Aluminum Paste for PERC Solar Cells
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Solution Overview
Problem
The production of PERC silicon solar cells faces challenges in maintaining the integrity of the perforated dielectric back-side passivation layer and achieving optimal electrical efficiency, as conventional aluminum pastes can damage the layer and exhibit poor adhesion or fire-through capabilities during firing.
Innovation Solution
Aluminum pastes comprising particulate aluminum, an organic vehicle, and specific glass frits with controlled softening point temperatures are used, which adhere well to the back-side perforated passivation layer and exhibit reduced fire-through capability, ensuring long durability and improved electrical efficiency of PERC silicon solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional aluminum pastes are used during firing, then aluminum back electrodes can be formed, but the perforated dielectric back-side passivation layer is damaged and adhesion is poor
Solution Approach 1:
The patent modifies the chemical composition parameters of the aluminum paste by incorporating specific glass frits with controlled softening points (500-700°C), silicon oxide (5-15 wt%), and aluminum oxide (3-8 wt%). These parameter changes enable the paste to adhere properly to the passivation layer at lower firing temperatures while preventing fire-through damage to the perforated structure.
Solution Approach 2:
The invention creates a composite aluminum paste formulation combining aluminum particles, glass frits, silicon oxide, aluminum oxide, and organic vehicles. This composite material provides both adhesion to the dielectric passivation layer and protection against excessive fire-through during firing, resolving the contradiction between bonding strength and layer integrity.
2Reliability
If conventional aluminum pastes are used, then aluminum back electrodes are formed, but fire-through capability is excessive causing damage
Solution Approach 1:
The patent controls the fire-through capability by adjusting paste composition parameters: glass frit softening point (500-700°C), silicon oxide content (5-15 wt%), and aluminum oxide content (3-8 wt%). These changes reduce excessive fire-through that damages the passivation layer while maintaining sufficient electrical contact through the perforations.
Solution Approach 2:
The modified aluminum paste provides localized adhesion quality at the interface with the passivation layer while maintaining controlled fire-through properties in the perforation areas. This local quality differentiation ensures both layer integrity and electrical functionality.
3Strength
If standard firing processes are used, then aluminum electrodes are formed, but adhesion to passivation layer is insufficient
Solution Approach 1:
The invention enables adhesion improvement by changing the paste's thermal and chemical parameters: glass frit softening point (500-700°C), oxide contents, and organic vehicle composition. These changes allow standard firing processes to achieve strong adhesion without requiring precise control adjustments, as the paste formulation itself provides the necessary bonding characteristics.
4Reliability
If aluminum paste with high fire-through capability is used, then electrical contact is achieved, but passivation layer integrity is compromised
Solution Approach 1:
The patent achieves the balance between electrical contact and layer integrity by modifying paste parameters: glass frit softening point (500-700°C), silicon oxide (5-15 wt%), and aluminum oxide (3-8 wt%). These changes provide sufficient fire-through for electrical contact while preventing excessive penetration that would compromise the passivation layer's structural integrity.
Solution Approach 2:
The composite aluminum paste formulation combines materials with complementary properties: aluminum particles for conductivity, glass frits for adhesion and controlled fire-through, and metal oxides for stability. This composite structure enables simultaneous achievement of electrical contact quality and passivation layer integrity.
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 described aluminum pastes enhance the electrical efficiency and durability of PERC silicon solar cells by maintaining the integrity of the perforated passivation layer and forming reliable local contacts without significant damage, leading to improved service life and performance.
Implementation Method 1
aluminum pastes comprising particulate aluminum, an organic vehicle and at least one glass frit... which adhere well to the back-side perforated passivation layer
Implementation Method 2
applying, for example printing, in particular screen-printing, an aluminum paste of the present invention on the back-side perforated dielectric passivation layer, and firing the aluminum paste so applied
Implementation Method 3
at least one glass frit selected from the group consisting of (i) lead-free glass frits with a softening point temperature in the range of 550 to 611° C. and (ii) lead-containing glass frits with a softening point temperature in the range of 571 to 636° C.
Data Source
AI summary
An aluminum paste comprising particulate aluminum, an organic vehicle and glass frit selected from (i) lead-free glass frits with a softening point temperature in the range of 550 to 611° C. and containing 11 to 33 wt.-% of SiO2, >0 to 7 wt.-% of Al2O3 and 2 to 10 wt.-% of B2O3 and (ii) lead-containing glass frits with a softening point temperature in the range of 571 to 636° C. and containing 53 to 57 wt.-% of PbO, 25 to 29 wt.-% of SiO2, 2 to 6 wt.-% of Al2O3 and 6 to 9 wt.-% of B2O3, useful in the production of aluminum back electrodes of PERC silicon solar cells.