Multi-Shell Metal Particles for Solar Cell Conductive Paste
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Solution Overview
Problem
Conventional methods for producing multicore metallic particles are inefficient and not easily integratable into current production lines, with issues such as instability in reaction conditions and uneven coating, particularly in the case of copper particles coated with electroless nickel, which can lead to corrosion and high silver consumption in solar cell applications.
Innovation Solution
The development of multi-shell metal coated particles with a copper core, a nickel barrier layer, and an outer silver layer, produced through an electroless method, which reduces silver consumption and provides even coating and improved conductivity, while the nickel layer prevents copper oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroless plating is used to coat nickel on copper particles, then the coating process is simple, but the coating is uneven and stability is poor
Solution Approach 1:
The coating process is divided into multiple sequential steps: copper particle preparation, nickel barrier layer deposition, and silver conductive layer deposition. Each layer is deposited independently with controlled thickness, ensuring uniform coating while maintaining process simplicity through modular execution.
Solution Approach 2:
The copper particle surface is pre-treated and activated before nickel deposition to ensure uniform nucleation and adhesion. This preliminary preparation step prevents uneven coating by creating a consistent surface morphology prior to the main coating process.
2Loss of substance
If copper particles are used directly as conductive material, then silver consumption is reduced, but copper oxidation occurs leading to corrosion
Solution Approach 1:
The structure consists of nested layers: copper core particles are surrounded by a nickel barrier layer, which is in turn surrounded by a silver conductive layer. This nested configuration allows the use of cost-effective copper while protecting it from oxidation and providing necessary conductivity through the silver outer layer.
Solution Approach 2:
The nickel barrier layer acts as an intermediary between the copper core and the silver outer layer, preventing direct contact between copper and oxygen while also serving as an adhesion promoter for the silver deposition process.
3Reliability
If thick silver layers are applied on copper particles, then conductivity is improved, but silver consumption increases
Solution Approach 1:
The silver layer is deposited with controlled local thickness on the outer surface of the nickel-coated copper particles, providing sufficient conductivity only where needed for current collection, while minimizing overall silver consumption by avoiding unnecessary thick deposits.
Solution Approach 2:
The deposition parameters (time, concentration, temperature) are optimized to achieve the minimum required silver layer thickness for adequate conductivity, reducing silver consumption while maintaining electrical performance through precise parameter control.
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 approach reduces silver usage, enhances conductivity, and prevents copper oxidation, resulting in a more efficient and stable conductive paste for solar cell applications with improved durability and performance.
Implementation Method 1
a first shell of a metal forming a barrier layer, which is coated directly on the copper particles, and a second shell of an electrically conductive metal, forming an outer layer of the particles
Implementation Method 2
The electroless method, which reduces silver consumption and provides even coating and improved conductivity
Implementation Method 3
the nickel layer prevents copper oxidation
Implementation Method 4
an outer layer formed from an electroless silver plating liquid... enhances conductivity
Data Source
AI summary
A composition comprising a plurality of coated metal particles with a metal core surrounded by nested shells formed by an electrically conductive layer and by a barrier layer, at least one of the shells being formed by electroless plating. The invention also comprises a method of producing such compositions as well as the use of the composition in, for example, crystalline-silicon solar cell devices having contact structures formed on one or more surfaces of a solar cell device, such as those used in back contact solar cell devices or emitter wrap through (EWT) solar cell devices.