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

We have grown BaSi 2 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 BaSi 2 was measured to be approximately 1.3 eV. The absorption coefficient reached approximately 3 × 10 4 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.