Asymmetric Aromatic Amine Derivative for OLED Hole Transport
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Solution Overview
Problem
Conventional organic electroluminescent elements face issues with luminous efficiency degradation, increased driving voltage, and shortened emission lifetime when exposed to high temperatures, primarily due to crystallization of hole transporting materials with numerous aromatic groups, which also lead to yield decreases and short service life.
Innovation Solution
A novel aromatic amine derivative with a specific structure is introduced, which is used in the hole transport layer or injection layer of organic electroluminescent elements, preventing crystallization and enhancing the efficiency and longevity of the elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a hole transporting material with many aromatic groups is used to increase glass transition temperature, then thermal stability is improved, but crystallization occurs leading to decreased yield and short service life
Solution Approach 1:
The patent applies asymmetry by introducing a specific asymmetric structural unit where a nitrogen atom is bonded to three different aromatic groups (first, second, and third aromatic groups). This asymmetric configuration disrupts the molecular packing and prevents crystallization while maintaining the high glass transition temperature needed for thermal stability, thereby resolving the contradiction between thermal stability and service life.
Solution Approach 2:
The patent changes the molecular structure parameters by specifying that the first, second, and third aromatic groups satisfy particular structural formulas with specific substituent patterns. This parameter optimization allows the material to achieve both high glass transition temperature and resistance to crystallization, improving both thermal stability and service life simultaneously.
2Temperature
If a hole transporting material with many aromatic groups is used, then glass transition temperature increases, but sublimation temperature becomes high causing decomposition during deposition
Solution Approach 1:
The patent optimizes molecular structure parameters by carefully selecting and combining different aromatic groups with specific substituent patterns. This structural optimization achieves a balance where the glass transition temperature is sufficiently high for thermal stability, but the sublimation temperature remains appropriate for deposition processes, preventing decomposition during manufacturing.
3Ease of manufacture
If conventional hole transporting materials are used, then element structure can be formed, but crystallization occurs causing defects and decreased yield
Solution Approach 1:
The asymmetric molecular structure with three different aromatic groups bonded to a central nitrogen atom prevents orderly molecular packing and crystallization. This allows the material to form high-quality amorphous thin films without crystallization defects, improving both ease of manufacture and manufacturing precision simultaneously.
Data Source
AI summary
There are provided an aromatic monoamine derivative having a fluorene structure-containing organic group and an aromatic hydrocarbon group-containing organic group, and an organic electroluminescent element containing an organic thin film layer composed of a single layer or plural layers while including at least a light emitting layer, the organic thin film layer being between a cathode and an anode, wherein at least one layer of the organic thin film layer, particularly a hole transport layer, contains the aromatic amine derivative alone or as a component of a mixture. An organic electroluminescent element which maintains high luminous efficiency even if exposed to a high temperature environment, and has a low driving voltage and a long emission lifetime, and an aromatic amine derivative capable of realizing the organic electroluminescent element are provided.