Toshio Joge

Applications and field tests of bifacial solar modules

In order to realize a photovoltaic (PV) system that is low cost and flexible in terms of installation, the authors have studied the vertical installation of bifacial solar modules. Simulations of output power and field testing were carried out to evaluate daily and yearly output power when bifacial modules are vertically installed at various azimuth angles. The yearly-generated power by a vertically installed bifacial module was found to be about 1.4 times larger than that of a vertically installed mono-facial module at the test location. Some applications of bifacial modules, such as fence-integrated PV systems and pole mounted PV systems, were successfully demonstrated on the basis of these results.

A thermal dynamical boron getter (pp+ getter) in Fe-contaminated mass production of the boron diffused n+pp+ BSF bifacial silicon solar cells

Thermal dynamical treatments for improving the lifetime of the p base of n+pp+ BSF bifacial silicon solar cells have been demonstrated using iron behavior parameters called pp+ getter. The SIMS for the wafers in mass production showed a precipitated high concentration of the iron region near the surface of the boron diffusion layer, and the phosphorus diffusion layer respectively. A high temperature treatment is supposed to increases iron in the p base by diffusing interstitially from the precipitated region, and low temperature treatment decreases the iron over the solubility diffusing to the precipitated region. So, the last thermal treatment needs a long time and the low temperature enough for improving the lifetime. The simulations and examinations on the changes of the lifetime through the cell process showed good consistency.