Multi-Junction Solar Cell Screening via Electroluminescence Imaging
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Solution Overview
Problem
Current methods for screening multi-junction solar cells for high intensity and high temperature environments are costly, time-consuming, and risk introducing artificial damage, as they require detailed electroluminescence imaging and exposure to simulated conditions, which is not feasible for large-scale solar arrays.
Innovation Solution
A method involving electroluminescence imaging to identify local intensity variations in homogeneous pn-junctions, separating cells into critical and uncritical groups, with further screening of critical cells to determine suitability for high sun intensity and high temperature environments, using a simplified and cost-effective process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If detailed electroluminescence imaging and simulated environment exposure are used for screening, then measurement precision and reliability are improved, but productivity increases and loss of time decreases
Solution Approach 1:
The screening process is divided into two distinct stages: a fast first pass using simplified electroluminescence imaging to identify obviously defective cells, and a second pass using detailed multi-junction imaging only on cells that failed the first screening. This segmentation allows the majority of cells to be screened quickly while maintaining high detection accuracy for critical defects.
Solution Approach 2:
The patent applies partial action by using only the necessary imaging depth and detail for each screening stage. The first pass uses superficial imaging sufficient to identify obvious shunts, while the second pass applies detailed imaging only where needed. This avoids the excessive action of applying full detailed imaging to all cells, thereby increasing productivity while maintaining measurement precision.
2Reliability
If simulated high intensity and high temperature environment exposure is used for screening, then reliability is improved, but object-generated harmful factors increase due to artificial damage
Solution Approach 1:
The patent performs preliminary screening using electroluminescence imaging to identify and eliminate obviously defective cells before subjecting them to simulated environment exposure. This preliminary action ensures that only cells with potential performance issues (not necessarily defective ones) are exposed to the simulated high intensity and high temperature environment, reducing the risk of artificial damage while maintaining reliability assessment accuracy.
Solution Approach 2:
The patent uses electroluminescence imaging as a non-destructive copy or proxy for assessing cell quality, rather than directly exposing all cells to the harsh simulated environment. The imaging creates a visual representation of cell health that can be analyzed without physical stress, reducing artificial damage while providing reliable performance predictions.
3Measurement precision
If detailed electroluminescence imaging of all junctions is performed, then measurement precision is improved, but device complexity and loss of time increase
Solution Approach 1:
The imaging system is segmented into two operational modes: a simple first pass using basic electroluminescence imaging with minimal filtering requirements, and a second pass using more complex multi-junction imaging with specific filters. This segmentation allows the system to maintain high measurement precision when needed while reducing device complexity for the majority of screenings.
Solution Approach 2:
The patent applies partial action by using the full complexity of multi-junction imaging only when necessary (in the second pass for cells that failed the first screening). For the majority of cells, a simpler imaging approach suffices. This reduces the average device complexity and time requirements while maintaining the capability for high-precision defect classification when needed.
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 method allows for rapid and cost-efficient screening of solar cells, reducing the risk of artificial damage and identifying cells susceptible to overheating, thereby ensuring reliable performance in extreme environments.
Implementation Method 1
The electroluminescence radiation emitted by a given junction is recorded with an appropriate detector
Data Source
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AI summary
The invention describes a method for screening of multi-junction solar cells to be operated in a high sun intensity and high temperature (HIHT) environment. Each of the solar cells comprises at least two pn-junctions (2,3,6) stacked on top of each other wherein one of the pn-junctions (6) is a completely homogeneous pn-junction assumed to be free of intrinsic defects. A number of solar cells to be screened for usability in a HIHT environment are provided. For each solar cell of the number of solar cells an electroluminescence (EL) image of the homogeneous pn-junction at a predefined bias current (Isc) is acquired. Further, for each of the solar cells, the spatial intensity distribution in the electroluminescence image is analyzed to determine whether there are local intensity variations which possibly dissipate power in a HIHT environment. The solar cells are assorted wherein solar cells having no local intensity variations in their electroluminescence image are put into a first group (A) of solar cells and solar cells having at least one local intensity variation in their electroluminescence image are put into a second group (B) of solar cells for further screening. The solar cells of the first group (A) are suitable for a HIHT environment and solar cells of the second group (B) are assumed to be potentially critical in a HIHT environment.