Enhancing downshift luminescence of double perovskites Cs2NaBiCl6:Er3+/Ho3+ through Sb3+ ions alloying and the anti-counterfeiting application

Here, a new type of Sb 3+ ions alloying with RE 3+ (RE = Er, Ho) ions heavy concentration doped Cs 2 NaBiCl 6 double perovskites (DPs) was successfully synthesized by solvothermal method. The structure and morphology of all samples were characterized with X-ray diffraction, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The excitation and emission spectra for all samples are investigated in detailed. Under 354 nm excitation, a strong broad blue emission band from 400 to 500 nm is obtained in Cs 2 NaBiCl 6 :15 mol%Sb 3+ DPs. Compared with the Cs 2 NaBiCl 6 :RE 3+ sample, the emission intensities of Er 3+ and Ho 3+ ions for Cs 2 NaBiCl 6 :Sb 3+ /RE 3+ DPs are enhanced by 38 and 29 times due to alloying Sb 3+ ions, respectively. And the self-trapped exciton (STE) emission intensity is also dramatically increased. The energy transfer process from free exciton (FE) to STE and excited state level of RE 3+ contribute to increased luminescence intensity. In addition, the temperature-dependent luminescence spectra of Cs 2 NaBiCl 6 :Sb 3+ /RE 3+ samples were measured from 83 to 423 K. The luminescence thermal enhancement phenomenon is obtained at lower temperature range. At last, the anti-counterfeiting application of Cs 2 NaBiCl 6 :Sb 3+ /RE 3+ samples is elaborated due to their bright multi-color emission under different excitation and temperatures.