OLED Emission Layer HOMO Energy Optimization
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Solution Overview
Problem
There is a demand for light emitting elements with long service life in organic electroluminescence display devices, and existing technologies have not effectively addressed the need for stable and durable light emitting elements that maintain performance over time.
Innovation Solution
A light emitting element is designed with a specific configuration including a first electrode, a second electrode, and an emission layer comprising a hole transporting host, an electron transporting host, a phosphorescent sensitizer, and a delayed fluorescent dopant, where the hole transporting host has a lower HOMO energy level than the delayed fluorescent dopant, and the phosphorescent sensitizer has a lower HOMO energy level than both hosts, optimizing energy levels to enhance current flow and reduce degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a conventional emission layer is used without optimized energy levels, then the device structure is simpler, but the service life is short and stability is poor
Solution Approach 1:
The patent applies parameter changes by optimizing the HOMO energy levels of the hole transporting host and phosphorescent sensitizer. Specifically, the hole transporting host has a lower HOMO energy level than the delayed fluorescent dopant, and the phosphorescent sensitizer has a lower HOMO energy level than both hosts. This energy level optimization reduces direct recombination and triplet exciton formation, thereby extending the service life of the light emitting element while maintaining a relatively simple emission layer structure comprising these four components.
2Reliability
If the emission layer uses standard materials without energy level optimization, then the manufacturing process is easier, but the current flow is insufficient and degradation is high
Solution Approach 1:
The patent implements parameter changes by carefully selecting materials with specific HOMO energy levels. The hole transporting host is chosen to have a lower HOMO energy level than the delayed fluorescent dopant, and the phosphorescent sensitizer is selected to have a lower HOMO energy level than both the hole transporting host and the delayed fluorescent dopant. This systematic energy level optimization improves current flow and reduces degradation, enhancing reliability while maintaining ease of manufacture through the use of organic electroluminescence materials.
3Duration of action of moving object
If direct recombination is not reduced, then the emission layer composition is simpler, but the triplet exciton formation is high and lifespan is short
Solution Approach 1:
The patent applies parameter changes by optimizing the energy level parameters of the emission layer components. The specific configuration where the hole transporting host has a lower HOMO energy level than the delayed fluorescent dopant, and the phosphorescent sensitizer has a lower HOMO energy level than both, effectively reduces direct recombination and triplet exciton formation. This extends the lifespan of the light emitting element while maintaining a composition that includes four key components: hole transporting host, electron transporting host, phosphorescent sensitizer, and delayed fluorescent dopant.
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 light emitting element achieves a satisfactory current value and extended lifespan by reducing direct recombination and triplet exciton formation, leading to improved stability and performance compared to elements without the delayed fluorescent dopant.
Implementation Method 1
an emission layer between the first electrode and the second electrode and including a hole transporting host, an electron transporting host, a phosphorescent sensitizer, and a delayed fluorescent dopant
Implementation Method 2
a phosphorescent sensitizer
Implementation Method 3
a hole transporting host has a lower absolute value of the Highest Occupied Molecular Orbital (HOMO) energy level than the delayed fluorescent dopant
Data Source
AI summary
A light emitting element includes a first electrode, a second electrode disposed on the first electrode, and an emission layer disposed between the first electrode and the second electrode. The emission layer may include a hole transporting host, an electron transporting host, a phosphorescent sensitizer, and a delayed fluorescent dopant. The delayed fluorescent dopant may have a greater absolute value of the HOMO energy level than the hole transporting host. Accordingly, the light emitting element including the delayed fluorescent dopant in an embodiment may exhibit long lifespan.