Abstract
The long-term stability of p-Si and c-Si photovoltaic modules manufactured in the 1990's has been studied. About 2,000 modules were investigated after nearly 10 years of exposure. About 150 modules out of these were evaluated by indoor I-V measurements. An average performance loss of less than 0.5%/year was estimated. We found three dominant degradation modes which are main problems for achieving 30-year life time; (1)visual defects caused by delamination between the cells and the potant and two modes without visual features. (2)One is accompanied by a decrease in the fill factor (FF), and (3)the other is accompanied by a decrease in both the short-circuit current (I_<SC>) and the open circuit voltage (V_<OC>). Destructive analyses of modules with degraded FF were conducted.
