| Summary: | Developing a secure anti-counterfeiting technology with more dimensional encryptions is urgently demanded. The lead-free double perovskite (DP) family represented by A<sub>2</sub>B<sub>I</sub>B<sub>III</sub>X<sub>6</sub> hold great potential for applications in advanced fluorescence anti-counterfeiting owing to of large-bandgap engineering via B<sub>I</sub>/B<sub>III</sub> site transmutation or exotic dopants. Herein, Ln<sup>3+</sup> (Ln<sup>3+</sup> = Eu<sup>3+</sup>, Ho<sup>3+</sup>, and Yb<sup>3+</sup>)-doped Cs<sub>2</sub>Ag<sub>0.3</sub>Na<sub>0.7</sub>InCl<sub>6</sub> DP microcrystals (MCs) were firstly successfully synthesized by a hydrothermal method. By selective excitation of different luminescence centrals through precise control of excitation wavelength, we demonstrate dynamic color tuning in the Ln<sup>3+</sup>-doped Cs<sub>2</sub>Ag<sub>0.3</sub>Na<sub>0.7</sub>InCl<sub>6</sub> DPMCs. Specifically, under various excitations of UV 300, 394, and NIR 980 nm, the as-synthesized DPMCs display triple emissions of warm yellow, red, and green, respectively. The warm yellow light stems from the self-trapped exciton (STE) downconversion (DC) luminescence of the DP matrix, while the red and green lights can be attributed to the strong Eu<sup>3+ 5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>J</sub> (J = 1, 2, 3, 4) DC luminescence and Ho<sup>3+</sup> (<sup>5</sup>F<sub>4</sub>→<sup>5</sup>I<sub>8</sub>) upconversion (UC) luminescence sensitized by Yb<sup>3+</sup>. Thus, the as-synthesized Ln<sup>3+</sup>-doped Cs<sub>2</sub>Ag<sub>0.3</sub>Na<sub>0.7</sub>InCl<sub>6</sub> DPMCs, which possess tunable combined DC/UC luminescence, show great potential to be an anti-counterfeiting material with a high security level.
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