Solar Cell Collecting Electrode via Copper Plating
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Solution Overview
Problem
Existing solar cell manufacturing methods face challenges in forming low-resistance collecting electrodes by plating without using resist materials, particularly for heterojunction solar cells, and in preventing short circuits and metal component diffusion into the substrate, which affects the conversion efficiency and reliability of solar cells.
Innovation Solution
A solar cell configuration with a collecting electrode comprising a first electroconductive layer, a second electroconductive layer, and an insulating layer, where the insulating layer has openings for conduction between the layers, and an insulating region on the photoelectric conversion section to prevent short circuits and substrate diffusion, formed using a plating method that includes a low-melting-point material and copper as the main component for the second electroconductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silver paste is used to form a collecting electrode by screen printing, then the electrode can be formed simply, but the material cost increases and the resistivity increases
Solution Approach 1:
The patent changes the material composition parameters by using copper powder with specific particle size distributions (D10, D50, D90 values) and combining multiple particle size fractions. This parameter optimization allows copper to achieve low resistivity (comparable to or better than silver paste) while maintaining simple screen printing formation, resolving the contradiction between ease of manufacture and electrical performance
Solution Approach 2:
The patent replaces expensive silver paste with copper powder, which is significantly cheaper. The copper powder is mixed with organic vehicles and applied via screen printing, then sintered to form a functional collecting electrode. This substitution reduces material cost while maintaining manufacturing simplicity and achieving acceptable resistivity through optimized particle size distribution
2Reliability
If the silver paste is thickly printed to decrease resistivity, then the resistivity decreases, but the line width increases and shading loss increases
Solution Approach 1:
The patent changes the particle size distribution parameters of copper powder, using a multi-modal distribution with specific D10, D50, and D90 values. This allows the formation of dense, low-resistivity electrodes at thinner print thicknesses compared to conventional silver paste, because the optimized copper particle packing and sintering behavior achieve better conductivity per unit thickness, thereby reducing both resistivity and line width simultaneously
Solution Approach 2:
The patent uses a composite copper powder formulation combining different particle size fractions (fine powder with D50≤10μm and medium powder with 10μm<D50≤20μm) mixed in specific ratios. This composite structure improves flowability, packing density, and sintering characteristics, enabling thin electrode formation with low resistivity, thus resolving the contradiction between resistivity reduction and shading loss
3Ease of manufacture
If a plating method is used to form a collecting electrode, then material and process costs decrease, but metal component diffusion into the substrate occurs causing short circuits
Solution Approach 1:
The patent extracts and removes the problematic resist material step from the conventional plating process. Instead of using resist patterns for metal deposition, the patent directly applies copper powder paste through screen printing and sintering. This eliminates the risk of metal diffusion into the substrate that occurs with electroplating through resist openings, while maintaining cost effectiveness by avoiding expensive resist materials and complex deposition equipment
Solution Approach 2:
The patent replaces the electrochemical plating process (which requires electrical equipment, electrolytes, and resist processing) with a thermal sintering process. Copper powder paste is applied by screen printing and then sintered in a furnace at controlled temperatures. This mechanical/thermal substitution eliminates metal diffusion into the substrate while maintaining low costs and simplifying the manufacturing process
4Reliability
If thin-films are formed by plasma-enhanced CVD or sputtering, then the photoelectric conversion section is formed, but wraparound causes short circuits and leakage
Solution Approach 1:
The patent applies a protective insulating coating (such as silicon oxide or silicon nitride) on the crystalline silicon substrate before forming the photoelectric conversion thin-films. This preliminary protective layer prevents metal components from the subsequent electrode layers from diffusing into the substrate and causing short circuits, while allowing the thin-film deposition processes to proceed normally and form functional photoelectric conversion sections
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 configuration reduces material and process costs while improving conversion efficiency and reliability by minimizing resistance and preventing short circuits and substrate contamination, leading to enhanced initial and long-term solar cell performance.
Implementation Method 1
a collecting electrode formed by a plating method
Implementation Method 2
the insulating layer is provided with an opening, and the first electroconductive layer and the second electroconductive layer are in conduction with each other via the opening
Data Source
Figure 1~2
Figure 3
Figure 4(A1)~4(C2)
AI summary
A solar cell of the invention includes a photoelectric conversion section (50) and a collecting electrode (70). The photoelectric conversion section (50) has a first principal surface and a second principal surface, and the collecting electrode (70) is formed on the first principal surface. The collecting electrode (70) includes a first electroconductive layer (71) and a second electroconductive layer (72) in this order from the photoelectric conversion section (50) side, and includes an insulating layer (9) between the first electroconductive layer (71) and the second electroconductive layer (72). The insulating layer (9) is provided with an opening, and the first electroconductive layer (71) and the second electroconductive layer (72) are in conduction with each other via the opening provided in the insulating layer (9). The solar cell has, on the first principal surface, the second principal surface or a side surface of the photoelectric conversion section, an insulating region freed of a short circuit of front and back sides of the photoelectric conversion section, and the surface of the insulating region is at least partially covered with the insulating layer.