Simple method to synthesize larger n 2D perovskite from (C(NH2)3)(CH3NH3)n[PbnI3n+1] of n = 1 using isopropanol

Two-dimensional (2D) perovskite of (C(NH2)3)(CH3NH3)n[PbnI3n+1] (shorten as (GA)MAn[PbnI3n+1]) is with alternating cations (GA+ and MA+) in the interlayer space (ACI). n = 1 of (GA)MAPbI4 film can transform from red to black in appearance after soaking in isopropanol (IPA) for 5 s, resulting in the peaks of PL from 570 nm to 770 nm. Using X-ray diffraction and Fourier-transform infrared spectroscopy, we find that the IPA can dissolve GA+ cation from the film effectively, thus n = 1 layered structure is destroyed, leaving larger n phases of (GA)MAn[PbnI3n+1] in film. By controlling the reaction time with IPA solvent, the n = 1 film can rearrange into new material of mixture with various n values, which present tunable absorption and photoluminescence spectra. Our work may not only explore the novel phenomena of ACI 2D perovskite, but also provide a simple method to synthesize quasi 2D perovskite with adjustable n values.