Induced Circularly Polarized Luminescence and Exciton Fine Structure Splitting in Magnetic-Doped Chiral Perovskites

Magnetic impurity doping in semiconductors has emerged as an important strategy to endow exotic photophysical and magnetic properties. While most reported hosts are centrosymmetric semiconductors, doping magnetic ions into a noncentrosymmetric chiral semiconductor can offer additional control of photonic and spin polarization. In this work, we synthesized a Mn²⁺-doped chiral two-dimensional (2D) perovskite, Mn²⁺:(R-MPA)₂PbBr₄ (R-MPA⁺ = R-methyl phenethylammonium). We found that the optical activity of chiral 2D perovskites is enhanced with an increased concentration of Mn²⁺ ions. Additionally, efficient energy transfer from the chiral host to the Mn²⁺ dopants is observed. This energy transfer process gives rise to circularly polarized luminescence from the excited state of Mn²⁺ (⁴T₁ → ⁶A₁), exhibiting a photoluminescence quantum yield up to 24% and a dissymmetry factor of 11%. The exciton fine structures of undoped and Mn²⁺-doped (R-MPA)₂PbBr₄ are further studied through magnetic circular dichroism (MCD) spectroscopy. Our analysis shows that chiral organic cations lead to an exciton fine structure splitting energy as large as 5.0 meV, and the splitting is further increased upon Mn²⁺ doping. Our results reveal the strong impacts of molecular chirality and magnetic dopants on the exciton structures of halide perovskites.