Manganese Ion-Sensitized Near-Infrared Light in Cs2NaBi1−xErxCl6 Lead-Free Double Perovskite

Lead-free double perovskites (DPs) with unique optical properties are of interest for broad applications. However, improving near-infrared (NIR) photoluminescence (PL) in lead-free DPs is still a challenge. Herein, in order to increase the NIR PL intensity and extend the infrared multicolor luminescence, transition metal Mn 2+ is doped into Cs 2 NaBi 1− x Er x Cl 6 lead-free DPs. Steady-state and time-resolved PL studies show that efficient energy transfer from Mn 2+ to Er 3+ is obtained, leading to NIR PL at ≈1.54 µm can be enhanced 11-fold compared to Er 3+ singly alloyed sample and a PL quantum yield of ≈14.2%. Moreover, the Mn 2+ -mediated sensitized strategy can expand to other NIR lanthanide ions (Ho 3+ at ≈0.98 µm or Nd 3+ at ≈1.07 µm). The as-synthesized Mn 2+ doped Cs 2 NaBi 1− x Er x Cl 6 DPs exhibit robust stability against heat, ultraviolet light, and environmental oxygen/moisture. Finally, the lead-free DPs phosphor-converted multifunctional white light-emitting diode device containing visible and NIR light is fabricated. This work guides constructing energy transfer pathways in DPs and opens new perspectives for the development of lanthanide-functionalized DPs as promising materials for optoelectronic devices operating in the NIR region.