Top-Emitting OLED Light-Scattering Layer for Aperture Ratio
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Solution Overview
Problem
Bottom-emitting OLED devices face challenges with low aperture ratio and inability to meet high resolution display requirements due to light emission limitations, which are exacerbated by the need for a bottom driving circuit.
Innovation Solution
A Top-Emitting Organic Light Emitting Diode (TEOLED) is developed with a substrate stack structure including an anode, hole-injecting, hole-transmitting, organic light-emitting, and electron-transmitting layers, topped with a cathode layer and a light-scattering layer composed of nano particles with a concave and convex structure, using materials like ZnO, TiO2, and SnO2 to enhance cathode transmittance and wavelength coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bottom-emitting OLED structure is used with bottom driving circuit, then the device can be manufactured with conventional processes, but the aperture ratio is low and high resolution display requirements cannot be met
Solution Approach 1:
The patent inverts the conventional bottom-emitting OLED structure to create a top-emitting OLED. The driving circuit is moved from the bottom to the top of the device, allowing light to emit from the top surface without being blocked by the driving circuit. This inversion resolves the contradiction by enabling high aperture ratio while maintaining manufacturability through conventional processes adapted for top-emission architecture.
Solution Approach 2:
The patent introduces a light-scattering layer with three-dimensional concave-convex structure formed by nanometer-sized particles. This dimensional transformation from flat to 3D surface structure enhances light extraction efficiency and cathode transmittance, allowing the device to achieve high resolution display capabilities while maintaining a manageable driving circuit configuration.
2Reliability
If conventional cathode structure is used in TEOLED, then the manufacturing process is simple, but the cathode transmittance is insufficient
Solution Approach 1:
The patent changes the physical parameters of the cathode structure by introducing a light-scattering layer with specific nanometer-sized particles (50-200 nm diameter) and controlled thickness (50-200 nm). This parameter optimization enhances light scattering and cathode transmittance without excessively complicating the manufacturing process, as the layer can be formed using conventional deposition techniques with controlled parameters.
Solution Approach 2:
The patent creates a composite cathode structure combining the cathode layer with a light-scattering layer containing nanometer-sized particles. This composite structure leverages the optical properties of the particles (high refractive index materials like TiO2, SiO2, or ZnO) to enhance light extraction and cathode transmittance while maintaining structural integrity and manufacturability.
3Adaptability or versatility
If single wavelength light emission is used, then the device structure is simple, but the light output modulation capability is limited
Solution Approach 1:
The patent applies local quality by creating a light-scattering layer with spatially distributed nanometer-sized particles that have specific size ranges (50-200 nm) and material compositions. This local optimization of particle distribution and properties enables wavelength-dependent light scattering and modulation capabilities, allowing the device to handle multiple wavelengths effectively while keeping the overall structure manageable through localized functional zones.
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 TEOLED design improves cathode transmittance and modulates light output across multiple wavelengths, effectively addressing the limitations of bottom-emitting OLEDs and enabling higher resolution displays.
Implementation Method 1
a light-scattering layer composed of nano particles and including a concave and convex structure
Implementation Method 2
The nano particles of high refraction index are prepared on the cathode layer to form the scattering layer
Data Source
AI summary
The present invention provides a Top-Emitting Organic Light Emitting Diode (TEOLED) and a manufacturing method thereof. The TEOLED includes a substrate; a stack structure on the substrate; a cathode layer covering the stack structure; and a light-scattering layer composed of nano particles and including a concave and convex structure. The present invention can effectively improve cathode transmittance of the TEOLED and modulate the coupling output of lights with multiple wavelengths.