Photovoltaic glass classification. Photovoltaic glass substrates used for solar cells generally include ultra-thin glass, surface-coated glass, and low-iron content (ultra-clear) glass. According to the nature of use and different manufacturing methods, photovoltaic glass can be divided into three types of products, that is, the cover plate of flat solar cells, which is generally rolled glass; the surface of flat glass is coated with semiconductor materials with a thickness of only a few microns. Conductive substrates for thin-film batteries; glass for lenses or mirrors used in thermal photovoltaic systems. The characteristics and functions of these three products are completely different, and their added value is also very different.
The most widely used solar photovoltaic glass today is high transmittance glass, which is glass with low iron content, which is commonly known as ultra-clear glass. Iron is an impurity in ordinary glass (except for heat-absorbing glass). The presence of iron impurities will not only color the glass, but also increase the heat absorption rate of the glass and reduce the light transmittance of the glass.
Iron in glass is introduced by the raw materials themselves, refractory materials or metal production equipment, and cannot be completely avoided. One can only reduce the iron content in glass as much as possible through production control. At present, the iron content of solar cell glass is between 0.008% and 0.02%, while the iron content of ordinary float glass is above 0.7%. Low iron content impurities can bring high solar light transmittance. As far as 3.2mm thick and 4mm thick glass are most used in China, the visible light transmittance of sunlight generally reaches 90%~92%.
As one of the most important components of solar energy devices, solar photovoltaic glass requires that the glass plate must be highly transparent. Therefore, the requirements for the iron content in silicon raw materials used to produce solar glass are very strict, and the Fe2O3 content is generally 140-150ppm.
