Investigation on the Surface Passivation of Intrinsic a-Si:H Thin Films Prepared by Inductively Coupled Plasma-Chemical Vapor Deposition for Heterojunction Solar Cell Applications

Abstract

Intrinsic a-Si:H thin films, which can have passivation functions on the surface of crystalline Si, were deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD). The properties of the films were investigated at deposition temperatures ranging from 50 to 400 °C. The Si—H stretching mode at 2000 cm−1, which indicates good film quality, was found in the range of 150∼400 °C, but the film quality was not good at deposition temperatures below 150 °C. The passviation quality was determined by measuring the effective carrier lifetime using the quasi-steady state photoconductance (QSS-PC) technique. Two, 5, 7.5 and 10 nm thick films were deposited at 150 °C and annealed at 200 °C for 1 hour. The carrier lifetime of these films was approximately 3 times higher than that observed before annealing. A p a-SiC:H/i a-Si:H/n c-Si hetero-structure solar cell with a 7.8% efficiency and approximately 85% quantum efficiency (QE) was obtained by inserting an intrinsic a-Si:H thin film (5 nm) between the interfaces. These results highlight the potential applications of a passivation layer to heterojunction solar cells.