Pressure-Induced Modulation of Band Characteristics in 2D Hybrid Perovskites

Since the advent of 2D hybrid perovskites for optoelectronic devices, achieving significant out-of-plane charge transport and strong organic–inorganic orbital coupling has been a major challenge. Recent research has focused on the incorporation of polycyclic amine-based spacer cations to address this issue. In this study, we used density functional theory to explore the pressure tunability of perovskite electronic structures. Applying external pressure to naphthalene-based spacer cation-containing 2D perovskites, specifically (NaphDA)PbI₄, resulted in significantly enhanced out-of-plane carrier transport, with a hole effective mass approaching 0.16 m₀. Additionally, for another perovskite, we noticed significant inorganic–organic orbital overlap at the band edges. We discovered that the direction of applied pressure alters the intramolecular band alignment: a material with a type I_a alignment can shift to a type II_a alignment under pressure.