Illumination‐Dependent Photoelectric Anisotropy in Cs₃Bi₂I₉ Single Crystal Sheets

Abstract

sessing the same electronic structure as Pb 2+ . Very recently, a few Bi-based substitutions have been successfully synthesized and applied to optoelectronics, [19][20][21][22][23][24][25] and the all-inorganic component design offers well material stability under higher temperatures and moisture conditions. [26] The latest research such as resistive switches, [27] achromatic quarter-waver plates [28] and high-performance X-ray detectors [19,20,22] have been reported.As well known, the Cs 3 Bi 2 I 9 is an isolated zero-dimensional molecular salt structure, wherein a pair of [BiI 6 ] 3− octahedra that share a common face form a [Bi 2 I 9 ] 3− dioctahedral cluster and their voids are filled with Cs + cations. While in this hexagonal structure, distinct dimer [Bi 2 I 9 ] 3− anions are placed in a layered arrangement along the cleavage plane (001). Therefore, it can be considered as a layered perovskite-like crystal structure according to the previous reports, [19,20] and the bi-layered [Bi 2 I 9 ] 3− are connected by the van der Waals forces. Up to now, the important influence of such anisotropic crystal structures on their photoelectric performance has not been widely recognized and investigated so far. [19] It should be noted that, in regular Ruddlesden-Popper phase perovskite, their adjacent perovskite octahedral layers are mutually connected by Coulombic-held organic chains (such as an aliphatic or aromatic alkylammonium), and corresponding anisotropy abruptly weakens with lessened intercalated organic layers. [10][11][12][13] As the He group demonstrated, the anisotropy of dark and photo-current dropped almost one-order magnitude when the sheet number of perovskite octahedral layers only increases from 1 to 3, [29] as well as their electric conductance and carriers mobility studied by the Priya group. [30] While in the layered perovskite-like phase, bi-layered close-packed octahedral frameworks are mutually connected by van der Waals forces instead of chemical bonds, [19,21] moreover, their crystal structure is a stationary type for the given elements. Thus, such a non-contact suspended spacer possesses much more significant anisotropy over the Ruddlesden-Popper phases.Very recently, only the Yang group observes the anisotropic X-ray photo-response based on a layered perovskite-like (NH 4 ) 3 Bi 2 I 9 single crystal, and its anisotropy is only measured at one-order magnitude. [19] Essentially speaking, its anisotropic photo-response originates from the photon-induced carriers' transmission differences along in-plane and cross-plane directions. [19,29,30] The investigation of anisotropy is conducive to the design of performance-improved devices, by contrasting the Lead-free all-inorganic perovskite single crystals are being pursued intensively because of their reduced biological toxicity and enhanced material stability, greatly relieving two major bottlenecks of practical device applications. However, the investigation of their predicted photoelectric anisotropy is still absent, especially under visible and nea...

Water Erosion Highly Recoverable and Flexible Photodetectors Based on Electrospun, Waterproof Perovskite–Polymer Fiber Membranes

“…Under a 1 V bias, the I – T curves show excellent stability and reproducible dynamic responses to rectangular switching illuminations. The response time is quick, measuring less than 0.12 s, which is comparable to the bare perovskite nanowire-based PDs. − This indicates that the polymer PMMA has no significant negative impact on the carrier transmission in the electric cycle. In the I – P test curves, the increment of photoresponse currents shows a decreasing trend with increasing illumination power, as indicated by the dashed blue lines in the diagram.…”

“…However, these slight changes in viscosity have minimal impact on the fiber diameters of PPFMs, as confirmed by the SEM characterizations in Figure S2. Figure b illustrates the corresponding current–time ( I – T ) curves under rectangular switching illuminations of four intensities and a bias of 1 V. The relationships between photocurrent under 1 V bias and illumination powers are depicted in Figure c, where the responsivity ( R ) is calculated from the current–power ( I – P ) slope, and the specific detectivity ( D ) is also evaluated in the diagram . Under the limited space constraints of microfibers, the increased abundance of precursors significantly enhances the contact between grain boundaries, thereby reducing the electric resistance for optoelectronic signals.…”

“…Metal-halide perovskites have emerged as promising materials for high-performance photodetectors (PDs) due to their excellent properties, including efficient light absorption, tunable bandgap, − long carrier diffusion length, and cost-effectiveness . Significant efforts have been devoted to improving PD performance, particularly with devices fabricated from the single-crystalline perovskite materials. − For instance, the Zhang group has proposed ultrasensitive PDs based on single-crystalline layered metal-halide perovskite nanowires . While the Pan group has demonstrated high-performance PDs based on ultralong directional nanowires .…”