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Recently, organolead halide-based perovskites have emerged as promising materials for optoelectronic applications, particularly for photovoltaics, photodetectors, and lasing, with low cost and high performance. Meanwhile, nanoscale photodetectors have attracted tremendous attention toward realizing miniaturized optoelectronic systems, as they offer high sensitivity, ultrafast response, and the capability to detect beyond the diffraction limit. Here we report high-performance nanoscale-patterned perovskite photodetectors implemented by nanoimprint lithography (NIL). The spin-coated lead methylammonium triiodide perovskite shows improved crystallinity and optical properties after NIL. The nanoimprinted metal-semiconductor-metal photodetectors demonstrate significantly improved performance compared to the nonimprinted conventional thin-film devices. The effects of NIL pattern geometries on the optoelectronic characteristics were studied, and the nanograting pattern based photodetectors demonstrated the best performance, showing approximately 35 times improvement on responsivity and 7 times improvement on on/off ratio compared with the nonimprinted devices. The high performance of NIL-nanograting photodetectors likely results from high crystallinity and favored nanostructure morphology, which contribute to higher mobility, longer diffusion length, and better photon absorption. Our results have demonstrated that the NIL is a cost-effective method to fabricate high-performance perovskite nanoscale optoelectronic devices, which may be suitable for manufacturing of high-density perovskite nanophotodetector arrays and to provide integration with state-of-the-art electronic circuits.

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Nickel and gold meshes having three-dimensional periodicity at optical wavelengths and nanoscale structural fidelity have been prepared by electrodeposition within closepacked silica sphere arrays.There is major current interest in the fabrication of nanoporous metal arrays. [1][2][3][4] Routine access to such materials could impact a variety of areas including photonics, magnetics, catalysis, electrochemical applications and thermoelectrics. Recent reports have described the formation of 3-D metal meshes within colloidal silica or polymer membranes through the use of molten metal infiltration, nanoparticle infiltration and electroless methods. 4-6 Though metal electrodeposition methods have been effectively used for membranes with one-dimensional pore structures, 7 the extension of this technique to threedimensional structures has not been reported. This electrochemical method has the major advantage of readily producing well defined metal meshes of materials melting at such high temperatures that melt infiltration is prohibited by template structural instability. Herein, we describe the use of this approach for the fabrication of nickel and gold arrays having three-dimensional periodicity at optical wavelengths.Silica membranes (opal) were prepared by published methods. 8 Silica spheres with a diameter of ca. 300 nm diameter were initially prepared from tetraethylorthosilicate (TEOS). The spheres were then formed into close-packed lattices through a sedimentation process over several months. This precipitate was then sintered at 120 °C for two days and then 750 °C for 4 h, producing a robust opalescent piece that could be readily cut into smaller sections. Electrodes were formed from the opal (typically 7 3 10 3 1.5 mm) by first depositing ca. 0.5 mm thick copper films on one side of the piece by magnetron sputtering. A length of wire was attached to the copper backing with silver paste (Ted Pella, Inc.) and the copper/wire side of the electrode, as well as the edges, were sealed off with neoprene glue (Elmer's). For metal deposition, the electrodes were immersed into nickel or gold plating solutions (Technic, Inc.) with a platinum wire counter electrode. Electrodeposition was carried out by a constant current method over a 36 h period; a low current density (0.50 mA cm 22 ) was used in an effort to achieve even deposition within the opal membrane. Low current densities such as that used here have been found to be effective in the growth of nanowires. After deposition, the opal was washed thoroughly with distilled water and the neoprene layer peeled off. To remove the silica matrix, the metal-opal pieces were soaked in a 2% HF solution for 24 h. This resulted in a dark opalescent metal membrane (ca. 100 mm thick). Scanning electron micrographs (SEM) were obtained on a JEOL JSM 5410 SEM. Magnetic measurements on the nickel mesh were performed on a Quantum Design MPMS-5S SQUID susceptometer. The mesh was fixed between two pieces of Kapton tape and placed in a commercially available soda straw. No correction for t...