Ion-exchange-induced MAPbI3 thin-film 3D–2D and 3D–1D conversions: unveiling structural transformations in films via synergistic and competitive approaches

Abstract

The gas-induced transformation of organic–inorganic halide perovskites shows unprecedented phenomena and applications in the area of optoelectronics. In this study, the chemical origins of the gas-induced dimensional transformation (GIDT) of MAPbI₃ have been investigated within CH₃NH₂ (MA), CH₃(CH₂)₅NH₂ (C6) and (CH₃CH₂)₃N (C6′) atmospheres. With the exposure of the as-synthesized MAPbI₃ perovskite thin film to the C6 gas, the rapid displacement of the MA⁺ cations by the C6⁺ cations is achieved, thus inducing the MAPbI₃ thin film structure to turn from a three-dimensional motif to two-dimensional (CH₃(CH₂)₅NH₃)₂PbI₄. By comparison, no response is observed when the same process is carried out in the presence of the tertiary amine C6′ gas. With MA acting as a coinduction conversion agent, the MAPbI₃ film transfers to a quasi-2D perovskite structure within MA and C6 mixture atmosphere, while it changes to a one-dimensional (C₆H₁₅NH)PbI₃ chain as MA combines with the C6′ gas, showing an effective mixed amine strategy for GIDT. Interestingly, the obtained quasi-2D perovskite films display tuneable absorption and emission luminescent characters associated with the volume ratios of MA/C6-mixed amines.