title: Enhanced Carrier Collection from CdS Passivated Grains in Solution-Processed Cu2ZnSn(S,Se)4 Solar Cells.
abstract: Solution processing of Cu2ZnSn(S,Se)4 (CZTSSe)-kesterite solar cells is attractive because of easy manufacturing using readily available metal salts. The solution-processed CZTSSe absorbers, however, often suffer from poor morphology with a bilayer structure, exhibiting a dense top crust and a porous bottom layer, albeit yielding efficiencies of over 10%. To understand whether the cell performance is limited by this porous layer, a systematic compositional study using (scanning) transmission electron microscopy ((S)TEM) and energy-dispersive X-ray spectroscopy of the dimethyl sulfoxide processed CZTSSe absorbers is presented. TEM investigation revealed a thin layer of CdS that is formed around the small CZTSSe grains in the porous bottom layer during the chemical bath deposition step. This CdS passivation is found to be beneficial for the cell performance as it increases the carrier collection and facilitates the electron transport. Electron-beam-induced current measurements reveal an enhanced carrier collection for this buried region as compared to reference cells with evaporated CdS.
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Melanie
authors.initials: M
authors.lastname: Werner
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Debora
authors.initials: D
authors.lastname: Keller
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Stefan G
authors.initials: SG
authors.lastname: Haass
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Christina
authors.initials: C
authors.lastname: Gretener
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bissig
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Fuchs
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Fabio
authors.initials: F
authors.lastname: La Mattina
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Rolf
authors.initials: R
authors.lastname: Erni
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Yaroslav E
authors.initials: YE
authors.lastname: Romanyuk
authors.affiliation: †Laboratory for Thin Films and Photovoltaics, §Electronics/Metrology/Reliability, and ‡Electron Microscopy Center, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
authors.forename: Ayodhya N
authors.initials: AN
authors.lastname: Tiwari
keywords: CdS; electron-beam-induced current; kesterites; thin film solar cells; transmission electron microscopy