Multi-wavelength NIR-II luminescence in lanthanide-doped Rb3InCl6 nanocrystals via Sb3+ sensitization

All-inorganic lead-free metal halide (MH) nanocrystals (NCs) have shown great promise for various optoelectronic applications; however, achieving efficient luminescence in the near-infrared-II (NIR-II) region remains a persistent challenge. Herein, we developed a new class of NIR-II-emitting materials based on Sb 3+ /Ln 3+ (Ln = Nd, Yb, Er) co-doped 0D Rb 3 InCl 6 NCs. By leveraging the spin-orbit allowed 1 S 0 → 3 P 1 transition of Sb 3+ as a sensitizer, we achieve intense multi-wavelength NIR-II emission arising from the 4f → 4f transitions of Nd 3+ , Yb 3+ , and Er 3+ under single-wavelength near-ultraviolet excitation, with a notable quantum yield of 7.1% for Er 3+ emission. The resulting NCs also demonstrate excellent ambient stability, enabling their use as visible/NIR dual emitters for applications such as bioimaging and night vision. This work provides a versatile co-doping strategy involving s- and f-electron ions to realize efficient NIR-II luminescence in lead-free MH NCs.