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 PbI 2 , a novel DJ-perovskitoid (DGA)PbI 4 is designed. From the comparison of (DGA)PbI 4 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 cm 2 V −1 s −1 ) and a pronounced sensitivity of 4869.0 µC Gy air −1 cm −2 are achieved using (DGA)PbI 4 , which are the best in 2D Pb-based PSC devices to date. Finally, the (DGA)PbI 4 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.