Busbar-Free Heterojunction Solar Cell Grid for Reliable Welding
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Solution Overview
Problem
Existing busbar-free heterojunction solar cells suffer from poor welding performance due to small contact points between welding bands and secondary grid lines, leading to issues like welding deviation, cold welding, and low yield rates.
Innovation Solution
A busbar-free heterojunction solar cell design featuring discontinuous first and second finger grid electrodes with different metal slurries, where the second electrode has better adhesion and a welding positioning groove for improved connectivity, ensuring both good conductive and welding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If busbars are directly removed to achieve busbar-free cell structure, then silver consumption and shading are reduced, but welding performance deteriorates due to small contact points between welding band and secondary grid lines
Solution Approach 1:
The finger grid electrode is segmented into two functional parts: first finger grid electrodes for current collection and second finger grid electrodes for welding connection. This segmentation allows each part to be optimized independently - the first electrodes maintain thin profile for low shading while the second electrodes provide adequate contact area for reliable welding, resolving the contradiction between reduced silver consumption and maintained welding performance
Solution Approach 2:
Different regions of the finger grid electrode structure are assigned different qualities: the first finger grid electrodes use conductive slurry optimized for electrical performance with lower adhesion, while the second finger grid electrodes use adhesive slurry optimized for welding connection with higher adhesion. This local differentiation enables simultaneous optimization of current collection efficiency and welding reliability without compromising overall performance
2Power
If conductive slurry is selected for first finger grid electrodes to focus on current collection, then electrical conductivity is improved, but adhesion force between slurry and cell body deteriorates
Solution Approach 1:
The patent applies different slurry formulations to different functional regions: the first finger grid electrodes use conductive slurry with high electrical conductivity but lower adhesion for optimal current collection, while the second finger grid electrodes use adhesive slurry with high bonding strength for reliable welding connections. This local quality differentiation resolves the contradiction by allowing each region to have the material properties it needs without compromising the other function
3Manufacturing precision
If welding positioning groove is added to second finger grid electrode, then welding precision is improved by preventing offsets, but device complexity increases
Solution Approach 1:
The welding positioning groove is pre-formed in the second finger grid electrode during the electrode fabrication process, creating a built-in positioning feature that guides the welding band placement. This preliminary action ensures accurate welding alignment without requiring additional positioning fixtures or complex assembly procedures, thus improving welding precision while minimizing increases in overall device complexity
Data Source
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AI summary
A busbar-free heterojunction solar cell comprises a cell body and a plurality of parallel finger grid electrodes provided on the front and back sides of the cell body, wherein each finger grid electrode comprises a plurality of first finger grid electrodes, a second finger grid electrode is provided between two adjacent first finger grid electrodes, both ends of the second finger grid electrode are respectively in lap-joint with the two adjacent first finger grid electrodes, and a welding positioning groove is formed in a middle portion of the second finger grid electrode. The structure of the solar cell can not only ensure good conductive performance of finger grid electrodes but also take into account good welding performance of the finger grid electrodes.