Fig. 1: Crystallization dynamics of quasi-2D thin films.

a XRD patterns of the PEASCN–FAHCOO-based films at different annealing times. 2 L denotes the bilayer (n = 2) Ruddlesden–Popper perovskite phase corresponding to PEA₂FASn₂I₅SCN₂, while 3D denotes the three-dimensional FASnI₃ phase. b Schematic diagrams of the structural evolution of PEASCN–FAHCOO-based films during the annealing process. c GIWAXS patterns of the unannealed PEASCN–FAHCOO-based films. d GIWAXS patterns of the PEASCN–FAHCOO-based films after annealing for 1 min. e PL spectra of the PEASCN–FAHCOO-based films at different annealing times. f XRD patterns of the PEAI-based films at different annealing times. g XRD patterns of the annealed PEASCN–FAHCOO-based and PEAI-based perovskite films, with a partially enlarged view of the (100) diffraction peak. h Azimuth curves of the integrated ring at q_r = 1.0 Å⁻¹.