Solar Cell Collecting Electrode Copper Diffusion Prevention
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Solution Overview
Problem
Solar cell modules used outdoors require improved reliability in addition to output characteristics, particularly in terms of sealing and longevity.
Innovation Solution
A solar cell module structure featuring a substrate with amorphous layers, transparent conductive layers, and collecting electrodes with a multilayer structure including a primary conductive layer of copper and an overcoat or undercoat layer to prevent copper diffusion and oxidation, enhancing contact characteristics and sealing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as the primary conductive layer for collecting electrodes, then electrical conductivity is improved, but copper diffusion and oxidation occur which deteriorate reliability
Solution Approach 1:
An overcoat layer made of nickel, tin, or their alloy is applied over the copper primary conductive layer. This intermediary layer physically separates the copper from the sealing layer and environment, preventing direct contact that would cause oxidation and diffusion, while maintaining electrical conductivity through the layered structure.
Solution Approach 2:
The collecting electrode is constructed as a composite structure with multiple layers: a copper-based primary conductive layer for high conductivity, and an overcoat layer of nickel, tin, or their alloy for protection. This composite approach combines the advantages of different materials - copper's conductivity with nickel/tin's oxidation resistance.
2Reliability
If a multilayer structure with overcoat layer is applied to prevent copper diffusion, then reliability is improved, but device complexity increases
Solution Approach 1:
The thickness of the overcoat layer is optimized to be between 0.1-10 μm, and the copper layer thickness is controlled at 1-20 μm. By optimizing these dimensional parameters, the structure achieves adequate protection without excessive complexity. The specific material composition ratios are also tuned to balance protection and conductivity.
3Ease of manufacture
If copper plating is used for collecting electrodes, then manufacturing cost is reduced and conductivity is improved, but thermal expansion causes sealing deterioration
Solution Approach 1:
The multi-layer electrode structure with copper core and nickel/tin overcoat creates a composite material system with optimized thermal properties. The different materials have complementary thermal expansion characteristics that reduce overall thermal stress compared to pure copper, while maintaining the cost-effectiveness of copper plating.
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 solution improves the reliability of solar cell modules by inhibiting copper diffusion and oxidation, reducing thermal expansion, and maintaining effective conductivity, thus enhancing the module's durability and performance.
Implementation Method 1
an overcoat layer which covers the entire exposed exterior of the primary conductive layer
Implementation Method 2
inhibiting copper diffusion and oxidation
Implementation Method 3
reducing thermal expansion
Implementation Method 4
solar cells which can convert solar light into electrical energy
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A solar cell (100) has a collecting electrode (24) formed therein. The collecting electrode (24) is provided with: a main conductive layer (24a) that contains copper; and an overcoat layer (24b) that covers at least a part of the main conductive layer (24a) .