Deterministic Structural Distortion in Mn²⁺-Doped Layered Hybrid Lead Bromide Perovskite Single Crystals

Dilute magnetic doping in wide-bandgap semiconductors has attracted significant interest due to its potential for tailored optical, spintronic, and spin-photonic properties. While extensive research has explored the optical and magnetic properties of these doped systems, the exact nature of dopant-induced structural properties, particularly in high-quality single crystals, requires further investigation. Here, we demonstrate the synthesis of Mn²⁺-doped (BA)₂PbBr₄ (BA=butylammonium) single crystals with well-defined crystal habits and no grain boundaries, enabling controlled investigation into significant crystal deformation as a function of Mn²⁺ incorporation. Structural analysis provides compelling evidence of crystal distortion, manifested by a smooth transition from square nanoplatelets to parallelogram shapes with an in-plane shear distortion of up to ∼6° and an out-of-plane contraction of 9.7% for the highest 4.95% Mn²⁺ concentration. This magnitude of structural change significantly exceeds the typical range observed in doped semiconductors by an order of magnitude. We show, using density functional theory calculations, that the structural distortion upon doping is driven by a thermodynamic energy gain. Static and time-resolved photoluminescence spectroscopy confirms the successful incorporation of Mn²⁺ with characteristic emission at 600 nm with an approximate 0.3 ms radiative lifetime. The uniform incorporation of Mn²⁺ into the host medium is further corroborated by the hyperfine structure in an electron paramagnetic resonance spectrum and the paramagnetic response in superconducting quantum interference device measurements. These findings offer crucial insights into dopant-induced structural modifications, supporting the rational design of dilute magnetic semiconductors for spin-based information technologies.