Two-Dimensional Dion-Jacobson Tin Perovskite Transistors with Enhanced Ambient Stability

Two-dimensional (2D) layered perovskites have garnered significant attention in optoelectronic applications, such as light-emitting diodes, solar cells, and transistors. These materials are characterized by metal halide octahedral slabs separated by organic spacers, providing structural stability, resistance to moisture and oxygen, and tunable optoelectronic properties through diverse chemical designs. In particular, the stability of the 2D layered structure is advantageous for tin (Sn²⁺) perovskites, which are prone to oxidation under ambient conditions. Sn²⁺ perovskites have a lower effective mass than lead-based materials, making them promising p-type semiconducting materials. Initial studies of 2D Sn²⁺ perovskites focused on Ruddlesden-Popper (RP) perovskites with the chemical formula A'₂A_n-1M_nX_3n+1, where A' is a monovalent organic cation spacer, A is a monovalent cation, M is a divalent metal cation, X is a halide anion, and n is the number of corner-sharing [MX₆]^4- octahedral layers. The monovalent organic spacers are connected via van der Waals interactions. Research on 2D RP perovskites has expanded to include new organic spacers, additive engineering, molecular doping, and device engineering.
A new class of 2D perovskites, Dion-Jacobson (DJ) perovskites, emerged by incorporating a diammonium cation, replacing two monovalent cations. DJ perovskites have the chemical formula A''A_n-1M_nX_3n+1, where A" represents a divalent organic spacer, which enhances stability through hydrogen bonding that directly connects adjacent inorganic slabs. Recently, aliphatic and aromatic diammonium spacers have been studied in DJ perovskites. Aromatic spacers possess higher dielectric constants than aliphatic spacers, reducing the dielectric mismatch between the inorganic slabs and organic layers, thereby weakening the dielectric confinement effect. This robust structural chemistry highlights the potential of DJ perovskites in Sn²⁺ perovskites, particularly in thin-film transistors (TFTs). While DJ perovskites have been extensively studied in photovoltaics, their application in TFTs remains relatively unexplored. Sn²⁺ perovskite TFTs have shown promising performance as p-type TFTs, and integrating DJ spacers into these devices could significantly improve their stability and open doors to industrial applications.
In this study, we present the utilization of 3-(aminomethyl)piperidinium (3AMP²⁺) and 4-(aminomethyl)piperidinium (4AMP²⁺) as diammonium organic spacers in 2D DJ Sn²⁺ perovskite TFTs. The altered -CH₂NH₃⁺ position on piperidine chair impacts the overall perovskite crystal lattice through forming different hydrogen bonding environment, consequently the distortion of bonded inorganic slabs. This difference has a major impact on the optical and electronic properties, resulting in a narrowed bandgap and enhanced charge transport performance in the least distorted structure, 3AMPSnI₄. Specifically, the field-effect mobility increased by 10 times, and on/off current ratio is boosted by two orders of magnitude. Furthermore, we assess the ambient air stability and long-term storage stability of TFTs both based on 3AMPSnI₄ and 4AMPSnI₄, comparing them with phenylethylammonium tin iodide (PEA₂SnI₄), a representative 2D RP Sn²⁺ perovskite. This study on piperidinium-based 2D DJ Sn²⁺ perovskites elucidates the intricate relationship between spacer design, crystal structure, film quality and device performance, expanding the research horizon of 2D Sn²⁺ perovskites towards achieving high stability and good electrical property.