First‐Principles Calculation Design for 2D Perovskite to Suppress Ion Migration for High‐Performance X‐ray Detection

Abstract

Ion migration is a key root-cause of photocurrent instability in perovskite X-ray detectors. Although 2D perovskite single crystal (PSC) is a good candidate to suppress ion migration compared with its 3D counterpart, its intrinsic stability still needs to be improved. In this work, it is first envisioned to conquer the ion migration by enhanced chemical bonding; the proposal is further confirmed by density functional theory calculations, in which the bonds are made stronger by introducing a fluorine atom into the ortho position of phenethylamine (o-F-PEA) to shorten the distance between adjacent organic cations in the crystal lattice for enhanced electrostatic interactions between the F atom and the neighboring benzene ring. It is further demonstrated experimentally that the activation energy for ion migration (AEIM) of (o-F-PEA) 2 PbI 4 PSC is increased compared with that of (PEA) 2 PbI 4 PSC. The improved AEIM is also confirmed by enhanced thermal stability. Consequently, the dark current in the (o-F-PEA) 2 PbI 4 2D PSC X-ray detectors is reduced by two times compared with the (PEA) 2 PbI 4 reference. Furthermore, the detector shows the sensitivity of 1724.5 μC Gy air −1 cm −2 at 1250 V mm −1 , and much improved photocurrent stability.

Supramolecular Interactions of Flexible 2D Perovskite in Microstrain Releasing and Optoelectronic Properties Recovery

“…Two-dimensional (2D) layered perovskites arise as efficient materials in light-emitting diodes, solar cells, photodetectors, and ionizing radiation detectors [1][2][3][4][5][6] due to their unique anisotropy structure, quantum confinement behavior, excellent environmental stability, suppressed ion migration property, and so on. [7][8][9][10] Different from three-dimensional (3D) halide perovskites where the A-site cations are fitted into the inorganic 2-fluorophenethylammonium (oFPEA), 3-fluorophenethylammonium (mFPEA), and 4-fluorophenethylammonium (pFPEA) were employed to synthesize perovskite materials, which were abbreviated as oFPI, mFPI, and pFPI, respectively. Due to the steric hindrance difference and intermolecular interaction between organic cations, the microstrain caused by the inorganic octahedron tilting or distortion can be modulated and released by compressive bending.…”

Perovskite Dimensional Evolution Through Cations Engineering to Tailor the Detection Limit in Hard X‐ray Response

“…The ions' mobile paths are not effectively blocked in this case since the organic molecules are not closely packed. [23] Perovskite materials of different dimensions show different X-ray detection performance, [4,[26][27][28][29][30][31] and it is still not clear the dimension impact on the LDDR in hard X-rays (80-140 keV) detection, which are practically employed on patients for routine inspections or medical exams. In this manuscript, we report the perovskite dimension evolution from 0D PEA 3 Sb 2 I 9 to 2D Ruddlesden-Popper-type (RP) lead-free perovskite single-crystal 4-fluorophenethylammonium antimony iodide (FPEA 3 SbI 6 ), leaving one-third of Sb 3+ ions vacancies in inorganic octahedrons.…”

Fluorosubstitution Boosting 2D Ruddlesden–Popper CsPbI3 with High Stability and Efficiency

“…[ 20 ] Subsequently, Zhang and his collaborators also confirmed the positive function of F‐substitution by density functional theory calculation where fluorine atom in PEA + cations tends to reduce the distance of adjacent organic cations and enhance electrostatic interactions between F atom and the neighboring benzene ring for enhanced thermal stability. [ 21 ]…”

“…[20] Subsequently, Zhang and his collaborators also confirmed the positive function of F-substitution by density functional theory calculation where fluorine atom in PEA þ cations tends to reduce the distance of adjacent organic cations and enhance electrostatic interactions between F atom and the neighboring benzene ring for enhanced thermal stability. [21] Importantly, the function of F substitution recently was also extended into crystal growth orientation and film quality, which exhibits out-of-plane growth orientation, ordered phase arrangement for carrier transition, and lower nonradiative recombination. [22] However, all of these researches are based on the F-substituted PEA þ , which simply elaborates the experimental conclusions, lacking the exploration of the universal mechanism.…”