Positional Isomerism\nof Aromatic Heterocyclic Spacer\nCations in Two-Dimensional Dion–Jacobson Hybrid Perovskites

Ligand engineering of aromatic heterocyclic cations in\ntwo-dimensional\n(2D) Dion–Jacobson (DJ) perovskites has been widely explored\nin recent years. In this study, how the positional isomers of aromatic\nheterocyclic cations tune the lattice of 2D perovskites, thereby influencing\nthe transport and recombination dynamics of charge carriers, has been\ninvestigated through nonadiabatic molecular dynamics simulations.\nWe demonstrate that the <i>meta</i>-substituted 3-(aminomethyl)pyridinium\n(3AMPY) cations greatly reduce the strength of electron–vibration\ncoupling since the strong hydrogen-bonding network introduced by the\nchanges in the arrangement of spacer cations significantly suppresses\nthe structural thermal fluctuations. Compared to the <i>para</i>-substituted 4-(aminomethyl)pyridinium (4AMPY) cation, using the\nasymmetric 3AMPY as a spacer cation can achieve improved in-plane\ntransport performance, enhanced thermal stability, and suppressed\ncharge carrier recombination through weakening electron–vibration\ninteractions. Our results explain the observed lifetime difference\nbetween the two types of DJ-phase perovskites in experiments and provide\nnew guidance for optimizing the performance of perovskite devices.