Lead-free halide perovskites have attracted widespread research interest due to their excellent optoelectronic properties and environmental friendliness. As one of the bismuth iodide compounds, Cs3Bi2I9 perovskite has been extensively explored in the field of photovoltaic devices and radiation detectors due to their non-toxic lead-free components and excellent stability. In this work, we successfully grow large-sized Cs3Bi2I9 single crystals (SC) with (l00) and (00l) crystal exposure facets by inverse temperature crystallization method. Under 525 nm light illumination with the intensity 15 mW cm−2 and 7 V bias, the (l00) Cs3Bi2I9 SC shows 2 times higher photocurrent, 3.6 times higher responsivity, and 2.8 times higher detectivity than the (00l) Cs3Bi2I9 SC, respectively. Superior response time in the scale of millisecond is obtained in both (l00) and (00l) Cs3Bi2I9 SCs. Based on the first-principle calculation, the (l00) SC possesses a higher charge distribution density and a wider dispersion distribution than (00l) SC, suggesting that more electrons in the (l00) SC can be excited in a wider range. The tighter arrangement of Cs+ and [BiI6]− octahedra in the (l00) SC than (00l) SC leads to the anisotropic photoelectric performance in (l00) and (00l) Cs3Bi2I9 SCs. Our results provide a strategy for the oriental growth of Cs3Bi2I9 SCs and the design of anisotropic optoelectronic devices with excellent performance.
Cs3Bi2I9 single crystals has attracted increasing attention in perovskite X-ray detectors due to its low cost, nontoxicity, high stability and low detection limit. With the gradual improvement of device performance, the growth of high-quality, low-defect single crystals becomes increasingly crucial. In this work, we developed a polypropylene glycol nucleation control strategy for the effective growth of Cs3Bi2I9 single crystals with fewer defects. The X-ray detectors prepared by this strategy exhibit excellent detection and imaging performance, reaching a sensitivity of
$173.9~\mu $
C
$\cdot $
Gy
$_{\text {air}}^{-{1}}\cdot $
cm
$^{-{2}}$
at 40 V
$\cdot $
mm
$^{-{1}}$
and a detection limit of
$1.57~\mu $
Gy
$_{\text {air}}\cdot $
s
$^{-{1}}$
, and showcasing sharp imaging ability. This research contributes to the advancement of next-generation X-ray detection.
The Cs 3 Bi 2 I 9 single crystal, as an all-inorganic non-lead perovskite, offers advantages such as stability and environmental friendliness. Its superior photoelectric properties, attributed to the absence of grain boundary influence, make it an outstanding X-ray detection material compared to polycrystals. In addition to material properties, X-ray detector performance is affected by the thickness of the absorption layer. Addressing this, a space-confined method is proposed. The temperature field is determined through finite element simulation, effectively guiding the design of the space-confined method. Through this innovative method, a series of thickness-controlled perovskite single crystal wafers (PSCWs) are successfully prepared. Corresponding X-ray detectors are then prepared, and the impact of single crystal thickness on device performance is investigated. With an increase in single crystal thickness, a rise followed by a decline in device sensitivity is observed, reaching an optimal value at 0.7 mm thickness at 40V mm −1 with a device performance of 11313.6µC Gy −1 cm −2 . This space-confined method enables the direct growth of high-quality perovskite single crystals with specified thickness, eliminating the need for slicing or etching.
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