Yb 3+ /Er 3+ activated upconversion (UC) materials have been widely applied in many advanced technologies owing to their high UC efficiency in the visible region. However, it is challenging to achieve efficient ultraviolet (UV) UC luminescence (UCL) in Yb 3+ /Er 3+ system, due to the dense energy levels of Er 3+ that impose deleterious nonradiative relaxation. Herein, we report a strategy to liberate the UV-UCL of Er 3+ based on the confined energy transfer in Yb 3+ /Er 3+ co-doped 0D Rb 3 InCl 6 with a low phonon energy and a large interionic distance. This facilitates the population of Er 3+ at the 4 G 11/2 state, which yields intense upconverted UV emission at 384 nm, with a much higher UV-to-green ratio ( I 384 / I 554 = 0.864) than that of traditional UC materials ( < 0.1). By leveraging the intense upconverted UV emission of Er 3+ , we demonstrate the application of Rb 3 InCl 6 :Yb 3+ /Er 3+ nanocrystals as a NIR-to-UV transducer for NIR-triggered anion exchange of CsPbX 3 perovskite nanocrystals with high efficiency and good controllability. These findings offer an approach for the exploration of novel UC materials via energy transfer and crystal lattice engineering towards versatile applications.
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.
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