In the recent years, chiral hybrid organic-inorganic perovskites (HOIPs) have gained a huge interest for applications in optoelectronics, spintronics, photodetection, energy harvesting and beyond, allowing for the absorption and subsequent emission of polarized light with enhanced tunability across the electromagnetic spectrum [1,2]. So far the research has widely centered on low dimensional systems, such as 2D and quasi-2D HOIPs, with fewer examples of 1D and 0D ones, demonstrating significant chiroptoelectronic and spin-polarization features. However, expanding the corner-sharing interconnection of the inorganic motif to the three dimensions is highly demanded for practical applications where a isotropic charge transport is demanded, since the organic layers usually behave as dielectrics in low-dimensional systems [3]. However, the steric constrains imposed by the bulky chiral cations usually prevent the accordance with the Goldschmidt tolerance factor.
In this scenario, we have developed novel chiral HOIPs derivatives displaying a 3D corner-sharing octahedral interconnection closely resembling that of prototypical perovskites [4]. This architecture is attained by integrating the relatively small ditopic cation R/S-3-aminoquinuclidine (R/S-3AQ) yielding the (R/S-3AQ)Pb₂Br₆ materials, featuring a direct bandgap and a isotropic electronic band structure in agreement with a 3D delocalized excitation, in stark contrast with the Ruddlesden-Popper counterpart (R/S-3AQ)₂PbBr₄·2Br showing typical 2D characteristics. The experimentally determined chiral anisotropy factor aligns well with theoretical predictions based on first-principles calculations for this type of chiral structure, and a pronounced Rashba-type spin splitting is detected in the conduction band, expected for a non-centrosymmetric semiconductor and driven by the combined effects of spin-orbit coupling and structural chirality. A reduced exciton binding energy was determined in the 3D material, index of a more stable excitonic population and favorable for an increased charge transport. Conductivity and spin-relaxation measurements are currently in progress to further assess the influence of these electronic properties on the material's potential for optoelectronic and spintronic applications. Thanks to their structural chirality and broad chemical tunability, these 3D chiral HOIP derivatives emerge as a promising foundation for the development of next-generation nonlinear functional materials.