TADF Organic Light-Emitting Elements Using 1,2,4-Azole Derivatives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional organic light-emitting elements face inefficiencies in harvesting triplet excitons, relying on expensive metals like Ir or Pt, and lack materials that exhibit thermally activated delayed fluorescence (TADF) characteristics.
Innovation Solution
Specifically substituted 1,2,4-triazole, 1,2,4-oxadiazole, and 1,2,4-thiadiazole derivatives are used in the light-emitting layer to facilitate thermally activated delayed fluorescence, enabling the up-conversion of triplet excitons to singlet excitons, thereby enhancing electroluminescent efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphorescent materials based on organometallic compounds containing Ir or Pt are used, then triplet exciton harvesting is improved, but cost and resource dependency increase
Solution Approach 1:
The patent replaces expensive, scarce organometallic phosphorescent materials (containing Ir or Pt) with organic compounds that exhibit TADF characteristics. These organic compounds are cheaper, more abundant, and can achieve comparable or superior triplet exciton harvesting efficiency through thermal up-conversion mechanisms, eliminating dependency on limited global metal resources.
Solution Approach 2:
The invention changes the fundamental material parameter from organometallic compounds to purely organic compounds with specific molecular structures (1,2,4-azole derivatives). This parameter change enables TADF behavior through carefully designed HOMO-LUMO separation that creates a small energy gap between S1 and T1 states, allowing thermal up-conversion without requiring rare metals.
2Quantity of substance
If conventional fluorescent materials are used, then material cost is reduced, but only singlet excitons (25%) are harvested
Solution Approach 1:
The patent introduces TADF materials as an intermediary mechanism that bridges the gap between conventional fluorescent and phosphorescent materials. The small energy gap between S1 and T1 states in TADF materials acts as a mediator, enabling thermal up-conversion of triplet excitons to singlet states, thereby allowing harvesting of both singlet and triplet excitons (approaching 100% efficiency) while using purely organic, cost-effective materials.
3Productivity
If TADF materials with small energy gap between S1 and T1 are used, then triplet exciton up-conversion is improved, but thermal energy requirements increase
Solution Approach 1:
The patent optimizes the energy gap parameter (ΔEST) between S1 and T1 states to be small but not excessively small. This allows the up-conversion process to be driven by ambient thermal energy (kBT at room temperature), achieving efficient triplet exciton harvesting without requiring excessive thermal energy input. The molecular structure is designed to achieve this optimal energy gap through controlled HOMO-LUMO separation.
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 use of these derivatives results in organic light-emitting elements with high external quantum efficiency and reduced efficiency roll-off at high luminance, utilizing a broader range of excitons and eliminating the need for expensive metals.
Implementation Method 1
The specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives and 1,2,4-thiadiazole derivatives exhibit TADF (thermally activated delayed fluorescence) characteristics, usually at 298 K
Implementation Method 2
TADF is an effective triplet-harvesting process that involves up-conversion of triplet (T1) to singlet (S1) excited states
Implementation Method 3
The organic light emitting elements show high electroluminescent efficiency
Data Source
AI summary
An organic light-emitting element which emits delayed fluorescence comprising specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives or 1,2,4-thiadiazole derivatives in the light-emitting layer, a light-emitting layer comprising the specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives or 1,2,4-thiadiazole derivatives, specific specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives and 1,2,4-thiadiazole derivatives and an organic light emitting element comprising the specific 1,2,4-azole derivatives as well as a light emitting layer comprising the specific 1,2,4-azole derivatives; the use of the specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives and 1,2,4-thiadiazole derivatives for electrophotographic photoreceptors, photoelectric converters, sensors, dye lasers, solar cell devices and organic light emitting elements, and the use of the specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives and 1,2,4-thiadiazole derivatives for generating delayed fluorescence emission.