Mechanochemical synthesis of one-dimensional (1D) hybrid perovskites incorporating polycyclic aromatic spacers: highly fluorescent cation-based materials

Three polycyclic aromatic cations, 2-ammonium fluorene (AF), 2-ammonium anthracene (AA) and 2,7-diammonium fluorene (DAF) are successfully assembled with inorganic PbBr 6 octahedra to synthesize (AF/AA) 2 PbBr 4 and (DAF)PbBr 4 one-dimensional (1D) hybrid perovskites. The synthesis of the perovskites is performed via an environmentally-friendly mechanochemical approach involving a solid-state solventless reaction. The analysis of the X-ray powder diffraction (XRD) data revealed that the crystal structure of these materials consisted of quasi-linear wires of PbBr 4 2− separated by polycyclic cations with alternating positions of NH 3 + groups. DFT calculations have shown a remarkable contribution of the orbitals of 2-ammonium fluorene to both the valence band maximum (VBM) and conduction band minimum (CBM) of the (AF) 2 PbBr 4 structure. Moreover, the same hybrid materials were effectively prepared as thin films by using the spin-coating method from a solution containing the precursors. Although these hybrid perovskites are not intrinsically emissive, the strong fluorescence signal from the organic cation is preserved.