Heteroleptic Bis-tridentate Os(II) Complexes for Near-Infrared OLED Emission
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Solution Overview
Problem
Current organic light-emitting diodes (OLEDs) face challenges in achieving a broad emission spectrum, particularly in the yellow to orange to red and near-infrared range, with existing phosphorescent emitters, which limits their application in color-tuning and design flexibility.
Innovation Solution
Development of heteroleptic bis-tridentate Os(II) or Ru(II) complexes with specific ligand configurations, such as those described by the compound MLALB, which exhibit a significant red shift in emission from 560 nm to 1200 nm, enabling emission in the yellow, red, and near-infrared regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional phosphorescent emitters are used in OLEDs, then the device structure is relatively simple and easy to manufacture, but the emission spectrum is limited primarily to green and yellow regions, lacking broad coverage into red and near-infrared ranges
Solution Approach 1:
The patent systematically varies ligand parameters including substituent types (electron-donating/withdrawing groups), substituent positions, and ligand backbone structures to tune the emission wavelength from green (560 nm) through yellow to red and near-infrared (1200 nm). This parameter optimization approach enables broad spectral coverage while maintaining the fundamental bis-tridentate ligand framework.
Solution Approach 2:
The invention employs composite ligand structures combining multiple functional components: N-heterocyclic carbene (NHC) units, aromatic backbones (benzene, naphthalene, anthracene), and various substituents (alkyl, aryl, heteroaryl groups). These composite ligands coordinate to Os(II) or Ru(II) centers to create emitters with tailored optical properties spanning a broad spectrum.
2Adaptability or versatility
If existing phosphorescent emitters are used, then the manufacturing process is straightforward, but the color-tuning capability is restricted to limited wavelength ranges
Solution Approach 1:
The ligand design is segmented into modular functional units that can be independently synthesized and then assembled. The bis-tridentate ligand framework is divided into separate NHC-containing fragments and aromatic backbone components, allowing parallel synthesis routes and simplifying the overall manufacturing process despite the complexity of the final emitter structures.
Solution Approach 2:
Systematic modification of ligand parameters including substituent electron-donating/withdrawing strength, substituent positions on aromatic rings, and core aromatic system size enables precise control over emission wavelength. This parameter optimization approach achieves broad spectral coverage from 560 nm to 1200 nm while maintaining feasible synthesis pathways.
3Illumination intensity
If conventional OLED materials are used, then the device structure remains simple, but the emission wavelength cannot be extended into the near-infrared region
Solution Approach 1:
The emission spectrum is extended by transitioning from conventional green/yellow emitters to near-infrared emitters, effectively adding a new wavelength dimension to the OLED output. This is achieved through strategic ligand design incorporating extended conjugation and specific aromatic systems that enable low-energy transitions in the 1000-1200 nm range.
Solution Approach 2:
Complex heteroleptic Os(II) and Ru(II) complexes are constructed with bis-tridentate ligands comprising N-heterocyclic carbene units coordinated to metal centers, combined with various aromatic backbones and substituents. These composite molecular structures enable access to the near-infrared region while maintaining reasonable structural organization for device fabrication.
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 compounds allow for a significant extension of the emission spectrum of OLEDs from green to red and into the near-infrared range, providing a broader design range for phosphorescent OLEDs and enhancing color-tuning capabilities.
Implementation Method 1
One application for phosphorescent emissive molecules is a full color display
Implementation Method 2
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
A compound of the formula MLALB where ligand LA is of Formula I, and ligand LB is of Formula II below.M is selected from Os(II) or Ru(II), and the compound MLALB has a formal neutral charge; and rings A, B, C, D, E, and F are independently a 5-membered or 6-membered aromatic ring, and RA, RB, RC, RD, RE,and RF each independently represent mono to the maximum allowable substitution, or no substitution.L1, L2, L3, and L4 independently represent a single bond or an organic linking group;W1, W2, W3, and W4 are independently selected from carbon or nitrogen;Y1, Y2, Y3, and Y4 are independently selected from carbon or nitrogen; andZ1, Z2, and Z3 are independently selected from carbon or nitrogen, and at least one of Z1, Z2, and Z3 is nitrogen. An organic electroluminescent device that includes an anode, a cathode, and an organic layer comprising a compound of the formula MLALB where ligand LA is of Formula I, and ligand LB is of Formula II above. A consumer product comprising an organic light-emitting device (OLED) above.