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Bright Blue Emitting Cu-doped Cs2ZnCl4 Colloidal Nanocrystals

preprint
submitted on 28.04.2020 and posted on 29.04.2020 by Dongxu Zhu, Valerio Pinchetti, Rosaria Brescia, Fabrizio Moro, Marco Fanciulli, Aiwei Tang, Ivan Infante, Luca De Trizio, Sergio Brovelli, Liberato Manna
We report here the synthesis of undoped and Cu-doped Cs2ZnCl4 nanocrystals (NCs), in which we could tune the concentration of Cu from 0.7% to 7.5%. According to electron paramagnetic resonance analysis, in 0.7% and 2.1% Cu-doped NCs the Cu ions were present in the +1 oxidation state only, while in NCs at higher Cu concentrations we could detect Cu(II) ions. The undoped Cs2ZnCl4 NCs were non emissive, while the Cu-doped samples had a bright intra-gap photoluminescence (PL) at 2.6eV mediated by band-edge absorption. The PL quantum yield was maximum (~55%) for the samples with low Cu concentration (≤ 2.1%) and it systematically decreased when further increasing the concentration of Cu, reaching 15% for the NCs with the highest doping level (7.5%). Density functional theory calculations indicated that the PL emission could be ascribed only to Cu(I) ions: these ions introduce intra-gap states that promote the formation of self-trapped excitons, through which an efficient emission takes place.

Funding

China Scholarship Council (CSC) (201807090085)

Horizon 2020 (2014-2020) under the Marie Skłodowska-Curie Grant Agreement COMPASS No. 691185

Italian Ministry of University and Research (MIUR) through grant “Dipartimenti di Eccellenza - 2017 Materials For Energy”

History

Email Address of Submitting Author

luca.detrizio@iit.it

Institution

Istituto Italiano di Tecnologia (IIT)

Country

Italy

ORCID For Submitting Author

0000-0002-1514-6358

Declaration of Conflict of Interest

no

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in Chemistry of Materials

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