Cs 3 Bi 2 I 6 Br 3 perovskite is one of the bismuth iodide family compounds. Because it contains no toxic lead, and has high stability in air and humidity, endowing a potential application prospects in photoelectric and radiation detectors. Herein, the Cs 3 Bi 2 I 6 Br 3 single crystal (Φ13 × 65 mm 3 ) with a (001) preferred direction was grown by using the melt method with solvent-synthesized polycrystalline particles, and the thin single wafer with a thickness up to 0.95 mm was obtained. The as-grown single crystal possesses high infrared transmittance of up to 70% in the range from 400 to 4000 cm −1 and an optical band gap of about 2.03 eV estimated from the visible absorption curve. A highly intrinsic resistivity 2.3 × 10 10 Ω·cm and a dielectric constant about 10 were obtained from the electrical performance parameter measurements. The X-ray sensitivity of the X-ray detector is 55.62 µC/Gy air /cm 2 (incident dose rate 0.24 mGy/s), as well as the signal-to-noise ratio, is up to 301. These results indicate Cs 3 Bi 2 I 6 Br 3 single crystals are a potential material for X-ray detection.
All-inorganic Cs 3 Bi 2 I 9 (CBI) halide perovskites are sought to be candidate for photoelectrical materials because of their low toxicity and satisfactory stability. Unfortunately, the discrete molecular [Bi 2 I 9 ] 3− clusters limit the charge-transport behaviors. Herein, the defect halide perovskite based on trivalent Bi 3+ is expanded to Cs 3 Bi 2 I 6 Br 3 (CBIB). Centimeter-size CBIB single crystal ( Φ 15 × 70 mm 3 ) was grown by the vertical Bridgeman method. The powder X-ray diffraction analysis shows that CBIB has P 3 ¯ m 1 structure with lattice parameters of a = b = 8.223 Å, c = 10.024 Å, α = β = 90° and γ = 120°. The density functional theory (DFT) calculations demonstrate that the charge density distribution was enhanced after the dimensional expansion. The enhancement of carrier transport ability of (00 l ) in-plane is characterized before and after dimensional improvement. The obtained CBIB (001) exhibited an electron mobility up to 40.03 cm 2 V −1 s −1 by time-of-flight (TOF) technique, higher than 26.46 cm 2 V −1 s −1 of CBI (001) . Furthermore, the X-ray sensitivity increases from 707.81 μC Gy −1 cm −2 for CBI (001) to 3194.59 μC Gy −1 cm −2 for CBIB (001) . This research will deepen our understanding of Bi-based perovskite materials and afford more promising strategies for lead-free perovskite optoelectronic devices modification.
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