Unveiling Mn2+ Dopant States in Two-Dimensional Halide Perovskite toward Highly Efficient Photoluminescence

Doping is able to create novel optoelectronic properties of halide perovskites, and the involved mechanism on efficient emission is still a challenge. Herein, Mn2+ substitution into two-dimensional (2D) layered perovskites (C8H20N2)PbBr4 was investigated, demonstrating broad-band orangered emission originating from 4T1→6A1 transition of Mn2+ dopant. The photoluminescence quantum yield (PLQY) of Mn2+ emission is up to 60.8% related with the energy transfer in coupled states. We verify the actual Mn2+ dopant as low as 0.476% to reach the high PLQY, whereas the nominal adding amount is 0.8 as the Mn2+/Pb2+ ratio. The small activation energy (∼6.72 meV) between the Mn2+ d state and trap state accounts for this high efficient energy transfer and photoluminescence. The proposed luminescence mechanism in Mn2+ doped 2D halide perovskites would provide unique insights into the doping designing toward high performance luminescence materials.