Surface passivation effect of RF-plasma processed a-Si:H layers on the optical properties of BaSi_2 epitaxial films

摘要

BaM2 is a good candidate for future solar cells. It has many advantages such as a band gap of1.3 eV, suitable for the solar spectrum, alarge absorption coefficient of 3×104 cm1 at1.5 eV, exceeding those of CIGS [1], and alarge minority-carrier diffusion length of ca.10 |im [2]. In our previous work, we have realized the conversion efficiency of 9.9% in a p-BaSi2/n-Si (111) heterojunction solar cell capped with pure amorphous Si (a-Si) layers. They have, however, a lot of dangling bonds to hinder the performance of solar cell [3]. An alternative is hydrogenated a-Si (a-Si:H) layer. We have already confirmed that a-Si:H can be grown by MBE method and radio-frequency (RF) plasma generator [4]. In this study, we investigated the effect of a-Si:H capping layers on the optical properties of crystalline Si (c-Si) substrates and BaSi2 epitaxial films.