Solar Cell Electrode Material for Narrow Groove Filling
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Solution Overview
Problem
Existing methods for forming buried-type electrodes in solar cells face challenges such as instability in electrode formation, high resistance loss, delamination, and increased series resistance due to issues with electrode material viscosity, composition, and firing processes, leading to reduced solar cell power and efficiency.
Innovation Solution
An electrode material comprising 75 wt % to 95 wt % silver powder with a specific grain size ratio and a glass frit, along with an organic vehicle, is used to create a stable and low-resistance electrode that can be easily filled into grooves, preventing delamination and resistance loss, and enhancing the solar cell's power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a screen printing method is used to form a finger electrode, then the electrode formation process is simple and fast, but the electrode width becomes large (120 μm) causing increased shadow loss and reduced light acceptance area
Solution Approach 1:
The electrode formation process is segmented into two distinct steps: first forming a narrow groove (30 μm width) in the semiconductor substrate, then filling the groove with electrode material. This segmentation allows the final electrode to have a narrow width that minimizes shadow loss while maintaining formation efficiency through the screen printing method.
Solution Approach 2:
The electrode is transitioned from a surface-level structure to a three-dimensional groove-filled structure. By forming the electrode within a groove rather than on the surface, the effective width is reduced while the cross-sectional area is increased, thereby reducing shadow loss without increasing resistance.
2Area of stationary object
If a plating method is used to form a buried-type electrode, then the electrode width can be reduced (30 μm) and light acceptance area enlarged, but the process becomes complex requiring strict control of bath components, pH, and temperature
Solution Approach 1:
The complex electrochemical plating process is replaced with a mechanical screen printing process. The screen printing method uses a simple mask-and-print mechanism to deposit electrode material into pre-formed grooves, eliminating the need for complex bath component control, pH adjustment, and temperature management required by plating methods.
3Ease of manufacture
If the electrode material viscosity is lowered to 40-100 Pa·s to enable easy flow into grooves, then the electrode material can be filled into grooves more easily, but the material leaks out of grooves causing blur and increased electrode width
Solution Approach 1:
The viscosity parameter of the electrode material is optimized to a specific range (40-100 Pa·s) that balances two competing requirements: low enough viscosity to enable complete filling of grooves during screen printing, but high enough to prevent leakage and blur. This precise parameter control ensures both ease of manufacture and manufacturing precision.
4Productivity
If a screen printing method is used with conventional electrode material, then the process is simple and fast, but the binder component is burnt out during firing causing constriction of silver grains, insufficient groove filling, and delamination
Solution Approach 1:
The composition parameters of the electrode material are modified by adjusting the silver powder content (75-95 wt%) and using a dual-grain-size distribution. This compositional change ensures that during firing, the material maintains adequate binder content to prevent delamination while achieving complete groove filling and proper sintering, all through a simple screen printing process.
Solution Approach 2:
The electrode material is formulated as a composite with specific silver powder grain size distribution (0.5-3 μm and 4-8 μm) combined with binder and other components. This composite structure ensures that during firing, the material exhibits appropriate flow characteristics for complete groove filling while maintaining adhesion to prevent delamination, resolving the contradiction between simple processing and reliable electrode formation.
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
The proposed electrode material allows for the stable formation of narrow-line-width electrodes with reduced resistance loss, preventing delamination and breaking, and achieving high-power solar cell production with improved efficiency and cost-effectiveness.
Implementation Method 1
a viscosity of the electrode material is 150 Pa·s to 400 Pa·s
Implementation Method 2
decomposition gas in the time of the burning-out loses vents and expands in the groove
Implementation Method 3
a binder component contained in the electrode material is burnt out in firing the electrode material
Implementation Method 4
the electrode material is constricted by sintering of silver grains
Data Source
AI summary
The present invention is an electrode material comprising at least, a silver powder, a glass frit, and an organic vehicle, wherein a rate of Ag content of the electrode material is 75 wt % to 95 wt %, and a ratio of contents of Ag grains having an average grain diameter of 0.5 μm to 3 μm and Ag grains having an average grain diameter of 4 μm to 8 μm in the electrode material is (the Ag grains having an average grain diameter of 0.5 μm to 3 μm):(the Ag grains having an average grain diameter of 4 μm to 8 μm)=20-80 wt %:80-20 wt %, and a solar cell comprising an electrode formed by using the electrode material. Thereby, an electrode material that can be stably filled in an electrode groove formed on a semiconductor device and that an electrode with narrow line width and small resistance loss can be easily formed by, and a solar cell with high power having an electrode formed by using the electrode material are provided.