Bright Blue Emitting Cu-Doped Cs2ZnCl4 Colloidal Nanocrystals

• DOI: 10.1021/acs.chemmater.0c02017
• Publication Date: 2020-06-05T15:16:56Z
• Authors: Dongxu Zhu; Matteo L. Zaffalon; Valerio Pinchetti; Rosaria Brescia; Fabrizio Moro; Mauro Fasoli; Marco Fanciulli; Aiwei Tang; Ivan Infante; Luca De Trizio; Sergio Brovelli; Liberato Manna
• Keywords: Quantum yield; Absorption edge

We report here the synthesis of undoped and Cu-doped Cs2ZnCl4 nanocrystals (NCs) in which we could tune concentration Cu from 0.7 to 7.5%. has a wide band gap (4.8 eV), its crystal structure is composed isolated ZnCl4 tetrahedra surrounded by Cs+ cations. According our electron paramagnetic resonance analysis, 2.1% NCs ions were present +1 oxidation state only, while at higher concentrations detect Cu(II) (isovalently substituting Zn(II) ions). The non emissive, samples had bright intragap photoluminescence (PL) ∼2.6 eV mediated band-edge absorption. Interestingly, PL quantum yield was maximum (∼55%) for with low ([Cu] ≤ 2.1%), it systematically decreased when further increasing Cu, reaching 15% highest doping level = 7.5%). same (∼2.55 eV) emission detected under X-ray excitation. Our density functional theory calculations indicated that be ascribed only Cu(I) ions: these promote formation trapped excitons, through an efficient takes place. Overall, NCs, their high photo- radio-luminescence blue spectral region free reabsorption, are particularly suitable applications ionizing radiation detection.