Enhancing Stability and Emission in Metal Halide Perovskite Nanocrystals through Mn²⁺ Doping

Metal halide perovskite (MHP) nanocrystals (NCs) offer great potential for high-efficiency optoelectronic devices but suffer from structural softness and chemical instability. In this work, we synthesize Mn-doped methylammonium lead bromide (MAPbBr₃) NCs using the ligand-assisted reprecipitation method and investigate their structural and optical stability. X-ray diffraction confirms Mn²⁺ substitution at Pb²⁺ sites and lattice contraction. Photoluminescence (PL) measurements show a blue shift and a significant PL quantum yield enhancement, reaching 72% at 17% Mn²⁺ doping, a 34% increase over undoped samples, attributed to effective defect passivation and reduced non-radiative recombination, supported by time-resolved PL data. Mn²⁺ doping also improves stability under ambient conditions. Low-temperature PL reveals crystal phase transitions, while Mn²⁺ incorporation promotes self-assembly into superlattices with larger crystal sizes, better structural order, and higher superlattice density. These results demonstrate that Mn²⁺ doping enhances both optical performance and structural robustness, advancing the potential of MAPbBr₃ NCs for stable optoelectronic applications.