Light-guide Sheet with Concentric Diffraction Grating
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Solution Overview
Problem
Conventional light-guide sheets face challenges in efficiently trapping and guiding incident light over a wide area due to limitations in refractive index and diffraction grating design, which restricts the angle and wavelength range of light that can be coupled and propagated.
Innovation Solution
A light-guide sheet with a stacked structure of alternating higher and lower refractive index layers, featuring a diffraction grating with a concentric circular or polygonal pattern, that changes the traveling direction of incident light and enhances the emission angle, allowing for efficient trapping and guiding of light with a wide wavelength and angle range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional diffraction grating with linear or simple periodic pattern is used, then the structure is simple and easy to manufacture, but the light coupling efficiency and wavelength range are limited
Solution Approach 1:
The patent applies curved diffraction grating patterns including concentric circular patterns, arc patterns, and patterns following curved lines. This curvature enables the diffraction grating to couple light over a wider wavelength range and incident angle range compared to linear periodic patterns, while maintaining manufacturability through standard photolithography and etching processes.
Solution Approach 2:
The diffraction grating pattern is divided into multiple independent curved line segments that can be independently optimized. These segmented curved patterns allow for broader light coupling by distributing diffraction effects across multiple orientations and curvatures, improving overall efficiency without complicating the manufacturing process.
2Device complexity
If a single-layer light-transmissive structure is used, then the structure is simple, but the light trapping efficiency and guiding capability are insufficient
Solution Approach 1:
The patent employs a composite multi-layer structure consisting of alternating high-refractive-index and low-refractive-index layers. This composite structure creates enhanced light trapping through repeated refraction and reflection at interfaces, improves waveguiding capability, and broadens the operational wavelength range while maintaining a relatively simple planar fabrication process.
Solution Approach 2:
The light-guide sheet structure nests multiple functional layers within each other, with the diffraction grating pattern embedded within the multi-layer light-transmissive structure. This nested configuration allows the diffraction grating to work in conjunction with the layered refractive index modulation to achieve superior light trapping and guiding efficiency.
3Productivity
If the diffraction grating pattern covers the entire light-guide sheet, then the light trapping is maximized, but the manufacturing precision and pattern alignment become difficult to control
Solution Approach 1:
The diffraction grating pattern is segmented into multiple independent curved line segments distributed across the light-guide sheet. This segmentation allows each segment to be independently formed during manufacturing, reducing the cumulative alignment errors that would occur with a continuous full-sheet pattern, while still achieving comprehensive light trapping coverage.
Solution Approach 2:
Rather than requiring complete continuous coverage, the patent uses multiple discrete curved pattern segments that provide sufficient light trapping efficiency through their distributed arrangement. This partial coverage approach reduces manufacturing complexity and alignment requirements while maintaining effective light management across the device area.
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 proposed light-guide sheet effectively traps and directs incident light over a wide area, improving coupling efficiency and enabling efficient photoelectric conversion by guiding light to a photoelectric conversion element, thereby enhancing power generation capabilities.
Implementation Method 1
a diffraction grating that is disposed on the light-transmissive layer and changes a travelling direction of the incident light
Implementation Method 2
a light-transmissive layer that is continuously stacked with the lower refractive index layer and has a refractive index that is higher than a refractive index of the lower refractive index layer
Data Source
AI summary
A light-guide sheet according to the present disclosure is a light-guide sheet that takes in incident light and waveguides light in a direction intersecting with an incident direction of the incident light inside the light-guide sheet. The light-guide sheet includes: a lower refractive index layer; a light-transmissive layer that is continuously stacked with the lower refractive index layer and has a refractive index that is higher than a refractive index of the lower refractive index layer; and a diffraction grating that is disposed on the light-transmissive layer and changes a travelling direction of the incident light. A pattern of the diffraction grating is divided into a plurality of partial patterns on the light-transmissive layer, and each of the plurality of partial patterns has a concentric circular shape or a concentric polygonal shape.