Photovoltaic Cell Interconnection by Localized Laser Welding
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Solution Overview
Problem
Existing interconnection methods for photovoltaic cells, particularly in space applications, face challenges with temperature constraints and thermal expansion issues, leading to material embrittlement and cracking, especially when using materials like tin and requiring localized high-temperature welding without damaging temperature-sensitive cells.
Innovation Solution
A laser welding device and method for interconnecting photovoltaic cells by localized fusion, utilizing a laser head with a turning unit and gripping members to rotate cells, allowing welding on both sides without excessive heat exposure, using a laser beam mask for precise welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If localized high-temperature welding is used to interconnect photovoltaic cells, then interconnection strength and electrical conductivity are improved, but temperature-sensitive cells may be damaged due to excessive heat exposure
Solution Approach 1:
The patent applies localized heating through a laser beam that concentrates thermal energy precisely at the interconnection points between photovoltaic cells. The heating unit moves along the cells to deliver heat only where needed, maintaining high interconnection temperatures without exposing the entire cell structure to damaging thermal conditions. This resolves the contradiction by creating a local high-temperature zone for reliable welding while preserving the integrity of temperature-sensitive cell regions.
2Reliability
If conventional brazing with filler metal is used for interconnection, then good ohmic contact is achieved at temperatures below 400°C, but material embrittlement and cracking occur in space applications due to thermal expansion issues
Solution Approach 1:
The patent eliminates filler metals from the interconnection process by using direct laser welding of the base metals (silver, copper, aluminum). This extraction of the filler metal component removes the source of thermal expansion mismatch that causes embrittlement and cracking in space applications. The process achieves reliable ohmic contact through direct metal-to-metal welding without the intermediate filler layer that creates structural weaknesses under thermal cycling.
Solution Approach 2:
The patent replaces the mechanical brazing process with a thermal laser welding process. Instead of using filler metal and conventional heating methods, a laser beam provides concentrated thermal energy to melt and fuse the base metals directly. This substitution eliminates the mechanical constraints of brazing and the associated thermal expansion problems, achieving both good electrical contact and resistance to embrittlement.
3Stability of the object's composition
If simultaneous brazing of front and back faces is performed by heating, then bowing is prevented, but the required temperature exceeds 200°C which is incompatible with temperature-sensitive photovoltaic cells
Solution Approach 1:
The patent divides the interconnection process into separate sequential steps for the front face and back face of the photovoltaic cells. The laser welding unit performs localized welding on one face, then moves to the other face independently. This segmentation allows precise temperature control at each location and time, preventing the accumulation of thermal energy that would require excessive temperatures for simultaneous brazing, while still maintaining cell stability through controlled localized heating.
Solution Approach 2:
The patent performs preliminary positioning and preparation of the photovoltaic cells before laser welding begins. The cells are properly aligned and secured on the support structure, ensuring stability during the welding process. This preliminary action prevents bowing and misalignment without requiring excessive heating temperatures, as the mechanical stability is established before thermal processing begins.
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 robust interconnection with excellent ohmic conductivity, overcoming thermal expansion challenges and maintaining cell integrity, suitable for various cell types including temperature-sensitive ones.
Implementation Method 1
a laser welding unit (20) comprising a laser head (20t) configured to perform at least one laser shot for a localized fusion of at least one connecting conductor (6)
Implementation Method 2
a unit for turning said at least one photovoltaic cell, comprising: a first gripping member (30p1) for gripping one of the front or rear faces of said at least one photovoltaic cell, the first gripping member being capable of pivoting through a first angle of rotation of at least 180°
Data Source
Figure 1
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AI summary
The invention relates to a laser welding interconnection device (100) of photovoltaic cells (4) to form at least one chain (S) of photovoltaic cells (4) interconnected by connecting conductors (6), characterized in that it comprises: a laser welding unit (20) comprising a laser head (20t) configured to perform at least one laser shot for the local fusion of at least one connecting conductor (6) positioned on the front face (4a) or the rear face (4b) of at least one photovoltaic cell (4); and a turning unit (30), comprising a first gripping member (30p1) for gripping one of the front face (4a) or the rear face (4b), capable of pivoting according to a first angle of rotation (R1) of at least 180°, and a second gripping member (30p2) for gripping the other of the front face (4a) or the rear face (4b).