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

Kumar, A., Dalapati, G. K., Hidayat, H., Law, F., Tan, H. R., Widenborg, P. I., Hoex, B., Tan, C. C., Chi, D. Z., Aberle, A. G.
RSC advances 2013 v.3 no.21 pp. 7733-7738
aluminum, annealing, cell structures, glass, iron, silicon, solar cells, temperature
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.