Copper Gridline Electroplating for Breakage-Resistant Solar Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in existing copper gridline manufacturing is the occurrence of gridline breakage and gridline false breakage during the electroplating process, which significantly affects the production yield and conversion efficiency of solar cells.
Innovation Solution
A method involving a degreasing treatment followed by a second development process to enhance the solubility of residual photoresist at the bottom of patterned recesses, forming copper grid lines with a positive trapezoidal cross-section morphology, thereby improving contact with the copper seed layer and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If copper electroplating interconnection is used to replace screen-printed silver paste, then metallization cost is significantly reduced, but gridline breakage and gridline false breakage occur frequently
Solution Approach 1:
The patent applies preliminary action by performing a degreasing treatment on the solar cell substrate before the second development step. This preliminary degreasing removes organic contaminants and prepares the surface, ensuring better adhesion and reducing gridline defects during subsequent electroplating. The degreasing treatment is conducted before photoresist removal to prevent gridline breakage and false breakage.
2Loss of energy
If gridline width is reduced to minimize shadowing loss, then power loss from shadowing is reduced, but gridline breakage and false breakage increase significantly
Solution Approach 1:
The patent applies preliminary action by performing a degreasing treatment on the solar cell substrate before the second development step. This preliminary degreasing removes organic contaminants and prepares the surface, ensuring better adhesion and reducing gridline defects during subsequent electroplating. The degreasing treatment is conducted before photoresist removal to prevent gridline breakage and false breakage.
Solution Approach 2:
The patent applies parameter changes by modifying the photoresist development process parameters. Specifically, it introduces a second development step with controlled development time and solution concentration, which optimizes the etching profile to create copper grid lines with better mechanical strength and reduced susceptibility to breakage, even at reduced widths.
3Device complexity
If conventional single development process is used, then manufacturing process is simple, but residual photoresist remains at the bottom of patterned recesses causing gridline defects
Solution Approach 1:
The patent applies segmentation by dividing the photoresist development process into two distinct steps: a first development step and a second development step. The first development creates the initial pattern, while the second development, performed after degreasing, completely removes residual photoresist from the bottom of patterned recesses. This segmented approach ensures high manufacturing precision and eliminates gridline defects.
Solution Approach 2:
The patent applies preliminary action by performing a degreasing treatment on the solar cell substrate before the second development step. This preliminary degreasing removes organic contaminants and prepares the surface, ensuring better adhesion and reducing gridline defects during subsequent electroplating. The degreasing treatment is conducted before photoresist removal to prevent gridline breakage and false breakage.
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 effectively reduces gridline breakage and false breakage, enhancing production yield and conversion efficiency by optimizing the copper grid line morphology and reducing light-shielding areas.
Implementation Method 1
performing exposure and a first development on the negative photoresist layer sequentially to form a patterned recess on the negative photoresist layer
Implementation Method 2
performing a degreasing treatment on the solar cell substrate after the first development, so as to increase solubility of a negative photoresist at both sides of a bottom of the patterned recess in a developing solution
Implementation Method 3
performing electroplating in the patterned recess after the second development to form copper grid lines
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Provided in the present application are a solar cell and a preparation method therefor. The preparation method comprises the following steps: providing a solar cell substrate, wherein the surface of the solar cell substrate is provided with a copper seed layer; forming a negative photoresist layer on the copper seed layer; sequentially performing exposure and first development on the negative photoresist layer to form a patterned recess on the negative photoresist layer; performing degreasing treatment on the solar cell substrate that has been subjected to first development, so as to increase the solubility, in a developing solution, of negative photoresist at both sides of the bottom of the patterned recess; performing second development on the negative photoresist layer that has been subjected to degreasing treatment; and performing electroplating in the patterned recess that has been subjected to second development, so as to form copper grid lines. The preparation method in the present application can effectively alleviate the situation where copper grid lines have grid-line breakage and virtual grid-line breakage, thereby improving the production yield and conversion efficiency of solar cells.