Twisted Lead Halide Perovskite Microbelts with Enhanced Chiroptical Activity via Chiral Ligand-Assisted Self-Assembly of Nanoplatelets

Chiral metal halide perovskites are promising for circularly polarized optoelectronic devices, yet achieving strong chiroptical responses across a broad spectral range on a large scale remains challenging. Here, we demonstrate the hierarchical self-assembly of CsPbBr3 nanoplatelets functionalized with enantiomeric phenylethylammonium (PEA) bromide ligands into twisted microbelts with controlled handedness (R/S), driven by solvent evaporation and accompanied by a phase transition toward a hybrid 2D/0D (R-/S-PEA)2PbBr4/Cs4PbBr6 structure. The resulting microbelts exhibit broadband circular dichroism in a spectral range from 200 to 750 nm and an absorption dissymmetry factor (gabs) of up to 2.3 × 10–3, increasing from the 10–5 range for the pristine chiral nanoplatelets and thus representing an enhancement of approximately 2 orders of magnitude. Our study establishes hierarchical self-assembly assisted by chiral ligands with the subsequent crystal phase transition as a powerful strategy for engineering large-scale chiral perovskite architectures with programmable chirality.