Boosting multi-center luminescence in Cs₇Cd₃Br₁₃via synergistic defect passivation and sensitization of Cu(I)

Driven by the demand for efficient and tunable lead-free optoelectronic materials, low-dimensional metal halides featuring multi-coordination structures have attracted widespread attention. Herein, a series of Cu⁺-doped Cs₇Cd₃Br₁₃ phosphors featuring a unique mixed 0D/1D crystal structure were successfully synthesized. We demonstrate that the Cu⁺ dopant not only effectively passivates intrinsic defects to suppress non-radiative recombination, but also acts as an efficient sensitizer. It substantially promotes energy transfer from the 0D [CdBr₄]^2- sublattice to the 1D [CdBr₆]^4- self-trapped exciton (STE) states. Consequently, the phosphors exhibit distinct excitation-dependent photoluminescence: an ultrabroadband emission covering the entire visible spectrum under 320 nm excitation, a robust orange emission at 375 nm excitation, and a temperature-dependent multi-band emission under 282 nm excitation driven by Jahn-Teller distortion. Benefiting from the highly efficient single-component broadband emission and emission tunability, Cu⁺-doped Cs₇Cd₃Br₁₃ reveals tremendous potential for applications in solid-state white lighting and advanced anti-counterfeiting.