TADF Luminescent Layer Torsion Control for Higher OLED Efficiency
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Solution Overview
Problem
Organic Light Emitting Diode (OLED) devices based on fluorescent luminescence have low internal quantum efficiency due to a high proportion of triplet-state excitons not emitting light, as they do not transition to the ground state effectively.
Innovation Solution
A light emitting device with a luminescent layer comprising a thermally activated delayed-fluorescence material, where specific torsion angles between donor and receptor groups and a linking group reduce the energy-level difference between singlet and triplet states, facilitating reverse intersystem crossing and enhancing the utilization of triplet-state excitons for luminescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluorescent-luminescence materials are used in OLED devices, then the device structure is simple and manufacturing is easier, but the internal quantum efficiency is low because 75% of triplet-state excitons do not emit light
Solution Approach 1:
The patent changes the energy level parameters of the luminescent material by designing specific molecular structures with donor and receptor groups connected by linking groups with particular torsion angles (45°-90°). This structural parameter change reduces the energy difference between singlet and triplet states, enabling efficient reverse intersystem crossing and achieving high internal quantum efficiency while maintaining fluorescent material simplicity
Solution Approach 2:
The patent creates composite luminescent materials by combining donor groups (e.g., triphen胺, carbazole), receptor groups (e.g., pyridine, pyrimidine), and linking groups (e.g., phenyl, heteroaryl) to form thermally activated delayed fluorescent (TADF) materials. This composite structure enables both ease of manufacture and high internal quantum efficiency by facilitating triplet-to-singlet exciton conversion
2Loss of energy
If phosphorescent-luminescence materials are used in OLED devices, then the internal quantum efficiency reaches 100%, but the device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The patent modifies the energy level parameters of fluorescent materials by introducing specific donor-receptor-linking group structures with controlled torsion angles, transforming ordinary fluorescent materials into TADF materials that can achieve near-100% internal quantum efficiency without requiring phosphorescent materials or heavy metal complexes
Solution Approach 2:
The patent replaces expensive and complex phosphorescent materials with simpler, more stable TADF materials that have longer operational lifetimes and easier processing requirements, achieving high efficiency without the manufacturing complexities associated with phosphorescent OLEDs
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
This configuration significantly increases the luminous efficiency of the light emitting device by converting a high proportion of triplet-state excitons into singlet-state excitons, which can emit light, thereby improving the overall performance.
Implementation Method 1
converting a high proportion of triplet-state excitons into singlet-state excitons, which can emit light
Implementation Method 2
the luminescent layer comprises a thermally activated delayed-fluorescence material
Data Source
AI summary
A light emitting device and a displaying device. The light emitting device includes a luminescent layer, wherein the luminescent layer includes a thermally activated delayed-fluorescence material; the thermally activated delayed-fluorescence material includes a donor group, a receptor group and a linking group; the donor group and the receptor group bond to the linking group; and a torsion angle between a plane where the donor group is located and a plane where the linking group is located is θ1, and a torsion angle between a plane where the receptor group is located and the plane where the linking group is located is θ2; wherein θ1 and θ2 enable an energy-level difference between a singlet-state energy level of the thermally activated delayed-fluorescence material and a triplet-state energy level of the thermally activated delayed-fluorescence material to be less than a constant quantity T, wherein 0 eV<T<0.3 eV.