Delayed Fluorescent Dicyanobenzene Compounds for High-Current OLEDs
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Solution Overview
Problem
Existing delayed fluorescent materials face challenges in achieving high emission efficiency, particularly in high-current density regions, and their chemical structures and properties are not well understood, limiting their practical use in light-emitting devices.
Innovation Solution
A dicyanobenzene derivative substituted with a donor group and specific aryl groups, represented by a general formula, is developed to enhance light-emitting properties, allowing for effective utilization of both excited singlet and triplet states for fluorescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If delayed fluorescent materials are used to increase light emission efficiency by utilizing both excited singlet and triplet states, then emission efficiency is improved, but the materials suffer from accumulation of excitons in high-current density regions and rapid degradation in continuous long-term driving
Solution Approach 1:
The patent modifies molecular parameters by introducing specific substituents (carbazole derivatives, bridged amines, electron attracting groups) at ortho-positions to alter the electronic structure and energy levels of the delayed fluorescent material, thereby improving exciton management and reducing degradation while maintaining high emission efficiency
Solution Approach 2:
The patent creates composite molecular structures by combining multiple functional groups (donor groups, acceptor groups, carbazole derivatives, bridged amines) within a single molecule to achieve synergistic effects that simultaneously enhance emission efficiency and improve device stability through better exciton distribution
2Illumination intensity
If cyanobenzene derivatives are used as delayed fluorescent materials, then delayed fluorescence emission is achieved, but the emission efficiency is not high and the emission efficiency in high-current density regions is great
Solution Approach 1:
The patent introduces electron attracting groups at specific ortho-positions of the cyanobenzene derivative to create localized electronic modifications that enhance the reverse intersystem crossing rate and improve emission efficiency specifically in high-current density regions without compromising delayed fluorescence emission
Solution Approach 2:
The patent optimizes the electronic parameters of cyanobenzene derivatives by incorporating carbazole derivatives and bridged amines as substituents, which adjust the HOMO-LUMO gap and triplet energy levels to achieve both high delayed fluorescence emission and improved emission efficiency
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 compound achieves high emission efficiency and reduces degradation in high-current density regions, improving the performance of organic light-emitting devices.
Implementation Method 1
A delayed fluorescent material is a compound which, in an excited state, after having undergone reverse intersystem crossing from an excited triplet state to an excited singlet state, emits fluorescence when returning back from the excited singlet state to a ground state thereof
Implementation Method 2
Fluorescence through the route is observed later than fluorescence from the excited singlet state directly occurring from the ground state (ordinary fluorescence), and is therefore referred to as delayed fluorescence
Implementation Method 3
emits fluorescence when returning back from the excited singlet state to a ground state thereof
Data Source
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AI summary
A compound represented by the following general formula is an excellent light-emitting material. R1 to R5 each independently represent a hydrogen atom or a substituent, and one of R1 to R5 is a cyano group, one to three of R1 to R5 each are an aryl group Ar optionally substituted with an alkyl group or an aryl group, and one to three of R1 to R5 each are a donor group D (but excepting one that corresponds to Ar).