Chemical bonding technology for terrestrial photovoltaic modules. Status to February 1983

Encapsulated photovoltaic modules must hold together for 20 years, reliably resisting delamination and separation of any of the component materials. Delamination of encapsulation materials from each other, or from solar cells and interconnects, can create voids for accumulation of water, promoting corrosive failure. Delamination of silicone elastomers from unprimed surfaces was a common occurrence with early modules, but the incidences of silicone delamination with later modules decreased when adhesion promoters recommended by silicone manufacturers were used. An investigation of silicone delamination from unprimed surfaces successfully identified the mechanism, which was related to atmospheric oxygen and moisture. This early finding indicated that reliance on physical bonding of encapsulation interfaces for long life in an outdoor environment would be risky. For long outdoor life, the material components of a module must therefore be held together by weather-stable adhesion promoters that desirably form strong, interfacial chemical bonds. The Environmental Isolation Task of the Flat-Plate Solar Array Project (FSA), managed by the Jet Propulsion Laboratory (JPL) for the US Department of Energy (DOE), conducts a program to identify, develop, and validate weather-stable chemical bonding adhesion promoters for terrestrial photovoltaic modules. This report is intended to accomplish three purposes: provide a status report on chemicallymore » bonding adhesion promoters, with data on bond strength performance; describe and discuss the theories of the chemically bonded interface; and identify processing considerations relevant to achieving long-term interfacial chemical bonding.« less