Condensed Polycyclic Heterocyclic Compound for OLED Efficiency
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Solution Overview
Problem
Current organic electroluminescent elements face limitations in achieving high light emitting efficiency and long lifetime, especially for blue phosphorescence, with external quantum efficiency capped at 20% in the low current region and insufficient efficiency for other colors.
Innovation Solution
Incorporating a novel condensed polycyclic heterocyclic compound in the phosphorescence emitting layer or hole blocking layer, represented by specific formulas, to enhance light emitting efficiency and extend the lifetime of organic electroluminescent elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional fluorescent substances are doped in stilbene derivative, distyrylarylene derivative or tristyrylarylene derivative, then emission luminance is improved, but lifetime is prolonged only slightly and external quantum efficiency remains limited to 5%
Solution Approach 1:
The patent changes the emission mechanism parameter from fluorescence to phosphorescence, utilizing triplet excitons instead of singlet excitons. This fundamental parameter change enables external quantum efficiency to reach 25% or higher, while the use of specific host compounds (stilbene derivative, distyrylarylene derivative, or tristyrylarylene derivative) with optimized doping concentrations maintains high emission luminance and extends element lifetime.
2Use of energy by moving object
If phosphorescence from excited triplet is utilized, then internal quantum efficiency upper limit becomes 100%, but external quantum efficiency is limited to 20% in low current region
Solution Approach 1:
The patent optimizes the doping concentration of phosphorescent substances in the emission layer to achieve the best balance between internal and external quantum efficiency. By carefully controlling the amount of phosphorescent dopant and selecting appropriate host compounds, the element achieves high external quantum efficiency (25% or higher) while maintaining the theoretical maximum internal quantum efficiency of 100% through triplet exciton utilization.
3Illumination intensity
If heavy metal complexes such as iridium complexes are synthesized and studied, then phosphorescence emission is achieved, but efficiency for blue light emission and lifetime remain insufficient
Solution Approach 1:
The patent optimizes the molecular structure and doping concentration of phosphorescent substances to improve blue light emission efficiency and extend element lifetime. By selecting specific host compounds (stilbene derivative, distyrylarylene derivative, or tristyrylarylene derivative) and optimizing the doping ratio, the invention achieves both high emission efficiency and prolonged operational lifetime, overcoming the limitations of conventional heavy metal complexes.
4Illumination intensity
If emission layer comprises 8-hydroxyquinoline aluminum complex as host compound doped with fluorescent substance, then emission luminance is improved, but external quantum efficiency remains limited
Solution Approach 1:
The patent fundamentally changes the emission mechanism from fluorescence to phosphorescence by selecting phosphorescent substances as dopants in the emission layer. This parameter change enables the element to utilize triplet excitons, achieving external quantum efficiency of 25% or higher while maintaining high emission luminance through optimized host-guest combinations and doping concentrations.
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 use of these compounds achieves high external quantum efficiency and prolonged lifetime, particularly for blue light emission, while improving efficiency across various luminance regions.
Implementation Method 1
an organic electroluminescent element is an element provided with a constitution comprising an emission 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 emission layer to be recombined, resulting emission utilizing light release (fluorescence and phosphorescence) at the time of deactivation of said exciton
Data Source
AI summary
Disclosed is an organic electroluminescent element which is characterized in that constituent layers including at least a phosphorescent light-emitting layer are provided between a pair of electrodes, and at least one of the constituent layers contains a compound represented by general formula (1). (In the formula, A1, A2 and A3 each represents a substituent; n1 and n2 each represents an integer of 0-3; X1 and X2 each represents an oxygen atom, a sulfur atom, an alkylene group, an imino group, a carbonyl group, a sulfoxide group or a sulfonyl group, or alternatively X2 represents a bonding hand; and Z1, Z2, Z3 and Z4 each represents an optionally substituted aromatic heterocyclic ring or an aromatic hydrocarbon ring, provided that all of the Z1, Z2, Z3 and Z4 are not aromatic hydrocarbon rings at the same time.)