Electronic structure of molybdenum-involved amorphous silica buffer layer in MoOx/n-Si heterojunction

Abstract

An amorphous silica layer containing Mo component (a-SiOx(Mo) ∼ 3.5–4.0 nm) is naturally formed in the process of evaporating MoO3 power onto n-type silicon, which plays a significant role on the non-equilibrium carriers’ transport of MoOx/n-Si heterojunction photovoltaic device. The electronic structure and the charge transition levels of the amorphous silicon oxide doped with Mo are derived from density functional theory. The density of states show that the five local states are existed in the band gap of amorphous silicon oxide, caused by the hybridization of Mo 4d orbital and O 2p orbital. The charge transition level of ε(+1/0) is located at 3.59 eV above the valance band maximum of a-SiO2, which could be a passageway of holes produced in the opto-electric conversion. Defects level-assisted quantum transport mechanism is put forwarded to explain hole transport phenomenon in the MoOx/SiOx(Mo)/n-Si PV device.