Solar Energy Materials and Solar Cells 2018-02-07

Properties of mixed phase silicon-oxide-based passivating contacts for silicon solar cells

I. Mack, J. Stuckelberger, P. Wyss, G. Nogay, Q. Jeangros, J. Horzel, C. Allebé, M. Despeisse, F.-J. Haug, A. Ingenito, P. Löper, C. Ballif

文献索引：10.1016/j.solmat.2017.12.030

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摘要

We investigate the properties of an electron selective front contact based on a phosphorous doped mixed-phase SiOxSiOx/Si layer stack at device level. The addition of the SiOxSiOx phase to the Si layer targets reduced optical absorption, pursuing the goal of a broad-band transparent full-area passivating contact for front-side application. To demonstrate the validity of our approach we realised a planar hybrid solar cell with the mixed-phase SiOxSiOx/Si-based passivating contact on the front side and a hydrogenated amorphous (i/p) silicon heterojunction as rear hole-selective contact. With this structure, we obtained a VOCVOC of 691 mV, a JSCJSC of 33.9 mA/cm2cm2, a fill factor of 79.4% and an efficiency of 18.6% on a planar n-type FZ Si-wafer. Temperature-dependent IVIV-measurements at solar cell level were performed in order to understand the physical mechanisms behind charge carrier transport and surface passivation of the mixed-phase SiOxSiOx/Si layer stack. The results were compared to those of a standard silicon heterojunction (SHJ) cell on a similar planar substrate. The temperature dependence of the IVIV-curves in the range from –100°C to +75°C reveals that the hybrid cell is less temperature sensitive with respect to the SHJ cell. Furthermore, at low temperatures, the analysis reveals a reduction of the VOCVOC temperature coefficient of the hybrid cell, whereas for the SHJ cell a saturation occurs. This behaviour hints that the barrier imposed by the SiOxSiOx/Si-based contact is less pronounced than the barrier imposed by a standard SHJ contact.