Defect-Induced Circularly Polarized Luminescence of Chiral Perovskite Films

Defect-induced strategy is employed to prepare green emission chiral perovskite films (GECP films) with circular polarized luminescence (CPL) via spin-coating a mixture of S/R-MBAPbBr(3) chiral perovskite and methylamine bromide (MABr). The circular dichroism (CD) spectra show the characteristic mirrored CD signals, behaving as a pair of enantiomers similar to the nonemission chiral perovskite films (NECP films). The CPL response can be obtained, and the dissymmetry luminescence factor (g(lum)) reaches |4 x 10(-3)| for the GECP films. Both GECP films and NECP films exhibit identical X-ray diffraction (XRD) patterns, indicating that no impurity can be observed. Furthermore, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) clearly indicate that chiral photoluminescence originates from the bromine vacancy (V-Br) for GECP films. This work not only provides a new strategy to realize the fluorescence emission and CPL of chiral perovskites but also gives insights into the structure-property relationship.