title: Nanocrystal grain growth and device architectures for high-efficiency CdTe ink-based photovoltaics.
abstract: We study the use of cadmium telluride (CdTe) nanocrystal colloids as a solution-processable "ink" for large-grain CdTe absorber layers in solar cells. The resulting grain structure and solar cell performance depend on the initial nanocrystal size, shape, and crystal structure. We find that inks of predominantly wurtzite tetrapod-shaped nanocrystals with arms ∼5.6 nm in diameter exhibit better device performance compared to inks composed of smaller tetrapods, irregular faceted nanocrystals, or spherical zincblende nanocrystals despite the fact that the final sintered film has a zincblende crystal structure. Five different working device architectures were investigated. The indium tin oxide (ITO)/CdTe/zinc oxide structure leads to our best performing device architecture (with efficiency >11%) compared to others including two structures with a cadmium sulfide (CdS) n-type layer typically used in high efficiency sublimation-grown CdTe solar cells. Moreover, devices without CdS have improved response at short wavelengths.
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Crisp
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Panthani
authors.forename: William L
authors.initials: WL
authors.lastname: Rance
authors.forename: Joel N
authors.initials: JN
authors.lastname: Duenow
authors.forename: Philip A
authors.initials: PA
authors.lastname: Parilla
authors.forename: Rebecca
authors.initials: R
authors.lastname: Callahan
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Dabney
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Berry
authors.forename: Dmitri V
authors.initials: DV
authors.lastname: Talapin
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Luther
keywords: CdTe; device architecture; grain growth; nanocrystal; photovoltaic; sintering; solution-processed