Green TADF Material for OLED Internal Quantum Efficiency
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Solution Overview
Problem
Current thermally activated delayed fluorescent materials exhibit low photoluminescence quantum yield and proportion, limiting the efficiency of organic electroluminescent devices, particularly for green light emission.
Innovation Solution
A green light thermally activated delayed fluorescent material is synthesized by reacting an electron donor and a planar electron acceptor with a fluorine atom or fluorine-containing group, featuring a triplet energy state between 2.0 to 3.0 eV, using a specific molecular structure and synthesis method involving palladium acetate and tri-tert-butylphosphine tetrafluoroborate, followed by purification through silica gel column chromatography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluorescent materials are used in OLEDs, then the device structure is simple and production is easy, but the internal quantum efficiency can merely reach 25%
Solution Approach 1:
The patent changes the energy state parameters of the luminescent material by using TADF materials with small singlet-triplet energy gaps (ΔEST), enabling efficient reverse intersystem crossing from triplet to singlet states, thereby achieving high internal quantum efficiency without heavy metals
Solution Approach 2:
The patent replaces the heavy metal-based phosphorescent mechanism with an organic TADF mechanism, substituting spin-orbit coupling of heavy atoms with thermal activation and reverse intersystem crossing in organic molecules, achieving similar efficiency without precious metals
2Use of energy by moving object
If heavy metal complex phosphorescent materials are used, then the internal quantum efficiency can reach 100%, but the materials are expensive and blue light materials have yet to be developed
Solution Approach 1:
The patent uses cheap organic TADF materials instead of expensive heavy metal complexes, replacing precious metals (Ir, Pt) with readily available organic compounds that can achieve similar or better performance without the cost and stability issues of metal complexes
Solution Approach 2:
The patent extracts and eliminates the heavy metal component from the phosphorescent system, isolating the essential function of triplet exciton utilization through pure organic TADF mechanisms, thereby removing the dependency on expensive and potentially unstable metal complexes
3Use of energy by moving object
If conventional TADF materials are used, then the singlet and triplet energy states can be utilized, but the photoluminescence quantum yield is low and the proportion of TADF materials is low
Solution Approach 1:
The patent optimizes the local molecular structure by introducing specific electron-donating and electron-withdrawing groups with appropriate HOMO-LUMO energy level differences, creating localized regions of high electron density that facilitate efficient reverse intersystem crossing and enhance photoluminescence quantum yield
Solution Approach 2:
The patent creates composite molecular structures combining electron-donating groups (e.g., triphenylamine, carbazole) with electron-withdrawing groups (e.g., fluorinated aromatics), forming D-A type TADF materials that exhibit synergistic effects for improved radiative decay rates and 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 synthesized material achieves a fast reverse intersystem crossing constant and high photoluminescence quantum yield, enhancing the luminous efficiency and brightness of organic electroluminescent devices.
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
green light thermally activated delayed fluorescent material
Implementation Method 3
then to a ground state by a radiation transition to emit light
Implementation Method 4
synthesized by a reaction of an electron donor and an electron acceptor
Data Source
AI summary
The present invention provides a green light thermal activation delayed fluorescent material, a synthesizing method thereof, and an electroluminescent device. The green light thermal activation delayed fluorescent material is a target compound having a molecular structure of D-A and synthesized by a reaction of an electron donor and an electron acceptor, wherein the electron acceptor being a planar electron acceptor in an ultra-low triplet energy state, and a triplet energy state of the target compound ranging from 2.0 to 3.0 eV. The method for synthesizing a green light thermal activation delayed fluorescent material includes the following steps: a reaction solution preparation step; a target compound synthesis step; an extraction step; and a target compound purification step. The electroluminescent device includes: a substrate layer; a hole transporting and injecting layer; a light emitting layer; an electron transporting layer; and a cathode layer.