Solar cells are semiconductor devices that directly convert solar radiation into electrical energy based on the photovoltaic effect of semiconductors. Now commercialized solar cells mainly include the following types: monocrystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, and currently cadmium telluride cells, copper indium selenide cells, nano-titanium oxide sensitized cells, polycrystalline silicon Thin-film solar cells and organic solar cells, etc. Crystalline silicon (monocrystalline, polycrystalline) solar cells require high-purity silicon raw materials, generally requiring a purity of at least %, that is, a maximum of 2 impurity atoms are allowed to exist in 10 million silicon atoms. The silicon material is made of silicon dioxide (SiO2, also known as sand) as a raw material, which can be melted and impurities removed to obtain coarse silicon. From silicon dioxide to solar cells, it involves multiple production processes and processes, which are generally roughly divided into: silicon dioxide->metallurgical-grade silicon->high-purity trichlorosilane->high-purity polysilicon->monocrystalline silicon rod or Polycrystalline silicon ingot 1 > silicon wafer 1 > solar cell.
Monocrystalline silicon solar cells are mainly made of monocrystalline silicon. Compared with other types of solar cells, monocrystalline silicon cells have the highest conversion efficiency. In the early days, monocrystalline silicon solar cells occupied the majority of the market share, and after 1998, they retreated to polycrystalline silicon and took the second place in the market share. Due to the shortage of polysilicon raw materials in recent years, after 2004, the market share of monocrystalline silicon has increased slightly, and now most of the batteries seen on the market are monocrystalline silicon. The silicon crystal of monocrystalline silicon solar cells is very perfect, and its optical, electrical and mechanical properties are very uniform. The color of the cells is mostly black or dark, which is especially suitable for cutting into small pieces to make small consumer products. Conversion Efficiency Achieved in Laboratory of Monocrystalline Silicon Cells
It is %. The conversion efficiency of ordinary commercialization is 10%-18%. Due to the production process of monocrystalline silicon solar cells, generally the semi-finished silicon ingots are cylindrical, and then go through slicing->cleaning->diffusion junction->removal of the back electrode->making electrodes->corroding the periphery->evaporation reduction. Reflective film and other industrial cores are made into finished products. Generally, the four corners of monocrystalline silicon solar cells are rounded. The thickness of monocrystalline silicon solar cells is generally 200uM-350uM thick. The current production trend is to develop towards ultra-thin and high-efficiency. German solar cell manufacturers have confirmed that 40uM thick monocrystalline silicon can achieve 20% conversion efficiency. In the production of polycrystalline silicon solar cells, the high-purity silicon as the raw material is not purified into single crystals, but is melted and cast into square silicon ingots, and then processed into thin slices and similar processing as single crystal silicon. Polycrystalline silicon is easy to identify from its surface. The silicon wafer is composed of a large number of crystalline regions of different sizes (the surface is crystalline).
The oriented grain group is easy to interfere with photoelectric conversion at the grain interface, so the conversion efficiency of polysilicon is relatively low. At the same time, the consistency of optical, electrical and mechanical properties of polysilicon is not as good as that of monocrystalline silicon solar cells. The highest efficiency of the polycrystalline silicon solar cell laboratory is %, and the commercialized one is generally 10%-16%. The polycrystalline silicon solar cell is a square piece, which has the highest filling rate when making solar modules, and the products are relatively beautiful. The thickness of polycrystalline silicon solar cells is generally 220uM-300uM thick, and some manufacturers have produced solar cells with a thickness of 180uM, and they are developing towards thinness to save expensive silicon materials. Polycrystalline wafers are right-angled squares or rectangles, and the four corners of single wafers are chamfered close to a circle.
The one with a money-shaped hole in the middle of the piece is a single crystal, which can be seen at a glance
Post time: Dec-30-2022