The Making of a Solar Panel
What is a solar panel made of? Simply of sand – the most common element on planet earth. Self-evidently, it requires several production steps to obtain a finished solar panel:
The basic raw material required for the production of solar cells is silica sand (crystalline silicon). Planet earth provides it in large amounts – for instance, in form of silicon oxide, i.e. quartz, in each and every sand dune. Due to its semiconductor functions and large deposits, silicon is the perfect raw material for solar industries.
2. Crude silicon
A multi-stage process serves to derive high-purity crude silicon from silica sand.
Under high temperatures (1400-1800°C), so-called ingots are obtained from crude silicon. For polycrystalline ingots, the crude silicon is cast to blocks. To obtain monocrystalline ingots, a “bar” is drawn from liquid silicon melt (similar to candle dipping).
By means of high-tech wire saws or waterjet cutting, the ingots are cut to thin disks of 0.25 - 0.4 mm. These “wafers” are pure silicon disks, which can be processed to solar cells.
5. Solar cells
Solar cells consist of two differently charged layers. In order to create those layers, foreign atoms are deliberately incorporated with both top and bottom layer. This is for instance achieved by allowing foreign atoms to enter (“diffuse”) into one side of the silicon disk, by using an appropriate gas and high temperatures. The respective process is also known as doping. Subsequently, a usually blue shimmering anti-reflective layer is applied. It serves to achieve a maximum of light absorption. In order to facilitate tapping the voltage generated by the boundary layer-effect from both of the solar cell’s sides, metal contacts need to be applied to its front and backside. Usually, metal grids are printed on the cell’s front side (for instance, by screen printing). On the one hand, the respective grids serve to ensure optimal surface utilization for power production. At the same time they must allow a maximum of light incidence into the solar cell. In contrast, the metal contacts applied to the cell’s backside may cover all over.
6. Solar panel
Solar panel laminating: being exposed to vacuum and heat, the cells are permanently laminated between a Tedlar film and the glass by means of “EVA“.
Now, several solar cells are connected (soldered) in series. In order to protect them from weather and mechanical stress, the cells are laminated.
Finally, the laminate is equipped with a frame, which serves as weather protection – and you’ve got a solar panel to produce free electricity for 20 to 50 years!