No abstract

Controlled synthesis of lead halide perovskite (LHP) nanostructures not only benefits fundamental research but also offers promise for applications. Among many synthesis techniques, although catalytic vapor–liquid–solid (VLS) growth is recognized as an effective route to achieve high-quality nanostructures, until now, there is no detailed report on VLS grown LHP nanomaterials due to the emerging challenges in perovskite synthesis. Here, we develop a direct VLS growth for single-crystalline all-inorganic lead halide perovskite (i.e., CsPbX3; X = Cl, Br, or I) nanowires (NWs). These NWs exhibit high-performance photodetection with the responsivity exceeding 4489 A/W and detectivity over 7.9 × 1012 Jones toward the visible light regime. Field-effect transistors (FET) based on individual CsPbX3 NWs are also fabricated, where they show the superior hole mobility of up to 3.05 cm2/(V s), higher than other all-inorganic LHP devices. This work provides important guidelines for the further improvement of these perovskite nanostructures for utilizations.

Recently, due to the possibility of thinning down to the atomic thickness to achieve exotic properties, layered materials have attracted extensive research attention. In particular, PbI , a kind of layered material, and its perovskite derivatives, CH NH PbI (i.e., MAPbI ), have demonstrated impressive photoresponsivities for efficient photodetection. Herein, the synthesis of large-scale, high-density, and freestanding PbI nanosheets is demonstrated by manipulating the microenvironment during physical vapor deposition. In contrast to conventional two-dimensional (2D) growth along the substrate surface, the essence here is the effective nucleation of microplanes with different angles relative to the in-plane direction of underlying rough-surfaced substrates. When configured into photodetectors, the fabricated device exhibits a photoresponsivity of 410 mA W , a detectivity of 3.1 × 10 Jones, and a fast response with the rise and decay time constants of 86 and 150 ms, respectively, under a wavelength of 405 nm. These PbI nanosheets can also be completely converted into MAPbI materials via chemical vapor deposition with an improved photoresponsivity up to 40 A W . All these performance parameters are comparable to those of state-of-the-art layered-material-based photodetectors, revealing the technological potency of these freestanding nanosheets for next-generation high-performance optoelectronics.

Quasi two-dimensional (2D) layered organic-inorganic perovskite materials (e.g., (BA)(MA) PbI; BA = butylamine; MA = methylamine) have recently attracted wide attention because of their superior moisture stability as compared with three-dimensional counterparts. Inevitably, hydrophobic yet insulating long-chained organic cations improve the stability at the cost of hindering charge transport, leading to the unsatisfied performance of subsequently fabricated devices. Here, we reported the synthesis of quasi-2D ( iBA)(MA) PbI perovskites, where the relatively pure-phase ( iBA)PbI and ( iBA)MAPbI films can be obtained. Because of the shorter-branched chain of iBA as compared with that of its linear equivalent ( n-butylamine, BA), the resulting ( iBA)(MA) PbI perovskites exhibit much enhanced photodetection properties without sacrificing their excellent stability. Through hot-casting, the optimized ( iBA)(MA) PbI perovskite films with n = 4 give the significantly improved crystallinity, demonstrating the high responsivity of 117.09 mA/W, large on-off ratio of 4.0 × 10, and fast response speed (rise and decay time of 16 and 15 ms, respectively). These figure-of-merits are comparable or even better than those of state-of-the-art quasi-2D perovskite-based photodetectors reported to date. Our work not only paves a practical way for future perovskite photodetector fabrication via modulation of their intrinsic material properties but also provides a direction for further performance enhancement of other perovskite optoelectronics.

to potentially fabricate numerous hierarchical and periodic micro/nanostructure arrays in a large scale. [1][2][3][4][5] Importantly, these ordered micro/nanostructure arrays are essential active components for many technological applications, ranging from data storage, [6] solar cells, [7][8][9] plasmonics to functional coatings, and many others. [10][11][12][13][14][15] Combined with the recent advance in colloidal science, the colloidal spheres with uniform morphology and excellent disperse stability can be further realized by a number of methods, which include the suspension, [16,17] dispersion polymerization, [18,19] emulsion, [20,21] and Stöber techniques. [22] The diameter of colloidal spheres can also be precisely controlled in a wide range, spanning from several micrometers all the way to down to tens of nanometers. Uniquely, these colloidal spheres can be self-assembled into 2D monolayers and 3D periodic multilayers, where they are subsequently utilized as the versatile masks (e.g., optical lens) to achieve fabrication templates by simple surface patterning onto underlying substrates, facilitating the construction of micro/nanostructure arrays with excellent tunability. [23][24][25] Since then, these 2D monolayer colloidal crystals (MCCs) and 3D multilayers have attracted extensive attention for many of their further utilizations. For instance, by using the oxygen plasma and reactive ion etching (RIE) methods, the periodicity, the size, and the shape of individual spheres of MCCs are accurately controlled. [26,27] With further modification, etching, and decoration, the MCCs can be exploited as either the masks for metal catalyst deposition to generate hierarchical and periodic nanostructures on underlying substrates, or the templates for the growth of patterned nanostructures. [28,29] Furthermore, these MCCs can also be utilized as optical lens to construct the periodic nanostructures with photosensitive materials, broadening the preparing routes of hierarchical and periodic nanostructures. [30] In order to prepare the periodic nanostructures, the fabrication process, including the self-assembly of MCCs, the morphological modification of MCCs, and the functionalized decoration, is commonly referred as the nanosphere lithography (NSL). [31][32][33] As compared with conventional lithographic techniques, such as photolithography, [34,35] electron beam lithography, [36] and focused ion beam lithography, [37] NSL can distinctively reduce the manufacturing cost and complexity, The current research status on the self-assembly of colloidal spheres for the fabrication of various hierarchical and periodic nanostructures is summarized, in which these structures exhibit unique properties for different technological applications in plasmonics, surface-enhanced Raman scattering, solar cells, and others. The fundamentals of colloidal self-assembly are first introduced. After which, the functions of the obtained monolayer of colloidal spheres (e.g., nanosphere monolayer) to act as the patterned mask for the subsequent ...