Tailoring the Fabrication Method of Dion–Jacobson 2D Halide Perovskites toward Highly Crystalline and Oriented Films

Abstract Halide perovskites are potential next‐generation optoelectronic devices. However, the film quality of this charming material fabricated by the conventional spin‐coating method is far from satisfactory, significantly affecting the optoelectronic devices' performance. Here, one facile slow‐evaporating solvent (SE) method is demonstrated to synthesize high‐quality organic–inorganic halide perovskite films. Compared with the conventional spin coating method, the films fabricated by this SE method show much higher crystallinity, oriented lattice, smoother surface morphology, and lower trap density. Besides, the photodetector manufactured by the SE method‐based film also performs much better than the ones by the spin‐coating method. Importantly, this universal method can be applied to different organic–inorganic halide perovskites, such as Dion–Jacobson (DJ) type and Ruddlesden–Popper type 2D halide perovskites and conventional 3D halide perovskites. This work gives an effective solution to improve the quality of the DJ‐type halide perovskites, which endows the halide perovskites with a more practical chance to be commercialized cosmically.