Laser Beam Processing for Thin Film Solar Cells
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Solution Overview
Problem
Current laser beam processing methods face challenges in achieving high precision on elements with low mechanical stability and low light transmittance, such as thin film solar cells, due to limited lateral precision, difficulty in establishing the laser beam position, and inadequate contrast for image processing.
Innovation Solution
A method and apparatus for laser beam processing that involves illuminating the element with light of a predetermined wavelength, recording residual light, determining and adjusting the laser beam position using alignment marks, and employing a scanning unit and mounting means to maintain precision, especially for elements with low total transmittance of at least 10−5, allowing for high-precision processing of multilayered thin films on substrates like polymer or glass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera with suitable optics is used to determine the exact position of the laser beam, then measurement precision is improved, but device complexity increases due to the need for additional optical components and beam separation
Solution Approach 1:
Instead of observing the laser beam directly through complex optical paths, the invention illuminates the workpiece from the opposite side and observes the transmitted light pattern. This inversion of the observation approach eliminates the need for beam separation optics and complex camera systems while maintaining high positioning precision
Solution Approach 2:
The invention extracts only the essential information needed for positioning by using simple transmission light observation through the workpiece, removing the complexity of beam separation optics, dichotic beam splitters, and chromatic error compensation components required in conventional methods
2Ease of operation
If scanning mirrors are used to deflect the laser beam, then ease of operation is improved, but manufacturing precision deteriorates due to temperature and long term drift
Solution Approach 1:
The invention uses real-time observation of the transmitted light pattern to continuously monitor and determine the actual laser beam position, providing feedback that compensates for any drift or positioning errors, thereby maintaining high manufacturing precision despite the use of scanning mirrors
Solution Approach 2:
The invention replaces reliance on mechanical stability of scanning mirrors with an optical observation system that directly measures the laser beam position through transmitted light patterns, substituting mechanical precision requirements with optical measurement
3Measurement precision
If illumination is used to improve image contrast for low transmittance elements, then measurement precision is improved, but object-generated harmful factors increase due to reflections from the top surface
Solution Approach 1:
Instead of illuminating from the top side where reflections occur, the invention illuminates the workpiece from the bottom side and observes transmitted light, inverting the illumination and observation path to eliminate surface reflection interference while maintaining image contrast
Solution Approach 2:
The invention converts the low light transmittance of the workpiece, which was previously a harmful factor reducing image contrast, into a beneficial feature by observing the transmitted light pattern that directly reveals the laser beam position through the workpiece structure
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
This approach enables precise positioning and processing of laser beams on elements with low light transmittance, improving the accuracy and effectiveness of laser beam processing for thin film solar cells and other low-contrast substrates by enhancing contrast and maintaining precise alignment.
Implementation Method 1
illuminating the to-be-processed element on the other side by light of a illumination unit, the light having at least one predetermined wavelength; recording residual light on the one side, which residual light results from a light transmission through the to-be-processed element
Data Source
AI summary
A method and an apparatus for laser beam processing of an element (12) that has a total transmittance for light of at least 10−5, comprising a laser unit (1) for generating a laser beam on one side of the to-be-processed element (12), an illumination unit (7), an imaging system (10) comprising a sensor unit on the one side of the to-be-processed element (12), the sensor unit recording residual light that results from light of the illumination unit (7), a scanning unit (2) for adjusting the laser beam processing position, and a control unit. The control unit is operatively connected to the laser unit (1), the imaging system (10) and the scanning unit (2), and the illumination unit (7) is positioned on the other side of the to-be-processed element (12) in relation to the laser unit (1). Since the to-be-processed element (12) allows light to pass through an otherwise opaque or almost opaque layer, a good contrast is obtained that is used to determine the position of the laser beam with high precision.Therefore, high precision laser processing is possible for materials with low transmission for light and low mechanical stability like flexible thin film solar cells.