Transparent Perovskite Wafers via Nanocrystals Ordered Coalescence Toward Sensitive and Stable X‐Ray Detection and Imaging

Abstract Metal halide perovskite wafers have shown significant potential in large‐area X‐ray detection and imaging. However, a distinct difference in optical transparency between state‐of‐the‐art perovskite wafers and single crystals indicates the inferior crystal quality of perovskite wafers, which limits the performance and stability of wafer‐based X‐ray detectors. Here, nano‐sized MAPbBr 3 powders are utilized to fabricate dense perovskite wafers by low‐temperature hot‐pressing with high transparency above 60% within the 552–800 nm wavelength range. Adjacent nanocrystals assemble following the ordered coalescence mechanism, resulting in the exclusion of nanoscopic pores and crystallographic reorientation. The transparent MAPbBr 3 wafer‐based detectors achieve an impressively high X‐ray sensitivity of 1.14 × 10 5 µC Gy air −1 cm −2 and a low detection limit of 149 nGy air s −1 , which is superior to opaque MAPbBr 3 wafer detectors (5.64 × 10 4 µC Gy air −1 cm −2 and 316.7 nGy air s −1 ) and comparable to MAPbBr 3 single‐crystal detectors. Moreover, the detectors demonstrate high uniformity and outstanding stability under continuous X‐ray irradiation of a total dose of up to 5.9 Gy air , equaling to 29 500 times posteroanterior chest examinations. The high sensitivity and low detection limit of the detectors lead to clear X‐ray imaging performance.