HOMO Offset Induced Hole Trapping in Conjugated Dion‐Jacobson Perovskites

ABSTRACT Although significant efforts have focused on hot electron transport in two‐dimensional hybrid organic–inorganic perovskites (2D HOIPs), exploring the mobility of carriers when in thermal equilibrium with the lattice may widen their applicability as semiconductors in energy conversion and electronics. While Dion–Jacobson (DJ) perovskites with conjugated ligands are expected to enhance charge transport through dielectric screening and interlayer delocalization, we report a surprising finding that conjugated DJ perovskite films exhibit significantly lower conductivity than Ruddlesden–Popper (RP) perovskite films with insulating ligands, both in intrinsic and doped states. In addition to weaker orbital overlap within the inorganic layer due to increased octahedral tilting in the conjugated DJ phase, we experimentally demonstrate that the highest occupied molecular orbital (HOMO) of the conjugated organic layer lies ∼1.5 eV above the valence band maximum (VBM) of the inorganic layer. The HOMO offset leads to hole trapping, thereby reducing free carrier concentration in the inorganic layer and suppressing the bulk conductivity of the conjugated DJ perovskite. These findings reveal that carrier delocalization through the conjugated ligands can only be advantageous when the HOMO‐VBM offset is sufficiently small and comparable to carrier thermal energy.