TADF OLED Compound Design for High Quantum Yield
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Solution Overview
Problem
Current OLED materials, particularly fluorescent and phosphorescent materials, face limitations in internal quantum yield and stability due to high production costs and efficiency drops under high electric current density, while thermally activated delayed fluorescence (TADF) materials are scarce and require development for efficient OLED devices.
Innovation Solution
A compound with a D-A type molecular structure, featuring electron-donating and electron-accepting groups, is developed to enhance photoluminescence quantum yield and light-emitting efficiency by optimizing energy level differences and molecular configuration, suitable for use as a host or guest material in OLED light-emitting layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphorescent materials are used to achieve high internal quantum yield, then triplet excitons can be utilized effectively, but production cost increases due to heavy metal content
Solution Approach 1:
The patent replaces expensive phosphorescent materials containing heavy metals (Ir, Pt, Os, Re, Ru) with organic TADF materials that are cheaper and do not contain rare metals. The TADF materials achieve comparable internal quantum yield through thermal activation of delayed fluorescence without requiring expensive heavy metal complexes, thus resolving the contradiction between high reliability and ease of manufacture.
Solution Approach 2:
The patent modifies the energy level parameters of the organic compounds to achieve small energy gaps between S1 and T1 states (ΔEST < 0.3 eV), which enables efficient reverse intersystem crossing and TADF. By changing the molecular structure parameters (introducing electron-donating and electron-accepting groups), the material achieves high internal quantum yield without heavy metals, resolving the cost-yield contradiction.
2Productivity
If phosphorescent materials are used to achieve high efficiency, then triplet excitons can be utilized, but device stability deteriorates under high electric current density
Solution Approach 1:
The patent replaces phosphorescent materials with TADF materials that do not suffer from the same stability issues under high current density. The organic TADF compounds maintain their light-emitting efficiency without the substantial efficiency fall observed in phosphorescent materials, thus resolving the contradiction between productivity and reliability.
3Ease of manufacture
If fluorescent materials are used, then production cost is low, but internal quantum yield is limited to 25%
Solution Approach 1:
The patent changes the photophysical parameters of organic compounds by designing specific molecular structures with electron-donating and electron-accepting groups to achieve small S1-T1 energy gaps. This enables reverse intersystem crossing and TADF, allowing the material to utilize both singlet and triplet excitons for light emission, thus achieving internal quantum yield up to 100% while maintaining the cost advantage of organic materials.
Solution Approach 2:
The patent creates composite molecular structures combining electron-donating groups (e.g., carbazolyl, diphenylamino, triphenylamino, acridinyl) and electron-accepting groups (e.g., aryl boron-based groups, nitrogen-containing heterocyclic groups, cyano-containing groups, carbonyl-containing groups). This composite approach enables TADF properties while keeping the material composition simple and cost-effective.
4Reliability
If TADF materials are developed to achieve high internal quantum yield and low cost, then organic compounds without rare metals can be used, but the number of available TADF materials is limited
Solution Approach 1:
The patent segments the molecular structure into distinct electron-donating and electron-accepting units that can be independently selected and combined. This modular approach allows for systematic design and synthesis of multiple TADF materials with different properties, expanding the availability of TADF materials while maintaining high internal quantum yield.
Solution Approach 2:
The patent develops a universal design platform for TADF materials using a set of standard electron-donating and electron-accepting groups that can be combined in various configurations. This universal approach enables the creation of multiple TADF materials applicable to different OLED devices, resolving the limitation of scarce TADF 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 compound achieves higher photoluminescence quantum yield and light-emitting efficiency, improving the performance of OLED devices by effectively utilizing triplet excitons and reducing production costs, with energy level differences optimized for efficient TADF properties.
Implementation Method 1
when an energy level difference between the singlet excited state and the triplet excited state is relatively small, a reverse intersystem crossing (RISC) may occur among the molecules, and the excitons are converted from T1 state to S1 state by absorbing the ambient heat
Implementation Method 2
the excitons are converted from T1 state to S1 state by absorbing the ambient heat, so that 75% of triplet excitons and 25% of singlet excitons can be utilized at the same time
Implementation Method 3
A light-emitting material of the light-emitting layer includes one or more of the compounds according to the present disclosure
Data Source
AI summary
The present disclosure relates to the technical field of OLED, and provides a compound having TADF property. In an embodiment the compound has a structure according to Formula (1), in which X1-X5 are each independently selected from a carbon atom and a nitrogen atom, and at least one of X1-X5 is a nitrogen atom; R11-R20 are each selected from the group consisting of a hydrogen atom, a fluorine atom, alkyl, alkoxy, cyano, trifluoromethyl, an electron-accepting group, and an electron-donating group; at least one of R11-R15 is an electron-donating group or an electron-accepting group, and at least one of R16-R20 is an electron-donating group or an electron-accepting group; when each of R11-R15 is an electron-accepting group, at least one of R16-R20 is an electron-donating group, and each of R11-R15 is an electron-donating group, at least one of R16-R20 is an electron-accepting group.