Photovoltaic Cell Metallization Using Copper and Solder
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The high manufacturing cost of photovoltaic (PV) cells due to the reliance on silver (Ag) in their metallization, which constitutes a significant portion of the overall cost, particularly in the fingers and busbars, necessitates a more cost-effective solution for forming PV cells while maintaining efficiency.
Innovation Solution
The use of a composition comprising copper (Cu) and a solder with a low melting point, such as Sn63/Pb37, in conjunction with a polymer binder, to form busbars and fingers, reducing the amount of silver required and minimizing the metal-silicon interface area to enhance efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver (Ag) is used as the primary component in fingers and busbars, then electrical conductivity is excellent, but manufacturing cost increases substantially
Solution Approach 1:
The patent changes the material composition parameters by using copper (Cu) as the primary metal component instead of silver (Ag), and controlling the metal particle size distribution (0.5-5 μm and 5-10 μm ranges) to achieve optimal conductivity and adhesion properties at lower cost
Solution Approach 2:
The patent creates a composite metallization paste containing copper particles, solder particles (Sn, Pb, Bi, Zn, In, or their alloys), and organic vehicle components that work together to provide both electrical conductivity and adhesion to the silicon substrate, replacing pure silver with a multi-component composite system
2Reliability
If the metal-silicon interface area is reduced, then efficiency and durability are enhanced, but adhesion and electrical contact may be compromised
Solution Approach 1:
The patent applies different material properties to different regions: copper particles provide bulk conductivity, while solder particles specifically at the interface with silicon provide strong adhesion and electrical contact, creating local optimization of properties throughout the metallization layer
Solution Approach 2:
The solder particles act as an intermediary material between the copper metal particles and the silicon substrate, facilitating both mechanical adhesion and electrical contact while minimizing direct metal-silicon interface area, thereby enhancing efficiency without compromising contact quality
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 results in improved open-circuit voltage (VOC) and short-circuit current density (JSC) while reducing manufacturing costs by minimizing silver usage and preventing silver diffusion into the PV cell, thus enhancing the overall performance and longevity of the PV cells under damp heat conditions.
Implementation Method 1
a composition comprising copper (Cu) and a solder with a low melting point, such as Sn63/Pb37
Implementation Method 2
a composition comprising copper (Cu) and a solder with a low melting point, such as Sn63/Pb37, in conjunction with a polymer binder, to form busbars and fingers
Implementation Method 3
a composition comprising copper (Cu) and a solder with a low melting point, such as Sn63/Pb37, in conjunction with a polymer binder
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
A photovoltaic (PV) cell comprises a base substrate comprising silicon and including an upper doped region. A coating layer is disposed on the upper doped region and has an outer surface. Fingers are disposed in the coating layer. Each finger has a lower portion in electrical contact with the upper doped region, and an upper portion extending outwardly through the outer surface. Each finger comprises a first metal. A busbar is spaced from the upper doped region, which is free of physical contact with the busbar. The busbar is in electrical contact with the upper portions of the fingers. The busbar comprises a second metal and a third metal different from the first and second metals. The third metal has a melting temperature of no greater than about 300 °C. A method of forming the PV cell is also provided.