Exciplex Host TADF OLED Efficiency Rolling

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Solution Overview

Problem

Organic electroluminescent devices using an exciplex as the host material experience severe Triple-Triplet Annihilation (TTA), Triplet-Polaron Annihilation (TPA), and Singlet-Triplet Annihilation (STA) in the light-emitting layer, leading to accelerated efficiency rolling-down and shortened service life.

Innovation Solution

An organic electroluminescent device with a light-emitting layer comprising a host material exciplex formed by an electron donor and receptor material, where the guest material is thermal activated delayed fluorescent (TADF) material, and the singlet energy level of the host material is lower than that of the guest material, with specific energy level differences and mass ratios to enhance energy transfer and prevent high-energy exciton generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If an exciplex host material is used in the light-emitting layer, then the internal quantum efficiency is improved, but severe Triple-Triplet Annihilation (TTA), Triplet-Polaron Annihilation (TPA) and Singlet-Triplet Annihilation (STA) occur leading to accelerated efficiency rolling-down and shortened service life

Engineering Contradiction:

Improveinternal quantum efficiencyVSAvoidservice life

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent adjusts the energy level parameters of the host and guest materials, specifically setting the singlet energy level of the host material lower than that of the guest material, and controlling the energy level difference to be less than 0.3 eV. This parameter optimization enables efficient energy transfer while avoiding high-energy exciton generation that causes annihilation, thus resolving the contradiction between efficiency and service life

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite light-emitting layer comprising both host material (exciplex formed by electron donor and receptor materials) and guest material (TADF material). This composite structure leverages the advantages of both materials: the exciplex host provides efficient energy transfer and the TADF guest material enables high internal quantum efficiency through reverse intersystem crossing, while the controlled energy level difference prevents harmful annihilation effects

Inventive Principle:

Principle #40Composite materials

2Productivity

If an exciplex host material with narrow energy gap is used to sensitize guest material, then the utilization rate of excitons is increased, but high excitation energy causes severe annihilation phenomena leading to accelerated efficiency rolling-down

Engineering Contradiction:

Improveutilization rate of excitonsVSAvoidefficiency rolling-down

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent optimizes the energy level parameters by setting the singlet energy level of the host material lower than that of the guest material, with the energy level difference controlled to be less than 0.3 eV. This parameter adjustment ensures that energy transfer occurs without generating high-energy excitons that would cause annihilation, thus maintaining high exciton utilization while preventing efficiency loss

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of high excitation energy into a benefit by carefully controlling the energy level difference between host and guest materials. The small energy gap enables efficient energy transfer (benefit) while the specific energy level configuration prevents high-energy exciton generation that would cause annihilation (harm prevention), effectively turning the narrow energy gap from a potential source of damage into a mechanism for efficient energy transfer

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 significantly alleviates efficiency rolling-down, prolongs the light-emitting service life, and achieves high light-emitting efficiency by reducing exciton annihilation and promoting energy transfer, resulting in stable and long-lasting performance.

Implementation Method 1

in the process of Forster energy transfer between the host material and the guest material

Methodology Applied

Scientific EffectForster energy transfer:

Implementation Method 2

the triplet state excitons can be converted into singlet state excitons by the process of Reverse Intersystem Crossing (RISC)

Methodology Applied

Scientific EffectReverse Intersystem Crossing:

Implementation Method 3

the Thermally Activated Delayed Fluorescence (TADF) mechanism has been proposed

Methodology Applied

Scientific EffectThermally Activated Delayed Fluorescence:

Data Source

PatentUS11063224B2Organic electroluminescent device

Publication Date: 2021.07.13 KUNSHAN GO VISIONOX OPTO ELECTRONICS CO LTD

AI summary

The present application discloses an organic electroluminescent device including a host material and guest material, the host material is an exciplex formed by electron donor material and electron receptor material, the guest material is thermal activated delayed fluorescent material, a singlet energy level of the host material is lower than a singlet energy level of the guest material.