Adhesives have become prevalent in solar applications to replace mechanical fasteners and welding. Solar assemblies need to withstand harsh environmental conditions (e.g., UV, rain, wind, sand) and temperature cycling (i.e., panels get cold at night, hot during the day, and cold again at night) for long periods of time.

Silicones have become a workhorse of the industry and are particularly used in sealant applications where their moisture resistance, UV resistance, and long-term durability are well proven. One-component moisture-curing products are used, and two-component versions are used when very fast curing is required or for filling large gaps. Although silicones do not have very high tensile shear strengths compared to other types of adhesives, they have proven successful in some structural adhesive applications.

The other technology that has become important is reactive acrylics. Acrylics are quite resistant to UV light (check out the acrylic paint on your house!). They bond very well to dissimilar substrates such as metals and plastics and have very high bond strengths where high tensile shear forces are experienced. I have read reports where solar assemblies were decommissioned after 30 years in use, and the acrylic bonds were still intact.

Although not as flexible as silicones, acrylics are tough enough to withstand temperature cycling and mechanical shock. Electrically conductive acrylics are also available for applications such as linking photovoltaic cells together.
 

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