In recent years, with the improvement of photovoltaic technology, double-glass solar modules have developed rapidly. Compared with the traditional single-glass module, the double-glass module uses photovoltaic glass instead of the backplane, which greatly improves the performance of the module in terms of water vapor resistance, corrosion resistance, fire protection, sand abrasion resistance, etc. At the same time, because of the light transmittance of the double-glass module, it can be used for agricultural/fishing light complementation and general buildings, expanding the application range of solar photovoltaic modules.

Compared with single-glass module, double-glass module has greater advantages.

First of all, because the water vapor transmittance of glass is almost zero, it is not necessary to consider the problem of water vapor entering the module to induce the hydrolysis of EVA film, especially for photovoltaic power stations in areas with high humidity such as the seaside and waterside;

Secondly, the glass has good wear resistance, weather resistance and corrosion resistance, so that the components can be used in areas with heavy wind and sand, acid rain and salt fog;

Third, the fire protection level of the double-glass module is improved, which is applicable to residential buildings, factories and other areas that need to avoid fire hazards;

Fourth, the high insulation of glass makes the module suitable for higher system voltage and saves the system cost of the power station.

At present, the packaging film for double-glass module mainly includes EVA film and POE film. EVA adhesive film is an ethylene-vinyl acetate copolymer, which has the advantages of low melting point, good fluidity, high transparency, mature lamination process, and is the main packaging material for double-glass modules at present.

However, due to the low strength of EVA adhesive film, high water vapor transmission and water absorption, and poor weather resistance, edge sealing is required for double-glass components. However, in the normal use process, there will still be water vapor transmission, resulting in the atomization of the adhesive film, affecting the light transmittance, and reducing the power generation of the components.

POE is an ethylene-octene copolymer, a new polyolefin thermoplastic elastomer with narrow relative molecular weight distribution and narrow comonomer distribution and controllable structure developed with metallocene as catalyst.

At present, there are two kinds of POE adhesive films on the market. One is the non-crosslinked polyolefin packaging materials that do not contain cross-linking agents and make the heat resistance and adhesion of the materials meet the use requirements through the combination of functional polymers, represented by the ENLIGHT packaging materials of Dow Chemical; The other is the cross-linked polyolefin packaging material containing peroxide crosslinking agent or silane crosslinking agent and tackifier. This kind of adhesive film has similarities with EVA adhesive film in production technology and process.

Compared with EVA adhesive film, the biggest advantage of POE adhesive film is low water vapor permeability and high volume resistivity, which ensures the safety and long-term aging resistance of the module under high temperature and high humidity environment, so that the module can be used for a long time. Specifically, the performance of POE film is superior to that of EVA film:

1、 POE adhesive film is a copolymer of ethylene and octene, which is a saturated aliphatic chain structure, and has less tertiary carbon atoms in the molecular chain, showing good weather resistance, ultraviolet aging resistance, excellent heat and low temperature resistance, so POE adhesive film has better aging resistance than EVA adhesive film.

2、 The adhesion of POE film to glass, back plate and other materials is improved by means of photografting polar monomer, plasma surface treatment or reactive grafting modification of POE, with excellent interfacial adhesion.

3、 It is applicable to high-efficiency double-sided battery, which can effectively enhance the conversion efficiency of the battery, improve the power generation rate and reduce the cost of kilowatt-hour power generation compared with the ordinary single-sided power generation module. At the same time, the module can be placed vertically and has more utilization ways.

4、 POE adhesive film has lower water vapor permeability and greater cohesion, which is more suitable for double-glass components. It can make the double-glass components produced without edge sealing and have longer service life.

However, in addition to the above advantages, there are also some disadvantages of POE adhesive film at present, such as small fluidity, difficult processing, and difficult to control uniformity, which affect the large-scale use of POE adhesive film in component production.