Bimetallic Co-Occupation and Multiple Interlayer Interactions in Aromatic Double Perovskite for Highly Sensitive and Stable Self-Driven X-Ray Detection.

Polar lead-free double perovskites with intrinsic bulk photovoltaic effect (BPVE) under X-ray irradiation can provide an innovative platform for the development of green self-powered X-ray detectors. However, this type of detector still faces two major challenges, including low sensitivity due to limited carrier transport efficiency and operational instability caused by ionic migration. Here, a polar lead-free aromatic double perovskite, (TFMPEA)4AgBiI8 (2, TFMPEA is 2-(4-trifluoromethyl-phenyl)-ethylamine) is reported, where Ag⁺/Bi3⁺ bimetallic co-occupation and interlayer multiple interactions enable highly sensitive and stable X-ray detection. In detail, bimetallic co-occupation narrows the bandgap and flattens the inorganic framework arrangement, achieving a self-driven sensitivity of 184 µC Gyair -1 cm-2. Notably, the compound 2 exhibits a sensitivity of up to 9191 µC Gyair -1 cm-2 at 1100 V cm-1, surpassing most reported X-ray detectors. More importantly, the device exhibits excellent environmental stability due to multiple interlayer interactions. Even after prolonged exposure to air, the photocurrent density does not decrease significantly. This work first reports highly stable and sensitive X-ray detection via bimetallic co-occupation and interlayer interactions, offering insights into green perovskite optoelectronic devices.