Nano-confined crystallization of organic ultrathin nanostructure arrays with programmable geometries

Abstract

Fabricating ultrathin organic semiconductor nanostructures attracts wide attention towards integrated electronic and optoelectronic applications. However, the fabrication of ultrathin organic nanostructures with precise alignment, tunable morphology and high crystallinity for device integration remains challenging. Herein, an assembly technique for fabricating ultrathin organic single-crystal arrays with different sizes and shapes is achieved by confining the crystallization process in a sub-hundred nanometer space. The confined crystallization is realized by controlling the deformation of the elastic topographical templates with tunable applied pressures, which produces organic nanostructures with ordered crystallographic orientation and controllable thickness from less than 10 nm to ca . 1 μm. The generality is verified for patterning various typical solution-processable materials with long-range order and pure orientation, including organic small molecules, polymers, metal-halide perovskites and nanoparticles. It is anticipated that this technique with controlling the crystallization kinetics by the governable confined space could facilitate the electronic integration of organic semiconductors.

Metal Halide Perovskites Functionalized by Patterning Technologies

“…[ 27,30–33,51 ] Moreover, the thickness of the single crystals was expected to be reduced to 10 nm by exerting pressure on the substrate during solvent evaporating. [ 33 ] Another group used polydimethylsiloxane (PDMS) templates with cylindrical holes or rectangular grooves to coat on the perovskite precursor solution on a hydrophobic SiO 2 /Si substrate under mild pressure (<20 kPa) (Figure 2c). [ 47,48 ] Therefore, followed by the slow evaporation of solvents, the crystal seeds nucleated and gradually grew into perovskite microdisks or nanowires confined by the PDMS templates (Figure 2d).…”

“…Patterned template‐assisted crystallization of MHPs can create high‐quality nano/microcrystals with perfect surface and homogeneous crystal size. The patterned templates are usually composed of silicon, [ 27,30–33 ] silicon oxide, [ 34 ] alumina, [ 21,35–37 ] 2D materials, [ 38–40 ] and polymer [ 13,26,41–49 ] by the means of photolithography, direct laser writing, focused‐ion‐beam etching, or electron‐beam etching. The perovskite precursor solution is usually dropped on the hydrophilic substrates and confined by hydrophobic patterned molds to create crystal seeds and grow ordered crystal arrays.…”

“…Perovskite nanowires with different widths as well as solid or hollow microplates can be created by simply tailoring the morphology of the micropillars (Figure 2b). [ 27,30–33,51 ] Moreover, the thickness of the single crystals was expected to be reduced to 10 nm by exerting pressure on the substrate during solvent evaporating. [ 33 ] Another group used polydimethylsiloxane (PDMS) templates with cylindrical holes or rectangular grooves to coat on the perovskite precursor solution on a hydrophobic SiO 2 /Si substrate under mild pressure (<20 kPa) (Figure 2c).…”

“…Reproduced with permission. [ 33 ] Copyright 2019, Springer Nature. c) Illustrations of a PDMS template with cylindrical holes for confining the crystallization of CsPbX 3 microdisks and d) microscopic fluorescent image of the obtained CsPbCl 3 microdisk arrays under UV light.…”

Highly Conductive MXene Film Actuator Based on Moisture Gradients

“…When the MXene film is situated away from the moist filter paper, it is unbending and then unloads the object (see Videos 5), indicating the realization of a smart excavator function. Given its high sensitivity to moisture, the MXene film can sense the existence of a fingertip at a distance and can bend away from the finger (Figure e; see Videos 6), implying that it is expected to be used in humidity sensors, and an ultrathin MXene structure capable of sensing micro water vapor might be realized by referring to other processing strategies . High electrical conductivity is a great advantage of MXene over GO, thus the MXene film has shown promise in electrical switches (Figure f; see Videos 7).…”