Integration of β-FeSi2 with poly-Si on glass for thin-film photovoltaic applications

Aluminum-alloyed polycrystalline p-type beta-phase iron disilicide p-beta-FeSi2(Al) films with different thicknesses are successfully integrated with n-type polycrystalline silicon films on glass for thin-film solar cell applications. A sharp and high-quality interface is formed between 49 nm thick beta-FeSi2(Al) and poly-Si, through the formation of a thin layer (similar to 7 nm) of Al-doped p(+) epitaxial Si. The quality of the interface between poly-Si and p-beta-FeSi2(Al) is found to degrade with increasing p-beta-FeSi2(Al) thickness. An similar to 5 nm thick amorphous layer is observed at the interface for the 145 nm thick p-beta-FeSi2(Al) layer. The structural and photovoltaic characteristics of the p-type beta-FeSi2/p(+) Si/n(-) Si/n(+) Si solar cell samples are investigated in detail. For a sample annealed at 650 degrees C, a one-Sun open-circuit voltage of 320 mV and pseudo fill factor of 67% are obtained, using an similar to 49 nm p-type beta-FeSi2 film on n-type poly-Si. The efficiency of the investigated solar cell structure decreases with increasing annealing temperature and thickness of the beta-FeSi2 film.