Deuterated Delayed Fluorescent Compounds for Higher-Efficiency OLEDs
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Solution Overview
Problem
Existing organic electroluminescence devices face limitations in internal quantum efficiency, particularly with fluorescent devices capped at 25% due to the ratio of singlet and triplet excitons, and there is a need for improved performance in terms of luminance, emission wavelength, chromaticity, luminous efficiency, drive voltage, and lifetime.
Innovation Solution
Incorporation of a delayed fluorescent compound with at least one deuterium atom in the molecule, represented by a specific formula, within the emitting layer of the device to enhance the utilization of triplet excitons for higher efficiency and potentially extend the device's lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fluorescent organic EL device uses light emission from singlet excitons, then the device can be applied to full-color displays, but the internal quantum efficiency is limited to 25%
Solution Approach 1:
The patent introduces a deuterium-containing delayed fluorescent compound where hydrogen atoms are replaced by deuterium atoms. This isotopic substitution changes the vibrational frequency and energy levels of the molecule, enabling efficient triplet exciton utilization through thermally activated delayed fluorescence while maintaining singlet exciton emission, thereby achieving internal quantum efficiency exceeding 25% in full-color display applications
Solution Approach 2:
The patent employs a composite emitting layer containing both a deuterium-containing delayed fluorescent compound and a host material. The host material facilitates exciton formation and energy transfer, while the deuterium-containing compound provides dual functionality of singlet and triplet exciton utilization, creating a synergistic system that overcomes the 25% efficiency limitation
2Use of energy by moving object
If triplet excitons are utilized through thermally activated delayed fluorescence, then luminous efficiency can be improved, but the energy difference between singlet and triplet energy levels must be precisely controlled
Solution Approach 1:
The deuterium substitution in the delayed fluorescent compound inherently modifies the energy levels through isotopic effects on vibrational frequencies. This provides a built-in mechanism to control the energy difference between singlet and triplet states, achieving the required ΔEST for efficient TADF without requiring complex molecular design adjustments
3Device complexity
If conventional fluorescent compounds are used in the emitting layer, then the device structure can be kept simple, but the lifetime of the device is limited
Solution Approach 1:
The patent uses deuterium-containing compounds which provide enhanced molecular stability and reduced non-radiative decay pathways due to the deuterium isotope effect. This extends the operational lifetime of the device while maintaining the simple delayed fluorescent emitting layer structure without requiring additional functional materials
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 introduction of the deuterium-containing compound in the emitting layer enhances the device's performance by improving efficiency and extending its operational lifespan, addressing the limitations of traditional organic electroluminescence devices.
Implementation Method 1
A thermally activated delayed fluorescence (TADF) mechanism uses such a phenomenon in which inverse intersystem crossing from triplet excitons to singlet excitons thermally occurs when a material having a small energy difference (ΔST) between singlet energy level and triplet energy level is used
Implementation Method 2
When voltage is applied to an organic electroluminescence device, holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected holes and electrons are recombined in the emitting layer to form excitons.
Data Source
AI summary
An organic electroluminescence device includes an anode, a cathode, and an emitting layer, in which the emitting layer contains a delayed fluorescent compound M2 represented by a formula (1), and the compound M2 has at least one deuterium atom in a molecule. In the formula (1), CN is a cyano group, D11 and D12 are each independently a group represented by a formula (11), (12) or (13), at least one D11 is a group represented by the formula (12) or (13), and R is a hydrogen atom, an aryl group, etc.