Sand: The basic raw material
Most solar panels produced today are made from Silicon, the second most abundant element on Earth and the primary ingredient in beach sand. The first step in making a solar panel is to create silicon ingots, giant blocks of high-purity (99.999999%) silicon.
To do this, Yingli put hundreds of pounds of silicon chunks (i.e. rocks) into a giant crucible and add a little boron (called a ‘dopant’) to give the silicon positive polarity. Then, we cook it altogether at over 2,000 degrees Fahrenheit!
Ingots & Wafers
Yingli let the large silicon ingot cool down before slicing it into thin wafers using wire saws. Each fresh-cut silicon wafer is less than 200 microns thick – similar to a heavy piece of paper. These wafers must be carefully handled, inspected and cleaned before further processing. The next step is to reduce the reflectivity of the wafer from about 30% to 10% through a chemical surface texturing process that creates tiny pyramids on the wafer’s surface. Now, when a photon (sunlight) hits the wafer's surface, it is more likely to be reflected into the wafer rather than back into space.
Making Cells: From "Photo" to "Voltaic"
Solar Panel Assembly
To make a solar panel, Yingly string together 48, 60, or 72 of our solar cells and lay them carefully within an encapsulant, which attaches high-transparency glass on the front surface and a highly durable, polymer-based backsheet on the backside. Then, they warm the whole stack (like a toasted solar sandwich to create a protective cocoon around the solar cells.
Next, for structural stability and long-term protection, they place rigid aluminum frames around the perimeter, bonded together with a waterproof adhesive. Finally, a junction box is added to the back of the solar panel: a connector to facilitate the flow of electricity. Then, the solar panel is ready for quality testing, packaging, and delivery.