In Situ Plasma-Grown Silicon-Oxide for Polysilicon Passivating Contacts

Abstract

Large-scale manufacturing of polysilicon-based passivating contacts for high-efficiency crystalline silicon (c-Si) solar cells demands simple fabrication of thermally stable SiOx films with well controlled microstructure and nanoscale thickness to enable quantum-mechanical tunneling. Here, plasma-dissociated CO2 is investigated to grow in situ thin (<2 nm) SiOx films on c-Si wafers as tunnel-oxides for plasma-deposited, hole-collecting (i.e., p-type) polysilicon contacts. It is found that such plasma processing offers excellent thickness control and superior structural integrity upon thermal annealing at 1000 °C, compared to state-of-the-art wet-chemical oxides. As a result, p-type polysilicon contacts are achieved on n-type c-Si wafers that combine excellent surface passivation, resulting in an implied open-circuit voltage exceeding 700 mV, with a contact resistance as low as 0.02 Ω cm2.