Seven-Layered 2D Hybrid Lead Iodide Perovskites

Two-dimensional hybrid halide perovskites provide high chemical versatility, strong potential in optoelectronics. Herein, we discuss the highest layer thickness perovskites yet to be crystallographically characterized, for the Dion-Jacobson (DJ) family. The seven-layered DJ phase (4AMP)(MA)6Pb7I22 (4AMP = 4-aminomethylpyperidinium) shows less distortion in the crystal structure than the Ruddlesden-Popper (RP) phase (BA)2(MA)6Pb7I22 (BA = butylammonium). The comparison of the DJ and RP perovskites reveals that the fine structural details still influence the optical properties, with the DJ phase maintaining a lower energy absorption edge and photoluminescence emission (1.53 and 1.70 eV) than the RP phase (1.57 and 1.74 eV). Density functional theory (DFT) calculations show that the localized density of states of conduction band minimum and valence band maximum are situated at different parts of the layers, implying separate channels in the structure followed by electrons and holes. Unlocking high-layer-thickness layered perovskites provides accessibility to new perovskites for high-performance optoelectronics.