The manufacturing process of photovoltaic (PV) modules
The specific manufacturing process of photovoltaic (PV) modules includes the following steps: laser cutting, cell welding, stacking, laminating, framing, curing, cleaning, and IV & EL testing.
Laser Cutting
Laser cutting uses low-temperature laser technology in combination with the principle of thermal expansion and contraction. The silicon wafer naturally separates through thermal stress, and no microcracks are produced on the cutting surface. The mechanical strength of the cut cells is equivalent to that of the uncut whole cell.
Cell Welding
The cells are separated according to requirements, then inspected and corrected before being placed on the conveyor belt. Infrared contact welding is used to connect the cells with the busbars to form a string.
Stacking
In the stacking process, the cell strings are further connected in an electrical circuit, and the cells are encapsulated and protected using glass, EVA (ethylene-vinyl acetate) film, and a backsheet.
Laminating
During the laminating process, the stacked assembly is placed into a laminating machine. Under specific conditions, the EVA melts and bonds the cells, glass, and backsheet together.
Framing (Including Junction Box Installation)
Framing is the process of sealing and protecting the module edges with an aluminum frame, which also facilitates installation. The junction box is also installed during this step.
IV & EL Testing
IV Testing: Under specific testing conditions (25°C temperature, 1000W/㎡ light intensity, AM1.5 spectrum), the module's power is tested. The open-circuit voltage (Voc), short-circuit current (Isc), polarity, maximum power point voltage (Vmpp), current (Impp), and peak power (Pmax) are measured. The fill factor (FF) of the photovoltaic module/string is also measured.
EL Testing: Based on the characteristics of semiconductor radiation recombination and photon emission, a forward voltage is applied to inject non-equilibrium carriers into the module. The photons released during recombination of non-equilibrium carriers are detected by a photon detector. The higher the concentration of non-equilibrium carriers (in the normal areas), the more photons are emitted, and the EL image appears brighter. In contrast, the lower the concentration of non-equilibrium carriers (in defect areas), the fewer photons are emitted, and the EL image appears darker. By analyzing the brightness of the EL image, defects within the cells can be identified.
This concludes the introduction to the manufacturing process of photovoltaic modules by Hengyuantai.