2, University of Oregan, Eugene, Oregon, United States
3, The Hong Kong University of Science and Technology, Hong Kong, , China
Optoelectronics based on hybrid halide perovskite devices have emerged rapidly due to many reasons such as the strong optical absorption, large quantum yields, high charge-carrier mobility and long diffusion length of halide perovskites. Their low-temperate solution processability also make them as a potential for the cost-effective fabrication of optoelectronic devices. Integrating nanophotonic design strategies by incorporation of perovskite nanostructures in devices allow precise control over light propagation, absorption and emission. Therefore, fabricating high-quality monocrystalline perovskite nanostructures with fast and scalable solution-processed techniques is an essential requirement for further improvement of this field. Template-assisted synthesis is a well-known technique to fabricate nanomaterials. Anodized alumina oxide (AAO) template is one of the most common templates which have been used in this technique so far due to its inexpensive and commercial availability. The drawback of using this template for synthesis of perovskites is that only embedded nanowires in the template are obtainable because wet or dry etching of AAO would affect perovskites severely as well.
In this study we use a nano-extrusion technique to fabricate perovskite nanowires by passing the solution through AAO template while applying a pressure gradient. This technique is similar to the commercial extrusion used vastly in food, ceramic, plastic and many other industries and yields uniform free-standing nanowire arrays of perovskites in large-scale. Single nanowires are collected from these arrays to study their crystal structure and optical quality. Transmission electron microscopy (TEM) confirms the monocrystallinity of the CH3NH3PbBr3 nanowires. Mapping the photoluminescence quantum yield (PLQY) along the nanowires shows values as high as ~30% for the fresh wires. The extrusion approach can be potentially extended to the fabrication of other single crystalline perovskite nanostructures with different shapes and sizes, because the exit profile of the template defines the final geometry.