TADF Compound with S=O Group for OLED Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current OLED materials, such as fluorescent, phosphorescent, TTA, and TADF materials, face limitations in internal quantum yield, light extraction efficiency, and stability due to high production costs, efficiency roll-off, and scarcity of effective TADF materials suitable for large-scale production.
Innovation Solution
A novel compound with a specific structure incorporating an S═O double bond as an electron withdrawing group, providing a bipolar host material or TADF luminescent material with enhanced electron accepting properties and improved light-emitting efficiency, is introduced. This compound features a sp3 hybridized LUMO energy level, ortho-position connections for increased steric hindrance and molecular rigidity, and suitable for blue light-emitting and phosphorescent host applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used to improve internal quantum yield, then the EQE can reach 20%, but the production cost increases due to heavy metal complexes
Solution Approach 1:
The patent replaces expensive phosphorescent materials containing heavy metals (Ir, Pt, Os, Re, Ru) with organic TADF materials that are cheaper and suitable for large-scale production. The TADF materials achieve comparable or superior performance without requiring rare metal elements, directly addressing the cost issue while maintaining high internal quantum yield
Solution Approach 2:
The patent modifies molecular parameters by designing specific organic compounds with particular structural features (spirobifluorene core, nitrogen-containing electron donor units, specific substituent patterns) to achieve the desired TADF properties. This parameter optimization allows the material to reach 100% internal quantum yield through reverse intersystem crossing without using heavy metals
2Ease of manufacture
If fluorescent materials are used, then the production cost is low, but the internal quantum yield does not exceed 25% due to spin-statistics
Solution Approach 1:
The patent changes the fundamental photophysical parameters of the material by introducing TADF characteristics with small singlet-triplet energy gaps (ΔEST < 0.3 eV). This enables reverse intersystem crossing from T1 to S1 state, allowing 75% of triplet excitons to be utilized and achieving 100% internal quantum yield while maintaining the cost advantages of organic materials
Solution Approach 2:
The patent creates a composite molecular structure combining electron-donating units (carbazolyl, acridinyl, diarylamino, triarylamino groups) with the spirobifluorene electron-accepting core. This composite structure enables both the cost-effectiveness of organic compounds and the high efficiency of TADF through synergistic electronic interactions
3Use of energy by moving object
If TADF materials are used to achieve 100% internal quantum yield, then the production cost is low, but there are few TADF materials discovered so far suitable for large-scale production
Solution Approach 1:
The patent segments the molecular structure into modular components: a spirobifluorene core unit, nitrogen-containing electron donor units (carbazolyl, acridinyl, diarylamino, triarylamino groups), and various substituent groups. This modular segmentation allows for systematic synthesis and large-scale production by combining pre-synthesized building blocks
Solution Approach 2:
The patent optimizes key parameters including ΔEST < 0.3 eV for efficient RISC, specific HOMO-LUMO energy levels, and molecular structures with restricted rotation to minimize non-radiative transitions. These parameter optimizations ensure the materials are not only high-performance but also suitable for practical manufacturing
4Illumination intensity
If phosphorescent materials are used under high electric current density, then the light emission is enhanced, but efficiency roll-off occurs leading to deterioration of device stability
Solution Approach 1:
The patent changes the photophysical mechanism from phosphorescence to TADF, utilizing reverse intersystem crossing instead of heavy metal-mediated phosphorescent emission. This parameter change eliminates efficiency roll-off under high current density while maintaining high light emission intensity and improving device stability
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 high light-emitting efficiency, improved luminescence color purity, and stability by optimizing the spatial structure and energy levels, enabling effective utilization of triplet excitons and reducing non-radiative transitions, thus enhancing the performance of OLEDs.
Implementation Method 1
when an energy level difference between the singlet excited state and the triplet excited state is relatively small, a reverse intersystem crossing (RISC) may occur in the molecules, and the excitons are converted from T1 state to S1 state by absorbing the ambient heat
Implementation Method 2
thermally activated delayed fluorescence (TADF) materials
Implementation Method 3
by introducing an S═O double bond, the compound has a stronger electron withdrawing ability, and the core unit has characteristics of an electron acceptor
Implementation Method 4
an intersystem crossing of molecules can be enhanced by spin coupling due to a heavy atom effect of the phosphorescent materials
Implementation Method 5
phosphorescent materials
Data Source
AI summary
Provided is a compound represented by formula 1, and a display panel and a display apparatus including the compound. In formula 1, L1 and L2 are each independently selected from the group consisting of a single bond, C6-C30 aryl, and C4-C30 heteroaryl; a and b are each independently selected from 0, 1, 2, 3, or 4; D1 and D2 are each independently a nitrogen-containing electron donor unit selected from the group consisting of carbazolyl and derivative groups thereof, acridinyl and derivative groups thereof, diarylamino and derivative groups thereof, and triarylamino and derivative groups thereof; and c and d are each independently selected from 0, 1, 2, 3, or 4, and c+d≥1.