Dynamically tunable multicolor emissions from zero-dimensional Cs3LnCl6 (Ln: europium and terbium) nanocrystals with wide color gamut

This study demonstrates dynamically tunable multicolor emissions from a single component, zero-dimensional (0-D) cesium europium chloride (Cs3EuCl6) and cesium terbium chloride (Cs3TbCl6) nanocrystals (NCs). Highly uniform colloidal Cs3EuCl6 and Cs3TbCl6 NCs are synthesized via the heating-up method. Excitation-wavelength-dependent multicolor emissions from Cs3EuCl6 and Cs3TbCl6 NCs are observed. Under excitation of 330-400 nm, both NCs exhibit blue photoluminescence (PL). Under wavelengths shorter than 330 nm, characteristic red and green emissions are observed from Cs3EuCl6 and Cs3TbCl6, respectively, owing to the atomic emissions from the f-orbitals in trivalent europium (Eu3+) and terbium (Tb3+) ions. Cs3EuCl6 and Cs3TbCl6 NCs exhibit broadband excitation spectra and enhanced absorption properties. Particularly, Cs3EuCl6 NCs exhibit a very narrow full-width at half-maximum in both blue and red PL and no overlap between the two spectra. The photophysical properties of these NCs are further investigated to understand the multicolor PL origins by time-resolved and temperature-dependent PL measurements. Finally, the potential applications of Cs3EuCl6 and Cs3TbCl6 NCs as anti-counterfeiting inks for high-level security are demonstrated. Given their broadband excitation with enhanced absorption properties and dynamically tunable colors with a wide color gamut, Cs3EuCl6 and Cs3TbCl6 NCs have great potential as novel multicolor NC emitters for many emerging applications.