Design of Active Defects in Semiconductors: 3D Electron Diffraction Revealed Novel Organometallic Lead Bromide Phases Containing Ferrocene as Redox Switches

Once the optical, electronic or photocatalytic properties of a semiconductor are set by adjusting composition, crystal phase and morphology, one cannot change them anymore, respectively on demand. Materials enabling a post-synthetic and reversible switching of features such as absorption coefficient, band-gap or charge carrier dynamics represent are highly desired. Hybrid perovskites facilitate exceptional possibilities for progress in the field of smart semiconductors because active organic molecules become an integral constituent of the crystalline structure. We report the integration of ferrocene ligands into semiconducting 2D phases based on lead bromide. The complex crystal structures of the resulting, novel ferrovskite phases were determined by 3D electron diffraction. The ferrocene ligands exhibit strong structure directing effects on the 2D hybrid phases, which is why the formation of exotic types of face and edge sharing lead bromide octahedra is observed. The band gap of the materials ranges from 3.06 eV up to 3.51 eV, depending on the connectivity of the octahedra. Deploying the redox features of ferrocene, one can create defect states or even a defect band leading to the control over the direction of exciton migration and energy transport in the semiconductor.