Semiconducting β-FeSi2 for high efficiency and low cost photovoltaics

Abstract

The beta phase of iron disilicide, β-FeSi2, behaves as a semiconductor and possesses three desirable material properties: direct band gap of around 0.87 eV, close lattice match with silicon (2-4% mismatch) and abundant availability of its constituent elements on the earth's crust. Moreover, its high optical absorption coefficient (one to two orders of magnitude higher than silicon) makes it a promising next generation semiconductor for photovoltaics with high performance and low environmental burden. The purpose of this work is to examine fundamental properties of β-FeSi2 material for application towards higher efficiency and low cost photovoltaics. Sputter deposition of Fe/Si multilayers was used to fabricate β-FeSi2 films. Conversion of the multilayer films to β-FeSi2 was accomplished by a thermal treatment under N 2atmosphere. β-FeSi2 films fabricated exhibited polycrystalline grains, with a direct energy band gap of 0.87 eV, an absorption coefficient in the order of 105 cm-1 and a residual carrier concentration due to electrons in the order of 1019 cm-3. Results of characterization using x-ray photoelectron spectroscopy, x-ray diffraction, scanning electron microscopy, UV-VIS-IR spectrophotometer measurements and Hall effect measurements have been discussed. © 2010 IEEE.