Triple‐Cation and Mixed‐Halide Perovskite Single Crystal for High‐Performance X‐ray Imaging

Abstract

X-ray detectors have attracted significant attention because they are widely used in applications such as computed tomography (CT), homeland security, and environmental monitoring. [1,2] In particular, there is an ever-increasing demand to invent better semiconductor material and device design to attain even higher sensitivity and lower manufacturing cost. [3,4] In the past decades, various traditional semiconductors have been studied for X-ray detection applications, like silicon (Si), [5] high-purity germanium (HP-Ge), [6] amorphous selenium (α-Se), [7] mercury iodide (HgI 2), [8] cadmium zinc telluride (CdZnTe), [9] and so on. Unfortunately, none of them is very ideal, more specifically, neither HP-Ge nor CdZnTe is costeffective; Si and CdZnTe require high working voltage; Si and α-Se have low X-ray absorption coefficient and large leakage current. Also, the CdZnTe, Si, and HP-Ge require very high growth temperature exceeding 500 °C, Hg and Cd are highly toxic. Recently, solution-processable organic-inorganic metal-halide perovskites have been demonstrated as a promising candidate for high performance X-ray detectors. They are advantageous in strong X-ray absorption, processable at low temperature, low-cost fabrication, and superior semiconducting properties like low defect density, large mobility-lifetime product (μτ), long carrier diffusion length, etc. Noticeably, the recently reported X-ray detectors based on 3D perovskites including MAPbI 3 [4,10-12] and CsFAMA [13] microcrystalline thin films or MAPbX 3 (X = Cl, Br, I and their mixture), [14-24] Cs x FA 1−x PbI 3 , [25] CsPbBr 3 , [26-29] and Cs 2 AgBiBr 6 [30-32] single crystals have realized high sensitivity with the highest up to 2.1 × 10 4 µC Gy air-1 cm-2 , significantly larger than the state-of-the-art α-Se X-ray detectors. [33] Unfortunately, the dark current is too high and as is the photocurrent drift in X-ray detectors made of these hybrid organic and inorganic 3D perovskites, and this is expected based on serious ion migration in the materials. Even worse, ionic migration is recognized as the main root cause for material decomposition and performance degradation in perovskite devices. In order to obtain perovskites with low ion migration, low-dimensional perovskite single crystals, like inchsized 0D MA 3 Bi 2 I 9 [34-37] and Cs 3 Bi 2 I 9 , [38-40] 2D Cs 2 TeI 6 [41] and (NH 4) 3 Bi 2 I 9 , [42] have been adventured first by our group and Low ionic migration is required for a semiconductor material to realize stable high-performance X-ray detection. In this work, successful controlled incorporation of not only methylammonium (MA +) and cesium (Cs +) cations, but also bromine (Br-) anions into the FAPbI 3 lattice to grow inch-sized stable perovskite single crystal (FAMACs SC) is reported. The smaller cations and anions, comparing to the original FA + and Ihelp release lattice stress so that the FAMACs SC shows lower ion migration, enhanced hardness, lower trap density, longer carrier lifetime and diffusion length, higher charge mobility and the...

Interfaces in metal halide perovskites probed by solid-state NMR spectroscopy

“…171 Halide redistribution is impacted by the A-site cations, and the effect can be minimized in mixed-cation MHPs. 150,172 ssNMR is wellsuited to characterize halide redistribution because of its sensitivity to the halide coordination environment of B-site cations as well as the ability to probe the local structure of halides. 64,67 The pursuit of more environmentally friendly and less-toxic lead-free MHPs has inspired the development of halide perovskites with different B-site cations.…”

Nanoscale interfacial engineering enables highly stable and efficient perovskite photovoltaics

“…Metal halide perovskites are poised to revolutionize nextgeneration optoelectronics, enabling economically viable and highly efficient photovoltaics, [1][2][3][4] light-emitting diodes, 5,6 and photodetectors. 7,8 The leap forward in the power conversion efficiency (PCE) enabled by lead (Pb) halide perovskites is unprecedented, with PCEs emerging from 3.8% in its first study 9 to a recent certified value of 25.5% in single-junction perovskite solar cells (PSCs). 10 Nevertheless, the functional instability associated with these materials under operational conditions [11][12][13][14] constrains their widespread applications in optoelectronic devices.…”

Ternary Hybrid Perovskite Solid Solution Single Crystals: Growth, Composition Determination and Phase Stability in Highly Moist Atmosphere

“…This class of perovskite single crystals possesses a shape of truncated rhombic dodecahedron with {110} and {100} plane families as natural crystallographic facets. X‐ray rocking curve of (220) diffraction peak shows a satisfactory crystalline quality of the single crystal (Figure 2h), as the FWHM is about 460 arcsec, comparable but a bit larger than those high‐quality undoped perovskite single crystals obtained by ITC method reported by other groups, [13,43] which might be ascribed to distortion of lattice caused by ion doping.…”

“…Hybrid organic‐inorganic perovskites (HOIPs), with chemical formula ABX 3 , have been extensively studied in the past decade due to their remarkable optoelectronic properties such as long carrier diffusion lengths, [1] long carrier lifetimes [2] and large absorption coefficients, [3] and potential applications in solar cells, [4,5] light‐emitting diodes (LEDs), [6,7] photodetectors [8–10] and X‐ray detectors [11–13] . Among all kinds of HOIPs, the methylammonium lead iodide (MAPbI 3 ) was the first one to be reported with photovoltaic effects [4] .…”

“…While most of these works are based on polycrystalline thin films, perovskite single crystals co‐doped in both A‐site and X‐site have been reported by different groups recently [13,32–36] . Chen et al.…”