Chirality-Dependent Photoluminescence Redshift of 2D Perovskites Under High Pressure

Abstract

The precise discrimination between the racemate and its enantiomers is critical in materials science. Given the nonintuitive limitation of traditional methods, luminescence-based identification translates microscopic structural differences into macroscopic optical signals, providing an ideal pathway for visual chiral identification. However, subtle luminescence disparity between racemates and enantiomers, coupled with scarce mechanistic insights, hinders the development of this field. Herein, using (Rac, S, R)-3BrMBA₂PbI₄ 2D perovskites as paradigms, a visual identification window based on high-pressure-induced chirality-dependent luminescence redshift is constructed; within 0-8 GPa, Rac-3BrMBA₂PbI₄ exhibits a remarkable transition from green to red emission, whereas S- and R-3BrMBA₂PbI₄ remain green-emitting. Excited-state and electron-hole effective mass calculations substantiate the free-exciton origin of emission. Comparative band and structural analyses reveal that the remarkable redshift of Rac-3BrMBA₂PbI₄ stems from substantial direct bandgap reduction, induced by stable octahedral contraction within its high-symmetry structure. Conversely, pressure induces asymmetric halogen bond formation and enhances asymmetric hydrogen bonds in chiral enantiomers. This amplified asymmetry significantly increases the spin-splitting via chirality transfer but facilitates inefficient phonon-assisted indirect transitions and the limited bandgap narrowing, limiting the emission redshift. This work leverages high pressure to amplify luminescence disparity between the racemate and enantiomers, elucidating symmetry's pivotal role in 2D perovskite emission and offering a new perspective for visual chiral identification.

Keywords

2D chiral organic-inorganic hybrid perovskites / chirality-dependent luminescence redshift / enantiomers / high pressure / racemates / spin-splitting

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2026 The Author(s). Aggregate published by SCUT, AIEI, and John Wiley & Sons Australia, Ltd.