Solar Cell Seed Layer Alloy for Bonding and Light Trapping
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Solution Overview
Problem
The insufficient bonding force between copper and silicon in solar cells leads to delamination and reduced performance due to copper diffusion, and the use of nickel as a seed layer enhances bonding but has a poor reflection effect, reducing light trapping and conversion efficiency.
Innovation Solution
A conductive contact structure for solar cells is introduced, featuring a seed layer composed of an alloy material with aluminum as the main component and additional metals like Mo, Ni, Ti, or W as improved components, which enhances bonding and light trapping while maintaining low costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a nickel layer is used as the seed layer between copper and silicon substrate, then the bonding force between copper and silicon is enhanced, but the light trapping effect is reduced due to poor reflection
Solution Approach 1:
The patent uses a composite seed layer comprising multiple metal elements (Al, Si, Ni, Mo, Ti, W, Cr, Mn, Pd, Bi, Nb, Ta, or Pa) instead of a single nickel layer. This composite structure combines the bonding enhancement properties of nickel with the light reflection properties of metals having refractive indices less than 2, thereby simultaneously improving both bonding force and light trapping effect
Solution Approach 2:
The patent changes the material parameter (refractive index) of the seed layer by selecting metals with refractive indices less than 2 in the wavelength range of 850-1200 nm. This parameter change enables the seed layer to reflect light more effectively while maintaining bonding strength, thus resolving the contradiction between bonding force and light trapping
2Quantity of substance
If copper is used as the conductive layer, then cost is reduced compared to silver, but bonding force with silicon is insufficient and copper diffusion occurs
Solution Approach 1:
The patent introduces a seed layer as an intermediary between copper and silicon substrate. This intermediate layer prevents direct contact between copper and silicon, thereby preventing copper diffusion into the silicon substrate while also providing sufficient bonding force to prevent delamination, thus improving reliability while maintaining cost-effectiveness
3Illumination intensity
If the seed layer uses metals with low refractive index, then light trapping effect is improved, but bonding force with copper may be reduced
Solution Approach 1:
The patent creates a composite seed layer that combines metals with low refractive indices (for light trapping) with metals that provide good bonding (such as nickel and other listed elements). This composite approach ensures that the seed layer simultaneously achieves excellent light reflection properties and strong bonding with both copper and silicon substrate
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 proposed solution improves the adhesion between the seed layer and the copper conductive layer, enhances the light trapping effect, and maintains cost-effectiveness by reducing the need for expensive silver and improving the reliability of the solar cells.
Implementation Method 1
the at least one main component is one or more metals having an average refractive index lower than 2 and a wavelength in a range of 850-1200 nm... the nickel layer has a poor reflection effect, which reduces a light trapping effect of the solar cell
Implementation Method 2
diffusion of the copper of the conductive layer into the silicon substrate reduces performance of the solar cell... a seed layer 300 is added between the copper conductive layer and the silicon substrate, to enhance the bonding force
Implementation Method 3
an insufficient bonding force between copper and silicon easily causes the conductive layer to fall off the silicon substrate... the nickel layer increases the bonding force between the copper conductive layer and the silicon substrate
Data Source
AI summary
A conductive contact structure of a solar cell is provided, includes a substrate; a semiconductor region; and an electrode. The semiconductor region is disposed on or in the substrate. The electrode is disposed in the semiconductor region. The electrode includes a seed layer in contact with the semiconductor region. The seed layer includes an alloy material, and includes at least one main component and at least one improved component. The at least one main component is one or more metals having an average refractive index lower than 2 and a wavelength in a range of 850-1200 nm, and the at least one improved component includes any one or more of Mo, Ni, Ti, W, Cr, Mn, Pd, Bi, Nb, Ta, Pa, Si, and V.