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

Abstract 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.