TADF Compound with Donor-Acceptor Structure for OLED Efficiency
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Solution Overview
Problem
Current organic electroluminescent materials, particularly phosphorescent materials, face challenges such as high production costs, efficiency roll-off at high current densities, and poor stability, while thermally activated delayed fluorescence (TADF) materials lack efficient separation of singlet and triplet states, leading to suboptimal quantum yields.
Innovation Solution
A compound with a D-A molecular structure incorporating thiophene groups is developed, where the electron donor and acceptor units are linked to adjacent —CH— on a ring, enhancing dihedral angle and steric hindrance, facilitating efficient separation of HOMO and LUMO, and promoting reverse inter-system crossing for improved photoluminescence quantum yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used for light emitting layers, then internal quantum yield can reach 100%, but production cost increases and stability deteriorates
Solution Approach 1:
The patent changes the material composition parameters by using organic TADF materials with specific molecular structures (formulas I-VI) that eliminate heavy metals while achieving high quantum yield through controlled energy level parameters (ΔEST < 0.3 eV) and optimized donor-acceptor unit combinations
Solution Approach 2:
The patent replaces expensive phosphorescent materials containing rare earth metals (Ir, Pt, Os, Re) with cost-effective organic TADF materials that can be synthesized from abundant elements, making the technology economically viable for large-scale production
2Illumination intensity
If phosphorescent materials are used at high current density, then brightness increases, but efficiency roll-off occurs
Solution Approach 1:
The patent converts the typically harmful non-radiative triplet exciton decay into beneficial light emission through reverse intersystem crossing (RISC), where triplet excitons are converted back to singlet excitons that radiatively decay, achieving high efficiency even at high current densities without efficiency roll-off
3Device complexity
If conventional fluorescent materials are used, then device complexity is low, but internal quantum yield does not exceed 25%
Solution Approach 1:
The patent creates composite molecular structures combining electron donor units (D) and electron acceptor units (A) in specific configurations (formulas I-VI with parameters m, n, in), forming TADF materials that integrate multiple functional elements to achieve superior performance beyond simple fluorescent materials
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 higher photoluminescence quantum yield and improved device performance by reducing exciton quenching and maintaining molecular rigidity, while being cost-effective and chemically stable, suitable for use as a host or dopant in organic light emitting display devices.
Implementation Method 1
facilitating efficient separation of HOMO and LUMO, and promoting reverse inter-system crossing for improved photoluminescence quantum yield
Implementation Method 2
the light emitting material is a thermally activated delayed fluorescence material
Data Source
AI summary
The disclosure relates to the technical field of organic electroluminescent materials, and particularly to a compound and an organic light emitting display device. The compound has structure shown as formula (I):where D represents an electron donor unit, A represents an electron acceptor unit, in and n are each independently selected from 1, 2 or 3, and m+n≤4. When the compound of the present disclosure is used as a light emitting material, a guest material, or a host material of an organic light emitting display device, higher light emitting efficiency can be achieved.