet excitons from host to dye (resulting in loss), the patent inverts the mechanism by employing TADF auxiliary host material that undergoes reverse intersystem crossing. This allows triplet excitons to be converted back to singlet excitons before transferring energy to the luminescent dye, thereby utilizing triplet excitons that would otherwise be lost and significantly improving exciton utilization efficiency.

Inventive Principle:

Principle #13The other way round (Inversion)

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 reduces triplet exciton loss, improves luminous efficiency, extends device lifetime, and lowers driving voltage, resulting in high external quantum efficiency and long-term device performance.

Implementation Method 1

facilitate reverse intersystem crossing and Förster energy transfer, reducing triplet exciton loss and enhancing energy transfer efficiency

Methodology Applied

Scientific EffectReverse intersystem crossing:

Implementation Method 2

facilitate reverse intersystem crossing and Förster energy transfer, reducing triplet exciton loss and enhancing energy transfer efficiency

Methodology Applied

Scientific EffectFörster energy transfer:

Implementation Method 3

The excitons return to the ground state and emit light by radiative transition of the fluorescent or phosphorescent process

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS12262636B2Organic electroluminescent devices and preparation methods thereof

Publication Date: 2025.03.25 KUNSHAN GO VISIONOX OPTO ELECTRONICS CO LTD

AI summary

The present disclosure discloses an organic electroluminescent device and a preparation method thereof. The device includes a light-emitting layer, the light-emitting layer includes a host material, an auxiliary host material and a fluorescent dye; the host material is an exciplex prepared by mixing an electron donor material and an electron acceptor material, the auxiliary host material is a thermally activated delayed fluorescence material, a singlet energy level and a triplet energy level of the exciplex are higher than the single energy level and triplet energy level of the auxiliary host material. The above organic electroluminescent device can promote the reverse intersystem crossing of the host material and the auxiliary host material from the triplet excitons to the singlet excitons, enhance the Foster energy transfer, reduce the triplet exciton quenching, therefore the efficiency roll-off of the device is small and the external quantum efficiency is high.