Deriving Chiroptical\nProperties from Intrinsically\nAchiral Building Blocks of One-Dimensional CsPbBr<sub>3</sub> Perovskite\nNanowires

Chirality is a ubiquitous feature in biological systems\nand occurs\neven in certain inorganic crystals. Interestingly, some inorganic\nnanocrystals have been shown to possess chirality, despite their achiral\nbulk forms. However, the mechanism of chirality formation and chiroptical\nresponses in such nanocrystals is still ambiguous due to the presence\nof chiral organic ligands used to passivate such nanocrystals. Here,\nwe recognize <i>intrinsic</i> chiroptical responses from\nlead halide perovskite nanowires with different length scales. Cube-connected\nnanowires with minimum interfacial contacts make their arrangement\nchiral for chiroptical responses even in the absence of chiral ligands.\nThe chiral nanowires with varying lengths serve as a systematic platform\nfor improving dissymmetric factors significantly with increasing lengths.\nThe dissymmetric factor of the longest nanowires reaches 1.4 ×\n10<sup>–2</sup>, which is the highest among the intrinsic chiral\nperovskite nanocrystals at present. The nanowires generate circularly\npolarized luminescence, which has been seldom reported in halide perovskite\nnanocrystals in the absence of any chiral ligands. Furthermore, we\nfind that chirality exists in the basic unit consisting of two corner-connected\ncubes in the form of a dimer. The intrinsic chirality of the nanowires\nis determined by the lattice rotation of connected cubes along the\ninterfacial boundaries, which is different from the commonly observed\nchirality induced by chiral ligands. Such chiral lead halide perovskite\nnanocrystals with robust chiroptical properties provide an ideal platform\nfor understanding the origin of intrinsic chirality and the rational\ndesign of anisotropic chiral nanostructures.