Trap engineering of Ba0.75Al11O17.25:Eu2+,Yb3+,Er3+ phosphors: Multimodal luminescence modulation for anti-counterfeiting and information encryption

Inorganic luminescent materials play a critical role in the fields of multimodal anti-counterfeiting. Although integrating multiple luminescence modes into a single matrix is considered a feasible strategy, it still faces significant challenges such as the regulation and identification of trap levels. Herein, Ba 0.75 Al 11 O 17.25 :Eu 2+ ,Yb 3+ ,Er 3+ phosphors integrating multiple luminescence modes, including afterglow, up-conversion luminescence (UCL), photo-stimulated luminescence (PSL), and thermoluminescence (TL) were developed. Importantly, the introduction of the Yb 3+ /Er 3+ ion pair not only suppresses the concentration of shallow traps but also induces the formation of numerous deep traps (1.62 eV), which are essential for multimodal luminescence and enhance the thermal stability of the luminescence. Furthermore, through comprehensive analysis of density functional theory (DFT) calculation, TL curves, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), it is confirmed that the trap levels primarily originate from oxygen vacancies and interstitial aluminum. Finally, a highly stable flexible film was fabricated, whose emission intensity and color can be controlled by external light/thermal stimuli, and its applications in anti-counterfeiting and information encryption are demonstrated. This work facilitates the research on advanced luminescent materials and traps regulation mechanisms.