As a widely distributed green, pollution-free and clean energy, solar energy is the first choice on the road to sustainable energy development of the country. Photovoltaic power generation is of great significance to energy conservation and emission reduction, winning the battle to defend the blue sky, and building a beautiful China.
 
After 2010, in the context of the slowdown in demand for the solar photovoltaic industry in Europe, my country's solar photovoltaic industry has risen rapidly and has become the main driving force for the development of the global solar photovoltaic industry. Relevant statistics show that by the end of 2017, my country's newly installed photovoltaic grid-connected capacity reached 53GW, a year-on-year increase of more than 50%, and the cumulative grid-connected installed capacity reached 131GW, ranking first in the world. In 2018, my country's newly installed photovoltaic power generation capacity exceeded 43GW, a year-on-year decrease of 18%, and the cumulative installed capacity exceeded 170GW. Although the introduction of the new PV 5.31 policy in 2018 resulted in a decline in the newly installed PV capacity in China, as the PV power generation industry has entered the era of grid parity, the domestic PV industry still has huge room for development in the future. The favorable policies to promote the healthy development of the photovoltaic industry are released. It is estimated that in 2019, China's newly installed photovoltaic capacity will reach 43GW, and the cumulative installed capacity will reach 216GW. In the future, the global photovoltaic market scale will continue to maintain a good growth trend under the leadership of China, Japan, the United States and other countries.
 
1. Basic composition and glue requirements of solar photovoltaic modules

 
A set of solar photovoltaic modules is roughly composed of seven parts: tempered glass, EVA film, cells, backplane, aluminum alloy frame, junction box, and module glue.
 
Solar photovoltaic modules are mainly used outdoors, so the selected sealant must adapt to the climatic differences in different regions when used outdoors for a long time, such as high temperature and high humidity, high and low temperature, strong ultraviolet rays, ozone, wind and rain and other natural conditions.
 
Because of its excellent high and low temperature resistance, excellent adhesion, excellent aging resistance, excellent insulation performance, good elasticity, hydrophobicity, simple application process and high production efficiency, silicone sealants are currently used in solar energy. It is widely used in photovoltaic module packaging production.
 
1. Requirements for adhesives used for bonding and sealing of frames, backplanes and junction boxes
 
Solar cells are the core components of solar photovoltaic power generation systems. Since solar cells have defects such as thinness, brittleness, and easy oxidation, it is necessary to carry out protective encapsulation to form solar cell modules with stable performance. Therefore, the performance requirements of its adhesive sealant are as follows:
 
(1) The curing speed is fast and the production operation process is simple;
 
(2) Good adhesion to various backplanes, frames and junction boxes;
 
(3) Small thermal stress, good heat dissipation, good weather resistance, good UV resistance, good waterproof performance, and good electrical insulation;
 
(4) Maintain the physical and electrical properties of the sealed components under a wide range of temperature (-40 ℃ ~ 150 ℃), humidity and harsh environmental conditions;
 
(5) Absorb the stress generated by shock and vibration, and the waterproof seal keeps the cells dry and not damaged by stress, resists yellowing, can be repaired, and has a life span of more than 20 years.
 
2. Requirements for junction box potting glue
 
The solar photovoltaic junction box is a connector between the solar cell array composed of solar cell components and the solar charging control device. It is an indispensable supporting component of solar power generation equipment. The performance requirements of its potting glue are as follows:
 
(1) Simple operation, good self-leveling and self-discharging properties, and fast curing;
 
(2) After curing, it has good waterproof, insulating and thermal conductivity, and good bonding;
 
(3) Excellent anti-aging properties, outdoor use can resist the adverse effects of ultraviolet light, ozone, moisture, acid, alkali, and maintain physical properties and electrical insulation properties.
 
The national recommended standard GB/T 29595-2013 "Seal Materials for Ground Photovoltaic Modules - Silicone Rubber Sealants" converts the above requirements into corresponding technical index requirements. Combined with the application, for the frame, backplane, and junction box bonding and sealing adhesives, the main things to be investigated are the curing speed and the adhesion, mechanical properties and electrical properties after moist heat aging; It is its pot life, adhesion, heat dissipation and electrical properties before and after moist heat aging.
2. Common problems and solutions of adhesives for solar photovoltaic modules
 
1. Adhesive for frame, backplane and junction box bonding and sealing
 
①Exploding glue:
 
Reason: For large barrel packaging, it is generally caused by the unstable pressure of the glue;
 
Solution: Use a stable air source and a well-matched pressure plate to solve this problem.
 
②Bubble:
 
Reason: Generally, the amount of glue is not enough to cause the gas to be sealed in the frame;
 
Solution: The amount of glue applied is greater than the filling amount required for the gap between the laminate and the frame to solve the bubble problem.
 
③Slow curing:
 
Reason: Silicone sealants are generally cured by absorbing moisture in the air. The curing speed is not only closely related to the formula, but also mainly related to the temperature and humidity of the sizing environment.
 
Solution: It can be improved by adjusting the ambient temperature and humidity.
 
2. Glue for junction box potting
 
①Inconsistent curing:
 
Reason: Generally, it is caused by the uneven mixing of A and B glue;
 
Solution: Mix A and B glue evenly before use, properly adjust the glue discharge pressure of A and B components, and fine-tune the ratio of A and B components to solve the problem.
 
②There are many pores inside the colloid after curing:
 
Reason: due to poor self-exhausting colloid;
 
Solution: Appropriately reduce the viscosity of component A, increase the fluidity of the colloid, and at the same time improve the equipment supporting process to eliminate air bubbles from the construction point of view.
 
③The bypass diode is damaged:
 
Reason: high temperature, poor thermal conductivity;
 
Solution: Choose a potting compound with excellent thermal conductivity and flame retardant properties to enhance the heat dissipation performance of the junction box.