Multinuclear Iridium Complexes for Deep Red Emission
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Solution Overview
Problem
Current metal complexes used in organic electroluminescent devices and sensors have limitations in luminescence lifetime, efficiency, and emission spectrum, particularly for red and infrared regions, where deep red-emitting compounds are needed for applications like infrared iris sensors.
Innovation Solution
Development of binuclear, trinuclear, and tetranuclear iridium/platinum complexes with specific ligand structures that enhance photoluminescence quantum yield, reduce luminescence lifetime, and enable oriented emission in the deep red or infrared spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If mononuclear iridium complexes with aromatic ligands are used as triplet emitters in phosphorescent OLEDs, then the complexes exhibit stable structure and tunable emission color, but the luminescence lifetime becomes too long (well above 1 μs) leading to high roll-off characteristics and reduced efficiency
Solution Approach 1:
The patent combines multiple iridium centers (forming binuclear, trinuclear, or tetranuclear complexes) into a single functional unit. This aggregation of metal centers creates new photophysical properties where the collective emission lifetime is shortened compared to mononuclear analogs, while the overall structural stability is maintained through the chelating ligand framework.
Solution Approach 2:
The patent systematically varies key parameters including the number of iridium centers (n=2,3,4), the specific ligand structures (L1, L2, L3), and substitution patterns (R groups) to optimize the balance between luminescence lifetime and efficiency. By changing these parameters, the emission lifetime can be tuned from the microsecond range down to sub-microsecond values while maintaining structural integrity.
2Illumination intensity
If red-emitting phosphorescent emitters with low triplet level T1 are used, then the emission color is tuned to the red region, but the photoluminescence quantum yield decreases due to enhanced non-radiative channels
Solution Approach 1:
By merging multiple iridium centers into clusters, the patent creates enhanced radiative pathways that compensate for the low T1 energy level. The collective emission from multiple metal centers increases the overall radiative rate, thereby improving quantum yield despite the red-shifted emission and low triplet energy.
Solution Approach 2:
The patent creates composite photofunctional materials combining multiple iridium centers with specifically designed organic ligands (L1, L2, L3). This composite structure allows simultaneous optimization of emission color (red region) and efficiency (quantum yield) by coordinating the metal centers with ligands that provide both the necessary electronic structure for red emission and pathways for efficient radiative decay.
3Device complexity
If conventional mononuclear complexes are used for infrared emission, then the structural design is simpler, but the photoluminescence quantum yield and emission efficiency in the infrared region are insufficient
Solution Approach 1:
The patent merges multiple iridium centers to achieve infrared emission with high quantum yield. The aggregated metal centers create low-energy emission states in the infrared region while maintaining efficient radiative transitions, overcoming the limitation of simple mononuclear complexes that cannot achieve both infrared emission and high 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
These complexes improve the efficiency and roll-off characteristics of organic electroluminescent devices and sensors by offering high photoluminescence quantum yield and short luminescence lifetime, enabling effective deep red and infrared emission.
Implementation Method 1
the compounds of the invention have an improved photoluminescence quantum yield and a distinctly reduced luminescence lifetime
Data Source
AI summary
The present invention relates to binuclear, trinuclear and tetranuclear metal complexes and to electronic devices, especially organic electroluminescent devices, comprising these metal complexes.