Electron‐Phonon Coupling Suppression by Enhanced Lattice Rigidity in 2D Perovskite Single Crystals for High‐Performance X‐Ray Detection

2D Dion-Jacobson (DJ) perovskite single crystals (PSCs) usually demonstrate better X-ray detection performance than Ruddlesden-Popper (RP) PSCs. However, the mechanism of the improved performance is still elusive. Here, by the aid of strong interactions between dimethylbiguanide (DGA) and PbI2 , a novel DJ-perovskitoid (DGA)PbI4 is designed. From the comparison of (DGA)PbI4 to other 2D PSCs, it is discovered that the tiniest lattice distortion and increased hydrogen bonds in the atom-scaled analysis strengthen lattice rigidity and weaken electron-phonon coupling to suppress disordered scattering of carriers, resulting in significantly improved carrier transport and stability. Therefore, high carrier mobility (78.1 cm2 V-1 s-1 ) and a pronounced sensitivity of 4869.0 µC Gyair-1 cm-2 are achieved using (DGA)PbI4 , which are the best in 2D Pb-based PSC devices to date. Finally, the (DGA)PbI4 devices exhibit good spatial resolution in X-ray imaging and excellent long-term stability to work as a promising candidate for medical diagnostics and nondestructive determination.