Vacuum‐Referred Binding Energies of Bismuth and Lanthanide Levels in LiTaO₃ Perovskite: Toward Designing Energy Storage Phosphor for Anti‐Counterfeiting, X‐Ray Imaging, and Mechanoluminescence

Abstract

Discovering UV-light or X-ray charged afterglow and storage phosphors with high charge carrier storage capacity remains challenging. Herein, a method is proposed by combining vacuum referred binding energy (VRBE) diagram construction and optimization of dopants' concentration and compound synthesis. The refined chemical shift model, optical spectroscopy, and thermoluminescence will be combined to construct the VRBE diagram of LiTaO 3 with the lanthanide and bismuth charge transition levels. Based on the constructed VRBE diagram of LiTaO 3 , Bi 3+ , and/or Ln 3+ (Ln = Tb or Pr) doped LiTaO 3 will be studied. By combining Bi 3+ with Tb 3+ , Pr 3+ , or Bi 3+ itself, Bi 3+ emerges to act as a ≈0.62 eV deep electron trap, while Tb 3+ , Pr 3+ , or Bi 3+ acts as about 1.5 eV deep hole capturing and recombination centres. The VRBE in the Bi 2+ 2 P 1/2 ground state will be derived by thermoluminescence study. Proof-of-concept X-ray imaging, compression force distribution monitoring, and color-tailoring for anti-counterfeiting will be demonstrated by using the developed Bi 3+ and/or Ln 3+ doped LiTaO 3 . This work promotes the understanding of trap level locations and on the trapping and release processes of charge carriers in Bi 3+ and/or lanthanides doped inorganic compounds for rational design of new afterglow and storage phosphors.

LiTaO3:Bi3+,Tb3+,Ga3+,Ge4+: A Smart Perovskite with High Charge Carrier Storage Capacity for X‐Ray Imaging, Stress Sensing, and Non‐Real‐Time Recording

“…The electron release process from Bi 2+ , as illustrated by arrow 3a, was studied in Bi 3+ and/or Ln 3+ (Ln = Tb or Pr) doped LiTaO 3 in Figure 4 in ref. [17] where a TL glow peaked at ≈283 K and extending from 225 to ≈320 K appears. This means that electron liberation from Bi 2+ and recombination with the hole captured at the Tb 4+ ion will partly contribute to the TL glow peak near 315 K in Figure 1b,c.…”

“…To the best of our knowledge, rare reports are published to discuss the force-induced charge carrier storage phenomenon. [17] An afterglow or storage phosphor is a compound that can capture and temporarily store the free electrons and holes in defectsbased traps during ionization radiation or high-energy photon excitation, like X-ray, gamma ray, or 254 nm UV-light. [18] The properties of the electron-hole recombination and luminescence centers determine the emission wavelength and decay time in a compound.…”

“…In our previous work in ref. [17], the VRBE diagram of LiTaO 3 containing the energy level locations of Bi 3+ , Bi 2+ , and different lanthanides has been constructed that was used to address above unclear mechanisms. However, it has not been fully utilized to exploit ML, afterglow, or storage phosphor.…”

“…Figure 1a shows the VRBE diagram of LiTaO 3 perovskite including the energy level locations of unintended defects, Tb 3+ , Bi 3+ , and Bi 2+ as was established in ref. [17]. Generally, Bi 3+ has a dual role.…”

“…To the best of our knowledge, rare reports are published to discuss the force‐induced charge carrier storage phenomenon. [ 17 ]…”