Blue Light TADF Material with Alkyl Chain and tert-Butylcarbazole for Solution Processing
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Solution Overview
Problem
Current blue light thermally activated delayed fluorescence (TADF) materials are scarce, and existing methods for their preparation, such as vacuum deposition, are complex, energy-intensive, and have low material utilization rates, limiting their application in OLEDs, which struggle to achieve high internal quantum efficiency due to the lack of efficient blue light phosphorescent heavy metal complexes.
Innovation Solution
A blue light TADF material with a specific chemical structure, processable by solution spin coating, is developed, involving a method that includes reacting alkyl chain-containing and tert-butylcarbazole units to enhance solubility and efficiency, allowing for non-doping of the luminescent layer and avoiding phase separation, thereby achieving high luminous and TADF efficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If vacuum deposition is used to process TADF materials, then material can be deposited, but the process becomes complex, energy-intensive, and has low material utilization rate
Solution Approach 1:
The patent replaces the mechanical vacuum deposition system with a solution-based spin coating process. The TADF material is dissolved in a solvent to form a solution, which is then coated onto the substrate by spin coating, eliminating the need for vacuum equipment and complex deposition mechanisms.
Solution Approach 2:
The patent changes the physical state of the TADF material from solid (requiring vacuum deposition) to dissolved solution (enabling spin coating). This parameter change in the material's state allows for simpler, more efficient processing with higher material utilization rates.
2Reliability
If heavy metal complex phosphorescent materials are used, then 100% IQE can be achieved, but precious metals like Ir and Pt are required
Solution Approach 1:
The patent replaces expensive precious metal complexes with organic TADF materials that do not contain Ir, Pt, or other costly metals. These organic materials achieve comparable 100% IQE through a different mechanism (reverse intersystem crossing) while being significantly cheaper and more abundant.
Solution Approach 2:
The patent extracts and eliminates the heavy metal component from the phosphorescent material system. By removing the precious metal requirement, the invention achieves the same functional outcome (100% IQE) through purely organic TADF materials with appropriate molecular design.
3Ease of operation
If fluorescent materials are used in OLEDs, then the device can operate, but the theoretical internal quantum efficiency can merely reach 25%
Solution Approach 1:
The patent employs composite molecular structures combining electron-donating and electron-accepting units to create TADF materials. This composite approach enables both triplet and singlet excitons to contribute to light emission, achieving 100% IQE while maintaining device operability.
Solution Approach 2:
The patent changes the energy level parameters of the luminescent material by designing specific HOMO-LUMO gaps and minimizing the energy difference between triplet and singlet states (ΔEST). This parameter optimization enables efficient reverse intersystem crossing and achieves 100% IQE while maintaining practical device operation.
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 blue light TADF material achieves high luminous and TADF efficiencies, enabling efficient processing by solution spin coating and reducing production costs, while maintaining remarkable TADF characteristics, thus overcoming the limitations of existing materials and methods.
Implementation Method 1
the excitons in the triplet energy state can be returned by reverse intersystem crossing (RISC) back to the singlet energy state
Implementation Method 2
blue light thermally activated delayed fluorescence (TADF) material
Implementation Method 3
processable by solution spin coating
Data Source
AI summary
The present invention provides a blue light thermally activated delayed fluorescence (TADF) material, a preparation method thereof, and an electroluminescent device. The blue TADF material achieves high luminous efficiency and TADF efficiency to realize excellent solubility by attaching an alkyl chain for increasing solubility to a periphery of the blue light TADF material, and by attaching a tert-butylcarbazole unit having a high energy state to an end of the alkyl chain of the blue light TADF material, thereby allowing the material to be processed by solution spin coating, and the terminal carbazole can act as a host, enabling non-doping of a luminescent layer while effectively avoiding phase separation.