Monocrystalline silicon solar cells are primarily manufactured using monocrystalline silicon, and they boast the highest conversion efficiency compared to other types of solar cells. Initially, monocrystalline silicon solar cells held the vast majority of the market share, only falling behind polycrystalline silicon after 1998 to become the second most popular type. Due to the recent shortage of polycrystalline silicon raw materials, the market share of monocrystalline silicon has slightly increased since 2004, and now most solar cells on the market are made of monocrystalline silicon.
Monocrystalline silicon solar cells have perfectly uniform silicon crystals, resulting in highly uniform optical, electrical, and mechanical properties. The cells are typically black or dark in color, making them ideal for cutting into small pieces for manufacturing small consumer products. The conversion efficiency of monocrystalline silicon solar cells achieved in the laboratory is 24.7%, while commercially available conversion efficiencies range from 10% to 18%. Due to manufacturing processes, monocrystalline silicon solar cells are generally produced by starting with a cylindrical silicon ingot, followed by slicing, cleaning, diffusion junction formation, back electrode removal, electrode fabrication, peripheral etching, and anti-reflective coating deposition to create the final product.
Generally, monocrystalline silicon solar cells have rounded corners. The thickness of monocrystalline silicon solar cell wafers is typically 200µm-350µm, and the current production trend is towards ultra-thin and high-efficiency. In the production of polycrystalline silicon solar cells, the high-purity silicon used as raw material is not further purified into monocrystalline silicon, but is melted and cast into square silicon ingots, and then processed in the same way as monocrystalline silicon, cut into thin slices and undergoing similar processing.
Polycrystalline silicon is easily identifiable by its surface. The silicon wafer is composed of a large number of crystalline regions of different sizes (the surface has a crystalline appearance). Its power generation mechanism is the same as that of monocrystalline silicon. However, because the silicon wafer is composed of multiple grains of different sizes and orientations, the photoelectric conversion at the grain interface is easily interfered with. Therefore, the conversion efficiency of polycrystalline silicon is relatively low. At the same time, the optical, electrical and mechanical properties of polycrystalline silicon are not as consistent as those of monocrystalline silicon solar cells.
Polycrystalline silicon solar cells achieve a laboratory efficiency of up to 20.3%, while commercially available cells typically range from 10% to 16%. Polycrystalline silicon solar cells are square wafers, offering the highest fill rate during solar module manufacturing, resulting in a relatively aesthetically pleasing product. The thickness of polycrystalline silicon solar cells is generally 220µm-300µm, with some manufacturers already producing 180µm thick cells, and the trend towards thinner cells further conserves expensive silicon materials. Polycrystalline wafers are right-angled squares or rectangles, while monocrystalline silicon has nearly rounded chamfers at its four corners. A module with a coin-shaped hole in the center is a monocrystalline silicon cell, making it easily identifiable.
1. Monocrystalline silicon solar cells
Currently, the photoelectric conversion efficiency of monocrystalline silicon solar cells is around 15%, with the highest reaching 24%, which is the highest among all types of solar cells. However, the manufacturing cost is very high, preventing its widespread and common use. Because monocrystalline silicon is typically encapsulated with tempered glass and waterproof resin, it is robust and durable, with a lifespan generally reaching 15 years, and sometimes up to 25 years.
2. Polycrystalline silicon solar cells
The manufacturing process of polycrystalline silicon solar cells is similar to that of monocrystalline silicon solar cells, but the photoelectric conversion efficiency of polycrystalline silicon solar cells is much lower, at about 12% (the world's highest efficiency polycrystalline silicon solar cell with an efficiency of 14.8% was launched by Sharp of Japan on July 1, 2004).
In terms of manufacturing costs, polycrystalline silicon solar cells are cheaper than monocrystalline silicon solar cells. They are simpler to manufacture, save on electricity, and have lower overall production costs, leading to their widespread adoption. However, polycrystalline silicon solar cells also have a shorter lifespan than monocrystalline silicon solar cells. In terms of performance-price ratio, monocrystalline silicon solar cells are slightly better.
