LED Metasurface Nanostructure for Light Extraction at Critical Angles
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Solution Overview
Problem
Existing light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs) suffer from low photon utilization due to reflection and refraction at the glass substrate-air boundary, leading to inefficient light extraction, and existing solutions like roughening substrates or using microlens arrays are complex and costly, making them unsuitable for mass production.
Innovation Solution
A metasurface with densely-packed nanostructures on a transmissive substrate, divided into quadrants by intersecting axes, which are polarization-insensitive and transmit optical radiation with different incident angles, improving light extraction efficiency without the need for complex fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If roughening substrate surface or embossing glass surface is used to improve light extraction efficiency, then light extraction efficiency is improved, but fabrication process complexity and cost increase
Solution Approach 1:
The patent changes the physical parameters of the substrate surface by introducing nanoscale roughness features with specific size ranges (50-500 nm) and density distributions. This transforms the optical interaction at the interface, enabling light extraction at angles greater than the critical angle while maintaining a relatively simple fabrication process through chemical etching or plasma treatment rather than complex embossing equipment.
Solution Approach 2:
The patent creates a porous or nanorough surface structure on the glass substrate that increases the effective surface area and provides multiple scattering paths for photons. This nanoscale porosity allows light to escape more efficiently by reducing total internal reflection, while the fabrication process remains simpler compared to precision embossing techniques.
2Loss of energy
If microlens array is adopted to improve light extraction efficiency, then light extraction efficiency is improved, but fabrication process complexity and cost increase
Solution Approach 1:
Instead of using three-dimensional microlens structures that require complex alignment and fabrication, the patent introduces nanoscale surface features in the vertical dimension (surface roughness layer) that modify optical properties without requiring precise lateral positioning or complex assembly. This dimensional approach simplifies manufacturing while achieving similar light extraction enhancement.
Solution Approach 2:
The patent replaces the mechanical microlens array system with a chemically or physically treated surface layer. Instead of mechanically assembling precise lens elements, the solution uses chemical etching or plasma treatment to create the desired optical effect, significantly simplifying the manufacturing process.
3Ease of manufacture
If conventional light extraction methods are used, then fabrication process is simple, but light extraction efficiency remains low due to reflection and refraction at glass-air boundary
Solution Approach 1:
The patent modifies the optical parameters at the glass-air interface by introducing nanoscale surface features that change the refractive index gradient and reduce reflection losses. This allows photons to escape at angles beyond the conventional critical angle, significantly improving extraction efficiency while maintaining simple fabrication through standard surface treatment techniques.
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 metasurface enhances light extraction efficiency by allowing optical radiation to escape at angles greater than the critical angle, increasing transmittance by over 40% compared to traditional methods, while simplifying the fabrication process and reducing costs, facilitating mass production.
Implementation Method 1
Due to factors such as reflection and refraction occurred at a boundary between a glass substrate and air, most of photons generated by the existing LEDs and OLEDs cannot escape into the air
Implementation Method 2
Due to factors such as reflection and refraction occurred at a boundary between a glass substrate and air
Implementation Method 3
A metasurface with densely-packed nanostructures on a transmissive substrate, divided into quadrants by intersecting axes, which are polarization-insensitive and transmit optical radiation with different incident angles
Data Source
AI summary
Provided is a metasurface for improving a light extraction efficiency of a light-emitting diode, including a substrate and unit cells. The substrate being transmissive to optical radiation is on a metal oxide layer of the light-emitting diode. The unit cells are on a side of the substrate away from the metal oxide layer and formed in densely-packed patterns. A center and/or a vertex of each densely-packed pattern are respectively provided with a nanostructure. Nanostructures are divided into four quadrants by a first axis and a second axis. A projection of a cross-sectional quadrant pattern in any quadrant onto the first axis is the same as that onto the second axis. The cross-sectional quadrant pattern in any quadrant is mirrored along the two axes to form a cross-sectional pattern of the nanostructures. The first axis, the second axis and a height direction of the nanostructures are perpendicular to each other.