Research Project Summary Information
Feasibility of Improving Front Metallization Lines for Photovoltaic Devices(STD11003)
SUNY, The Research Foundation of
As photovoltaic (PV) devices convert sunlight into electricity, the electricity generated is collected and transported via thin lines of metal on the top of the PV cells. It is important for PV device efficiency that these lines efficiently conduct electricity and provide minimal shading to the PV cell. PV cell manufactures use several metal contact fabrication techniques, but each has limitations. The metal lines on most PV cells are produced by screen printing a silver paste onto the cells. Screen printing is fast and relatively low cost; however, the conductivity of the contacts is low because of porosity and necessary additives, and the shading losses are relatively high due to large line widths. Photolithography and metal evaporation methods offer improved gridline quality, but are time-consuming and expensive.
Light-induced electroplating of silver metal on top of the front contact grid has shown promise in reducing line resistance and line shading, resulting in increased cell power output. This technique has received only limited acceptance in the industry due to the high cost of plating a precious metal layer. This project demonstrated the feasibility of using the light-induced electroplating technique using lower-cost, non-precious metals, such as nickel, copper, and tin.
The University at Albany College of Nanoscale Science and Engineering partnered with Technic Inc to demonstrate the feasibility of using a new low-cost line of plating solutions specifically created by Technic to meet the challenges of the PV industry. The team investigated two different methods to produce the metal lines. In the first method, the team used screen printing to deposit a thin seed layer of silver paste onto the solar cell, and then used electrodeposition to deposit layers of nickel, copper, and silver. The thin nickel layer protects the silver paste from the acidic solution used in the copper plating process. The copper layer is the main current carrier layer, and the thin layer of silver on top preserves the copper and makes the contact solderable.
The second method eliminated the screen-printed silver paste seed layer and instead used a seed layer of nickel silicide, which was formed by depositing a thin layer of nickel directly on the exposed silicon surface of the PV cell and then annealing the cell to convert the nickel layer into a nickel silicide layer. A thicker, conducting layer such as copper or nickel was then deposited.
Potential benefits include the following:
- improved performance and efficiency of solar cell technologies, which could lead to reduced electricity generation from fossil fuels
- increased research activity at Technic’s Long Island facility which could lead to additional jobs
The project successfully demonstrated a low-cost process for depositing higher-conducting, thinner metal lines on solar cells. Future work will further improve and characterize these promising techniques.
SUNY, The Research Foundation of
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SUNY at Albany
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