Tunable orange-deep red photoluminescence in amorphous KZn1−xMnx(PO3)3 phosphors and anti-counterfeiting applications

Abstract

Amorphous luminescence is a fascinating light emission phenomenon with significant implications for displays, sensors, and the anti-counterfeiting field. However, the development of amorphous materials is relatively limited due to the challenges in their synthesis and characterization, usually lagging behind those of their crystalline counterparts. This paper reports a triphosphate KZn_1−xMn_x(PO₃)₃ (0 ≤ x ≤ 1) phosphor that can form two crystal phases (α-phase and β-phase) and an amorphous phase (Am-phase) by adjusting the synthesis temperature. Research shows that the Am-KZn_1−xMn_x(PO₃)₃ phosphor exhibits superior luminescence properties compared to its crystalline counterparts. By varying the ratio of Zn/Mn, this amorphous phosphor can achieve multi-color photoluminescence (PL) ranging from orange to deep red (604 nm–693 nm), with a full width at half maximum (FWHM) of ∼100 nm. In addition, the Am-KZn_1−xMn_x(PO₃)₃ phosphor demonstrates fewer trap energy levels, while crystalline phosphors have abundant thermoluminescence (TL) traps. These structural and optical characteristics elucidate the luminescence mechanism of the phosphors dependent on Mn²⁺ and defects. Finally, by combining the PL and TL characteristics of the KZn_1−xMn_x(PO₃)₃ phosphor with different phases and Mn concentrations, an anti-counterfeiting code method was designed, indicating that this material has great potential for applications in the field of anti-counterfeiting and information storage.