Charge-Transfer Engineering in 0D/3D Rare-Earth Halide Heterostructures Enables Tunable and Efficient White Light-Emitting Diodes

Lead-free rare-earth metal halides hold great promise for solid-state white-light LEDs, yet efficient and spectrally tunable white emission remains challenging. Herein, we adopt an in situ alloying strategy with Ag + ions to design and synthesize a 0D/3D (Cs 3 LuCl 6 /Cs 2 AgLuCl 6 ) rare-earth halide heterostructure doped with Bi 3+ ions. The favorable type-I band alignment and built-in electric field drive efficient interfacial charge transfer, thereby significantly boosting radiative recombination. The heterostructure yields dual-peak self-trapped exciton emissions at 440 and 590 nm, with a photoluminescence quantum yield of up to 92.12%. By tuning the Bi 3+ doping concentration, the correlated color temperature can be continuously tuned across the white-light region. The corresponding phosphor-converted white LEDs achieve a color rendering index exceeding 90, excellent thermal stability, and 90% luminance retention after 100 h of operation. These findings provide new insights into the design and fabrication of high-performance white light-emitting luminescent materials for solid-state lighting.