As crystalline silicon solar cells themselves are easy to break and corrode, if exposed directly to the atmosphere, the photoelectric conversion efficiency will be reduced due to humidity, dust, acid rain and other factors, and the cells will be easily damaged. Therefore, crystalline silicon solar cells generally must be made into a flat structure by gluing and laminating, etc. As a power source, a number of single cells must be connected in series and parallel and tightly encapsulated, which is the solar cell module. The encapsulation of crystalline silicon solar cells into solar cell modules is a key part of solar cells can be used for a long time, can be isolated from the outside atmosphere of the large solar cell contact channel, to protect the electrodes and avoid corrosion of the interconnecting wires. In addition, the encapsulation with rigid material also prevents the solar cell from breaking, and the quality of the encapsulation determines the performance and service life of the crystalline silicon solar cell module. The encapsulation of crystalline silicon solar cells is mainly by vacuum hot pressing method, the solar cell monomer after positive and negative welding, after series and parallel connection to form an array of crystalline silicon solar cells, both sides using EVA (Ethylene Vinyl Ac etate, polyethylene vinyl acetate) material, and then on both sides with low-iron tempered glass and TPT, into the vacuum laminator, the lamination chamber vacuum, heating, the glass/EVA cells will be put into the vacuum laminating machine. Heating, the glass/EVA battery string/EVA/TPT is hot pressed together to ensure the practicality, interchangeability, reliability and longevity of use. Among them, TPT (Tedler Polyeast Tedler, composite fluoroplastic film) is the covering on the back side of solar cell, which is white fluoroplastic film. The modules are encapsulated with sufficient mechanical strength to withstand clashes, vibrations and other stresses that occur during transportation, installation and use, reducing overall power loss.
Structure of solar cell module
Conventional solar cell modules are available in the following structural forms: glass housing type structure,Flat-panel components,Fully gasketed assembly without cover plate.
Encapsulation materials for solar cell modules
The module life is one of the important factors to measure the quality of the module, and the working life of the module is related to the packaging material and the packaging process.
The module lifetime is an important factor to measure the module quality. Encapsulation materials play an important role in solar cells, such as glass, EVA, glass fiber and TPT.
Glass fiber and TPT also have an impact on the output power of the module after encapsulation. The materials, components and structures used in the modules are required to be
The materials, parts and structures used in the module are required to be consistent with each other in terms of service life to avoid the failure of the whole module due to one damage.
(1) Upper cover plate
The upper cover plate covers the front side of the solar cell module and constitutes the outermost layer of the module, which should have high light transmission rate and be strong to protect the cell for a long time.
It should be strong and play the role of long-term protection of the battery. The materials used for the upper cover are: tempered glass, polypropylene
Acid resin, fluorinated ethylene propylene, transparent polyester, polycarbonate, etc.
For the encapsulated glass used in solar cells, the current mainstream products are low-iron tempered embossed glass, which can be used in the wavelength range of the solar cell spectral response.
In the wavelength range of the spectral response of solar cells (320~1100nm), the iron content is extremely low (less than 0.015%).
Therefore, its light transmittance is extremely high (about 91% in the spectral range of 400~1100nm), and it looks white from its edge.
The glass is white, so it is also called white glass, and has high reflectivity for infrared light greater than 1200nm.
In addition, the glass is tempered, not only to maintain a high value of light transmission, but also to make the strength of the glass
The glass toughening process helps to improve the resistance of solar cell modules to hail and accidental blows, and ensures the strength of the whole module.
The glass tempering process helps to improve the solar cell module’s ability to resist hail and accidental blows and to ensure that the entire solar cell module has high enough mechanical strength. In order to reduce the reflection of light
reflection, the glass surface can be treated with some anti-reflective technology to make “anti-reflective glass”, whose measures are mainly
The main measure is to coat the glass surface with a thin film, which can effectively reduce the reflectivity of the glass.
Resins include room temperature curing silicone rubber, fluorinated ethylene propylene, polyvinyl butyral, transparent epoxy resin, polyvinyl acetate, etc.
Polyvinyl acetate, etc., the general requirements are as follows: ① high light transmission in the visible range: ② elasticity
(3) good electrical insulation performance: (4) suitable for automated module encapsulation, resin encapsulation is a simple
Resin encapsulation is a simple form of solar cell encapsulation, and the cost of the materials used is relatively low. It is widely used in small solar products with its flexibility and low price.
It is widely used in small solar products, such as solar lawn lamp, solar charger, solar teaching
solar toys, solar road signs and solar signal lights, etc.
(3) Organic silicone
The basic structural unit of silicone products is composed of silicon-oxygen links, and the side chains are connected with various organic groups through silicon atoms.
The side chains are connected with other organic groups through silicon atoms. Silicone is not only resistant to high temperatures, but also to low temperatures, and can be used in a wide range of temperatures.
The chemical properties and physical and mechanical properties of silicones vary very little with temperature.
Silicone products have good electrical insulation properties, including dielectric loss, voltage resistance, arc resistance, corona resistance, volume
The dielectric loss, voltage resistance, arc resistance, corona resistance, volume resistance coefficient and surface resistance coefficient are among the top insulating materials, and their electrical properties are very little affected by temperature and frequency.
Temperature and frequency of the impact is very small, and silicone curing is colorless and highly transparent.
(4) EVA film
EVA film is also known as solar cell film, used to bond the glass and solar cell array, solar cell
array and TPT film, and its light transmission rate is good. The standard solar cell module generally needs to add two layers of EVA film.
EVA is a copolymer of ethylene and vinyl acetate.
EVA is a copolymer of ethylene and vinyl acetate, unmodified EVA transparent, soft, hot melt adhesion, low melting temperature, melt flow characteristics.
Good melt fluidity and other characteristics. These characteristics meet the requirements of solar cell closure, but its heat resistance is poor, easy to extend
And low elasticity, low cohesive strength, easy to produce thermal contraction and solar cell fragmentation, so that the bonding delamination. In addition, the
solar cell module as a long-term outdoor use of the product, EVA film can withstand outdoor UV
aging and thermal aging is also a very important issue. EVA is used as raw material, add suitable modified additives
EVA solar cell film is made by heating and extrusion, which is easy to cut at room temperature;
The solar cell module is laminated and encapsulated according to the heating and curing conditions, and a permanent adhesive seal is produced after cooling.
The glass fiber layer is woven with glass fibers to remove the air bubbles that may be sealed inside the cell panel during lamination.
The glass fiber layer is woven with glass fiber to remove air bubbles that may have been sealed inside the panel during lamination.
(5) Back Material
The backside materials are generally tempered glass, aluminum alloy, Plexiglas, TPT, etc. TPT is used to prevent water vapor from entering the solar module and reflecting sunlight. TPT is used to prevent water vapor from entering the solar cell module, and to reflect sunlight, which can reduce the working temperature of the module because of its high infrared reflectivity. The thickness of TPT film is 0.12mm, and its reflectivity is in the spectrum of 400~1100nm. The average reflectance in the spectral range of 400~1100nm is 0.648. The film has the following characteristics: ① good weather resistance, can withstand outdoor temperature changes, UV aging and thermal aging, etc.: ② no change in the lamination temperature; ③ strong bonding with adhesive materials.
Flat panel components must have a frame to protect the components, components with a frame to form a square, frame with adhesive to form a seal on the end of the component side, the main materials are stainless steel, aluminum, rubber, reinforced plastic, etc., solar cell components