Circularly Polarized Photoluminescence of Chiral 2D Halide Perovskites at Room Temperature

Chiral halide perovskites have attracted considerable attention because of their chiroptical, second-harmonic generation, and ferroelectricity properties and their potential application in chiroptoelectronics and chiral spintronics. However, the fundamental research of these properties is insufficient. In this work, chiral perovskites were synthesized using precursor solutions with various stoichiometric ratios ⟨ n ⟩. The chiral perovskite film prepared from the solution with ⟨ n ⟩ = 1 is composed of ( R -/ S -/ rac -MBA) 2 PbBr 4, whereas the films prepared from the solutions with ⟨ n ⟩ larger than 1 are a mixture of ( R -/ S -/ rac -MBA) 2 (CsMA) n −1 Pb n Br 3 n +1 with n = 1 and large n values. A photoluminescence quantum yield of approximately 90 was obtained. Symmetric circular dichroism (CD) spectra were observed without an external magnetic field. Under various magnetic fields, magnetic field-induced CD features are superimposed with the intrinsic chirality-induced CD features. For the ⟨ n ⟩ = 1 chiral perovskite film, the energy level splitting induced by chiral molecules are a few 10 μeV, whereas the energy level splitting induced by magnetic fields are at the range of ∼−250 to ∼250 μeV. Circularly polarized photoluminescence spectra were observed at room temperature and associated with the spin-preserved energy funneling from highly energetic phases to the lower energetic phases.