Abstract
The aim of this paper was to analyze the surface passivation based on SiO2 for thin bifacial solar cells as well as to evaluate the influence of the type of substrate used to fabricate the cells. The n+pp+ structure was implemented, with phosphorus in the front face and boron and aluminum in the rear face, forming in the latter a selective back surface field. The Czochralski (Cz) and float zone (FZ) monocrystalline silicon wafers (145 μm thick) were used and a thermal step to grow a SiO2 layer to passivate the surfaces was implemented. The oxide passivated the surfaces, providing an absolute increase of 0.5% in FZ silicon solar cell efficiency. The solar cells produced in Si-Cz did not present the same increase because they showed a high series resistance. The more efficient thin solar cell was manufactured with Si-FZ and with oxidized surfaces, reaching the efficiency of 14.5% and 11.1%, for illumination by the n+ and p+ faces, respectively. The Si-Cz solar cells, even with a lower initial lifetime of minority carriers, reached slightly lower efficiencies than Si-FZ solar cells.
Keywords:
solar cells; bifacial solar cells; thin silicon wafers; surface passivation
