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How to Build a Screen Print Solar Cell

Solar cell technology is commonly used to create silicone disks that create an electric field that generates electricity from the sunlight. Solar cells are used in a wide variety of applications, including calculators, telecommunication equipment, solar panels and other applications. Multiple techniques exist for screen printing solar cells; however, the basic building block remains the same--use a "doped substrate" or silicone wafer and add other components. The manufacturing process must take place in a highly sanitized and pristine environment.

Things You'll Need

Silicone wafer
Boron
Silver paste
Sintering oven
Phosphorous gas
Plasma gas
Metal contacts

Instructions

- 1
  Start with a silicone wafer that's .0.55 mm thick and 10 by 10 cm square. The wafer must have completed the doping process, which requires small amounts of boron. Coat the wafer in cutting fluid because of the uneven surface caused by the circular saw used to cut the component.
- 2
  Apply an alkaline etch to clean the silicone wafer and remove the outer layer. Clean the wafer as quickly as possible and at the right depth. Heat the silicone wafer in a sintering oven at a temperature from 800 to 1000 Celsius. Perform this step in a phosphorous gas setting; this procedure forces phosphorous into the outer layers of the wafer.
- 3
  Stack two wafers; use plasma gas to remove the junction around the edges of the silicone wafers. Plasma etching removes the front junction to prevent contact with the rear of the solar cell. Screen print the back of the cell. Lower the screen along with the metal paste. Use silver paste, which creates a better performing cell with a back surface field. Apply a second print of the silver paste, which creates a solderable contact.
- 4
  Ensure that there's a proper "snap-off" distance between the screen and the silicone wafer. Move the squeegee mechanism across the screen. Check the speed and pressure of the squeegee before proceeding. This action forces the metal paste through the perforation in the print screen. Place the cell in a second oven at a higher temperature, but below the melting point of the silicone wafer--1,410 degrees Celsius. This binds the metal contact to the silicone wafer.
- 5
  Remove the screen. The wafer now has a thick layer of metal paste. Allow the paste to dry in the oven, which removes organic binders and solvents. The firing step demolishes the rear-n layer, which helps the metal make contact with the p-type bulk. Turn the cell to the front side and repeat the process. Heat the silicon in a sintering oven at a temperature from 500 to 800 Celsius. This step fires the metal paste and fuses it to the silicone wafer. Encapsulate the solar cell in a solar panel.

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