title: Silicon-Rich Silicon Carbide Hole-Selective Rear Contacts for Crystalline-Silicon-Based Solar Cells.
abstract: The use of passivating contacts compatible with typical homojunction thermal processes is one of the most promising approaches to realizing high-efficiency silicon solar cells. In this work, we investigate an alternative rear-passivating contact targeting facile implementation to industrial p-type solar cells. The contact structure consists of a chemically grown thin silicon oxide layer, which is capped with a boron-doped silicon-rich silicon carbide [SiCx(p)] layer and then annealed at 800-900 °C. Transmission electron microscopy reveals that the thin chemical oxide layer disappears upon thermal annealing up to 900 °C, leading to degraded surface passivation. We interpret this in terms of a chemical reaction between carbon atoms in the SiCx(p) layer and the adjacent chemical oxide layer. To prevent this reaction, an intrinsic silicon interlayer was introduced between the chemical oxide and the SiCx(p) layer. We show that this intrinsic silicon interlayer is beneficial for surface passivation. Optimized passivation is obtained with a 10-nm-thick intrinsic silicon interlayer, yielding an emitter saturation current density of 17 fA cm-2on p-type wafers, which translates into an implied open-circuit voltage of 708 mV. The potential of the developed contact at the rear side is further investigated by realizing a proof-of-concept hybrid solar cell, featuring a heterojunction front-side contact made of intrinsic amorphous silicon and phosphorus-doped amorphous silicon. Even though the presented cells are limited by front-side reflection and front-side parasitic absorption, the obtained cell with a Vocof 694.7 mV, a FF of 79.1%, and an efficiency of 20.44% demonstrates the potential of the p+/p-wafer full-side-passivated rear-side scheme shown here.
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.
authors.forename: Gizem
authors.identifier: http://orcid.org/0000-0001-9400-2346
authors.initials: G
authors.lastname: Nogay
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.
authors.forename: Josua
authors.initials: J
authors.lastname: Stuckelberger
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Wyss
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.|Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Jeangros
authors.affiliation: CSEM PV-Center , Jaquet-Droz 1. 2002 Neuchâtel, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Allebé
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.
authors.forename: Xavier
authors.initials: X
authors.lastname: Niquille
authors.affiliation: CSEM PV-Center , Jaquet-Droz 1. 2002 Neuchâtel, Switzerland.
authors.forename: Fabien
authors.initials: F
authors.lastname: Debrot
authors.affiliation: CSEM PV-Center , Jaquet-Droz 1. 2002 Neuchâtel, Switzerland.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Despeisse
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.
authors.forename: Franz-Josef
authors.initials: FJ
authors.lastname: Haug
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Löper
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, 2002 Neuchâtel, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Ballif
keywords: chemical oxide; passivating contacts; silicon carbide; solar cell; surface passivation