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HL: Fachverband Halbleiterphysik

HL 92: Poster Session: Structure and transport in organic photovoltaics; Photovoltaics; Impurities/Amorphous semiconductors; New materials

HL 92.18: Poster

Donnerstag, 14. März 2013, 16:00–20:00, Poster A

Defect states in amorphous silicon nitrides: a-Si₃N_xH_y — •Leif Eric Hintzsche¹, Gerald Jordan¹, Martijn Marsman¹, Machteld Lamers², Arthur Weeber², and Georg Kresse¹ — ¹University of Vienna, Faculty of Physics and Center for Computational Materials Science, Sensengasse 8/12, A-1090 Vienna, Austria — ²ECN Solar Energy, P.O. Box 1, 1755 ZG Petten, Netherlands

Amorphous silicon nitrides are commonly deposited as passivation layers on Si based solar cells with their stoichiometries depending mainly on the applied deposition process. By using ab initio molecular dynamics simulations, we investigated important structural and electronic properties, such as atomic coordination and electronic defect states, for different silicon nitride stoichiometries. We found two dominant defect classes in silicon nitrides: (a) under-coordinated Si atoms and (b) states localized on Si-Si bonds. Furthermore, we observed that in sub-stoichiometric silicon nitrides, percolation networks with longer Si chains lead to a considerable number of delocalized defect states in the band gap. While hydrogen can passivate under-coordinated Si atoms, electronic defects related to the latter class are hardly changed. These findings suggest that the dominant defect class also changes depending on the stoichiometry and the concentration of hydrogen.