Composition Engineering Growth of Cs₃Bi₂I₉ Single Crystals with Low Defect Density for X-ray Detectors

Abstract

Cs 3 Bi 2 I 9 (CBI) single crystal (SC) is a promising material for a higher-performance direct X-ray detector. However, the composition of CBI SC prepared by the solution method usually deviates from the ideal stoichiometric ratio, which limits the detector performance. In this paper, based on the finite element analysis method, the growth model of the top-seed solution method has been established, and then the influence of precursor ratio, temperature field, and other parameters on the composition of CBI SC has been simulated. The simulation results were used to guide the growth of the CBI SCs. Finally, a high-quality CBI SC with a stoichiometric ratio of Cs/Bi/I = 2.87:2:8.95 has been successfully grown, and the defect density is as low as 1.03 × 10 9 cm −3 , the carrier lifetime is as high as 16.7 ns, and the resistivity is as high as 1.44 × 10 12 Ω•cm. The X-ray detector based on this SC has a sensitivity of 29386.2 μC•Gy air −1 cm −2 at an electric field of 40 V•mm −1 , and a low detection limit of 0.36 nGy air •s −1 , creating a record for the all-inorganic perovskite materials.

Anisotropic optoelectronic properties of lead-free Cs3Bi2I9 single-crystal photodetectors

“…The full width at half maximum (FWHM) of the strongest diffraction is FWHM = 0.16 • for the (300) plane in (l00) SC and FWHM = 0.24 • for the (006) plane in (00l) SC. The smaller FWHM suggests that (l00) SC possesses better crystallinity and better crystal quality than (00l) SC [41]. Figure 1(c) displays the UV-visible light absorption spectra of (l00) and (00l) Cs 3 Bi 2 I 9 SCs.…”

“…Bismuth (Bi), as a green non-toxic metallic element [37], possesses not only the same 6s 2 6p 0 electronic structure as Pb 2+ [27,38] but also a suitable ionic radius, which makes it stable in the perovskite structure, resulting in excellent thermal and moisture stability [39,40]. Therefore, Bi-based lead-free perovskite devices, such as Cs 3 Bi 2 I 9 [39,41,42], Cs 3 Bi 2 Br 9 [38,43], and Cs 3 Bi 2 Cl 9 [40,44], attract intensive research interest due to the outstanding stability and high power conversion efficiency (PCE) [39,42]. Waykar et al [45] reported solar cells based on Cs 3 Bi 2 I 9 perovskite films with maximum PCE of 0.17%.…”

Exploring the synthesis, structure, and optoelectronic properties of lead-free halide perovskite Cs3Bi2I9 in single crystal and polycrystalline forms

“…The Cs 3 Bi 2 I 9 perovskite compound finds application in a variety of photovoltaic applications due to its strong stability against ambient conditions, appealing light harvesting capabilities, good photoluminescent features, impressive optoelectronic attributes, and rich structural diversity. Environmentally stable and non-toxic Cs 3 Bi 2 I 9 single crystals have been used in highly sensitive photodetectors [30,31], high-performance x-ray detection [32][33][34], light-emitting devices (LEDs) [29], alpha particle detectors [35], photocatalysts [36], and supercapacitor [37]. Similarly, polycrystalline Cs 3 Bi 2 I 9 perovskite thin films formed by simple and conventional spin coating methods found applications in memory devices [38], photodetectors [39,40], photobattery electrodes [41], flexible optoelectronic synaptic field-effect transistors [42], and various solar cell devices [43][44][45][46].…”