Possibility of Si-based new material for thin-film solar cell applications

We grow BaSi2 epitaxial films on Si(111) substrates by molecular beam epitaxy, and investigate their optical properties such as optical absorption coefficients, minority-carrier diffusion length, and minority-carrier lifetime. These are key parameters which determine the solar cell performance. The band gap of BaSi2 is measured to be approximately 1.3 eV. The absorption coefficient reaches approximately 3x10(4) cm(-1) at 1.5 eV. The minority-carrier diffusion length and minority-carrier lifetime are found to be about 10 mu m and 8 mu s, respectively. These values are sufficiently large for thin-film solar cell applications. Internal photoresponse spectra are deduced from data obtained experimentally.