Ligand-Induced Chirality in Novel 2D Tin Iodide Perovskite Cl-MBA2SnI4

Chiral perovskites possess a huge applicative potential in several areas of optoelectronics and spintronics. The development of novel lead-free perovskites with tunable properties is a key topic of current research. Herein, we report a novel lead-free chiral perovskite, namely (R/S-)ClMBA2SnI4 and the corresponding racemic system. The reported ClMBA2SnI4 samples exhibit a low band gap (2.12 eV) together with broad emission extending in the red region of the spectrum (1.7 eV). Chirality transfer from the organic ligand induces chiroptical activity in the 465-530 nm range. Density function theory calculations show a Rashba type band splitting for the chiral samples and no band splitting for the racemic isomer. Self-trapped exciton formation is origin of the large Stokes shift in the emission. Careful correlation with analogous lead and lead-free chiral perovskites confirms the role of the symmetry-breaking distortions in the inorganic layers associated with the ligands as the source of the observed chiroptical properties providing also preliminary structure-property correlation in 2D chiral perovskites.