Epitaxial Growth\nof Submillimeter-Thick CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> Perovskite Films via Nitrogen-Regulated\nSolvent Extraction during the Blade-Coating Process for Sensitive\nDirect X‑ray Detecti

Due to their exceptional responses to X-ray exposure,\nlead halide\nperovskites are recognized as ideal candidates for high-spatial-resolution\nX-ray detectors. However, an effective method to deposit a large-area,\nsubmillimeter-thick, dense perovskite film for X-ray detection has\nbeen lacking. In this study, a strategy that combines saturated-solution-induced\nepitaxial growth with a large-area blade-coating process has been\ndeveloped to produce large-size, submillimeter-thick CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> perovskite films. The successive deposition\nof a saturated precursor film does not dissolve the underlying perovskite\nfilm. Instead, it promotes epitaxial crystal growth by controlling\nthe crystal growth rate over the nucleation rate. The obtained films\nexhibit a columnar grain structure with fewer pinholes and negligible\nresidual lattice strain. As a result, under an X-ray source with a\nworking voltage of 40 kV, the obtained thick CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> film achieves X-ray sensitivity of up to\n1938 μC Gy<sub>air</sub><sup>–1</sup> cm<sup>–2</sup> under −3 V bias, a reduced dark current drift of 1.78 ×\n10<sup>–4</sup> nA s<sup>–1</sup> V<sup>–1</sup>, and a detection limit of 47 nGy<sub>air</sub> s<sup>–1</sup> under a −2 V bias; all the above are among the best performances\nreported for the CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub>-based\nX-ray detectors. Using the point-to-point current scanning method,\na clear X-ray image could be obtained. This study presents an effective\napproach for producing thick, dense, and crack-free perovskite films\ndirectly on substrates for future X-ray detection applications.