Chiral Methylbenzylammonium Bismuth Iodide with Zero-Dimensional Perovskite Derivative Structure

Chiral hybrid metal halide perovskites provide hopes of combining chirality induced by the organic sublattice with optoelectronic properties arising from the inorganic sublattice. The field is still in its infancy, with material space mainly focused on twodimensional hybrid lead halide perovskites. Here we report a zerodimensional Pb-free perovskite derivative structure with chemical composition [(R-/S-MBA)4Bi2I10], where MBA stands for methylbenzylammonium. Single-crystal X-ray diffraction data show that the enantiomerically pure R-MBA and S-MBA induce chirality in the Bi-I inorganic sublattice. Consequently, chiroptical properties like circular dichroism (CD) is observed for the excitonic transitions of (R-/Sshows excitonic and shallow-defect emissions, indicating fewer deepdefect trap states. Further ultrafast exciton many-body interactions studied by transient absorption spectroscopy reveal Stark effect, band gap renormalization, and shallow-defect states absorption near the band-edge. The material design, structure, and optical properties reported here will be useful to develop next-generation Pb-free perovskites for chiral optoelectronics.