Formula 1 Organic Electroluminescent Materials for TADF OLED Lifetime
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Solution Overview
Problem
Existing organic light-emitting diodes (OLEDs) face challenges such as low internal quantum efficiency, inefficient triplet exciton utilization, and short device lifetime, particularly in achieving saturated blue color and high brightness, which hinder their commercialization.
Innovation Solution
Development of compounds with a specific structure of Formula 1, incorporating various substituents and heterocycles, to enhance triplet-singlet transition and improve device performance, including an organic electroluminescent device design with these compounds in the emissive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fluorescent OLED is used, then the device structure is simple, but the internal quantum efficiency is only 25% due to wasted triplet excitons
Solution Approach 1:
The patent introduces compounds with specific molecular structures (Formula 1) that enable thermally activated delayed fluorescence (TADF) mechanism. By changing the molecular parameters including heterocyclic groups (X = O, S, or Se), substitution patterns (R1-R6), and structural components (A, B, C rings), the compound achieves small singlet-triplet energy gap that enables reverse intersystem crossing, allowing triplet excitons to convert to singlet excitons for light emission, thereby achieving high internal quantum efficiency without complex device structure
2Use of energy by moving object
If phosphorescent OLED is used to achieve high efficiency, then internal quantum efficiency reaches 100%, but device lifetime is short and operating voltage is high
Solution Approach 1:
The patent replaces expensive and unstable phosphorescent emitters (containing heavy metals like Ir or Pt) with organic compounds based on Formula 1 that exhibit TADF properties. These organic compounds are more stable, have longer device lifetime, and can be processed more easily, while still achieving high internal quantum efficiency through the TADF mechanism that converts triplet excitons to singlet excitons without requiring heavy metal complexes
3Illumination intensity
If blue phosphorescent emitter is used, then high brightness is achieved, but color saturation is poor and device lifetime is short
Solution Approach 1:
The patent applies local quality by introducing specific functional groups and heterocyclic structures at particular positions in the molecular structure (Formula 1). By controlling the substitution patterns (R1-R6), heteroatom types (X = O, S, or Se), and ring structures (A, B, C), the compound achieves localized electronic properties that enable saturated blue emission with high brightness while maintaining device stability and long lifetime through the TADF mechanism
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 compounds enhance device lifetime and efficiency by facilitating triplet-singlet transition, potentially achieving 100% internal quantum efficiency and improving color saturation, addressing the limitations of current OLED technologies.
Implementation Method 1
In the TADF device, the triplet excitons can go through reverse intersystem crossing to generate singlet excitons, resulting in high IQE
Implementation Method 2
Recently, Adachi achieved high efficiency through thermally activated delayed fluorescence (TADF) of organic compounds. These emitters have small singlet-triplet gap that makes the transition from triplet back to singlet possible
Implementation Method 3
Once a bias is applied to the device, green light was emitted from the device
Data Source
AI summary
Provided are an organic electroluminescent material and device. The organic electroluminescent material is a compound having a structure of Formula 1. Those novel compounds are applicable to electroluminescent devices and can provide better device performance, such as an increase in device lifetime. Further provided are an electroluminescent device containing the compound and a compound composition containing the compound.