OLED Nanoparticle Layer Enhances Photon Outcoupling
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Solution Overview
Problem
Conventional OLEDs face challenges in maximizing photon outcoupling efficiency due to metallic electrodes, which generate surface plasmons that cannot be directly recovered as photons, leading to reduced efficiency and stability, especially for blue light emitting devices.
Innovation Solution
The use of high-refractive index dielectric nanoparticles, integrated with transparent conducting electrodes, to outcouple electroluminescence through Mie scattering, minimizing losses associated with metallic electrodes and enhancing external quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If metallic electrodes are used in conventional OLEDs, then electrical conductivity is achieved, but surface plasmons are generated that cannot be directly recovered as photons, leading to reduced external quantum efficiency
Solution Approach 1:
The patent extracts the problematic metallic electrode component and replaces it with a transparent conducting oxide electrode. This removal of the metallic electrode eliminates the source of surface plasmon generation while maintaining electrical conductivity through the transparent conducting oxide material, thereby resolving the energy loss issue without sacrificing device stability
Solution Approach 2:
The patent changes the material parameter of the electrode from metallic to transparent conducting oxide. This parameter change fundamentally alters the optical properties of the electrode, eliminating surface plasmon generation while maintaining electrical conductivity. The transparent conducting oxide enables direct photon transmission without the energy losses associated with metallic surface plasmons
2Reliability
If metallic electrodes are used in OLEDs, then electrical conduction is maintained, but ohmic losses increase and device stability decreases
Solution Approach 1:
The patent removes the metallic electrode from the device architecture and replaces it with a transparent conducting oxide electrode. This extraction eliminates the source of ohmic losses and instability associated with metallic electrodes while maintaining the essential electrical conduction function through the transparent conducting oxide material
Solution Approach 2:
The patent employs transparent conducting oxides as a stable, non-degradable alternative to metallic electrodes that are prone to oxidation and degradation. The transparent conducting oxide provides long-term device stability and reduced ohmic losses, effectively replacing the short-lived metallic electrode component
3Ease of manufacture
If conventional OLED structures are used, then fabrication is simplified, but photon outcoupling efficiency is maximized limited by waveguide modes
Solution Approach 1:
The patent introduces a nanoparticle layer as an intermediary component between the transparent conducting oxide electrode and the organic emissive layer. This nanoparticle layer mediates the optical coupling by scattering waveguide modes out of the device, thereby enhancing photon outcoupling efficiency without complicating the overall fabrication process
Solution Approach 2:
The patent employs a composite structure combining transparent conducting oxide with a nanoparticle layer. This composite material approach enables simultaneous achievement of high electrical conductivity, optimized optical outcoupling, and maintained fabrication simplicity. The nanoparticle layer acts as an optical mediator that enhances photon extraction while the transparent conducting oxide provides stable electrical conduction
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 increases external quantum efficiency and stability by directing light emission without significant Purcell enhancement, while reducing ohmic losses, and can be driven at lower current densities without brightness loss.
Implementation Method 1
low-loss OLEDs which utilize Mie scattering of nanoparticles to increase the efficiency of OLED devices
Data Source
AI summary
Embodiments of the disclosed subject matter provide a device that may include an organic light emitting device (OLED) having a substrate, a first electrode disposed over the substrate, a second electrode disposed over the first electrode, and an organic emissive layer having a first surface positioned over a second surface is disposed between the first electrode and the second electrode. A nanoparticle layer may be disposed over the organic emissive layer and has a first surface that is positioned over a second surface. The nanoparticle layer may include a first plurality of nanoparticles comprising a dielectric material, and a surrounding medium. A distance from the second surface of the nanoparticle layer to the first surface of the organic emissive layer may be not more than 50 nm, and there may be a difference of at least 1.0 between a refractive index of the dielectric material and the surrounding medium.