Near-unity photoluminescence quantum yield Mn-doped two-dimensional halide perovskite platelets via hydrobromic acid-assisted synthesis

Although two-dimensional lead halide based perovskite has been developed for nearly five years, the room temperature preparation for achieving high efficiency Mn2+ emission in the lead halide perovskites is still facing huge challenges. Herein, we studied photoluminescent properties of highly emitting Mn2+ ions doped PEA(2)PbBr(4) perovskite platelets synthesized at room temperature by a facile hydrobromic acid-assisted (HBr-assisted) solid liquid mixing strategy. The Mn-doped platelets with different Mn doping levels were synthesized by controlling Mn/Pb molar feed ratio and HBr addition volume. The photoluminescence (PL) quantum yield (QY) of orange color (605 nm) of Mn-doped platelets reached 98%. Their optical properties were studied by steady-state and time-resolved PL spectroscopy. The temperature-dependent PL spectra revealed that the improvement mechanism of Mn luminescence and thermal stability was related to the reduction of the nonradiative defect/trap states through the HBr-induced surface passivation and enhancement of the exciton-to-Mn2+ energy transfer. This work provides a facile HBr solution-assisted method for preparing high-quality 2D Mn-doped perovskite platelets with stable and efficient luminescence.