Bifacial cells have been developed for use in flat-plate static-concentrator modules and bifacial photovoltaic modules. All but one of the fabrication processes are conventional mass production processes, making it possible to produce these cells at low cost. By using 12.5 x 12.5 cm SOG wafers, bifacial cells with about 15% front- and 10.5% rear-illumination efficiencies have already been developed, and cells achieving higher efficiencies for both surfaces are being developed now. By applying these cells, a bifacial-cell-type flat-plate static-concentrator module showed 82% optical-collection efficiency for normal-incident light with a 2.0 concentration ratio. We have also applied bifacial cells for non-concentrating bifacial modules and developed a new application that reduces the limitations on PV module installation. (C) 2002 Elsevier Science B.V. All rights reserved.