Dibenzoquinoxaline Host Material for OLED Efficiency
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Solution Overview
Problem
Current light-emitting elements using phosphorescent compounds face limitations in emission efficiency, reliability, emission characteristics, synthesis efficiency, and cost, necessitating the development of improved host materials for enhanced performance.
Innovation Solution
A novel organic compound with a dibenzo[f,h]quinoxaline skeleton and amino groups bonded through an arylene group is introduced, providing a bipolar host material with high triplet excited energy, which is used in a light-emitting layer to facilitate efficient electron and hole transport, thereby reducing driving voltage and improving emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a phosphorescent compound is used as a light-emitting substance, then the internal quantum efficiency can be theoretically increased to 100%, but concentration quenching and triplet-triplet annihilation occur, reducing emission efficiency
Solution Approach 1:
The phosphorescent compound is dispersed in a matrix of another compound (host material), separating the phosphorescent molecules spatially to reduce concentration quenching and triplet-triplet annihilation, while maintaining high internal quantum efficiency
Solution Approach 2:
A host material is introduced as an intermediary medium to accommodate the phosphorescent compound. The host material has higher triplet excited energy than the phosphorescent compound and bipolar properties, enabling efficient energy transfer and carrier transport while preventing direct interaction between phosphorescent molecules that causes quenching
2Loss of energy
If the phosphorescent compound is dispersed in a matrix of another compound, then concentration quenching is suppressed, but the device complexity increases due to the need for suitable host material selection
Solution Approach 1:
The host material is designed with specific parameter requirements: higher triplet excited energy than the phosphorescent compound and bipolar properties for efficient carrier transport. By defining these parameters, the selection and optimization of host materials becomes more systematic and less complex
3Ease of operation
If a host material with bipolar property is used, then holes and electrons can be accepted efficiently, but the manufacturing precision requirements increase
Solution Approach 1:
The host material is designed to perform multiple functions simultaneously: it serves as a matrix to disperse the phosphorescent compound, provides high triplet excited energy to prevent quenching, and exhibits bipolar properties for efficient carrier transport. This multi-functionality simplifies the overall device structure and reduces manufacturing precision requirements
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 novel organic compound enables light-emitting elements with lower driving voltage and higher current efficiency, leading to improved power consumption and emission characteristics in light-emitting devices.
Implementation Method 1
a substance that has high triplet excited energy also has high singlet excitation energy. Therefore the above substance that has high triplet excited energy is also effective in a light-emitting element using a fluorescent compound as a light-emitting substance
Implementation Method 2
When a substance used as a host material has a bipolar property, holes and electrons can be accepted efficiently
Implementation Method 3
with a compound that can convert energy of a triplet excited state into light emission (hereinafter, called a phosphorescent compound), light emission from the triplet excited state (phosphorescence) is observed
Implementation Method 4
since intersystem crossing (i.e., transition from a singlet excited state to a triplet excited state) easily occurs in a phosphorescent compound, the internal quantum efficiency can be theoretically increased to 100%
Implementation Method 5
In a basic structure of such a light-emitting element, a layer containing a light-emitting substance is interposed between a pair of electrodes. By applying voltage to this element, light emission from the light-emitting substance can be obtained
Data Source
AI summary
A novel organic compound which can be used as a host material for a phosphorescent compound is provided. A light-emitting element containing the organic compound is provided. A light-emitting device, an electronic device, and a lighting device each of which includes the light-emitting element are provided. In the light-emitting element including a light-emitting layer interposed between a pair of electrodes, the light-emitting layer contains at least an organic compound and a phosphorescent compound. In the organic compound, a dibenzo[f,h]quinoxaline skeleton and an amino group having two substituents are bonded to each other through an arylene group. The substituents are separately an aryl group or a heteroaryl group.