The mechanism of the Staebler-Wronski effect, which was responsible for the light-induced degradation of photovoltaic devices based on amorphous hydrogenated material, was still in question. It was assumed, for example, that a defect precursor A was transformed into the actual, metastable defect B by excitation and subsequent electron trapping. Calculations were made of large distorted Si clusters which contained vacancies/voids with up to 3 missing atoms. A sophisticated embedding procedure was employed where the atoms surrounding the vacancy/void were treated by means of a density functional (BP86) and the outer atoms were taken into account semi-empirically (AM1). Full geometry optimization results in novel and unprecedented structure information. Excitation energies and electron attachment energies were presented. These findings substantiate ideas regarding the nature of A and B.

Microstructure of Local Defects in Amorphous Si:H - a Quantum Chemical Study. T.Krüger, A.F.Sax: Physical Review B, 2001, 64[19], 195201 (11pp)