Crystalline–Amorphous Heterojunction for a Metal Halides Single Crystals X‐Ray Detector with Substantially Increased Sensitivity

Abstract Ion migration‐induced noise is the main limiting factor for metal halides (MHs) single crystals (SCs) X‐ray detectors, and heterostructure design is the most efficient method to overcome this puzzle. However, the conventional stepwise solution method or heteroepitaxial method is greatly limited by the SCs secondary dissolution and the lattice parameters matching. Here, simple and universal crystalline–amorphous heterojunction is developed that proves to be extremely effective in suppressing noise. MAPbBr 3 SCs are first chosen as representatives to form heterojunctions with amorphous MTP 2 MnBr 4 by the melting method, and the related device shows an enhanced X‐ray response with significant noise suppression. Computational and experimental results demonstrate that the gradient energy levels formation and improved ion migration energy are responsible for this. Finally, the optimized device shows a low dark current (reduced from ≈1000 to ≈0.12 nA), ultra‐high sensitivity (10 569 µC Gy air −1 cm −2 ), lower detection limit (82.64 nGy air s −1 ), and negligible performance deterioration at a total radiation dose of ≈17 000 mGy air . Moreover, six other SCs are selected to verify the universal effect of the heterojunctions, all of which show excellent improved sensitivity, proving its versatility. Hence, it is believed that this work will give a strong impetus to develop sensitive MHs SCs X‐ray detectors.