R&D Challenges and Opportunities in Si Photovoltaics

The PV industry has already begun to address the use of thinner Si wafers, dropping from 400 mm toward 200 mm. Such a reduction in the wafer thickness is expected to conserve Si usage with an added advantage of higher cell efficiencies. The test production lots, fabricated with thin wafers, have verified such improvements in the device performance with a reduction in wafer thickness. However, theyield of thin cells is far lower than that of its thicker counterparts. It is expected that automation can mitigate part of this problem. However, it is necessary to investigate the basic mechanisms of wafer breakage. In particular, factors such as sawing, texturing, and warpage by the asymmetric metal patterns, which cause a propensity to breakage, need to be well understood. The final frontierof the thinner cells, the thin-film Si solar cell, is already above the horizon. The transition of this laboratory device into pilot line and then to production, is a strong challenge.