Stability and efficiency of some amorphous silicon photovoltaic modules

Amorphous silicon photovoltaic modules from four US manufacturers were tested for their power generation. The modules were exposed in outdoor sunlight over a period of one year. Current-voltage (I- V) curve measurements were made on each module daily with the automated I-V curve tracer. From these measurements, module electrical performance characteristics were determined. It is shown that the power degradation of the amorphous silicon modules tested was 18 to 33% after one-year period of sunlight exposure. The degradation in the voltage parameters is generally lower than in the current parameters, being less than 7% for open-circuit voltage. About half of the degradation in the peak power is due to the degradation of the fill factor. The power output of the modules had nearly stabilized in the first eight months of the sunlight exposures and their stabilized efficiencies were in the range of 2.6 to 4.4%