Heterocyclic Compound Host Material for OLED Lifetime
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Solution Overview
Problem
Current light-emitting elements with a dibenzo[f,h]quinoxaline ring suffer from short lifetime due to easy crystallization and low triplet excitation energy, leading to reduced emission efficiency and power consumption, and are limited by the quinoxaline skeleton's poor hole-acceptance properties.
Innovation Solution
A compound with a dibenzo[f,h]quinoxaline ring bonded to two hole-transport skeletons via an aromatic hydrocarbon group is used, enhancing hole-acceptance and preventing crystallization, thus maintaining high triplet excitation energy and emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quinoxaline-based compounds with planar structure are used, then good electron-transport properties are achieved, but crystallization occurs leading to short lifetime and reduced emission efficiency
Solution Approach 1:
The molecule is divided into distinct functional segments: a quinoxaline core for electron transport, hole-transport skeletons for charge balance, and bulky substituents for steric protection. This segmentation allows each part to perform its specific function without compromising the others, preventing crystallization while maintaining transport properties
Solution Approach 2:
The invention creates a composite molecular structure combining multiple functional units (quinoxaline ring, hole-transport skeletons, bulky groups) into a single molecule. This composite approach integrates electron transport, hole transport, and crystallization prevention functions into one material system
2Reliability
If hole-transport skeletons are directly bonded to quinoxaline skeletons, then hole-acceptance is improved, but triplet excitation energy and band gap decrease
Solution Approach 1:
The bulky substituent groups act as intermediary elements between the quinoxaline core and hole-transport skeletons. These intermediaries provide the necessary spatial separation and electronic isolation to maintain high triplet excitation energy while still allowing effective hole transport through the skeleton structure
Solution Approach 2:
Different parts of the molecule are given different properties: the quinoxaline core provides electron transport, the hole-transport skeletons provide hole acceptance, and the bulky substituents provide steric bulk for crystallization prevention. Each local region is optimized for its specific function without compromising the overall molecular properties
3Duration of action of stationary object
If bulky groups are added to prevent crystallization, then element lifetime is improved, but molecular structure complexity increases
Solution Approach 1:
The invention changes key molecular parameters including the size and positioning of bulky substituents, the connectivity of hole-transport skeletons, and the overall molecular geometry. These parameter optimizations achieve crystallization prevention while controlling molecular complexity to maintain processability and device performance
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 a light-emitting element with low driving voltage, high current efficiency, and extended lifetime, reducing power consumption and improving reliability in light-emitting devices.
Implementation Method 1
a light-emitting element in which a phosphorescent material capable of converting the triplet excited state to light emission is used as an emission center substance can theoretically realize higher emission efficiency
Implementation Method 2
a fluorescent material capable of converting the singlet excited state to light emission is used as an emission center substance
Implementation Method 3
voltage application between electrodes, between which a light-emitting layer is interposed, causes recombination of electrons and holes injected from the electrodes. The recombination brings a light-emitting substance into an excited state, and the return from the excited state to the ground state is accompanied by light emission
Data Source
AI summary
To provide a novel heterocyclic compound that can be used as a host material in which a light-emitting substance of a light-emitting layer is dispersed. A heterocyclic compound comprising a dibenzo[f,h]quinoxaline ring and two hole-transport skeletons, where the dibenzo[f,h]quinoxaline ring and the two hole-transport skeletons are bonded to an aromatic hydrocarbon group. A heterocyclic compound represented by the following general formula (G1) is provided.Note that in the formula, A1 and A2 each independently represent any of a substituted or unsubstituted carbazole skeleton, a substituted or unsubstituted dibenzofuran skeleton, and a substituted or unsubstituted dibenzothiophen skeleton; B represents a substituted or unsubstituted dibenzo[f,h]quinoxaline skeleton; and Ar represents an arene skeleton having 6 to 13 carbon atoms. A light-emitting element including the heterocyclic compound is provided.