Unveiling the Structural Descriptor of A₃B₂X₉ Perovskite Derivatives toward X‐Ray Detectors with Low Detection Limit and High Stability

Abstract

Metal halide perovskites and derivatives exhibit a high sensitivity and low detection limit as direct X‐ray detectors. Inorganic 2D bismuth halide perovskites are promising for X‐ray detections, but have not been reported. Moreover, the quantitative relationship between the structural dimensionality of A3B2X9 perovskites and their compositions has never been investigated, and the underlying mechanism is unclear. Here, the key structural descriptors for 2D A3B2X9 perovskite derivatives are reported: i) octahedral factor μ, 0.377 < μ < 0895; ii) tolerance factor t, 0.8 < t < 1.06; iii) (rA‐0.55)/t < 1.48 Å. Accordingly, a new 2D A3B2X9 perovskite derivative, Rb3Bi2I9, with high X‐ray attenuation coefficients is found. The assembled X‐ray detector exhibits a high μτ product of 2.51 × 10−3 cm2 V−1, good sensitivity for 159.7 μC Gyair−1 cm−2, and a record low detection limit of 8.32 nGyair s−1 among all direct and indirect perovskite X‐ray detectors. The device also exhibits good stability toward external bias and continuous gamma ray radiations (480 000 Gy). This work provides crystal structural insights to rationally design 2D perovskites for new types of radiation detectors.

Metal Halide Perovskites for High‐Energy Radiation Detection

“…As already discussed, two key factors for enhancing the detection limit of perovskite direct X‐ray detectors, are the dark current, and the ion migration within the perovskite during electrical biasing (i.e., device operation). Xia et al., [ 118 ] attempted to tackle these issues by engineering single crystals of a 2D A 3 B 2 X 9 perovskite, namely Rb 3 Bi 2 I 9, with an energy bandgap of 1.89 eV. The ensuing detectors (device structure: Au/Rb 3 Bi 2 I 9 /Au) exhibited excellent physical (a crystal 0.4 mm thick was enough to stop 90% of 30 keV X‐ray photons) and electronic properties ( μ h/e × τ = 2.51 × 10 −3 cm 2 V −1 ).…”

Halide perovskites: A dark horse for direct X‐ray imaging

“…Meanwhile, a large electrical bias indeed increases the gain, while it also increases the dark current, worsens the on/off ratio and raises the noise amplitude. 44,47,55,56 Such dilemmas should be systematically considered and addressed when designing optimal perovskite X-ray detectors.…”

“…Likewise, a thin perovskite layer amplifies the gain by shortening the transit length, but the X‐ray attenuation ratio would be compromised. Meanwhile, a large electrical bias indeed increases the gain, while it also increases the dark current, worsens the on/off ratio and raises the noise amplitude 44,47,55,56 . Such dilemmas should be systematically considered and addressed when designing optimal perovskite X‐ray detectors.…”

Perovskite Nano‐Heterojunctions: Synthesis, Structures, Properties, Challenges, and Prospects

“…The 2D perovskite can be formed by alternating A and [B 2 X 5 ] À layers for AB 2 X 5 [25] or alternating [BX 6 ] 4À octahedras and large cation A for A 2 BX 4 or A 3 B 2 X 9 . [26,27] Generally, the 2D perovskite family is built upon the chemical slicing of 3D perovskite along (100), (110) and (111) crystal planes, yielding A 0 2 A n-1 B n X 3nþ1 , A 0 2 A m B m X 3mþ2 , and A 0 2 A q-1 B q X 3qþ3 , respectively. [28] The 3D perovskite also includes the A 2 B þ B 03þ X 6 -type structure, which is called double perovskite, [29] and the corresponding layered 2D perovskites.…”