Deterministic Lattice Distortion in Mn-Doped Hybrid Layered Perovskite Microcrystals Grown by Chemical Vapor Deposition

Two-dimensional (2D) layered organic-inorganic hybrid perovskite (OIHP) semiconductors have gained significant interest in optoelectronics due to their high exciton binding energy and enhanced photoluminescence (PL) quantum yield. Perovskites doped with external impurities have opened up new avenues for modulating the structural and optical properties and exploring novel phenomena by inducing energy transfer from the free excitons to the dopants. Extensive studies on Mn2+ incorporation as a dopant have revealed intriguing optical and magnetic properties, making them attractive for next-generation applications in light-emitting diodes (LEDs), low-threshold lasers, solar cells, and spintronics. Despite significant investigations in optical properties in Mn-doped quantum dots and nanocrystals, the growth of such system beyond the nanoscale is scarce, leaving the precise influence of doping on crystal structure elusive. In this work, we present the synthesis of single-crystalline microcrystals of Mn-doped butylammonium lead bromide (BA2PbBr4) via chemical vapor deposition. For the first time, we observe significant lattice distortions upon Mn doping, resulting in orthorhombic-to-monoclinic phase transition. The distortion angle, observed in optical images of nanoplatelets (NPLs), is corroborated by high-angle annular dark-field (HAADF) transmission electron microscopy (TEM) images. Powder X-ray diffraction (PXRD) patterns suggest a layered crystal structure with an interlayer spacing reduced from 27Å to 25Å after doping. While the exact origin of such phase transition is unclear, I will discuss several plausible mechanisms. Electron spin resonance (EPR) spectroscopy revealed hyperfine coupling peaks and broad PL centered at 600 nm exhibiting decay lifetime of 0.3 milliseconds, confirming the dilute incorporation of Mn2+ into the host lattice. These findings offer significant insights into the structural modifications induced by doping, highlighting the possibility of tailoring material's optical and physical properties through lattice deformation.