Orthorhombic Non‐Perovskite CsPbI₃ Microwires for Stable High‐Resolution X‐Ray Detectors

Abstract

Direct conversion X-ray detectors operate by directly converting X-ray photons into an electrical signal, while indirect conversion detectors (also called scintillators) first convert X-ray photons to visible light. Subsequently, this light is converted to an electrical signal using visible light detectors. Direct conversion detectors are simpler in configuration and offer higher spatial resolution than scintillators. [2] Among traditional semiconductors, amorphous selenium (a-Se), [3] and Cd 1−x Zn x Te (CZT, x < 20%)-based materials [4] dominate the market of commercial X-ray detectors. a-Se has a low device dark current and stable device performance; however, it possesses low X-ray absorptivity. On the other hand, CZT offers excellent absorptivity, but requires high-temperature processing conditions (>900 °C), [5] and suffers from structural imperfections [5,6] and compositional inhomogeneity. [6,7] These limitations demand the development of novel semiconductors for direct X-ray detectors.Solution-processed metal halide perovskites have recently emerged as a family of unique semiconductors for X-ray detectors. [2b,8] Due to their elemental constitution of heavy atoms such as lead and iodine, metal halide perovskites have a high X-ray attenuation coefficient. [2b,8b,9] However, conventional perovskites suffer from long-term instability, and high dark current (determines noise level). [10] Early diagnoses of diseases requires high spatial resolution, which is measured by recording the resolving power of a line-pair (lp) phantom. [11] For radiology, a minimum spatial resolution of 5.7 lp mm −1 is required for adequate resolution of small objects. [12] Imaging becomes more challenging when it comes to mammographic applications, where a resolution of 10 lp mm −1 is needed to resolve small microcalcifications. [13] Unfortunately, conventional direct conversion X-ray detectors have low resolution as they are integrated into transistor arrays with limited pixel dimensions. [14] Here we report a strategy to grow aligned orthorhombic δ-CsPbI 3 microwires offering one of the highest X-ray absorption coefficients. The crystals show a record-low dark current density of 12 pA mm −2 under 600 V mm −1 electric field. A Schottky junction with δ-CsPbI 3 is able to sense dose rates as low as 33.3 nGy air s −1 . We also show an X-ray spatial resolution of ≈12.4 lp mm −1 , which is one of the highest values reported to date (Table S1, Supporting Information). The fabricated X-ray detectors are used widely, but they suffer from short operational stability and insufficient absorptivity of X-ray photons. Here, a strategy for roomtemperature, solution-grown δ-CsPbI 3 monocrystalline microwires exhibiting one of the highest linear X-ray absorption coefficients among known semiconductors is reported. In a metal-semiconductor-metal architecture, δ-CsPbI 3 demonstrates one of the lowest detectable X-ray dose rates at 33.3 nGy air s −1 , enabled by its exceptionally low dark current density of 12 pA mm −2 . The detector remains stab...

Integration of Large-Area Halide Perovskite Single Crystals and Substrates via Chemical Welding Using an Ionic Liquid for Applications in X-ray Detection

“…Therefore, in this study, MAPbBr 3 was chosen as the most actively studied bromide perovskite. The linear absorption coefficient of MAPbBr 3 as a function of X-ray energy can be calculated from the composition and atomic cross-section of the constituent elements (Figure a). − The reciprocal of the linear absorption coefficient, known as the attenuation coefficient, represents the thickness of the layer required to absorb 63% of the incident X-ray intensity and is also shown in the same graph. To effectively absorb high-energy (60–120 keV) X-ray photons used in medical scan, it is necessary to have a MAPbBr 3 thickness of at least 0.5–1.5 mm.…”

Metal Halide Perovskite Nanowires: Synthesis, Integration, Properties, and Applications in Optoelectronics

“…Kundu et al reported solution-grown δ-CsPbI 3 microwires for X-ray detection with high performance. [195] Specifically, the ITO/δ-CsPbI 3 www.advancedsciencenews.com microwires/ITO device exhibited one of the lowest detectable X-ray dose rates at 33.3 nGy air s −1 , resulted from the exceptionally low dark current density of 12 pA mm −2 . Meanwhile, the microwires-based X-ray detector demonstrated excellent operational stability under a high continuous X-ray dose rate of 45 Gy air s −1 .…”

Supple Formamidinium-Based Low-Dimension Perovskite Derivative for Sensitive and Ultrastable X-ray Detection

“…However, it is currently challenging to produce millimeter-thick large-area films using traditional deposition techniques or blade coating. On the other hand, the production of perovskite single-crystal detectors is restricted by immature technology and high costs, particularly for the low-dimensional perovskite crystals. , Due to its highly tunable nature and cost-effective production processes, the fabrication of perovskite wafers represents a simple and commercially viable approach for developing X-ray detectors . This method can be easily scaled up using molds or patterns, making it preferable to using single crystals (SCs).…”