Enhanced Organic-Inorganic Electronic Coupling in Two-Dimensional Hybrid Perovskites through Molecular Engineering of Dipolar Pyrene-Based Cations

Exploration of the organic-inorganic electronic coupling in two-dimensional (2D) hybrid perovskites has garnered attention due to its potential for facilitating intercomponent wave function delocalization, consequently leading to enhanced interfacial charge transport and intriguing optoelectronic properties. However, to date, the identification in hybrid perovskites of substantial coupling strengths over 100 meV has remained elusive. Here, we investigate, at the density functional theory (DFT) level, 2D hybrid perovskites that incorporate pyrene-based spacers, denoted as (Pyr-Cx)₂PbI₄ (where x represents the length of the alkylammonium chains). (Pyr-C3)₂PbI₄ stands out by exhibiting a remarkable energy-level alignment and hole wave function delocalization, stemming from a substantial organic-inorganic electronic coupling. Tight-binding model analyses reveal an organic-inorganic coupling strength as high as 155 meV, which represents the highest value reported for hybrid perovskites. The excited-state properties of (Pyr-C3)₂PbI₄ were evaluated via time-dependent DFT calculations; the significant intercomponent coupling gives rise to substantial charge-transfer contributions to the low-lying absorbing excited states.