Steering Exciton–Phonon Coupling toward Dual-Color Emission and UV-Selective Anti-Counterfeiting in Sb3+-Doped C8H24N2ZrCl6 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.