Lanthanide Metal-Organic Coordination for OLED Stability
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Solution Overview
Problem
Current OLED emitter materials face inefficiencies due to intrametallic f-f transitions, leading to low light generation efficiency and chemical instability, especially with blue light emission, which results in short operational lifetimes and color purity issues.
Innovation Solution
A metal-organic coordination compound with a lanthanide ion coordinated by a polycyclic organic ligand is developed, providing geometrical and electronic stabilization, ensuring deep blue emission with high operational stability and efficiency by confining excitation within the central metal cation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intrametallic f-f transitions are used for lanthanide emission, then chemical stability is improved, but light generation efficiency deteriorates
Solution Approach 1:
The patent introduces organic ligands as intermediaries that absorb electrical excitation energy and transfer it to lanthanide ions. The ligands act as mediators between the electrical input and the intrametallic f-f transitions, enabling efficient energy transfer while maintaining the chemical stability of intrametallic transitions. This resolves the contradiction by using the ligand as a bridge to improve light generation efficiency without sacrificing the inherent stability of lanthanide f-f transitions.
2Use of energy by moving object
If TADF or phosphorescent emitters are used to improve light generation efficiency, then efficiency is improved, but chemical stability deteriorates
Solution Approach 1:
The patent segments the emitter into two distinct functional components: organic ligands responsible for light generation through TADF or phosphorescence, and lanthanide ions responsible for chemical stability through intrametallic f-f transitions. This segmentation allows each component to perform its optimized function independently, resolving the contradiction between efficiency and stability by combining their respective strengths in a coordinated complex.
3Manufacturing precision
If emission spectra are narrowed for color purity, then color purity is improved, but efficiency deteriorates due to color filters
Solution Approach 1:
The patent changes the fundamental parameter of emission mechanism from organic-based to lanthanide-based intrametallic transitions. These transitions naturally produce narrow emission spectra with high color purity without requiring external color filters. By changing the emission mechanism parameter, the patent achieves both narrow spectra and high efficiency simultaneously, as the intrinsic properties of f-f transitions provide both spectral narrowness and high quantum efficiency.
4Speed
If excited state lifetime is reduced for fast display refresh rates, then refresh rate is improved, but light generation efficiency deteriorates due to bimolecular quenching
Solution Approach 1:
The patent creates a composite material system combining organic ligands with long excited state lifetimes (for efficient light generation) and lanthanide ions with fast radiative decay rates (for fast refresh rates). The composite structure allows the organic component to provide the long-lived excited state for efficient energy capture and the lanthanide component to provide fast emission for high refresh rates, resolving the contradiction through material composition rather than relying on a single material's properties.
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 compound achieves high light generation efficiency and chemical stability, enabling long operational lifetimes and color purity in OLED devices by maintaining intrametallic transitions and avoiding energy transfer to the ligand, thus overcoming the limitations of existing emitter materials.
Implementation Method 1
Many applications relevant physical and in particular opto electronic processes make use of lanthanide ions with their chemically well shielded inner f-f transitions
Implementation Method 2
incorporation of quantum mechanical heavy metal effect into the emitter molecules, by introducing d-metal elements such as Iridium, Osmium, Gold or Platinum. The presence of heavy metal elements softens the selection rules for the excited states resulting in high internal light generation efficiencies; known as phosphorescence (Ph)
Implementation Method 3
thermally activated delayed fluorescence (TADF) has been used wherein thermal energy from the environment is harvested to convert non-emissive states back into emissive ones, resulting in high light generation efficiencies
Data Source
AI summary
A metal-organic coordination compound includes one lanthanide ion coordinated by a polycyclic organic ligand having the formula 1-1with L0, L1, L2 being independently each a divalent organic group formed by removing two hydrogen atoms from a substituted or non-substituted alkane, arylalkane, heteroarylalkane, arene, heteroarene, alkylarene, alkylheteroarene, dialkylarene or dialkylheteroarene, wherein alkane or alkyl can be interrupted by one or more oxygen or boron atoms, and with the sum of the number of atoms in the shortest sequences of atoms in L1, and L2 between the two linkages of -L1- and -L2- and the remainder of the polycyclic ligand being less than 16 atoms, and R2 to R5 independently in each occurrence representing hydrogen, deuterium, halogen, or an organyl group, and R1 representing hydrogen, deuterium, or an organyl group.