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 two-dimensional hybrid lead
halide perovskites. Here we report a zero-dimensional 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-/S-MBA)4Bi2I10. Temperature-dependent
(7–300 K) photoluminescence shows excitonic and shallow-defect
emissions, indicating fewer deep-defect 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.