Organic Electroluminescence Device with TADF Sensitizer
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Solution Overview
Problem
Traditional organic electroluminescence devices face issues with short service life, wide emission spectrum, and efficiency roll-off due to the limitations of traditional fluorescent and phosphorescent materials, as well as TADF materials, which often require heavy metals and suffer from high triplet state energy levels and intramolecular charge transfer.
Innovation Solution
An organic electroluminescence device utilizing a wide bandgap material as a host and a thermally activated delayed fluorescent (TADF) sensitizer to assist a resonance TADF dye, where the energy levels are carefully aligned to facilitate efficient energy transfer and reduce triplet exciton annihilation, thereby improving light emission efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional phosphorescent materials are used with heavy metal atoms to achieve 100% energy usage efficiency, then energy efficiency is improved, but cost increases and environmental pollution occurs
Solution Approach 1:
The patent replaces expensive and environmentally harmful heavy metal phosphorescent materials with organic TADF materials that are cheaper, environmentally friendly, and free from heavy metals like iridium and platinum, while maintaining high energy efficiency through triplet exciton utilization
Solution Approach 2:
The patent changes the material composition from inorganic heavy metal compounds to organic TADF materials, fundamentally altering the chemical parameters and eliminating heavy metal content while preserving the ability to achieve 100% energy usage efficiency through reverse intersystem crossing
2Object-affected harmful factors
If traditional TADF materials are used to emit light, then heavy metal usage is eliminated, but device service life becomes short and emission spectrum becomes wide
Solution Approach 1:
The patent introduces a sensitizer material as an intermediary component that receives excitons from the host material and transfers energy to the TADF dopant, improving energy transfer efficiency and reducing non-radiative decay pathways that limit device lifetime
Solution Approach 2:
The patent creates a composite light-emitting layer combining host material, TADF dopant, and sensitizer material, where each component contributes specific properties: the host provides exciton generation, the dopant provides narrowband emission, and the sensitizer enhances energy transfer efficiency
3Object-affected harmful factors
If traditional TADF materials are used to emit light, then heavy metal usage is eliminated, but emission spectrum becomes wide
Solution Approach 1:
The patent assigns different functional properties to different components: the TADF dopant is specifically designed with rigid molecular structures and localized emission characteristics to achieve narrowband emission, while the host and sensitizer handle exciton management and energy transfer
4Use of energy by moving object
If high doping concentration of TADF material is used to achieve 100% energy efficiency, then energy usage efficiency is improved, but device roll-off increases
Solution Approach 1:
The patent changes the energy transfer mechanism by introducing a sensitizer with appropriate triplet energy level, enabling efficient energy transfer at low dopant concentrations and avoiding the concentration quenching and triplet-triplet annihilation that cause roll-off at high brightness
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 solution enhances light emitting efficiency, reduces roll-off at high brightness, narrows the emission spectrum, and extends the service life of the device by utilizing both singlet and triplet excitons and inhibiting Dexter energy transfer, while maintaining high spectral purity.
Implementation Method 1
thermally activated delayed fluorescent (TADF) materials can absorb ambient heat to realize reverse intersystem crossing for the triplet excitons to a singlet state, thus emitting fluorescence from the singlet state
Implementation Method 2
absorb ambient heat to realize reverse intersystem crossing for the triplet excitons to a singlet state
Implementation Method 3
uses TADF as a sensitizer material to assist a sensitized resonance TADF dye to emit light
Implementation Method 4
inhibiting Dexter energy transfer
Implementation Method 5
An organic light emitting diode (OLED) is a device that achieves the purpose of light emission when driven by an electrical current. When an appropriate voltage is applied thereto, electrons and holes are combined in the organic light emitting layer to generate excitons, emitting light at various wavelengths
Data Source
AI summary
An organic electroluminescence device, a preparation method thereof, and a display apparatus, the organic electroluminescence device including an organic light emitting layer which includes a host material, a sensitizer material, and a resonance thermally activated delayed fluorescent material, where the host material is a wide bandgap material, and the sensitizer material is a thermally activated delayed fluorescent material. The singlet state energy level of the thermally activated delayed fluorescent material falls between the singlet state energy level of the wide bandgap material and the singlet state energy level of the resonance thermally activated delayed fluorescent material. The triplet state energy level of the thermally activated delayed fluorescent material falls between the triplet state energy level of the wide bandgap material and the triplet state energy level of the resonance thermally activated delayed fluorescent material.