Band-gap profiling in amorphous silicon-germanium solar cells

Profiled buffer layers at the interfaces of amorphous silicon-germanium (a-SiGe:H) solar cells are routinely used to avoid band-gap discontinuities and high-defect densities at the p/i and i/n interfaces. It is shown that such profiled a-SiGe:H buffer layers can be replaced by a constant band-gap a-Si:H buffer, an inverse profiled a-SiGe:H buffer, or even a 3-nm-thin (delta) buffer at some distance away from the interface without losses in the open-circuit voltage V-OC and fill factor while maintaining the same short current density j(SC). In view of these results, common model assumptions for a-SiGe:H solar cells have to be revised. (C) 2002 American Institute of Physics.