Crystalline Dion-Jacobson 2D Layered Sn-Based Perovskites for Field-Effect Transistors
A novel SVAD (solvent vapor assisted drop-casting) method is introduced to control crystallization and enhance the ordering of Dion–Jacobson (DJ) perovskites. By prolonging crystal growth, the approach enables systematic investigation of the rigidity and symmetry of diammonium cations, facilitating the formation of highly ordered 2D DJ layered structures based on the [SnI₆]⁴⁻ octahedral framework.
The current paper focuses on the role of organic diammonium cations in Dion-Jacobson (DJ) perovskites. While the bivalent monolayer ligands reduce the spacings between the inorganic octahedral layers favouring the charge carrier transport, DJ perovskites suffer from low molecular order due to demanding lattice match between the inorganic framework and the organic cations. To improve the perovskite ordering and to systematically study the role of diammonium cations of varied rigidity and symmetry, a novel solvent vapor assisted drop-casting (SVAD) method is introduced. This approach effectively prolongs the crystallization process allowing the self-assembly of the inorganic [SnI6]4- octahedral framework with the organic diammonium spacers into well-ordered 2D layered structures. A comprehensive structural analysis of the crystalline films together with Density Functional Theory calculations and transistor characterizations allowed us to establish structure-property correlations that rationalize the impact of the molecular design of the bivalent A-cations on crystal order and device performance of the studied DJ perovskites. It is disclosed that DJ perovskites with rigid and symmetric A-cations form a planar [SnI6]4- octahedral framework that favors structural order and the charge carrier transport. The insights of our work provide a general guideline for engineering organic spacer cations to further optimize the charge transport properties in layered DJ perovskites in the future.
