Organic Electroluminescent Element with Boron Compound
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Solution Overview
Problem
Current π-conjugated boron compounds used in organic electroluminescent elements lack sufficient stability and durability, especially in electrochemically severe environments, limiting their practical application in display and lighting apparatuses.
Innovation Solution
Incorporating a π-conjugated boron compound with a structure obtained by full annulation in three directions around the boron atom and introducing oxygen or sulfur atoms into ring-forming atoms within the light-emitting layers, which enhances electron transportability and emission efficiency while improving thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional π-conjugated boron compounds are used in organic electroluminescent elements, then electron transportability and emission efficiency can be achieved, but stability and durability in electrochemically severe environments are insufficient
Solution Approach 1:
The molecule is divided into distinct functional segments: a boron-containing core structure (for electron transport and emission), aromatic hydrocarbon substituents (for stability and steric protection), and electron-donating groups (for TADF activity). This segmentation allows optimization of each function independently while maintaining overall molecular stability in electrochemically severe environments.
Solution Approach 2:
The patent employs composite molecular structures combining boron compounds with aromatic hydrocarbons and electron-donating groups. This composite approach integrates the electron transport capability of boron compounds with the stability of aromatic systems and the TADF properties of electron-donating groups, achieving both reliability and performance.
2Use of energy by moving object
If phosphorescence is used to achieve high internal quantum efficiency, then emission efficiency is improved, but rare metal complexes (iridium or platinum) are required which cause future problems in reserves and price
Solution Approach 1:
The patent replaces expensive rare metal complexes with organic compounds containing common elements (carbon, hydrogen, oxygen, nitrogen, boron). These organic TADF materials are more abundant, cheaper, and environmentally friendly while achieving comparable internal quantum efficiency through delayed fluorescence mechanisms rather than phosphorescence.
Solution Approach 2:
The patent substitutes the phosphorescence mechanism (relying on heavy metal spin-orbit coupling) with a TADF mechanism based on reverse intersystem crossing in organic compounds. This substitution eliminates dependence on rare metals while maintaining high efficiency through thermal activation of triplet excitons to singlet states.
3Use of energy by moving object
If fluorescent materials are used with triplet-triplet annihilation to improve emission efficiency, then efficiency increases two to three times, but singlet excitons are still only generated at about 40% efficiency
Solution Approach 1:
The patent changes the fundamental parameter of exciton utilization by designing molecules with small singlet-triplet energy gaps (ΔEST). This allows thermal energy at operating temperatures to efficiently promote triplet excitons to singlet states via reverse intersystem crossing, enabling near-100% utilization of triplet excitons rather than the limited 40% achieved by triplet-triplet annihilation.
Solution Approach 2:
The TADF mechanism involves periodic thermal activation where triplet excitons are continuously converted to singlet excitons through thermal energy input, followed by fluorescence emission. This cyclic process of thermal activation and radiative decay enables sustained high efficiency by repeatedly utilizing triplet excitons that would otherwise be lost.
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 approach results in an organic electroluminescent element with improved emission efficiency and storage stability at high temperatures, enabling the development of more reliable display and lighting apparatuses.
Implementation Method 1
Incorporating a π-conjugated boron compound with a structure obtained by full annulation in three directions around the boron atom and introducing oxygen or sulfur atoms into ring-forming atoms within the light-emitting layers, which enhances electron transportability
Implementation Method 2
Organic EL elements (also referred to as 'organic electroluminescence light emitting elements'), which employ electroluminescence of organic materials
Implementation Method 3
When an electric field is applied to such an organic EL element, holes and electrons are respectively injected from an anode and a cathode into a light-emitting layer, and the injected holes and electrons are recombined in the light-emitting layer to generate excitons
Implementation Method 4
Incorporating a π-conjugated boron compound with a structure obtained by full annulation in three directions around the boron atom and introducing oxygen or sulfur atoms into ring-forming atoms within the light-emitting layers, which enhances electron transportability and emission efficiency while improving thermal stability
Data Source
AI summary
The purpose of the present invention is to provide an organic electroluminescent element having improved luminous efficiency and stability under high-temperature storage. The present invention is an organic electroluminescent element that has an anode, a cathode, and at least one light-emitting layer sandwiched between the anode and the cathode, and is characterized in that at least one of the light-emitting layers contains a π-conjugated boron compound having a structure represented by general formula (1).(In general formula (1), X1 to X9 each independently represents —CR or a nitrogen atom, R represents a hydrogen atom or a substituent, and Y1 to Y3 each independently represents an oxygen atom or a sulfur atom).