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Keywords:

  • amorphous silicon;
  • accelerated test;
  • irradiance and temperature cycle;
  • initial degradation;
  • seasonal variation;
  • long-term stability

ABSTRACT

An accelerated irradiance and temperature cycle test (AITCT) has been developed as a method to evaluate the long-term performance stability of amorphous silicon (a-Si) photovoltaic (PV) devices. The AITCT simulates the daily light–dark cycle in 6 min (0.1 h). It also simulates the annual temperature cycle while controlling the temperature at 45 °C above the average monthly outdoor ambient temperature. This allows the influence of the day–night cycle and seasonal variation to be included in the acceleration factor for single-junction a-Si PV devices. The initial degradation and seasonal variation of performance of a-Si PV devices simulated by the AITCT agreed well with experimental results of 4-year outdoor exposure. Subsequent tests with the AITCT equivalent of 30-year outdoor exposure revealed that rapid degradation in the efficiency of a-Si PV devices would not occur by repeating the cyclic changes corresponding to seasonal variations following the initial degradation. The AITCT is able to accelerate further recovery in addition to light-induced degradation. Furthermore, the AITCT is applicable to other PV devices with light-intensity dependencies related to light-induced degradation as well as thermal recovery dependencies, such as multi-junction PV devices consisting of a-Si layers and other materials. This point will be discussed. Copyright © 2012 John Wiley & Sons, Ltd.