Interface Engineering with Polymer Interlayers: Achieving Uniform and Stable Perovskite Thick Films for X-ray Detection

Interface stress is a critical challenge limiting the optoelectronic performance and stability of perovskite-based X-ray detectors, often causing severe issues such as surface roughness, cracking, and film detachment during fabrication. To address this, polymer interlayers have been employed as effective stress-buffering layers at the substrate/perovskite interface. However, the influence of the polymer layer properties on the growth and quality of the perovskite films has received limited attention. In this study, we systematically explore the processability, mechanical properties, solubility, thermal stability, and adsorption strength with perovskite materials of four polymers - poly(vinylidene fluoride) (PVDF), poly(vinylpyrrolidone) (PVP), polyimide (PI), and poly(l-lactic acid) (PLLA) - using a combination of experimental and theoretical methods, emphasizing the role of polymer molecular characteristics in enhancing CsPbI₂Br film quality. Among them, the CsPbI₂Br thick film with a PI buffer layer demonstrates the most uniform and dense morphology, along with strong adhesion to the substrate, maintaining integrity even under a 50 g load. The resulting perovskite X-ray detectors exhibit excellent uniformity and long-term stability over 30 days of continuous operation. Moreover, the integration of the PI/CsPbI₂Br thick film with a 64 × 64 thin-film transistor (TFT) enabled high-resolution X-ray imaging. This study provides valuable insights into selecting polymer interlayers to further optimize perovskite thick film-based X-ray detectors.