Copper Solar Cell Paste With Oxide Barrier Against Diffusion
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Solution Overview
Problem
The use of copper in solar panels poses challenges due to its degradation, oxidation, and the need for complex multi-layered structures, which increase capital costs and environmental, health, and safety issues, while alternatives like electroplating require significant investment and complicate manufacturing.
Innovation Solution
A copper-containing paste for solar cell metallization comprising an organic vehicle, copper particles, metal-oxide-containing nanoparticles, and secondary oxide particles that reduce to metal during heating, eliminating the need for silver and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper is used as an alternative to silver in solar panels, then cost is reduced, but copper degrades quickly and requires complex multi-layered structures
Solution Approach 1:
The patent introduces a glass frit barrier layer as an intermediary between the copper conductor and the silicon wafer. This glass frit layer acts as a diffusion barrier that prevents copper from degrading the silicon while allowing electrical contact to be maintained. This resolves the contradiction by enabling copper use (cost reduction) without requiring complex multi-layered protective structures, as the glass frit provides the necessary barrier function in a single integrated layer.
Solution Approach 2:
The patent creates a composite paste formulation containing copper particles, glass frit, and organic vehicle. This composite material combines the low cost and high conductivity of copper with the barrier properties of glass frit, achieving both cost reduction and simplified structure. The composite nature allows the paste to simultaneously provide electrical conductivity and diffusion protection, eliminating the need for separate protective layers.
2Reliability
If electroplating is used to deposit copper on silicon, then copper deposition is successful, but capital investment and manufacturing complexity increase significantly
Solution Approach 1:
The patent replaces the electroplating process (electrical/chemical system) with a screen-printing paste application process (mechanical system). The paste containing copper particles and glass frit is applied through screen printing, then fired to create the conductor. This substitution maintains reliable copper deposition while using existing solar panel manufacturing equipment, avoiding the need for new electroplating facilities and complex process control systems.
Solution Approach 2:
The patent changes the deposition method from electrochemical (electroplating) to thermal processing (firing). By formulating a paste with copper particles and glass frit that reacts during thermal firing, the process achieves reliable copper deposition through chemical reduction and sintering rather than electrochemical deposition. This parameter change allows use of standard solar panel firing furnaces instead of specialized electroplating equipment.
3Ease of manufacture
If copper is used without protective measures, then manufacturing cost is reduced, but copper oxidizes and degrades the solar cell
Solution Approach 1:
The glass frit in the paste formulation serves as an intermediary barrier between copper and oxygen. During firing, the glass frit forms a protective matrix around the copper particles, preventing direct exposure to oxygen and thus preventing oxidation. This intermediary layer maintains solar cell reliability by protecting copper from degradation while allowing the simple, cost-effective paste application process to be used.
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 paste enables cost-effective production of solar cells with copper conductors, reducing capital expenditures and environmental impacts, while maintaining performance by preventing copper diffusion and oxidation.
Implementation Method 1
secondary oxide particles that reduce to metal during heating
Implementation Method 2
When the paste is heated to a temperature at which the organic vehicle decomposes
Data Source
AI summary
A paste (32) for use in metallization of a solar cell (12) includes an organic vehicle (44) and a mixture of copper-containing particles (46), metal-oxide-containing nanoparticles (50), and secondary oxide particles (52) different from the metal-oxide-containing nanoparticles (50). The secondary oxide particles (52) include particles (42) of a metal oxide and a metal of the metal oxide capable of reducing at least some of the metal-oxide-containing nanoparticles (50) to metal when heated. The organic vehicle (44) is capable of reducing the metal oxide of the secondary oxide particles (52) upon decomposition of the organic vehicle (44). A paste (32) includes a mixture of particles (42) including metallic copper particles (46), nanoparticles (50), and metal oxide particles (52) in the organic vehicle (44). The nanoparticles (50) include at least one oxide of nickel, copper, cobalt, manganese, and lead. The metal oxide of the metal oxide particles (52) has a more negative Gibbs Free Energy of Formation than a metal oxide of the at least one oxide of the nanoparticles (50).