![]() Silicon wafers are often pre-doped with boron. These positive (p-type) and negative (n-type) doping materials are mostly boron, which has 3 electrons (3-valent) and is used for p-type doping, and phosphorous, which has 5 electrons (5-valent) and is used for n-type doping. ![]() Doping is basically the process of adding impurities into the crystalline silicon wafer to make it electrically conductive. By this method, the silicon is passed through the DSS ingot growth furnace and processed into pure quadratic silicon blocks.ĭuring the casting of the ingots, the silicon is often already pre-doped before slicing and selling the wafer disks to the manufacturers. In order to make multi-crystalline silicon cells, various methods exist:ģ.) directional solidification system (DSS)ĭSS is the most common method, spearheaded by machinery from renowned equipment manufacturer GT Advanced. By extracting the seeds from the melt with the puller, they rotate and form a pure cylindrical silicon ingot cast out from the melt and which is used to make mono-crystalline silicon cells. The impure part can then be easily cut off.Ĭrystal seeds of silicon are in the so-called Czochralski (CZ) process put into polycrystalline silicon melt of the Czochralski growth apparatus. This process pushes the 1% impure parts to one end, with the remaining 100% pure parts remaining on the other side. ![]() This molten silicon is 99% pure which is still insufficient to be used for processing into a solar cell, so further purification is undertaken by applying the floating zone technique (FTZ).ĭuring the FTZ, the 99% pure silicon is repeatedly passed in the same direction through a heated tube. That process, called carbon arc welding (CAW), reduces the oxygen from the silicon dioxide and produces carbon dioxide at the electrode and molten silicon. In this first step, crushed quartz is put in a special furnace, and then a carbon electrode is applied to generate a high-temperature electric arc between the electrode and the silicon dioxide. How are silicon wafers made?īefore even making a silicon wafer, pure silicon is needed which needs to be recovered by reduction and purification of the impure silicon dioxide in quartz. In the PV industry, the production chain from quartz to solar cells usually involves 3 major types of companies focusing on all or only parts of the value chain:ġ.) Producers of solar cells from quartz, which are companies that basically control the whole value chain.Ģ.) Producers of silicon wafers from quartz – companies that master the production chain up to the slicing of silicon wafers and then sell these wafers to factories with their own solar cell production equipment.ģ.) Producers of solar cells from silicon wafers, which basically refers to the limited quantity of solar PV module manufacturers with their own wafer-to-cell production equipment to control the quality and price of the solar cells.įor the purpose of this article, we will look at 3.) which is the production of quality solar cells from silicon wafers. ![]() In this article, we will explain the detailed process of making a solar cell from a silicon wafer. While most solar PV module companies are nothing more than assemblers of ready solar cells bought from various suppliers, some factories have at least however their own solar cell production line in which the raw material in form of silicon wafers is further processed and refined. Only a few manufacturers control the whole value chain from quartz to solar cells. The production process from raw quartz to solar cells involves a range of steps, starting with the recovery and purification of silicon, followed by its slicing into utilizable disks – the silicon wafers – that are further processed into ready-to-assemble solar cells. In chemical terms, quartz consists of combined silicon-oxygen tetrahedra crystal structures of silicon dioxide (SiO 2), the very raw material needed for making solar cells. In our earlier article about the production cycle of solar panels we provided a general outline of the standard procedure for making solar PV modules from the second most abundant mineral on earth – quartz.
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