Cyclodextrin-mediated circularly polarized luminescence in achiral two-dimensional blue perovskites

Circularly polarized luminescence (CPL) typically arises from materials with intrinsic chirality, but generating CPL in structurally symmetric systems remains challenging. In this work, we report blue CPL emission from intrinsically achiral two-dimensional (2D) benzylammonium lead bromide nanocrystals (NCs) by employing supramolecular encapsulation with chiral cyclodextrins (α, β, and γ-CDXs). Host–guest interactions create a chiral microenvironment at the perovskite surface without disrupting its centrosymmetric lattice. The pristine NCs exhibit narrow-band blue emission with a photoluminescence quantum yield (PL QY) of 82 %, which increases to 85–88 % after CDX encapsulation. All CDX-functionalized NCs display circular dichroism and CPL activity, with γ-CDX inducing the strongest dissymmetry due to its larger cavity and enhanced exciton–dipole coupling. This work demonstrates the first example of blue CPL from achiral 2D perovskites and establishes a supramolecular route to symmetry breaking and chiroptical functionality. Beyond fundamental insights, this scalable, solution-based approach provides new opportunities for chiral optoelectronic and photonic device architectures.