title: Screen-printable silver pastes with metallic nano-zinc and nano-zinc alloys for crystalline silicon photovoltaic cells.
abstract: Silver metallization pastes for crystalline silicon PV cells containing nanosized metallic zinc were found to be superior to commercial pastes containing micrometer-sized metallic zinc and micrometer sized zinc oxide in terms of efficiency and firing window. Efficiency performance decreases as the size of the particles increases: nano-Zn > 3.6 μm Zn > 4.4 μm Zn. Advanced electron microscopy techniques were used to investigate the interfacial microstructure between the front-side contact and the Si emitter of nanosized zinc additive based cells fired at temperatures from below to above optimal. These microstructural observations confirmed the possibility of a tunneling mechanism of current flow (a "nano-Ag colloid assisted tunneling" model) in the absence of Ag crystallites. Contact resistance maps were used to guide sampling, leading to a better understanding of the relationship between microstructure and contact resistance. Low contact resistance and higher cell efficiency, especially at under- and overfiring temperature conditions, are due to more uniform silicon nitride etching obtained through the use of nanosized metallic zinc additives.
authors.affiliation: DuPont Central Research & Development, Experimental Station, Wilmington, Delaware 19880-500, USA. alex.s.ionkin@usa.dupont.com
authors.forename: Alex S
authors.initials: AS
authors.lastname: Ionkin
authors.forename: Brian M
authors.initials: BM
authors.lastname: Fish
authors.forename: Zhigang Rick
authors.initials: ZR
authors.lastname: Li
authors.forename: Mark
authors.initials: M
authors.lastname: Lewittes
authors.forename: Paul D
authors.initials: PD
authors.lastname: Soper
authors.forename: John G
authors.initials: JG
authors.lastname: Pepin
authors.forename: Alan F
authors.initials: AF
authors.lastname: Carroll