Organic Electroluminescence Compound for High Efficiency Light Emission
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Solution Overview
Problem
Existing organic electroluminescence (OEL) devices face limitations in internal quantum efficiency due to the 25%:75% ratio of singlet to triplet excitons, which restricts their performance in terms of luminance, emission wavelength, chromaticity, luminous efficiency, drive voltage, and lifetime.
Innovation Solution
A compound represented by formula (1) is introduced, which includes specific structural elements such as nitrogen atoms, aromatic hydrocarbon rings, and heterocycles, designed to enhance the efficiency of light emission in OEL devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fluorescent organic EL device uses only singlet excitons for light emission, then the device structure is simple and manufacturing is easier, but the internal quantum efficiency is limited to 25%
Solution Approach 1:
The patent employs a composite emitting layer containing both fluorescent and thermally activated delayed fluorescence (TADF) materials. The fluorescent material provides immediate light emission from singlet excitons, while the TADF material converts triplet excitons to singlet excitons through thermal energy, enabling efficient utilization of both singlet and triplet excitons. This composite approach resolves the contradiction by maintaining manufacturing simplicity while dramatically improving internal quantum efficiency beyond the 25% limit.
Solution Approach 2:
The patent utilizes thermal energy (temperature parameter) to enable the TADF material to convert triplet excitons to singlet excitons. By changing the energy state parameter through thermal activation, the system can utilize the 75% triplet excitons that would otherwise be lost, transforming the efficiency limitation into an opportunity for enhanced luminous efficiency.
2Loss of energy
If the internal quantum efficiency is improved beyond 25%, then the luminous efficiency and lifetime are enhanced, but the device complexity increases
Solution Approach 1:
The TADF material acts as an intermediary between the fluorescent material and the triplet excitons. It receives triplet excitons from the fluorescent material and converts them to singlet excitons through thermal energy, which then feed back into the fluorescent emission process. This intermediary mechanism enables efficient energy utilization without requiring complete redesign of the device architecture.
3Loss of energy
If triplet excitons are fully utilized, then the internal quantum efficiency approaches 100%, but the emission wavelength and chromaticity control becomes more difficult
Solution Approach 1:
The patent applies local quality by using two materials with different emission characteristics in the same emitting layer. The fluorescent material provides controlled emission at specific wavelengths, while the TADF material contributes to efficiency enhancement. By carefully selecting the emission wavelengths of the individual materials, the system achieves both high efficiency and precise chromaticity control through the combined effect of locally optimized components.
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 use of the compound in OEL devices leads to improved light emission efficiency, allowing for enhanced performance in terms of luminance, chromaticity, and luminous efficiency, while also potentially extending the device's lifetime.
Implementation Method 1
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.
Implementation Method 2
Various studies have been made on a compound to be used for an organic EL device in order to enhance the performance of the organic EL device
Data Source
AI summary
A compound represented by a formula (1).In the formula (1): X1 to X4 are each independently a nitrogen atom or CRx; at least one of X1 to X4 is a nitrogen atom; a ring A, a ring B, and a ring C are each independently an aromatic hydrocarbon ring or a heterocycle; Ar1 is a hydrogen atom, an aryl group, or a group represented by a formula (2); and Ar2 is an aryl group or a group represented by a formula (3).