INTENSITY AND TEMPERATURE-DEPENDENCE OF PHOTODEGRADATION OF AMORPHOUS-SILICON SOLAR-CELLS UNDER INTENSE ILLUMINATION

The kinetics of the light-induced degradation of amorphous hydrogenated silicon (a-Si:H) based single junction solar cells was studied using an accelerated test with light intensity as high as 140 times that of the sun. A simple scaling law between the light intensity (I) and the exposure time (t), i.e., I1.8t = const, was found for the solar cell degradation. No apparent saturation was observed at 50-degrees-C after an equivalent one sun exposure time of over 25 000 h. Saturation, however, did occur at higher temperatures and the level of saturation was found to depend on both temperature and light intensity. These results suggest that the long-term stability of a-Si:H solar cells is governed by the competition between light-induced degradation and thermal annealing, instead of the total number of possible sites for defect generation.