Steering Exciton–Phonon Coupling toward Dual-Color Emission and UV-Selective Anti-Counterfeiting in Sb ³⁺ -Doped C ₈ H ₂₄ N ₂ ZrCl ₆ Perovskite

Most zirconium-based hybrids face limitations in indirect bandgap emissions due to low quantum efficiency and poor exciton utilization. Here, we demonstrate that trivalent antimony (Sb³⁺) serves as an effective dopant to induce broadband orange-red emission in the perovskite derivative C₈H₂₄N₂ZrCl₆ (CZC). Under 275 nm excitation, undoped CZC exhibits cyan photoluminescence at 480 nm, originating from self-trapped excitons (STEs). With the introduction of Sb³⁺, an additional wide emission band emerged at 650 nm, corresponding to the ³P₁ → ¹S₀ transition of Sb³⁺. The dual-band intensity ratio is tunable by the Sb³⁺ doping concentration with the maximum orange emission achieved at X = 25% within the investigated range (0 to 30%) (X, defined as the molar ratio of Sb³⁺/(Zr⁴⁺ + Sb³⁺)), achieving record-high photoluminescence quantum yields (PLQYs) of 87.8%. A white-light-emitting diode (LED) prototype fabricated with CZC:25% Sb³⁺ demonstrates stable electroluminescence spectra across 10-110 mA currents, with patterned films showing dual-mode anticounterfeiting labels under 275 and 365 nm UV lights. This work offers a dopant-mediated STE sensitization strategy for efficient, thermally stable, and spectrally tunable hybrid halide phosphors suitable for solid-state lighting and optical security applications.