Hybrid Cd ²⁺ -Based Halide Birefringent Crystals Achieving Tunable Dual-Color Emission for Multifunctional LED and Anticounterfeiting Applications

Tunable multicolor luminescent materials are of great significance in boosting the security of information encryption. Herein, one-dimensional (1D) (4-AMP)₂Cd₃Cl₁₀·4(H₂O) (4-AMP = 4-(aminomethyl)pyridine) new crystals, with a broadband blue emission, were successfully grown by the solution method. A notably large birefringence of 0.158@546 nm and a short ultraviolet (UV) absorption cutoff edge of about 264 nm were determined, indicating a promising application as a UV birefringent material. The Mn²⁺-doping strategy was adopted to modulate its photoluminescence properties, and a series of (4-AMP)₂Cd₃Cl₁₀·4(H₂O):xMn²⁺ (x = 10%, 20%, and 40%) with tunable multicolor emission were synthesized. Strikingly, (4-AMP)₂Cd₃Cl₁₀·4(H₂O):10%Mn²⁺ also exhibited a photoexcitation-induced tunable blue and red dual-color luminescence. Remarkably, (4-AMP)₂Cd₃Cl₁₀·4(H₂O):40%Mn²⁺ demonstrates a bright red emission at 632 nm, achieving a high PLQY of 73.06%. Combined experimental and theoretical investigations reveal that the red luminescence originates from ⁴T₁(G)→⁶A₁(S) of Mn²⁺, and the blue emission is principally attributed to organic units. Furthermore, LED devices and multifarious anticounterfeit encryption models were fabricated and designed to explore their applications. This work not only presents a novel UV-birefringent crystal to achieve tunable dual-color luminescence via dopant engineering but also provides a fresh mindset to expand their optoelectronic applications.