title: All-Inorganic Germanium Nanocrystal Films by Cationic Ligand Exchange.
abstract: We introduce a new paradigm for group IV nanocrystal surface chemistry based on room temperature surface activation that enables ionic ligand exchange. Germanium nanocrystals synthesized in a gas-phase plasma reactor are functionalized with labile, cationic alkylammonium ligands rather than with traditional covalently bound groups. We employ Fourier transform infrared and (1)H nuclear magnetic resonance spectroscopies to demonstrate the alkylammonium ligands are freely exchanged on the germanium nanocrystal surface with a variety of cationic ligands, including short inorganic ligands such as ammonium and alkali metal cations. This ionic ligand exchange chemistry is used to demonstrate enhanced transport in germanium nanocrystal films following ligand exchange as well as the first photovoltaic device based on an all-inorganic germanium nanocrystal absorber layer cast from solution. This new ligand chemistry should accelerate progress in utilizing germanium and other group IV nanocrystals for optoelectronic applications.
authors.affiliation: Chemistry & Nanoscience Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States.
authors.forename: Lance M
authors.initials: LM
authors.lastname: Wheeler
authors.affiliation: Chemistry & Nanoscience Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States.|Department of Chemistry, West Virginia Wesleyan College , 59 College Avenue, Buckhannon, West Virginia 26201, United States.
authors.forename: Asa W
authors.initials: AW
authors.lastname: Nichols
authors.affiliation: Chemistry & Nanoscience Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States.
authors.forename: Boris D
authors.initials: BD
authors.lastname: Chernomordik
authors.affiliation: Chemistry & Nanoscience Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Anderson
authors.affiliation: Chemistry & Nanoscience Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Beard
authors.affiliation: Chemistry & Nanoscience Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States.
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Neale
keywords: Germanium nanocrystal; inorganic ligand; ligand exchange; plasma synthesis; quantum dot