title: Highly Dynamic Ligand Binding and Light Absorption Coefficient of Cesium Lead Bromide Perovskite Nanocrystals.
abstract: Lead halide perovskite materials have attracted significant attention in the context of photovoltaics and other optoelectronic applications, and recently, research efforts have been directed to nanostructured lead halide perovskites. Collodial nanocrystals (NCs) of cesium lead halides (CsPbX3, X = Cl, Br, I) exhibit bright photoluminescence, with emission tunable over the entire visible spectral region. However, previous studies on CsPbX3 NCs did not address key aspects of their chemistry and photophysics such as surface chemistry and quantitative light absorption. Here, we elaborate on the synthesis of CsPbBr3 NCs and their surface chemistry. In addition, the intrinsic absorption coefficient was determined experimentally by combining elemental analysis with accurate optical absorption measurements. (1)H solution nuclear magnetic resonance spectroscopy was used to characterize sample purity, elucidate the surface chemistry, and evaluate the influence of purification methods on the surface composition. We find that ligand binding to the NC surface is highly dynamic, and therefore, ligands are easily lost during the isolation and purification procedures. However, when a small amount of both oleic acid and oleylamine is added, the NCs can be purified, maintaining optical, colloidal, and material integrity. In addition, we find that a high amine content in the ligand shell increases the quantum yield due to the improved binding of the carboxylic acid.
authors.affiliation: Sol-Gel Center for Research on Inorganic Powders and Thin Films Synthesis (SCRiPTS), Ghent University , B-9000 Ghent, Belgium.|Physics and Chemistry of Nanostructures Group (PCN), Ghent University , B-9000 Ghent, Belgium.|NMR and Structure Analysis Unit, Ghent University , B-9000 Ghent, Belgium.|Laboratory of Inorganic Chemistry, ETH Zürich , CH-8093 Zürich, Switzerland.
authors.forename: Jonathan
authors.initials: J
authors.lastname: De Roo
authors.affiliation: Laboratory of Inorganic Chemistry, ETH Zürich , CH-8093 Zürich, Switzerland.|Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology , CH-8600 Dübendorf, Switzerland.
authors.forename: Maria
authors.initials: M
authors.lastname: Ibáñez
authors.affiliation: Physics and Chemistry of Nanostructures Group (PCN), Ghent University , B-9000 Ghent, Belgium.|Center for Nano and Biophotonics, Ghent University , B-9000 Ghent, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Geiregat
authors.affiliation: Laboratory of Inorganic Chemistry, ETH Zürich , CH-8093 Zürich, Switzerland.
authors.forename: Georgian
authors.initials: G
authors.lastname: Nedelcu
authors.affiliation: Physics and Chemistry of Nanostructures Group (PCN), Ghent University , B-9000 Ghent, Belgium.|Center for Nano and Biophotonics, Ghent University , B-9000 Ghent, Belgium.
authors.forename: Willem
authors.initials: W
authors.lastname: Walravens
authors.affiliation: Physics and Chemistry of Nanostructures Group (PCN), Ghent University , B-9000 Ghent, Belgium.|Center for Nano and Biophotonics, Ghent University , B-9000 Ghent, Belgium.
authors.forename: Jorick
authors.initials: J
authors.lastname: Maes
authors.affiliation: NMR and Structure Analysis Unit, Ghent University , B-9000 Ghent, Belgium.
authors.forename: Jose C
authors.initials: JC
authors.lastname: Martins
authors.affiliation: Sol-Gel Center for Research on Inorganic Powders and Thin Films Synthesis (SCRiPTS), Ghent University , B-9000 Ghent, Belgium.
authors.forename: Isabel
authors.initials: I
authors.lastname: Van Driessche
authors.affiliation: Laboratory of Inorganic Chemistry, ETH Zürich , CH-8093 Zürich, Switzerland.|Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology , CH-8600 Dübendorf, Switzerland.
authors.forename: Maksym V
authors.initials: MV
authors.lastname: Kovalenko
authors.affiliation: Physics and Chemistry of Nanostructures Group (PCN), Ghent University , B-9000 Ghent, Belgium.|Center for Nano and Biophotonics, Ghent University , B-9000 Ghent, Belgium.
authors.forename: Zeger
authors.initials: Z
authors.lastname: Hens
keywords: CsPbBr3; NMR; absorption coefficient; surface chemistry