Fire-Through Aluminium Paste for Bifacial PERC Solar Cells
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Solution Overview
Problem
Conventional solar cell manufacturing methods require costly laser processing and thick silicon wafers to prevent wafer bowing, limiting the production of bifacial PERC solar cells and increasing production costs.
Innovation Solution
A fire-through aluminium paste composition comprising an aluminium component and a glass component with specific glass frits is used to directly contact the silicon substrate, eliminating the need for laser processing and allowing thinner wafers, enabling bifaciality and flexible solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full area screen printing of aluminium paste is used, then contact with semiconductor is achieved, but wafer bowing occurs due to differential thermal expansion
Solution Approach 1:
The patent applies local quality by transitioning from full area aluminium printing to selective local printing only at regions where contact is needed. This localized approach reduces the total aluminium coverage area, thereby minimizing differential thermal expansion effects that cause wafer bowing, while still achieving necessary electrical contact at specific semiconductor regions.
Solution Approach 2:
The patent segments the continuous full-area metallization into discrete localized contact regions. By dividing the metallization into separate functional segments rather than a continuous layer, the overall thermal expansion stress is reduced, preventing wafer bowing while maintaining effective electrical contact at each segmented contact point.
2Shape
If thicker silicon wafers are used, then wafer bowing is reduced and flatness is maintained, but production cost increases
Solution Approach 1:
The patent changes the parameter of metallization coverage from full-area to localized partial coverage. This parameter change reduces the interaction area between aluminium and silicon, thereby reducing differential thermal expansion effects. Consequently, thinner silicon wafers can be used without experiencing excessive bowing, reducing silicon material consumption and production costs.
3Manufacturing precision
If laser processing is used to open passivation layer, then local contact is achieved, but production cost increases
Solution Approach 1:
The patent replaces the laser processing mechanism with a screen printing mechanism. Instead of using laser energy to ablate or open the passivation layer, the invention uses screen printing to selectively deposit aluminium paste that chemically reacts with and penetrates the passivation layer. This substitution eliminates costly laser equipment and processing steps while achieving comparable local contact precision through controlled material deposition and thermal processing.
4Reliability
If full area aluminium print is used, then electrical contact is maximized, but bifaciality is blocked due to light opacity
Solution Approach 1:
The patent applies local quality by restricting aluminium metallization to specific localized regions rather than full-area coverage. This localized metallization approach maintains adequate electrical contact at contact regions while leaving other areas of the wafer surface transparent to light, thereby enabling bifacial operation where light can pass through to the rear surface for energy generation.
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 reduces production costs, enables thinner and flexible solar cells, and allows for larger format wafers without wafer bowing, enhancing production yields and enabling new market applications such as building integration and solar electric vehicles.
Implementation Method 1
the first glass frit (A) is an oxidizer of silicon nitride (SiNx) or hydrogenated silicon nitride (SiNx:Hy)
Implementation Method 2
forms a low viscosity liquid at a predetermined temperature
Data Source
AI summary
The present disclosure generally relates to a fire-through aluminium paste composition to selectively fire through a passivation layer, and fired compositions thereof. In particular, the fire-through aluminium paste composition of the present disclosure comprises an aluminium component and a glass component, wherein the glass component comprises at least two glass frits. The present disclosure also relates to a processes for preparing a fire-through aluminium paste composition, and its use in the manufacture of a bifacial PERC solar cell.