Effects of Cerium Removal from Glass on Photovoltaic Module Performance and Stability

Wednesday, July 14 2010

In photovoltaic (PV) modules, polymeric materials provide electrical insulation and protect modules from mechanical damage and environmentally induced corrosion. When used in front of a PV cell, the principal attributes of interest are that the encapsulant transmits photons and maintains adhesion to all surfaces. PV module qualification tests are designed to provide minimum standards for module durability and to demonstrate a degree of safety in the production of electricity.

Photovoltaic modules are exposed to extremely harsh conditions of heat, humidity, high voltage, mechanical stress, thermal cycling, and ultraviolet (UV) radiation. Because of the extreme difficulty of exposing production modules to concentrated light sources, the UV exposure required by these tests corresponds to an equivalent field exposure of several months to 1.5 years rather than the desired service life of 30 years. In the mid-1980s, there were a number of notable problems with ethylene vinyl-acetate (EVA) yellowing. This degradation was partially the result of polymer embrittlement, delamination, and/or discoloration (yellowing). One part of the solution to these issues was to use glass containing Cerium (Ce), which selectively blocks UVB radiation. In recent years, better stabilizer formulations for EVA have been developed, giving more confidence in the long-term stability of PV packaging materials. Because of this, some manufacturers have stopped using Ce-doped glass.