Spectrally Tunable Lead-Free Perovskite Rb₂ZrCl₆:Te for Information Encryption and X-ray Imaging

A series of lead-free Rb₂ZrCl₆:xTe⁴⁺ (x = 0%, 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, 5.0%, 10.0%) perovskite materials were synthesized through a hydrothermal method in this work. The substitution of Te⁴⁺ for Zr in Rb₂ZrCl₆ was investigated to examine the effect of Te⁴⁺ doping on the spectral properties of Rb₂ZrCl₆ and its potential applications. The incorporation of Te⁴⁺ induced yellow emission of triplet self-trapped emission (STE). Different luminescence wavelengths were regulated by Te⁴⁺ concentration and excitation wavelength, and under a low concentration of Te⁴⁺ doping (x ≤ 0.1%), different types of host STE emission and Te⁴⁺ triplet state emission could be achieved through various excitation energies. These luminescent properties made it suitable for applications in information encryption. When Te⁴⁺ was doped at high concentrations (x ≥ 1%), yellow triplet state emission of Te⁴⁺ predominated, resulting in intense yellow emission, which stemmed from strong exciton binding energy and intense electron-phonon coupling. In addition, a Rb₂ZrCl₆:2%Te⁴⁺@RTV scintillating film was fabricated and a spatial resolution of 3.7 lp/mm was achieved, demonstrating the potential applications of Rb₂ZrCl₆:xTe⁴⁺ in nondestructive detection and bioimaging.