Mononuclear Iridium Complexes for OLED Voltage Shift Reduction
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Solution Overview
Problem
Existing phosphorescent organic electroluminescent devices (OLEDs) face challenges in achieving high efficiency and long lifetime due to voltage shift issues when emitter concentration increases, leading to higher operating voltage and power consumption, and existing iridium complexes do not effectively balance efficiency and voltage stability.
Innovation Solution
Development of mononuclear iridium complexes with three ortho-metallated bidentate ligands or sub-ligands that exhibit oriented emission, with a specific angle between the transition dipole moment and electrical dipole moment of ≤40°, to minimize voltage shift and enhance operating voltage and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the emitter concentration in the emitting layer is increased to achieve good lifetime, then the device lifetime is improved, but the operating voltage increases due to voltage shift
Solution Approach 1:
The patent changes the molecular parameters of the emitter by controlling the angle between transition dipole moment and electrical dipole moment to be ≤40°, and by using specific ligand structures (three ortho-metallated bidentate ligands). This parameter optimization reduces the voltage shift effect, allowing high emitter concentration (7-12%) to be used for improved lifetime without significant increase in operating voltage.
2Duration of action of stationary object
If the emitter concentration in the emitting layer is increased to achieve good lifetime, then the device lifetime is improved, but the power consumption increases due to higher operating voltage
Solution Approach 1:
By optimizing the molecular parameters of the emitter (angle ≤40° between dipole moments, specific ligand configuration), the patent reduces the voltage shift that would otherwise occur at high emitter concentrations. This enables using 7-12% emitter concentration for improved lifetime while minimizing the power consumption penalty that would result from voltage-induced efficiency losses.
3Productivity
If the emitters are oriented horizontally to improve light outcoupling efficiency, then the external quantum efficiency is improved, but the voltage shift increases
Solution Approach 1:
The patent optimizes the molecular structure parameters (angle between transition dipole moment and electrical dipole moment ≤40°, three ortho-metallated bidentate ligands) to simultaneously achieve horizontal emitter orientation for improved light outcoupling while minimizing voltage shift. This dual optimization enables both high external quantum efficiency and stable operating voltage.
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 iridium complexes achieve improved external quantum efficiency and reduced voltage shift, resulting in better light outcoupling and prolonged device lifetime by aligning the transition dipole moment horizontally within the OLED layer plane.
Implementation Method 1
triplet emitters used in phosphorescent organic electroluminescent devices (OLEDs)
Implementation Method 2
maximizing the van der Waals interaction of these aromatic radicals with the matrix molecules in the layer
Implementation Method 3
improved external quantum efficiency and reduced voltage shift, resulting in better light outcoupling
Data Source
AI summary
The present invention relates to iridium complexes suitable for use in organic electroluminescent devices, especially as emitters.