Sb3+-Sensitized Self-Trapped Exciton Emission and Energy Transfer for Tunable Tricolor and Near-White Luminescence in Cs2NaScCl6 Double Perovskite Microcrystals

Metal-ion doping in lead-free double perovskites is an effective strategy for tailoring lattice structures and enhancing photoluminescence. Herein, Sb3+/Mn2+/Tb3+ codoped Cs2NaScCl6 microcrystals with tunable blue-green-red tricolor emission were synthesized via a solvothermal method. Under ultraviolet excitation, Sb3+ incorporation partially relaxes parity-forbidden transitions, enhances light absorption, and significantly promotes self-trapped exciton (STE)-related blue emission centered at ∼450 nm, increasing the photoluminescence quantum yield from 3.75% to 49.86%. Further codoping with Mn2+ and Tb3+ introduces red and green emission centers, respectively, enabling multipeak visible emission through efficient STE-mediated energy transfer. The optimized Cs2NaScCl6:1%Sb3+/4%Mn2+/30%Tb3+ microcrystals exhibit near-white-light emission with CIE coordinates of (0.3152, 0.3036) and a correlated color temperature of 6570 K. Time-resolved photoluminescence analysis verifies energy transfer from STE states to Mn2+ and Tb3+ activator centers, while thermogravimetric analysis demonstrates excellent thermal stability. These results demonstrate the potential of Sb3+/Mn2+/Tb3+ codoped Cs2NaScCl6 as a lead-free platform for tunable multicolor and near-white luminescence.