Beyond Spin Coating: Homogeneous All-Inorganic Perovskite Films via High-Pressure Recrystallization

TL;DR

The paper tackles the challenge of producing high‑quality all‑inorganic CsPbBr3 films from solution by introducing high‑pressure recrystallization as a scalable alternative. Using an automated imprinting platform, it systematically varies processing pressure up to 300 bar and precursor concentration to examine morphology, crystallinity, and optical performance, including ASE. Under optimized conditions at 300 bar, the films achieve smooth, pinhole‑free surfaces with single‑phase 3D CsPbBr3, enlarged crystallites, and sub‑nanometer roughness, while thickness is tunable via precursor concentration; ASE is strongly enhanced with a substantially lower threshold than non‑recrystallized regions. Temperature‑dependent XRD reveals reversible orthorhombic–tetragonal–cubic phase transitions, accompanied by a predominant out‑of‑plane fiber texture, suggesting anisotropic excitonic properties and potential for polaritonic devices. Overall, pressure‑driven recrystallization provides a fast, reproducible, and scalable route to high‑quality CsPbBr3 films for LEDs, lasers, and other optoelectronic applications.

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 CsPbBr$_3$ offer superior thermal and chemical stability. However, obtaining high-quality CsPbBr$_3$ thin films via solution processing remains challenging due to the precursor's low solubility, 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 CsPbBr$_3$ 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 CsPbBr$_3$ films for optoelectronic devices.

Figures (7)

• Figure 1: Schematic of the two-step fabrication process: the pristine spin-coat includes (a) spin coating of the precursor solution, followed by (b) annealing to induce crystallization, also called non-recrystallized thin film. (c) Recrystallization involves applying high pressure and a controlled crystallization temperature, resulting in (d) a flattened perovskite layer with larger crystal sizes and improved surface coverage.
• Figure 2: (a-c) are the SEM image, AFM image, and XRD spectrum of the non-recrystallized perovskite film, respectively. (d-f) and (g-i) are the SEM images, AFM images, and XRD spectra of the recrystallized perovskite film under 100 bar and 300 bar, respectively. The precursor concentration of PbBr$_2$ is 0.23 M.
• Figure 3: Optical image of the non-recrystallized (left) and the recrystallized (right) CsPbBr$_3$ thin film under 300 bar of pressure, both samples correspond to the precursor concentration of 0.23 M.
• Figure 4: (220) XRD pole figure of the recrystallized layer (0.4 M, 300 bar)
• Figure 5: (a) Absorption spectrum of CsPbBr$_3$ thin film before (black) and after recrystallization (red) on transparent fused silica substrate, the inset is an image of the sample on Si/SiO2 substrate used for ASE measurement. (b,c) Low excitation fluence photoluminescence (PL) spectra of the non-recrystallized (black) and recrystallized (red) part of the same CsPbBr$_3$ thin film sample prepared with 0.4 M of precursors on Si/SiO$_2$ substrate, measured in the (b) 45° and (c) 90° excitation-detection configuration, as schematized in the insets.