D-A OLED Emitter Composition Balancing LE and CT Excited States
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Solution Overview
Problem
Existing organic light-emitting diode (OLED) technologies face challenges in achieving high photoluminescent efficiency and exciton utilization rate due to the dominance of either locally excited or charge-transfer states, leading to issues like low fluorescent quantum yield and reddish chromaticity.
Innovation Solution
A D-A type organic light-emitting material is designed with a specific donor and acceptor moiety structure and a twist angle between 35 to 80 degrees, balancing locally excited and charge-transfer states to create a hybridized excited state, enhancing photoluminescent efficiency and exciton utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pure charge-transfer state is used to achieve high exciton utilization, then exciton utilization rate is improved, but fluorescent quantum yield deteriorates and chromaticity becomes reddish
Solution Approach 1:
The patent modifies the molecular structure parameters of the organic light-emitting material by introducing a specific donor moiety with formula (I) containing divalent aryl/heteroaryl groups with cyano and methylimino substituents, and combining it with a fused aromatic or heterocyclic acceptor moiety. This structural parameter change creates a hybridized excited state that simultaneously achieves high exciton utilization rate and maintains high fluorescent quantum yield, resolving the contradiction between these two performance indicators.
2Illumination intensity
If a pure locally excited state is used to achieve high fluorescent quantum yield, then fluorescent quantum yield is improved, but exciton utilization rate deteriorates
Solution Approach 1:
The patent creates a composite excited state system by combining locally excited state characteristics and charge-transfer state characteristics into a hybridized excited state. The donor moiety with specific substituents (cyano, methylimino) and the fused aromatic/heterocyclic acceptor moiety work together to produce an excited state that exhibits both high fluorescent quantum yield and high exciton utilization rate, effectively resolving the contradiction between these opposing requirements.
3Ease of manufacture
If conventional OLED materials are used to achieve simple manufacturing process, then ease of manufacture is improved, but photoluminescent efficiency deteriorates
Solution Approach 1:
The patent applies local quality modification by introducing specific functional groups (cyano and methylimino substituents) at particular positions on the divalent aryl/heteroaryl donor moiety. This localized structural enhancement creates the hybridized excited state necessary for high photoluminescent efficiency while maintaining the overall simplicity of the manufacturing process, as the material can still be synthesized using conventional organic chemistry methods.
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 D-A type organic light-emitting material achieves improved photoluminescent efficiency and exciton utilization by balancing LE and CT states, avoiding issues of pure CT states, with enhanced stability and reduced roll-off at high current densities.
Implementation Method 1
An organic light-emitting diode (OLED) has characteristics of self-luminescence...
Implementation Method 2
achieving high photoluminescent efficiency and exciton utilization rate
Data Source
AI summary
A D-A type organic light-emitting material includes a donor moiety and an acceptor moiety. The donor moiety is represented as follows:L is selected from any of aryl, heteroaryl, fused aryl and fused heteroaryl. When L is selected from any of aryl and heteroaryl, aryl and heteroaryl each have one or more substituents each selected from any of deuterium, tert-butyl, phenyl, cyano and methylimino, and at least one substituent is selected from cyano and methylimino. When L is selected from any of fused aryl and fused heteroaryl, fused aryl and fused to heteroaryl each have or do not have a substituent. When fused aryl and fused heteroaryl each have a substituent, the substituent is selected from any of deuterium, tert-butyl, phenyl, cyano and methylimino. The acceptor moiety is selected from any of a substituted or unsubstituted fused aromatic rings and a substituted or unsubstituted fused heterocyclic ring.