Boron-Nitrogen TADF Compound for OLED Efficiency
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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 applications.
Innovation Solution
A compound with a specific molecular structure featuring an electron donor and acceptor connected through a biphenyl unit, allowing for intramolecular charge transfer and space charge transfer, enhancing light absorption and vibration strength, and incorporating boron-containing structural units for improved optical properties and color purity, is developed for use 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 the theoretical maximum internal quantum yield can reach 100%, but the production cost increases due to heavy metal complexes
Solution Approach 1:
The patent replaces expensive phosphorescent materials containing heavy metals (Ir, Pt, Os, Re, Ru) with organic TADF materials that do not contain rare metal elements. This substitution dramatically reduces production cost while maintaining high internal quantum yield through the TADF mechanism that utilizes both singlet and triplet excitons.
Solution Approach 2:
The patent modifies molecular structures by adjusting the energy level difference between singlet and triplet excited states to enable reverse intersystem crossing (RISC). By controlling this energy gap parameter, the material achieves efficient TADF with high internal quantum yield without requiring heavy metals, thus resolving the contradiction between performance and cost.
2Reliability
If phosphorescent materials are used to achieve high internal quantum yield, then the theoretical maximum internal quantum yield can reach 100%, but the stability deteriorates under high electric current density
Solution Approach 1:
The patent replaces unstable phosphorescent materials with stable organic TADF materials. The TADF mechanism operates efficiently under high electric current density without the efficiency roll-off problem that plagues phosphorescent materials, thereby improving device stability while maintaining high internal quantum yield.
3Ease of manufacture
If fluorescent materials are used for light emission, then the production process is simple, but the maximum internal quantum yield does not exceed 25% due to spin-statistics
Solution Approach 1:
The patent modifies the energy level parameters of organic compounds to enable reverse intersystem crossing from triplet to singlet state. By adjusting the energy gap between S1 and T1 states to be small enough, thermal energy can promote RISC, allowing utilization of both singlet and triplet excitons and achieving internal quantum yield up to 100% while maintaining production simplicity of organic materials.
Solution Approach 2:
The patent designs composite molecular structures combining electron-donating groups and electron-accepting groups to create push-pull systems with appropriate energy level alignment. This composite structure enables efficient charge transfer and RISC processes, achieving high internal quantum yield while maintaining the ease of organic material synthesis.
4Reliability
If TADF materials are developed to utilize both singlet and triplet excitons, then the theoretical maximum internal quantum yield can reach 100%, but the number of available TADF materials is scarce
Solution Approach 1:
The patent divides the TADF material design into modular electron-donating units and electron-accepting units that can be independently optimized and combined. This segmentation approach enables systematic development of multiple TADF materials with different properties by mixing and matching functional groups, thereby increasing the quantity of available TADF materials while maintaining high internal quantum yield.
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 external quantum efficiency and improved stability by effectively utilizing triplet excitons for light emission, offering a cost-effective and efficient solution for OLEDs with enhanced color purity and reduced half-peak width.
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 is an electron acceptor containing a boron atom and is bonded to a benzene ring through the boron atom... D is an electron donor containing a nitrogen atom and is bonded to a benzene ring through the nitrogen atom
Data Source
AI summary
A compound according to Formula (1),in which D is an electron donor containing a nitrogen atom and is bonded to a benzene ring through the nitrogen atom; A is an electron acceptor containing a boron atom and is bonded to a benzene ring through the boron atom; m and n are each an integer selected from 1, 2 or 3; and R11, R12, R13, R14 are each independently selected from the group consisting of a hydrogen atom, alkyl, alkoxy, cyano, trifluoromethyl, an electron acceptor A′, and a nitrogen-containing electron donor D. In the compound, biphenyl acts as a linking unit between the electron donor D and the electron acceptor A, such that units D and A are located at different positions of the molecule, realizing effective separation between HOMO and LUMO. In addition, the light absorption and vibration strength of the molecule are enhanced.