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

Abstract

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