OLED Plasmonic Electrode Light Extraction
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Solution Overview
Problem
Conventional OLEDs suffer from low light extraction efficiency due to total internal reflection and in-plane emission, with existing solutions either improving optical coupling at the cost of electrical efficiency, lifetime, or complicating fabrication processes.
Innovation Solution
Incorporating a nano-meter metallic layer with a plasmonic photonic crystal structure as an electrode, which suppresses surface plasmon polariton generation and enhances light transmission through a bandgap in the frequency range of surface plasmons, and optionally using a grating formation on the electrode for further light enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional transparent electrode and reflective cathode structure is used, then device simplicity is maintained, but light extraction efficiency is limited to approximately 20% due to total internal reflection and in-plane emission
Solution Approach 1:
The patent applies composite materials by combining a metallic layer with a dielectric layer to form a plasmonic photonic crystal structure. This composite structure enables simultaneous achievement of simple device architecture and enhanced light extraction efficiency by utilizing both metallic and dielectric properties in a single integrated electrode design.
Solution Approach 2:
The patent changes the optical parameters of the electrode by introducing a plasmonic photonic crystal structure with specific periodicity and material composition. This parameter change enables the electrode to support surface plasmon polaritons and create optical bandgaps, thereby improving light extraction efficiency without complicating the overall device structure.
2Use of energy by moving object
If hole and electron transport layers are added to optimize electrical properties, then electrical efficiency is improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The plasmonic photonic crystal electrode structure serves multiple functions simultaneously: it acts as an electrical electrode for charge injection and as an optical enhancement structure for light extraction. This multi-functionality reduces the need for separate specialized layers, thereby maintaining electrical efficiency without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the electrical function and optical function into a single integrated electrode structure. The metallic-dielectric composite electrode simultaneously performs charge injection and light extraction enhancement, eliminating the need for separate transport layers and reducing overall device complexity.
3Loss of energy
If micro lens array or large half sphere lens is used on substrate surface to reduce total internal reflection, then light extraction is improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent extracts the optical enhancement function from the substrate surface and integrates it into the electrode layer. By placing the plasmonic photonic crystal structure in the electrode rather than on the substrate surface, the invention eliminates the need for complex surface lens structures while maintaining light extraction improvement.
Solution Approach 2:
The plasmonic photonic crystal structure acts as an intermediary between the organic electroluminescent layer and the external environment. It mediates the extraction of light by supporting surface plasmon polaritons and creating optical bandgaps, thereby improving light extraction without requiring complex substrate modifications.
4Loss of energy
If low refractive index porous aerogel or photonic crystal pattern is embedded in glass substrate to extract trapped light, then light extraction is improved, but device complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent changes the structural parameters of the electrode by introducing a plasmonic photonic crystal with specific periodicity and material composition. This parameter change enables effective light extraction through surface plasmon polariton support and optical bandgap creation, achieving enhanced light extraction with standard fabrication precision rather than requiring sub-UV wavelength precision.
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 significantly increases light output by reducing absorption losses and enhancing light extraction, while maintaining electrical efficiency and simplifying the OLED structure, with calculated results showing doubled or five times greater light enhancement compared to conventional OLEDs.
Implementation Method 1
a nano-meter metallic layer with a plasmonic photonic crystal structure configured having a bandgap in the frequency range of surface plasmon polaritons generated at the surface of the one electrode
Implementation Method 2
plasmonic photonic crystal structure configured having a bandgap in the frequency range of surface plasmon polaritons
Implementation Method 3
an organic electroluminescent layer formed between the first electrode and the second electrode, whereby the electroluminescent organic semiconductor material emits light when a voltage is applied
Implementation Method 4
light extraction inefficiencies exist because light generated within a high-index organic material has difficulty propagating into the surrounding lower-index Anode/Glass substrate owing to total internal refection (TIR) at the glass/air interface
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
There is provided an organic light emitting diode (OLED) comprising an organic electroluminescent layer formed between a first electrode and a second electrode, characterised in that one of the first and second electrodes comprises a nano-meter metallic layer having a plasmonic photonic crystal structure formed thereon, and wherein the plasmonic photonic crystal structure is configured to interact with surface plasmon polaritons generated at a surface of the one electrode thereby providing for transmission of electromagnetic radiation having a wavelength of between 350 nm to 750 nm from the OLED.