Phase Transformation Directed Mn 2+ Incorporation and Chiral Self‐Assembly Unlocks Tunable Multicolor and Circularly Polarized Light Emission in Metal Halide Perovskite Nanoparticles

ABSTRACT This study leverages the phase transformation of zero‐dimensional (0D), non‐emissive, cesium lead bromide (Cs 4 PbBr 6 ) nanoparticles (NPs) to introduce controlled manganese (Mn 2+ ), lead (Pb 2+ ), and halide ions (Br − ,Cl − ) to the perovskite matrix in a bid to engineer a range of three‐dimensional (3D) Mn 2+ doped Cs(Pb 1−x Mn x )(Br 1−y Cl y ) 3 NPs with discreet ion densities that display tunable, multicolor light (aided by perovskite and dopant emissions) for multiplexing and photonic data encryption. Competing photophysical and structural parameters are quantified that regulate the sensitized Mn 2+ emissions in these 3D Cs(Pb 1−x Mn x )(Br 1−y Cl y ) 3 NPs. Co‐assembling the 3D Cs(Pb 1−x Mn x )(Br 1−y Cl y ) 3 NPs with chiral lipid gelators results in the induction of chirality in the NPs that triggers circularly polarized light (CPL) emissions from the perovskite NPs and the Mn 2+ with a wide color gamut and a maximum luminescence dissymmetry |g lum | in the order of 10 −3 . These results bring the 3D Cs(Pb 1−x Mn x )(Br 1−y Cl y ) 3 NPs to the forefront of anticounterfeit technology and expand the library of CPL emitting chiral 3D perovskites for applications in spintronics.