Highly Crystalline CsPbBr 3 Thin Films With Amplified Spontaneous Emission via High‐Pressure Recrystallization

ABSTRACT Metal halide perovskites are promising materials for optoelectronic applications owing to their outstanding optical and electronic properties. Among them, all‐inorganic perovskites such as offer superior thermal and chemical stability. However, obtaining high‐quality thin films via solution processing remains challenging due to the low solubility of the precursor, and current additive or solvent engineering strategies are often complex and poorly reproducible. High‐pressure recrystallization has recently emerged as a promising route to improve film quality, yet its impact on film properties remains insufficiently explored. Here, we systematically investigate the morphological, structural, and optical properties of thin films prepared by high‐pressure recrystallization, in comparison with standard non‐recrystallized films. Optimized recrystallization at 300 bar produces smooth, pinhole‐free, single‐phase 3D perovskite layers with sub‐nanometer roughness, while the film thickness is precisely tunable via precursor concentration. The process enhances both grain and crystallite sizes, leading to amplified spontaneous emission with a reduced excitation threshold and improved photostability. Temperature‐dependent X‐ray diffraction further reveals the orthorhombic–tetragonal–cubic phase transition, consistent with single‐crystal behavior. This study provides fundamental insights into pressure‐driven recrystallization and establishes a reproducible, scalable approach for fabricating high‐quality films for optoelectronic devices.