Wide-range tuning of trap depths in double perovskite phosphors enabling tunable NIR persistent luminescence

Abstract

Persistent Luminescence (PersL) materials, which use traps to store energy and emit photons over a long period, have found important applications in the fields of optical information storage, security labeling, and biological imaging. The trap depth is a crucial factor determining the performance of these materials; however, achieving the desired trap depth with high precision remains a great challenge. Here, we provide double perovskite phosphors (Cs₂SnCl₆-Cs₂ZrCl₆-Cs₂HfCl₆ series) with highly compatible crystal structures, enabling continuous and precise tuning of trap depth over an ultra-wide range of 0.11–1.25 ​eV. By incorporating W⁴⁺ as the luminescent centers, these phosphors exhibit outstanding near-infrared (NIR) PersL performance at approximately 900 ​nm and a lasting emission duration exceeding 10 ​h. The underlying mechanism of PersL is elucidated, and the wide-range tunability of trap depth is attributed to the universal applicability of band-gap engineering in the entire material system. Furthermore, we demonstrate the practical application of these materials by designing a flexible detector plate for X-ray imaging. The detector plate exhibits a storage time of more than 1 week, a detection limit of 0.83 μGy_air·s⁻¹ in the near-infrared region, and real-time and delay-time imaging resolutions of 14.2 lp·mm⁻¹ and 2.5 lp·mm⁻¹, respectively. These attributes demonstrate strong potential for X-ray luminescence extension imaging.