Dimensionality Engineering and Spin-Splitting Enhancement in Heterostructured Perovskites Through Organic Cation Chirality

Enhanced spin-splitting driven by inversion asymmetry can be effectively achieved through the incorporation of chiral organic cations in hybrid organic-inorganic systems. Herein, we investigated the mechanisms and implications of chirality transfer in heterostructured perovskites belonging to the (PbBr₂)₂A₂PbBr₄ family, where A represents the organic cation. These structures are characterized by an inorganic-organic-inorganic stacking configuration comprising one perovskite monolayer and one PbBr₂ intergrowth domain. Our findings indicate that all heterostructures are likely to exhibit energetic stability. Importantly, the presence of chiral cations introduces local asymmetries that facilitate significant spin-splitting effects. Additionally, a racemic mixture of chiral cations can induce a transition from two-dimensional to zero-dimensional character within the perovskite domain of the heterostructure. The dimensionality transition observed for the racemic mixture of isomers within the structure is attributed to the effect of hydrogen bond asymmetries and the enhanced lattice strain, leading the 2D perovskite framework to disrupt into isolated octahedra that allow breaking of centrosymmetry, in stark contrast with racemic 2D perovskites previously reported in the literature. Consequently, we predict that the introduction of chiral cations into perovskite heterostructures can create stable systems where a single degree of freedom effectively modulates both spin-resolved properties and dimensionality. This discovery provides a vital design principle for the simultaneous tuning of spin splitting and perovskite dimensionality.