Outdoor performance studies of a-Si alloy multi-junction solar cells using simulated solar illumination

A comparison of various a-Si alloy photovoltaic devices-singles, tandems, and triples-under incident solar irradiance with widely different spectral content was made in an outdoor performance study. The spectral irradiance was varied over a range of the three most crucial atmospheric parameters that affect the incident spectrum: air mass, water vapor and turbidity. A multisource solar simulator was used to simulate the spectrum throughout the day for each of five different days. I-V curves of the solar cells were then measured under these various spectral conditions, and their performances were compared. The results reveal that the power output of the multijunction devices, when normalized at solar noon and integrated over the day, shows a difference of only ±4% with respect to the single-type cells, indicating a similarity in response among the different types of devices