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

Abstract

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−1cm−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.

Bilayered Dion–Jacobson Hybrid Perovskite Bulk Single Crystals Constructed with Aromatic Diammonium for Ultraviolet–Visible–Near-Infrared Photodetection

“…Second, the rigidity of aromatic diammonium is stronger than that of aliphatic diammonium, which will cause the minimum distortion of the inorganic skeleton. 24 Finally, the aromatic ring has free π-electrons, which can improve the charge transport (Scheme 1). 31,32 From this point of view, the performance of DJ HP devices based on aromatic diammonium should be better than those based on aliphatic diammonium.…”

“…20−23 For example, most recently, Liu's group verified that the X-ray detection performance of DJ HP single crystals ((dimethylbiguanide)PbI 4 ) is better than that of RP HP single crystals ((ortho-fluoro-phenethylamine) 2 PbI 4 ). 24 The mechanisms of carrier transport performance and stability improvement for DJ HP (dimethylbiguanide)PbI 4 are mainly due to the tiniest lattice distortion and increased hydrogen bonds. In addition, we know that the natural quantum well structure of 2D HPs makes in-plane carrier transport efficiency superior to that of out-of-plane carrier transport, and hence the poor carrier transport property along the out-of-plane direction for all known RP HPs.…”

“…Compared with three-dimensional (3D) organic–inorganic hybrid perovskites (HPs), low-dimensional HPs exhibit improved stability, higher tunability of physical properties, and new capabilities. − Particularly, two-dimensional (2D) layered organic–inorganic HPs with quantum-well-like systems have gradually become a class of high-performance semiconductors due to their excellent stability and good carrier transport performance. − Up to now, 2D HPs are dominated by the Ruddlesden–Popper (RP) phase, which possesses the characteristics of two offset layers per unit cell and has pairs of interdigitated interlayer monovalent (+1) cations. − However, recent studies have shown that 2D Dion–Jacobson (DJ) phase HPs with divalent (+2) interlayer spacers have more structural stability than RP HPs, which is mainly because diammonium cations can be directly connected to both ends of the adjacent inorganic sheets through chemical bonds, thus eliminating the van der Waals gap. − More importantly, DJ phase HPs have a shorter interlayer distance and enhanced lattice rigidity than RP phase HPs, which will weaken the electron–phonon coupling and is conducive to high-efficiency carrier transport. − For example, most recently, Liu’s group verified that the X-ray detection performance of DJ HP single crystals ((dimethylbiguanide)­PbI 4 ) is better than that of RP HP single crystals ((ortho-fluoro-phenethylamine) 2 PbI 4 ) . The mechanisms of carrier transport performance and stability improvement for DJ HP (dimethylbiguanide)­PbI 4 are mainly due to the tiniest lattice distortion and increased hydrogen bonds.…”

“…First, the dielectric constant (ε b ) of aliphatic diammonium is generally below 3, while the ε b of aromatic diammonium is ∼3 or more. , In this way, the organic layer constructed with aromatic diammonium will have a better dielectric match with the inorganic skeleton layer (ε b ∼ 6). Second, the rigidity of aromatic diammonium is stronger than that of aliphatic diammonium, which will cause the minimum distortion of the inorganic skeleton . Finally, the aromatic ring has free π-electrons, which can improve the charge transport (Scheme ).…”

Incorporating an Aromatic Diammonium To Assemble Bilayered Dion–Jacobson Perovskite Crystals for Weak Light Detection

“…The closer the Pb−Br−Pb bond angle is to 180°, the less the lattice distortion and the higher the charge transport. 18 In addition to the comparison to monolayer (3AMPY)PbBr 4 , we also compared the structure of bilayer DJ hybrid perovskite (3AMPY)(EA)Pb 2 Br 7 (EA is ethylammonium) in Figure S1a of the Supporting Information, which used EA as the perovskitizer. 40 From the difference between MA and EA, EA (274 pm) has a larger effective radius than MA (217 pm).…”