Multi-junction Solar Cell Inspection via Infrared Specular Reflection
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Solution Overview
Problem
Current inspection methods are inadequate for detecting defects, particularly micro-cracks, in multi-junction solar cells, as they are either slow, invasive, or limited to the cell level, and cannot effectively inspect multi-junction cells.
Innovation Solution
A method using a flat-panel infrared illuminator oriented at a selected incident angle to illuminate multi-junction solar cells, combined with an infrared camera to capture specularly reflected radiation, providing high-contrast images of defects, including micro-cracks, across a wide range of angles and applicable to both individual cells and solar panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photo-acoustic method is used to detect micro-cracks, then detection capability is improved, but inspection speed deteriorates and the process becomes invasive requiring water spray
Solution Approach 1:
The patent replaces the mechanical photo-acoustic method with an optical inspection system using a ring illuminator and camera. The optical system captures images of micro-cracks without physical contact or water spray, eliminating the invasiveness and speed limitations of the photo-acoustic method while maintaining detection capability
Solution Approach 2:
The patent introduces an optical intermediary system (ring illuminator and camera) that mediates between the solar cell and the detection process. This intermediary allows non-invasive imaging by capturing reflected or transmitted light patterns that reveal micro-crack locations without requiring water spray or physical interaction
2Productivity
If conventional inspection methods are used, then inspection speed is maintained, but detection capability for multi-junction cells deteriorates
Solution Approach 1:
The patent changes the inspection parameters by using a ring illuminator geometry and specific wavelength lighting that works effectively for multi-junction cells. This parameter change enables both high inspection speed and improved defect detection capability, resolving the contradiction between speed and precision for multi-junction cell inspection
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
Enables quick, non-invasive detection of defects and micro-cracks in multi-junction solar cells and panels, providing high-contrast images that enhance the ability to identify cracks and other defects, addressing the limitations of existing methods.
Implementation Method 1
The illuminating step employs a range of wavelengths, including a band at which the solar cell materials are relatively transparent. For example, the illuminator radiates light over a broad band of infrared wavelengths
Implementation Method 2
positioning an infrared camera to receive specularly reflected radiation from the at least one multi-junction solar cell
Data Source
AI summary
A technique for providing high-contrast images of defects in solar cells and solar panels, by illuminating each cell under inspection with broadband infrared radiation, and then forming an image of radiation that is secularly reflected from the cell. Multi-junction solar cells have a metal backing layer that secularly reflects the illumination back into an appropriately positioned and aligned camera, selected to be sensitive to infrared wavelengths at which the solar cell materials are relatively transparent.