OLED Device Deep HOMO Emitter Charge Balance
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Solution Overview
Problem
Conventional OLED devices with shallow HOMO emitters face challenges in achieving efficient device performance and long lifetime due to inefficient HOMO-LUMO level alignment and charge balance in the organic emissive layer, leading to emission quenching by charge carriers.
Innovation Solution
The implementation of a deep HOMO emitter with specific energy level alignment and layer configurations, including an anode, electron blocking layer, organic light emissive layer, hole blocking layer, and cathode, where the organic light emissive layer comprises a host compound, a phosphorescent emitting compound with a HOMO of 5.2 eV or lower and a LUMO of 2.5 eV or higher, and additional hole and electron transporting compounds, to enhance charge balance and minimize emission quenching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional shallow HOMO emitters are used in OLED devices, then the device structure is simpler, but the HOMO-LUMO level alignment is inefficient and charge balance is poor, leading to emission quenching and reduced device lifetime
Solution Approach 1:
The patent applies local quality by creating distinct regions within the organic light emissive layer with different functional properties. The first sub-layer contains the deep HOMO emitter with specific HOMO-LUMO alignment optimized for charge balance, while the second sub-layer has different compositional characteristics. This local differentiation allows each region to perform its specific function optimally, resolving the contradiction between improved reliability and device complexity.
Solution Approach 2:
The organic light emissive layer is segmented into multiple sub-layers, each with specific compositional and functional characteristics. This segmentation allows independent optimization of charge transport, recombination, and emission in different regions, thereby improving overall device lifetime while managing the complexity through structured organization.
2Productivity
If deep HOMO emitters with specific energy level alignment are implemented, then charge balance and emission efficiency are improved, but the device requires more complex layer configurations and material selection
Solution Approach 1:
The patent implements parameter changes by specifically selecting materials with defined HOMO and LUMO energy levels. The deep HOMO emitter has a HOMO level of 5.2 eV or lower and a LUMO level of 2.5 eV or higher, creating optimal energy level alignment for efficient charge balance. This parameter optimization directly improves emission efficiency while the complexity is managed through systematic material selection criteria.
Solution Approach 2:
The organic light emissive layer structure is designed to perform multiple functions simultaneously: charge transport, charge recombination, and light emission. By incorporating both hole transporting and electron transporting compounds along with the deep HOMO emitter in an integrated structure, the system achieves multi-functionality that improves productivity while consolidating what could otherwise be separate components.
3Reliability
If multiple transporting compounds and sub-layers are added to optimize charge balance, then emission quenching is reduced and device lifetime is extended, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the energy level alignment and compositional ratios of the transporting compounds and emitter materials during the design phase. The deep HOMO emitter is selected with specific HOMO-LUMO levels before device assembly, and the sub-layer structures are predetermined with specific thicknesses and compositions. This preliminary optimization reduces the need for complex real-time adjustments during manufacturing, thereby improving reliability while easing fabrication complexity.
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 configuration results in high efficiency and extended relative lifetime of OLED devices by optimizing HOMO-LUMO level alignment and charge transport, achieving high external quantum efficiency (EQE) and reduced voltage requirements.
Implementation Method 1
a first emitting compound capable of phosphorescence emission at room temperature
Data Source
AI summary
An OLED device includes, in order, an electron blocking layer, an organic emissive layer, and a hole blocking layer. Its organic emissive layer contains at least four components: an electron transporting compound, a host, a hole transporting compound, and an emitting compound capable of phosphorescence emission at room temperature. The emitting compound has HOMO energy level of 5.2 eV or lower and a LUMO energy level of 2.5 eV or higher.