title: The formation mechanism for printed silver-contacts for silicon solar cells.
abstract: Screen-printing provides an economically attractive means for making Ag electrical contacts to Si solar cells, but the use of Ag substantiates a significant manufacturing cost, and the glass frit used in the paste to enable contact formation contains Pb. To achieve optimal electrical performance and to develop pastes with alternative, abundant and non-toxic materials, a better understanding the contact formation process during firing is required. Here, we use in situ X-ray diffraction during firing to reveal the reaction sequence. The findings suggest that between 500 and 650 °C PbO in the frit etches the SiNx antireflective-coating on the solar cell, exposing the Si surface. Then, above 650 °C, Ag(+) dissolves into the molten glass frit - key for enabling deposition of metallic Ag on the emitter surface and precipitation of Ag nanocrystals within the glass. Ultimately, this work clarifies contact formation mechanisms and suggests approaches for development of inexpensive, nontoxic solar cell contacting pastes.
authors.affiliation: National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, USA.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Fields
authors.affiliation: SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Md Imteyaz
authors.initials: MI
authors.lastname: Ahmad
authors.affiliation: SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Vanessa L
authors.initials: VL
authors.lastname: Pool
authors.affiliation: Department of Electrical Engineering, Stanford University, 350 Serra Mall, Stanford, California 94305, USA.
authors.forename: Jiafan
authors.initials: J
authors.lastname: Yu
authors.affiliation: SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Van Campen
authors.affiliation: National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Parilla
authors.affiliation: SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Michael F
authors.identifier: http://orcid.org/0000-0002-7513-1166
authors.initials: MF
authors.lastname: Toney
authors.affiliation: National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, USA.
authors.forename: Maikel F A M
authors.initials: MF
authors.lastname: van Hest