Organic OLED Emitters with Inert Additives for Triplet Harvesting
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Solution Overview
Problem
Current triplet emitters in OLEDs, which are efficient but chemically unstable due to metal-ligand bond breakages, require expensive noble metals and have inadequate long-term stability.
Innovation Solution
Development of organic molecules with specific electronic structures and singlet-triplet energy separations, combined with additives that enhance spin-orbit coupling to facilitate 'singlet harvesting,' allowing for efficient conversion of both singlet and triplet excitons into light, thereby improving stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If triplet emitters with transition metal complexes are used in OLEDs, then emission efficiency is improved through triplet harvesting, but chemical stability deteriorates due to metal-ligand bond breakages
Solution Approach 1:
The patent removes the transition metal complex from the emitter system entirely, extracting the harmful metal component while retaining the desired triplet harvesting function through purely organic molecules combined with optically inert atoms or molecules that enhance spin-orbit coupling
Solution Approach 2:
The patent introduces optically inert atoms or molecules as intermediaries that mediate between the organic emitter and the triplet excitons, facilitating spin-orbit coupling and enabling efficient triplet harvesting without the chemical instability caused by metal-ligand interactions
2Productivity
If triplet emitters are used to achieve 100% quantum yield, then emission quantum yield is improved, but device lifetime is reduced due to chemical reactivity in excited states
Solution Approach 1:
The patent employs purely organic emitter molecules that are chemically stable and do not suffer from the long-term degradation issues of metal complexes, effectively replacing expensive but unstable metal-based emitters with stable organic alternatives that maintain high quantum yield
3Reliability
If purely organic singlet emitters are used, then chemical stability is improved, but emission efficiency deteriorates due to maximum 25% exciton conversion
Solution Approach 1:
The patent changes the photophysical parameters of organic molecules by introducing optically inert atoms or molecules that enhance spin-orbit coupling, thereby enabling triplet harvesting and achieving near-100% exciton conversion while maintaining the chemical stability of purely organic materials
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
This approach enables high emission quantum yields, reduces emission decay times, and enhances the long-term stability of OLEDs by converting triplet excitations into light via the singlet state, potentially reaching 100% quantum yield and extending device lifetime.
Implementation Method 1
an optically inert atom or molecule which interacts with the organic molecule such that the intersystem crossing time constant of thermal repopulation, i.e. the up-intersystem crossing time constant, of the organic molecule is reduced to less than 300 ms
Implementation Method 2
the ΔE(S1−T1) value of the organic molecule being less than 3000 cm−1, and an optically inert atom or molecule which interacts with the organic molecule such that the intersystem crossing time constant of thermal repopulation
Implementation Method 3
The recombination gives rise to excitons (=excited states) which transfer their excess energy to the respective electro-luminescent compound. This compound can then be converted to a particular electronic excited state which is then converted very substantially and with substantial avoidance of radiationless deactivation processes to the corresponding ground state by emission of light.
Implementation Method 4
triplet emission, which is referred to as phosphorescence, exploits and converts all excitons and emits them as light (triplet harvesting)
Data Source
AI summary
The invention relates to a composition having an organic emitter molecule, which has a ΔE(S1−T1) value between the lowest excited singlet state (S1) and the triplet state thereunder of less than 3000 cm−1 and an atom or molecule for reducing the intersystem crossing time constant of the organic molecule.