Efficient energy transfer from organic triplet states to Mn2+ dopants for dynamic tunable multicolor afterglow in 1D hybrid cadmium chloride

Abstract

Metal ion-doped organic–inorganic hybrid metal halides have emerged as promising room-temperature phosphorescence (RTP) materials owing to their tunable afterglow properties and significant potential in information security applications. However, optimizing RTP performance and achieving dynamic control over afterglow colors remain challenging in 1D hybrid systems, primarily because of the inefficient energy transfer from RTP-active organic components to external emissive sites. Herein, we report a novel 1D hybrid metal halide benchmark material, [(NBP)Cd₂Cl₅H₂O] (NBP-Cd, NBP = N-benzylpiperidone), and a series of Mn²⁺-doped derivatives, NBP-Cd:xMn²⁺ (where x represents doping levels from 1% to 50%). The undoped compound exhibits blue-white fluorescence and exceptional long-lasting yellow-green organic RTP with a duration of up to 2 s. Upon Mn²⁺ doping, the afterglow color transitions progressively from yellow-green (1–5%) to yellow (10%), orange (20%), and finally red (50%), accompanied by a reduction in afterglow duration. This dynamic multicolor afterglow behavior is attributed to efficient energy transfer from the stable triplet states within the organic component to the ⁴T₁ level of the Mn²⁺ dopants. Remarkably, the NBP-Cd:10% Mn²⁺ crystal demonstrates exceptional excitation-dependent dual-mode photoluminescence properties. These distinctive features underscore the significant potential of this model system for advanced applications in anti-counterfeiting technologies and high-level information encryption systems.