Enhancing Photoluminescence and Stability of Mn-Doped Cs2InCl5·H2O Microcrystals with Introduced Bi3+ Ion

In this work, lead-free zero-dimensional (0D) all-inorganic perovskite Mn2+-doped Cs2InCl5·H2O microcrystals (MCs) with introduced Bi3+ ion were synthesized by supersaturation recrystallization at room temperature. The electronic bandgap of the MCs is tuned from ∼5.1 to ∼3.1 eV, and the electronic absorption is enhanced in the 200–400 nm region by Bi3+ incorporation. Upon excitation at 365 nm, the MCs with introduced Bi3+ exhibit strong red emission peaking at 640 nm, which is attributed to the Mn2+ transition (4T1g → 6A1g). Simultaneous Mn2+ and Bi3+ incorporation into Cs2InCl5·H2O shows 60 times enhancement of the 640 nm emission band compared to Mn2+ alone. This PL enhancement is attributed to the energy transfer (ET) from the [BiCl6]3– octahedron, which acts as a UV light absorber and exciton donor, to [MnCl6]4–. In addition, a yellow-light-emitting diode (LED) device based on the Cs2In0.45Bi0.55Cl5·H2O:17%Mn MCs was fabricated and evaluated, showing high color saturation at a drive current of 420 mA and good stability. This study demonstrates a new method for achieving efficient red emission by incorporating ns2 metal ions and Mn ions in 0D lead-free metal halides.