Organic EL Host Compound for Phosphorescent Emission Efficiency
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Solution Overview
Problem
Current organic electroluminescent elements face challenges in achieving high emission efficiency and long emission lifetime, particularly when using phosphorescent emission materials, with existing solutions not fully satisfying the requirements for practical applications.
Innovation Solution
The development of an organic electroluminescent element incorporating a compound represented by specific formulas, which includes a phosphorescence emitting metal complex, such as an Ir complex, within a light emitting layer to enhance emission efficiency and lifetime, with a detailed structure and layer configuration that optimizes the recombination of electrons and holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescence emitting metal complex is used in organic EL element, then emission efficiency is improved, but element lifetime is shortened
Solution Approach 1:
The patent introduces a host compound as an intermediary material that mediates between the phosphorescence emitting metal complex and the electrodes. The host compound (formula A) with specific structural features including nitrogen-containing six-membered aromatic rings and electron-withdrawing groups creates an optimized microenvironment that protects the metal complex from degradation while maintaining high phosphorescence efficiency, thus resolving the contradiction between improved emission efficiency and shortened lifetime
Solution Approach 2:
The patent systematically changes key parameters of the host compound including the type of nitrogen-containing aromatic rings, the position and type of electron-withdrawing groups, and the overall molecular structure (formula A). These parameter changes optimize the host-guest interaction, energy transfer efficiency, and stability of the phosphorescence emitting metal complex, achieving both high emission efficiency and prolonged element lifetime
2Duration of action of stationary object
If conventional fluorescent substance doping is used, then element lifetime is prolonged, but emission efficiency is limited to approximately 5%
Solution Approach 1:
The patent exploits the phase transition properties of the phosphorescence emitting metal complex from non-emissive to highly emissive states through energy transfer from the host compound. The host compound (formula A) absorbs electrical energy and transfers it to the metal complex, inducing a phase transition in the emission mechanism from inefficient fluorescent emission to efficient phosphorescent emission, achieving over 25% external quantum efficiency while maintaining prolonged element lifetime
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
This approach results in organic EL elements with high emission efficiency and prolonged lifetime, suitable for both display devices and lighting applications, offering improved performance compared to conventional elements.
Implementation Method 1
an element having an organic emitting layer comprising a 8-hydroxyquinoline aluminum complex as a host compound which is doped with quinacridone type dye
Implementation Method 2
an organic electroluminescent element is an element provided with a constitution comprising an emitting layer containing a emitting substance being sandwiched with a cathode and an anode, and an exciton is generated by an electron and a positive hole being injected into the emitting layer to be recombined, resulting emission utilizing light release (fluorescenceâ‹…phosphorescence) at the time of deactivation of said exciton
Data Source
AI summary
Disclosed is an organic electroluminescent device having long life, while exhibiting high luminous efficiency. Also disclosed are an illuminating device and a display, each using such an organic electroluminescent device. In the organic electroluminescent device, a compound represented by the general formula (A) which is suitable as a host material for a phosphorescent metal complex is used at least in one sublayer of a light-emitting layer.