Toward Si-based high-efficiency thin-film solar cells using semiconducting BaSi2

Abstract

We have grown BaSi2 epitaxial films on Si(111) substrates by molecular beam epitaxy, and investigated their optical properties such as optical absorption coefficients, minority-carrier diffusion length and minority-carrier lifetime. These are key parameters which determine the performance of solar cells. The band gap of BaSi2 was measured to be approximately 1.3 eV. The absorption coefficient reached approximately 3×104 cm−1 at 1.5 eV The minority-carrier diffusion length and minority-carrier lifetime were found to be about 10 μm and 8 μs, respectively. These values are great enough for thin-film solar cell applications. Control of carrier type and carrier concentration was also demonstrated.