Back-Contact Solar Cell String Bonding to Reduce Warping
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Solution Overview
Problem
The existing methods for manufacturing photovoltaic modules using back contact solar cells face issues with warping due to soldering stress, leading to increased defective rates and hidden cracks, as the positive and negative electrodes on the rear surface cannot effectively manage soldering stress.
Innovation Solution
A method involving the application of an insulating adhesive on the rear surface of back contact solar cells, where the solder strip is bonded using ultraviolet curing, ensuring stable connection and reducing warping by preventing direct soldering stress, and optionally reinforcing the solder strip with additional adhesive for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If soldering is used to connect the solder strip to the solar cell, then the connection strength is improved, but the solar cell warping increases due to soldering stress
Solution Approach 1:
The patent introduces an insulating adhesive as an intermediary substance between the solder strip and the solar cell. This adhesive layer serves as a mediator that provides mechanical bonding without transmitting the harmful thermal and mechanical stress of soldering to the solar cell, thereby preventing warping while maintaining connection strength.
Solution Approach 2:
The patent replaces the traditional soldering process (which relies on thermal-mechanical bonding) with an adhesive bonding process. This substitution eliminates the need for high-temperature soldering and the associated thermal stress, thereby preventing solar cell warping while achieving reliable electrical and mechanical connection.
2Reliability
If soldering stress is applied to back contact solar cells, then the solder strip connection is achieved, but the defective rate increases due to hidden cracks
Solution Approach 1:
The insulating adhesive acts as a protective intermediary that decouples the solder strip from direct contact with the solar cell's fragile back contact structure. This intermediary layer distributes mechanical stress uniformly and prevents concentrated loads that would otherwise cause hidden cracks in the solar cell.
Solution Approach 2:
The patent applies the insulating adhesive beforehand to create a cushioning layer that absorbs and distributes mechanical stress before it reaches the solar cell. This pre-established protective layer prevents the formation of hidden cracks during subsequent handling and module assembly processes.
3Reliability
If the solder strip is directly connected to the busbar without insulating adhesive, then the electrical connection is improved, but the warping and defective rate increase
Solution Approach 1:
The insulating adhesive serves as a functional intermediary that simultaneously provides mechanical bonding and electrical insulation. It enables the solder strip to be securely mounted on the solar cell while electrically isolating it from the busbar, preventing short circuits and maintaining reliable electrical connection through the intended soldering path.
Solution Approach 2:
The patent applies the insulating adhesive locally at specific positions where the solder strip contacts the solar cell, rather than uniformly across the entire surface. This localized application provides precise mechanical support and electrical insulation only where needed, maintaining good electrical contact at the busbar interface while preventing warping.
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 reduces the warping of solar cells, improves the connection reliability, and decreases the defective rate of photovoltaic modules by stabilizing the solder strip connection and enhancing the structural integrity of the module.
Implementation Method 1
curing the insulating adhesive by irradiation with an ultraviolet lamp to fixedly connect the solder strip to the solar cells
Data Source
AI summary
A method for manufacturing photovoltaic module includes: providing solar cells and a solder strip; applying insulating adhesive on rear surface of the solar cells; laying the solar cells along a first direction; placing the solder strip on the solar cells so that, along the first direction, one end of the solder strip abuts against a positive busbar of one solar cell, and is bonded to the insulating adhesive, and the other end of the solder strip abuts against a negative busbar of another solar cell adjacent thereto, and is bonded to the insulating adhesive; curing the insulating adhesive by irradiation with an ultraviolet lamp, so that the solar cells form a solar cell string; arranging the solar cell strings along a second direction, and connecting to form a photovoltaic cell pack; providing and laminating front packaging structure, the photovoltaic cell pack, and back packaging structure to form the photovoltaic module.