Substituted diammonium cations impact on structure-property-stability in two-dimensional perovskites

Abstract

As emerging semiconductor materials, Dion-Jacobson (DJ) phase two-dimensional (2D) perovskites exhibit remarkable stability and structural diversity. However, their limited charge transport capability hinders further advancement, and the underlying carrier transport mechanisms require deeper investigation. In this work, six diammonium spacer cations and their corresponding DJ-phase 2D perovskite single crystals were rationally designed and synthesized to explore how spacer characteristics (such as heterocyclic type and amino group substitution position) affect the properties of 2D perovskites. Diammonium cations with meta-substituted amino groups tended to adopt a tilted configuration to balance the interactions between both ends of the cation and the inorganic layers. This orientation helped reduce the interlayer spacing, weakened hydrogen bonding between the cation and the inorganic framework, and lowered lattice distortion, promoting efficient carrier generation and transport. Beyond steric hindrance from branched side chains, the thermal stability of perovskites was also closely related to the nature of the heterocycle within the spacer. Diammonium cations bearing flexible aliphatic rings can buffer thermal deformation of the inorganic layers, dissipating internal thermal stress and enhancing overall thermal stability.