Cold-Sprayed Copper on Aluminum Back-Sheet for PV Modules
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Solution Overview
Problem
Conventional photovoltaic modules face issues with high cost due to copper usage, poor solderability of aluminum, contact resistance, and corrosion sensitivity, leading to power output decay and mechanical instability under damp heat aging.
Innovation Solution
An electro-conductive back-sheet comprising an aluminum layer with a cold-sprayed metal layer, such as copper, tin, or silver, on a polymeric back-sheet with an oxygen transmission rate (OTR) of at least 20 cm3/m2.atm per day, which reduces corrosion sensitivity and maintains mechanical properties over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper layer is applied via thermal spray to improve solderability and reduce contact resistance, then electrical conductivity and ease of connection are improved, but thermal degradation and oxidation of the metal layer occur
Solution Approach 1:
The patent replaces thermal spray technology with cold spray technology. Instead of using thermal energy to melt or soften the metal, cold spray uses a high-velocity gas stream to accelerate metal particles to supersonic speeds, where they impact and bond to the substrate through kinetic energy and plastic deformation. This mechanical/kinetic approach eliminates the thermal degradation and oxidation problems while achieving dense, adherent metal coatings with excellent electrical conductivity and solderability.
2Reliability
If a copper layer is applied to improve electrical conductivity and solderability, then connection quality is improved, but contact corrosion between dissimilar metals increases
Solution Approach 1:
The patent applies copper coating selectively only in the contact areas where electrical connections are needed, rather than covering the entire aluminum surface. This localized application minimizes the area where galvanic corrosion can occur between dissimilar metals, while still providing excellent solderability and electrical conductivity at the critical connection points. The rest of the aluminum back sheet remains exposed or covered with protective polymer without copper, reducing overall corrosion risk.
3Object-affected harmful factors
If a polymeric back-sheet with low OTR is used to reduce corrosion, then corrosion resistance is improved, but mechanical properties and UV stability decrease
Solution Approach 1:
The patent divides the back sheet into functional zones: the bulk polymer matrix provides mechanical strength, UV stability, and controlled OTR, while copper is applied only in specific contact areas for electrical conductivity. This segmentation allows each component to optimize its function without compromising the others - the polymer maintains structural integrity and environmental resistance, while the localized copper provides corrosion-resistant electrical connections.
4Quantity of substance
If aluminum is used to reduce cost, then material cost is reduced, but solderability and contact resistance performance worsen
Solution Approach 1:
The patent creates a composite structure combining aluminum and copper. The aluminum base layer provides cost-effectiveness and good electrical conductivity, while the copper coating layer provides excellent solderability and enhanced electrical performance at connection points. The cold spray process creates a metallurgical bond between the two metals, forming a composite material that exhibits properties superior to either metal alone for photovoltaic interconnection applications.
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 results in reduced power output decay and improved durability of photovoltaic modules, with stable mechanical properties and decreased corrosion sensitivity, even after prolonged damp heat aging.
Implementation Method 1
The metal layer is applied on the aluminum layer via cold spray. The cold spray process is a relatively new process whereby a powder of the metal to be sprayed is mixed with a gas flow and sprayed at high flow rate and at relatively low temperature on the surface of the aluminum layer
Data Source
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AI summary
The present invention relates to an electro-conductive back-sheet for back-contact photovoltaic cell technologies comprising an aluminum layer, a cold sprayed metal layer on top of the aluminum layer and a polymeric back-sheet having an (OTR) of at least 20 cm3/m2.atm per day. The metal used for the metal layer is chosen from the group consisting of copper, tin, silver or nickel, or mixtures of two or more thereof or alloys of two or more thereof. Preferably the metal is copper. The metal layer preferably has a thickness in the range of 50 nm-10 µm. The present invention further relates to process for the manufacturing of the electro-conductive back-sheet. The present invention also relates to a photovoltaic module comprising the electro-conductive back-sheet.