The growing demands for optical anti-counterfeiting technology require the development of new environmentally friendly materials with single component, multimodal fluorescence and high stability. Herein, the Bi/Sb codoped Cs2Ag0.1Na0.9InCl6 lead-free double perovskite material is reported as an efficient multimodal luminescence material with excitation-wavelength-dependent emission. When excited by 360 nm UV light, dual-emission is observed at 455 and 560 nm, which comes from the 3P1–1S0 transition of Sb3+ ions and self-trapped excitons (STEs), respectively. Under the 320 nm UV lamp, the microcrystals show only a blue emission centered at 455 nm. Therefore, the Bi/Sb codoped Cs2Ag0.1Na0.9InCl6 double perovskite emits blue and yellow lights under the 320 and 360 nm UV lamp, respectively. Moreover, the obtained double perovskite shows a high PLQY up to 41% and excellent stability against both air and high temperature, which make it a promising anti-counterfeiting material.

In this work, a two-dimensional perovskite Rashba piezoelectrics (TPRP) is proposed by a density functional theory study. The Rashba spin splitting in TPRP is optimized via the dipole moment of A-site organic cations and the atom displacement in inorganic [PbBr6]2– octahedrons. The Rashba spin splitting energy and the corresponding parameter (αR) of unstrained (ATHP)2PbBr4 TPRP are calculated as 41 meV and 0.65 eV·Å, respectively. This value should be the highest for any Br-based lead halide perovskites to the best of our knowledge. In addition, the value of αR, responsible for the piezoelectric potential, is further tuned from 0.41 to 0.81 eV·Å via adjusting the local polarization by applying a strain from +0.01 to −0.01 along the c axis.

Lead-free copper-doped cesium halide nanocrystals with excellent stability and bright tunable emission are synthesized via simple single-step ultrasonic method.

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