Monocrystalline silicon solar cells are cut from cylindrical ingots, not complete squares, resulting in some waste of refined silicon materials. Therefore, most of the monocrystalline silicon will have gaps in the four corners, which are easy to distinguish in appearance. The structure and production process of monocrystalline silicon solar cells have been finalized, and the products have been widely used in space and on the ground. In order to reduce production costs, solar cells currently used on the ground use solar-grade monocrystalline silicon rods, and the material performance indicators have been relaxed. Some can also use the head and tail materials and waste monocrystalline silicon materials processed by semiconductor devices to be redrawn into monocrystalline silicon rods dedicated to solar cells.
Monocrystalline silicon solar cells use high-purity monocrystalline silicon rods as raw materials, and the purity is required to be 99.999%. During production, the monocrystalline silicon rods are cut into slices, and the thickness of the slices is generally about 0.3mm. The silicon wafer is polished, cleaned and other processes to make the raw silicon wafer to be processed. The processing of solar cells requires doping and diffusion on the silicon wafer first. Generally, the dopants are trace amounts of boron, phosphorus, and ladders. Diffusion is carried out in a high temperature diffusion furnace made of quartz tubes, thus forming a PN junction on the silicon wafer. Then, the screen printing method is used to print the finely prepared silver paste on the silicon wafer to make grid lines. After sintering, the back electrodes are formed at the same time, and the surface with the grid lines is coated with materials to reduce light reflection to prevent a large amount of light reflection. of photons are reflected off the smooth silicon surface. After the single crystal silicon solar cell produced by the single-crystal silicon solar cell is checked by random inspection, the solar cell module with a certain output voltage and current can be formed by the method of series and parallel connection according to the required specifications. Finally encapsulate with frame and material. According to the system design, the user can form the solar cell components into various sizes of solar cell arrays, also known as solar cell arrays. The characteristics of monocrystalline silicon solar cells are as follows:
(1) The reserves of raw silicon are abundant. Since the density of sunlight is extremely low, a large-area solar cell is required, so the supply of raw materials is very important.
(2) The density of Si is low, the material is light, and the Si material itself has a very low impact on the environment.
(3) Compared with polycrystalline silicon and amorphous silicon solar cells, its conversion efficiency is higher.
(4) The power generation characteristics are stable, and the durability is about 20 years.
(5) In the main region of the solar spectrum, the light absorption coefficient is only 103cm-1. To enhance solar spectral absorption properties, 100 μm thick silicon wafers are required.
At present, the development of monocrystalline silicon solar cells mainly focuses on reducing costs and improving efficiency. The conversion efficiency of monocrystalline silicon solar cells is 15% to 17%, and the conversion efficiency of solar cell modules composed of monocrystalline silicon solar cells is 12%~15%, the definition of the conversion efficiency of a solar cell module is based on the minimum solar cell conversion efficiency benchmark in the module, rather than the average conversion efficiency of solar cells.
The most important problem in the practical application of solar cells is to develop solar cells with high cost performance. In fact, only a thin layer of a few microns on the surface of semiconductors is involved in photoelectric conversion in solar cells. At present, the most commonly used and most successful preparation technology is to use the vapor deposition method of thermally decomposing SiH4 gas to deposit a single crystal silicon film on sapphire.