2019 Volume 14 Pages 4406141
Light-induced degradation is an important problem concerning hydrogenated amorphous silicon (a-Si:H) solar cells. A-Si:H films of lower Si-H2 bond density exhibit less light-induced degradation. In this study, Raman spectroscopy measurements of a-Si:H films with P-layer/I-layer structure reveal that high-density Si-H2 bonds exist in the I-layer within 60 nm of the P/I interface. These Si-H2 bonds originate from surface reactions of SiH3 radicals, as the alternative origin (i.e., cluster incorporation) is considerably suppressed by a multi-hollow discharge plasma chemical vapor deposition method. For an I-layer thickness of 20 nm, the density ratio of Si-H2 and Si-H bonds in the I-layer decreases from 0.133 to 0.053 as the substrate temperature increases from 170◦C to 250◦C. Fine tuning of the substrate temperature during the initial stage of I-layer deposition is thus effective in suppressing Si-H2 bond formation at the P/I interface.
