Most bulk silicon PV modules consist of a transparent surface, an encapsulation, a back and a frame around the outer edge. In most components, the top surface is glass, the encapsulant is EVA (ethyl vinyl acetate), the back side is PET, this is just glass solar panels, the flexible module surface may be ETFE or PET, and the back side of the patch module is PCB.
Surface materials for photovoltaic modules
The front surface of the PV module must have high light transmittance in the wavelength range where the solar cells in the PV module can be used. For silicon solar cells, the top surface must have high light transmittance in the wavelength range of 350 nm to 1200 nm. In addition, the reflection of the front surface should be low. While in theory this reflection can be reduced by applying an anti-reflective coating to the top surface, in practice these coatings are not strong enough to withstand the conditions of use of most photovoltaic systems. Another technique to reduce reflections is to "roughen" or texture the surface. However, in this case, dust and dirt are more likely to adhere to the top surface and are less likely to be dispersed by wind or rain. Therefore, these components are not "self-cleaning", and the advantages of reduced reflections are quickly offset by losses due to increased dirt on the top surface.
In addition to reflection and transmission properties, the surface material should be impermeable, should have good impact resistance, should remain stable under long-term ultraviolet radiation, and should have low thermal resistivity. Water or water vapor entering the PV module will corrode the metal contacts and interconnects, greatly reducing the service life of the PV module. In most components, the front surface is used to provide mechanical strength and stiffness, so the surface or rear surface must have mechanical stiffness to support the solar cells and wiring.
There are several options for surface materials, including acrylic, polymer, and glass. Tempered, low-iron glass is the most commonly used because it is low-cost, strong, stable, highly transparent, impermeable to water and gas, and has good self-cleaning properties.
PV module encapsulants
Encapsulants are used to provide tack between the top and rear surfaces of solar cells, photovoltaic modules. The encapsulator should be stable at high temperatures and high UV exposure. It should also be optically transparent and should have low thermal resistance. EVA (ethyl vinyl acetate) is the most commonly used encapsulation material. EVA is lamella, which is inserted between the solar cell and the top and back. This interlayer is then heated to more than a hundred degrees, allowing the EVA to polymerize and bond the components together.
Rear surface of photovoltaic modules
The main feature of the rear surface of a PV module is that it must have low thermal resistance and must be protected from the ingress of water or water vapor. In most modules, thin polymer panels are used on the back surface Some photovoltaic modules, known as bifacial modules, are designed to receive light from the front or back of the solar cell. In a bifacial assembly, both the front and rear parts must be optically transparent
PV module frame
The last structural component of a solar panel is the frame or frame of the solar panel. Traditional PV module frames are usually made of aluminum. The frame structure should be free of bumps that could cause water, dust or other substances to entrap.