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 significantly lower, at around 17-18%. Polycrystalline silicon wafer production consumes less energy and is pollution-free, making it more economical than monocrystalline silicon solar cells.
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, thus leading to their widespread adoption. However, polycrystalline silicon solar cells also have a shorter lifespan than monocrystalline silicon solar cells.
Composition of polycrystalline silicon solar cells
Polycrystalline silicon solar cells are composed of tempered glass, EVA, anti-reflective layer, solar panel chip, EVA, TPT and outer frame.
1. Tempered glass: Its function is to protect the main body of power generation (battery cells). There are requirements for its selection. (1) The light transmittance must be high (generally above 91%); (2) Ultra-white tempered treatment.
2. EVA: Used to bond and fix tempered glass and the main power generation unit (solar cells). The quality of transparent EVA material directly affects the lifespan of the module. EVA exposed to air is prone to aging and yellowing, which affects the light transmittance of the module and thus the power generation quality of the module. In addition to the quality of the EVA itself, the lamination process of the module manufacturer also has a great impact. For example, if the EVA adhesiveness is not up to standard, or if the bonding strength between EVA and tempered glass and backsheet is insufficient, it will cause the EVA to age prematurely and affect the lifespan of the module.
3. Solar Cells: Their main function is to generate electricity. The mainstream solar cells on the market are crystalline silicon solar cells and thin-film solar cells. Each has its advantages and disadvantages. Crystalline silicon solar cells have relatively low equipment costs, but high consumption and cell costs. However, they also have high photoelectric conversion efficiency and are more suitable for generating electricity under outdoor sunlight. Thin-film solar cells have relatively high equipment costs, but very low consumption and cell costs. However, their photoelectric conversion efficiency is only slightly more than half that of crystalline silicon solar cells. They have excellent low-light performance and can generate electricity even under ordinary light, such as the solar cells on calculators.
4. EVA: Its function is as described above; it mainly bonds and encapsulates the power generation unit and the backsheet.
5. Backsheet: Its functions include sealing, insulation, and waterproofing (generally, materials such as TPT and TPE are used, which must be resistant to aging. Module manufacturers offer a 25-year warranty. Tempered glass and aluminum alloy are generally fine. The key is whether the backsheet and silicone can meet the requirements).
6. The aluminum alloy protective laminate provides a certain degree of sealing and support.
7. Junction Box: Protects the entire power generation system and acts as a current transfer station. If the module is short-circuited, the junction box will automatically disconnect the short-circuited battery string to prevent the entire system from burning out. The most critical part of the junction box is the selection of diodes. The corresponding diodes are different depending on the type of battery cells in the module.
8. Silicone: Used for sealing, sealing the junction between components and aluminum alloy frames, and between components and junction boxes. Some companies use double-sided tape or foam to replace silicone, but silicone is widely used in China because it is simple, convenient, easy to operate, and has a low cost.
The production of monocrystalline silicon solar cells requires a large amount of high-purity silicon material, and the manufacturing process for these materials is complex and consumes a lot of electricity, accounting for more than half of the total cost of solar cell production. Furthermore, the pulled monocrystalline silicon rods are cylindrical, and the sliced solar cells are also circular, resulting in low planar utilization of the assembled solar modules. Due to the presence of obvious grain interfaces and lattice dislocations within polycrystalline silicon, its efficiency is also relatively low. In addition, carrier mobility, lifetime, and diffusion length are all significantly lower in polycrystalline silicon solar cells compared to monocrystalline silicon solar cells.
