Perovskite Nanowire Extrusion

Abstract

The defect tolerance of halide perovskite materials has led to efficient optoelectronic devices based on thin-film geometries with unprecedented speed. Moreover, it has motivated research on perovskite nanowires because surface recombination continues to be a major obstacle in realizing efficient nanowire devices. Recently, ordered vertical arrays of perovskite nanowires have been realized, which can benefit from nanophotonic design strategies allowing precise control over light propagation, absorption, and emission. An anodized aluminum oxide template is used to confine the crystallization process, either in the solution or in the vapor phase. This approach, however, results in an unavoidable drawback: only nanowires embedded inside the AAO are obtainable, since the AAO cannot be etched selectively. The requirement for a support matrix originates from the intrinsic difficulty of controlling precise placement, sizes, and shapes of free-standing nanostructures during crystallization, especially in solution. Here we introduce a method to fabricate free-standing solution-based vertical nanowires with arbitrary dimensions. Our scheme also utilizes AAO; however, in contrast to embedding the perovskite inside the matrix, we apply a pressure gradient to extrude the solution from the free-standing templates. The exit profile of the template is subsequently translated into the final semiconductor geometry. The free-standing nanowires are single crystalline and show a PLQY up to ∼29%. In principle, this rapid method is not limited to nanowires but can be extended to uniform and ordered high PLQY single crystalline perovskite nanostructures of different shapes and sizes by fabricating additional masking layers or using specifically shaped nanopore endings.

A Review of Diverse Halide Perovskite Morphologies for Efficient Optoelectronic Applications

“…A syringe connected with a plastic tube was used to facilitate the filling of the perovskite precursor into the AAO pores, which rapidly led to extrusion of the perovskite precursor through the bottom of AAO template. Finally, the MAPbBr 3 NWs were formed by removal of the AAO template by postannealing treatment …”

Low‐dimensional metal halide perovskites and related optoelectronic applications

“…Oener et al devised a nanowire extrusion method where precursor was first dropped on the AAO templates with double‐sided pores. Then a reduced pressure by a syringe was applied to enable the precursor to fill in the pores of the template and extrude out on the bottom (Figure D) . Transfer of the template onto glass spacers positioned on a hot plate would remove the solvent residue and promote the final formation of MAPbBr 3 nanowires (Figure E‐G).…”

Morphology‐Tailored Halide Perovskite Platelets and Wires: From Synthesis, Properties to Optoelectronic Devices

“…f) MAPbBr 3 vertical wire arrays extruded from AAO nanopores: SEM images of i) vertical wire arrays and ii,iii) individual wires. Reproduced with permission . Copyright 2017, American Chemical Society Publications.…”

“…However, the AAO surrounding the wires cannot be dissolved, which limited their applications. Later, Oener et al introduced a different method to fabricate vertical free‐standing MAPbBr 3 wires arrays . The solution was extruded from the template driven by a pressure gradient, thereby wire‐shaped intermediate crystal phase was formed by rapid evaporation of the solvent near the pore exits, as shown in Figure f‐i.…”