Triplet-Triplet Fusion OLED Emissive Layer Design
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Solution Overview
Problem
Fluorescent organic light emitting diodes (OLEDs) face efficiency limitations due to the tradeoff between triplet-triplet fusion and singlet-triplet annihilation, with existing technologies not fully understanding the role of triplets in determining efficiency.
Innovation Solution
The development of OLEDs with specific configurations, including an emissive layer comprising an organic host compound and emitting compounds with controlled triplet and singlet energies, and the use of dopants like tetraphenyldibenzoperiflanthene in rubrene, to optimize triplet-triplet fusion and minimize singlet-triplet annihilation, achieving high electroluminescent internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If triplet-triplet fusion is enhanced to improve efficiency, then electroluminescent internal quantum efficiency increases, but singlet-triplet annihilation increases causing efficiency to decrease
Solution Approach 1:
The patent changes the energy parameters of the host and emitter materials. Specifically, it selects a host compound with triplet energy of 2.1 eV and singlet energy of 4.0 eV, and an emitter with triplet energy of 2.2 eV and singlet energy of 3.8 eV. This parameter configuration ensures that twice the host triplet energy plus 0.3 eV is greater than the host singlet energy, creating optimal conditions for triplet-triplet fusion while minimizing singlet-triplet annihilation
Solution Approach 2:
The patent uses a composite emissive layer combining a host compound (rubrene or its derivatives) with an emitter compound (tetraphenyldibenzoperiflanthene or other dopants). This composite material system allows the host to provide triplet states for fusion while the emitter provides fluorescent emission, achieving both high efficiency and bright emission
2Productivity
If host triplet energy is increased to enhance triplet-triplet fusion, then efficiency improves, but the energy gap to singlet state decreases potentially causing other losses
Solution Approach 1:
The patent precisely controls the energy parameters by selecting materials where the host triplet energy is 2.1 eV and singlet energy is 4.0 eV. This specific parameter combination ensures that the condition (2 × host triplet energy + 0.3 eV > host singlet energy) is satisfied, optimizing triplet-triplet fusion while maintaining adequate energy gap to prevent other loss mechanisms
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 configurations result in very high efficiency fluorescent OLEDs with peak external quantum efficiency exceeding 6.7% and internal quantum efficiency up to 51%, guiding the design of molecules and structures for improved efficiency in OLEDs and organic photovoltaics.
Implementation Method 1
at least one organic emitting compound capable of fluorescent emission at room temperature
Implementation Method 2
triplet-triplet (T-T) fusion
Implementation Method 3
singlet-triplet (S-T) annihilation
Implementation Method 4
electroluminescent internal quantum efficiency
Data Source
AI summary
A first device is provided. The first device further comprises an organic light emitting device. The organic light emitting device further comprises an anode, a cathode, and an emissive layer disposed between the anode and the cathode. The emissive layer may include an organic host compound and at least one organic emitting compound capable of fluorescent emission at room temperature. Various configurations are described for providing a range of current densities in which T-T fusion dominates over S-T annihilation, leading to very high efficiency fluorescent OLEDs.