Amorphous silicon and silicon germanium materials for high-efficiency triple-junction solar cells

In this paper, we report our recent progress in the amorphous silicon (a-Si)-based photovoltaic research program at The University of Toledo (UT). We have achieved the fabrication of (1) wide bandgap a-Si solar cells with an open-circuit voltage of 0.981 and a fill factor of 0.728 using high hydrogen dilution for the i-layer deposition, (2) mid bandgap a-SiGe solar cells having an open-circuit voltage of 0.815 and a fill factor of 0.65, (3) narrow bandgap a-SiGe solar cells with 9.17% initial efficiency, and (4) triple-junction, spectrum-splitting a-Si/a-SiGe/a-SiGe solar cells with 10.6% initial efficiency.