A-Si:H buffer in a-SiGe:H solar cells

Profiled a-SiGe:H-buffer layers between the doped and the absorption layers of amorphous silicon germanium (a-SiGe:H) solar cells are routinely used to avoid bandgap discontinuities and high-defect densities at the p/i- and i/n interface. Here, we present a much simpler approach replacing the profiled a-SiGe:H-buffer layers at both interfaces by a-Si:H-buffer layers. It is demonstrated that for a-SiGe:H solar cells (thickness of the EG=1.5 eV part is 54 nm) these structures yield similar open circuit voltage VOC and fill factor (FF) compared to the bandgap profiled layer at the same short circuit current density jSC. The influence of thickness, optical bandgap and position of the buffer layers on the solar cell performance is investigated.