Mn²⁺ as an “Optical Energy Shutter” to Regulate Red‐to‐NIR Luminescence in Rare Earth Doped Layered Quadruple Perovskites

Abstract Metal halide perovskites (MHPs) have shown great application prospects in the field of optoelectronics owing to their superior optical and optoelectronic properties. Bandgap engineering and impurity doping are effective ways to achieve regulation of luminous properties in the visible light region. However, realizing efficient deep red and wide‐range tunable near‐infrared (NIR) emission remains a challenge. Here, a series of rare earth (RE³⁺) ions (RE = Nd, Dy, Ho, Er, Tm, Yb) doped Cs₄Cd_1−xMn_xSb₂Cl₁₂ (0 ≤ x ≤ 1) quadruple perovskites are designed. An efficient tunable luminescence from red to NIR light is achieved based on the energy transfer (ET) from Mn²⁺ to RE³⁺ by building the Mn²⁺ energy bridge, which covers the NIR‐I (650–900 nm) and NIR‐II (900–1700 nm) regions. Moreover, the ET efficiency is availably influenced by the doping concentration of Mn²⁺. Interestingly, the energy bridge from Mn²⁺ to RE³⁺ is cut off because of the increased bandgap when Bi³⁺ is introduced into the RE³⁺‐doped Cs₄Cd_0.4Mn_0.6Sb_2−yBi_yCl₁₂ (0 ≤ y ≤ 2) lattice. Through bandgap engineering, the ET from Mn²⁺ to RE³⁺ resembles an “optical energy shutter” which quenches the NIR emission of RE³⁺ owing to the mismatched energy level but enhances the emission of Mn²⁺.