Optical Mask Microstructures for LED Light Extraction
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Solution Overview
Problem
LEDs suffer from significant photon loss due to total internal refraction, leading to inefficient light extraction, which can be improved by using patterned sapphire substrates with nano-arrays to enhance luminosity and light extraction efficiency.
Innovation Solution
An optical mask with an array of microstructures on a mask substrate is used in photolithography to transform uniform optical exposure into specific patterns, allowing for the fabrication of patterned substrates with nano-arrays that optimize light reflection and extraction, utilizing self-assembly monolayers of microstructures with refractive indices greater than 1.4 and materials like polystyrene or PMMA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a flat sapphire substrate is used, then the manufacturing process is simple, but light extraction efficiency is poor due to total internal refraction
Solution Approach 1:
The patent applies spherical microstructures (microspheres) on the sapphire substrate surface to replace the flat surface. These spherical structures act as microlenses that focus and extract light more efficiently, reducing total internal refraction losses while maintaining manufacturing simplicity through self-assembly processes
Solution Approach 2:
The patent employs self-assembly of microspheres on the substrate surface, where the microspheres automatically organize into ordered arrays without requiring complex external patterning tools. This self-organizing behavior simplifies the manufacturing process while achieving the desired light extraction enhancement
2Productivity
If nano-arrays are applied on the sapphire-air interface, then light extraction efficiency is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent utilizes the self-assembly property of microspheres to automatically form ordered nano-arrays on the sapphire substrate. This self-organization eliminates the need for complex lithography or nanofabrication tools, significantly reducing manufacturing complexity while achieving high light extraction efficiency
Solution Approach 2:
The patent uses a template or intermediate substrate that guides the self-assembly of microspheres into the desired pattern. This template copying approach allows replication of complex nano-arrays without requiring direct fabrication of each feature, simplifying the manufacturing process
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 optical mask effectively enhances light extraction efficiency by creating precise nanostructures on sapphire substrates, improving LED performance by over 400% compared to planar substrates, and allows for cost-effective and high-throughput fabrication of patterned substrates with improved luminosity.
Implementation Method 1
each of the microstructures is arranged to at least partially converge the uniform optical exposure thereby forming the array of optical exposure patterns
Implementation Method 2
Due to total internal refraction, which is the reflection of photons upon entering a different medium with a lower refractive index
Implementation Method 3
the array of microstructures defines a self-assembly monolayer of microstructures on the mask substrate
Implementation Method 4
the step of forming the self-assembly monolayer of microstructures on a solution surface
Data Source
AI summary
An optical mask for use in a photolithography process, a method for fabricating the optical mask, and a method for fabricating an array of patterns on a substrate using the optical mask, wherein the optical mask includes an array of microstructures disposed on a mask substrate, and wherein the array of microstructures is arranged to transform a uniform optical exposure passing therethrough to an array of optical exposure patterns.