Organic Electroluminescent Device with Aromatic Host Material
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Solution Overview
Problem
Current organic electroluminescent devices face challenges in achieving high light emission efficiency and durability, particularly when using phosphorescent materials like iridium or platinum complexes, as existing materials with condensed rings or long conjugate systems quench light emission, especially at short wavelengths.
Innovation Solution
Incorporating an aromatic compound with a specific structure in the organic compound layer, characterized by a glass transition temperature of 130 to 450°C and a lowest excited triplet energy level of 63 to 95 kcal/mol, which includes a light-emitting layer with a phosphorescent material such as an iridium or platinum complex, to enhance light emission efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If materials with condensed rings or long conjugate systems are used in phosphorescent devices, then durability is improved, but light emission efficiency decreases due to quenching
Solution Approach 1:
The invention changes the energy level parameter of the host material by selecting compounds with lowest excited triplet energy levels of 63-95 kcal/mol, which matches the emission characteristics of blue phosphorescent materials. This parameter optimization prevents energy quenching while maintaining the material's durability, resolving the contradiction between reliability and energy efficiency.
Solution Approach 2:
The invention applies different functional requirements to different parts of the material system: the host material is designed with specific structural characteristics (aromatic compounds with controlled triplet energy levels) to prevent quenching, while the phosphorescent dopant provides the light emission function. This local optimization of material properties allows both durability and efficiency to coexist.
2Loss of energy
If phosphorescent materials like iridium or platinum complexes are used, then light emission efficiency is improved, but durability decreases
Solution Approach 1:
The invention introduces a specifically designed host material as an intermediary between the phosphorescent dopant and the device environment. This host material with controlled triplet energy levels acts as a protective medium that maintains the phosphorescent material's efficiency while providing structural stability and durability, thus resolving the contradiction between efficiency and reliability.
3Reliability
If materials with low T1 level are used for high durability, then reliability is improved, but light emission efficiency decreases due to quenching
Solution Approach 1:
The invention optimizes the T1 energy level parameter within a specific range (63-95 kcal/mol) that is high enough to prevent quenching of blue phosphorescent emission but low enough to maintain material stability and durability. This precise parameter control resolves the contradiction between reliability and energy efficiency.
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 proposed solution results in an organic electroluminescent device with improved light emission efficiency and durability, particularly in the blue region, as demonstrated by increased brightness and extended brightness half-life compared to comparative examples.
Implementation Method 1
An organic electroluminescent device is being aggressively studied and developed because light emission of high brightness can be obtained by low-voltage driving. The organic electroluminescent device has an organic layer between a pair of electrodes, and this is a device where an electron injected from a cathode and a hole injected from an anode are recombined in the organic layer and the energy of an exciton produced is utilized for light emission.
Implementation Method 2
In recent years, the devices are becoming highly efficient by the use of a phosphorescent material. There have been disclosed inventions related to a phosphorescent device using an iridium complex, a platinum complex (see, U.S. Pat. No. 6,303,238 and International Publication 00/57676, pamphlet) or the like as the phosphorescent material
Data Source
AI summary
An organic electroluminescent device includes: a pair of electrodes; and at least one organic compound layer therebetween, the at least one organic compound layer comprises at least a light-emitting layer, wherein at least one of the at least one organic compound layer comprises at least one compound represented by a particular formula.