Spray Coating of Thick Perovskite Films for Photodetectors: The Aerosol–Liquid–Solid Mechanisms and Sensing Applications

Spray coating has emerged as a transformative technique for fabricating high-quality perovskite thick films, which are essential for advanced photodetectors such as X-ray and narrowband sensors. This review surveys and systematically elucidates the physicochemical mechanisms underlying the aerosol-liquid-solid (ALS) transformation during spray deposition, focusing on three core stages: aerosol generation (via pneumatic, electrospray, or ultrasonic methods), droplet deposition and wetting dynamics, and liquid-to-solid crystallization. The interplay among precursor properties, spray parameters, and substrate characteristics dictates film morphology, crystallinity, and defect density. We highlight optimization strategies, including solvent engineering, additive incorporation, and process control, that enable the growth of dense, vertically aligned, and large-grained perovskite films with thicknesses up to hundreds of micrometers. Furthermore, the integration of dimensional engineering and heterojunction design through sequential spray deposition enhances charge transport, suppresses ion migration, and improves detection performance. Applications of these films are demonstrated in direct X-ray detectors and filter-free narrowband photodetectors with high sensitivity, low detection limits, and excellent spatial resolution. Remaining challenges are also discussed in understanding dynamic phase transitions and ensuring large-area uniformity of the spray-deposited films. Advancing in situ characterization and intelligent process control will accelerate the transition of spray coating from a laboratory technique to a scalable precision-manufacturing platform for next-generation perovskite optoelectronics.