Copper Electrodes in Solar Cells Using Germanium-Glass Frit Paste
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Solution Overview
Problem
The use of precious metals like silver in solar cell electrodes is costly, and copper, although cheaper, oxidizes easily, requiring expensive nitrogen-based firing processes, which increases capital investment and electrode resistance.
Innovation Solution
A copper-containing conductive paste with a powder mixture of copper and crystalline germanium particles, dispersed in an organic medium with glass frit, is applied and fired in air, reducing oxidation and achieving low resistance electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper powder is used instead of precious metals, then material cost decreases, but copper oxidizes easily requiring nitrogen atmosphere firing which increases capital investment
Solution Approach 1:
Glass frit acts as an intermediary substance that forms a protective barrier around copper particles during firing, preventing direct contact between copper and oxygen in the air atmosphere, thus eliminating the need for expensive nitrogen atmosphere equipment while maintaining low oxidation
Solution Approach 2:
The conductive paste is formulated as a composite material containing copper powder, glass frit, and organic vehicle. This composite structure allows copper to benefit from glass frit's oxidation resistance properties, enabling air firing without requiring expensive inert atmosphere equipment
2Quantity of substance
If copper powder is used instead of precious metals, then material cost decreases, but electrode resistance increases due to oxidation
Solution Approach 1:
Glass frit serves as a protective intermediary that forms a glassy matrix around copper particles during firing, physically isolating copper from oxygen and preventing oxidation that would increase resistance, thereby maintaining low electrode resistance while using inexpensive copper
Solution Approach 2:
The composite paste formulation combines copper's excellent conductivity with glass frit's protective characteristics, creating a synergistic material that achieves both low cost and low resistance performance that neither material could achieve alone
3Device complexity
If copper is fired in air, then capital investment decreases, but copper oxidation increases leading to higher resistance
Solution Approach 1:
The paste formulation accepts the presence of oxygen in air atmosphere but converts the potential harmful oxidation into a beneficial process where glass frit reacts with oxygen to form a protective glassy phase that actually protects the copper, allowing air firing without resistance increase
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 solution allows for the use of inexpensive copper in solar cell electrodes, enabling air firing and achieving low resistivity, thereby reducing material costs and capital investment while maintaining effective conductivity.
Implementation Method 1
drying the Cu-containing conductive paste
Implementation Method 2
firing the Cu-containing conductive paste to form the at least one Cu electrode
Data Source
AI summary
Disclosed herein are solar cells comprising semiconductor substrates and Cu electrodes attached thereto, wherein, the Cu electrodes are derived from conductive pastes containing powder mixtures of Cu particles and crystalline Ge particles and glass frits dispersed in organic media.