Organic EL Emitting Layer Comatrix for Triplet Exciton Use
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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 luminous efficiency and performance in electronic devices.
Innovation Solution
Incorporating a specific combination of compounds in the emitting layer, including a first compound represented by formula (1) and a second compound represented by formula (2), with a third compound exhibiting delayed fluorescence, where the singlet energies of these compounds satisfy certain relationships, and ensuring the absence of carbonyl groups, to enhance hole and electron injectability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fluorescent organic EL device uses only singlet excitons for light emission, then the device structure is simple, but the internal quantum efficiency is limited to 25%
Solution Approach 1:
The patent employs composite host materials comprising multiple compounds with different energy levels (first host material with higher triplet energy, second host material with lower triplet energy) to create a system that可以利用 both singlet and triplet excitons for light emission, achieving internal quantum efficiency exceeding 25% while maintaining device functionality
Solution Approach 2:
The patent modifies the energy level parameters of the host materials by selecting compounds with specific triplet energy values (T1 levels) to enable efficient triplet exciton utilization through thermal activation, thereby converting the 75% triplet excitons that would normally be lost into useful light emission
2Loss of energy
If triplet excitons are utilized through thermally activated delayed fluorescence, then the internal quantum efficiency is improved, but the device requires precise energy level matching between multiple compounds
Solution Approach 1:
The patent systematically adjusts the energy level parameters of host materials by selecting compounds with specific triplet energy values, where the first host material has higher T1 energy and the second has lower T1 energy, creating optimal conditions for thermal activation of triplet excitons while maintaining manageable device complexity through parameter optimization
3Ease of manufacture
If conventional host materials are used in the emitting layer, then the manufacturing process is simple, but the luminous efficiency and device lifetime are insufficient
Solution Approach 1:
The patent replaces conventional single-host material systems with composite host materials consisting of multiple compounds in specific ratios, which improves luminous efficiency and device lifetime by enabling efficient charge transport and exciton management while maintaining relatively simple manufacturing processes
4Device complexity
If the emitting layer uses a single host material, then the device structure is simple, but the charge transport and exciton management are insufficient for high efficiency
Solution Approach 1:
The patent employs composite host materials comprising multiple compounds with complementary properties (different triplet energy levels, mobility characteristics) to enhance charge transport and exciton management efficiency, achieving high luminous efficiency while keeping the emitting layer structure manageable through careful material selection
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 proposed organic electroluminescence device achieves higher luminous efficiency, improved device lifetime, reduced drive voltage, and enhanced luminance by optimizing the supply of holes and electrons through the use of a 'comatrix' of host materials.
Implementation Method 1
a highly efficient fluorescent organic EL device using thermally activated delayed fluorescence (hereinafter, sometimes simply referred to as "delayed fluorescence") has been proposed and studied
Implementation Method 2
When a voltage is applied to an organic electroluminescence device (hereinafter, occasionally referred to as an "organic EL device"), holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected electrons and holes are recombined in the emitting layer to form excitons.
Data Source
AI summary
An organic EL device includes: an anode, a cathode, and an emitting layer, in which the emitting layer contains a first compound of a formula (1), a second compound of a formula (2), and a third compound that exhibits delayed fluorescence, and singlet energies S1 of the first compound, the second compound, and the third compound satisfy Numerical Formula 1 and Numerical Formula 2.In the formula (1), A represents a group of a formula (a1) or the like, L represents a linking group or the like, and B represents an aryl group or the like. The first compound of the formula (1) has no carbonyl group. In the formula (2), Y21 to Y26 each independently represent an N atom, CRA, or the like. RA represents a substituent, a group of a formula (2A), or the like.