Efficiency evaluation of a-Si and c-Si solar cells for outdoor use

We have achieved the world's highest stabilized efficiency of 8.9% for an a-Si single-junction solar cell (1 cm/sup 2/) and 10.6% for an a-Si/a-SiGe tandem solar cell (1 cm/sup 2/). To apply these results to practical outdoor power use, the annual output power of a-Si single-junction (a-Si) and tandem (a-Si/a-Si) solar cells and a crystalline silicon (c-Si) solar cell was calculated based on annual meteorological data and the solar spectrum in Tokyo, Japan, including the effect of the output power dependence on temperature, incident irradiance and solar spectrum. As a result, this simulation revealed that the annual change of efficiency for the c-Si solar cell is most affected by the solar spectrum among the three types of solar cells, and the annual fluctuations of the a-Si and a-Si/a-Si solar cells are mostly caused by recovery by the annealing effect.