Three-dimensional (3D) nanoarchitectures have offered unprecedented material performances in diverse applications like energy storages, catalysts, electronic, mechanical, and photonic devices. These outstanding performances are attributed to unusual material properties at the nanoscale, enormous surface areas, a geometrical uniqueness, and comparable feature sizes with optical wavelengths. For the practical use of the unusual nanoscale properties, there have been developments for macroscale fabrications of the 3D nanoarchitectures with process areas over centimeter scales. Among the many fabrication methods for 3D structures at the nanoscale, proximity-field nanopatterning (PnP) is one of the promising techniques that generates 3D optical holographic images and transforms them into material structures through a lithographic process. Using conformal and transparent phase masks as a key factor, the PnP process has advantages in terms of stability, uniformity, and reproducibility for 3D nanostructures with periods from 300 nm to several micrometers. Other merits of realizing precise 3D features with sub-100 nm and rapid processes are attributed to the interference of coherent light diffracted by phase masks. In this review, to report the overall progress of PnP from 2003, we present a comprehensive understanding of PnP, including its brief history, the fundamental principles, symmetry control of 3D nanoarchitectures, material issues for the phase masks, and the process area expansion to the wafer-scale for the target applications. Finally, technical challenges and prospects are discussed for further development and practical applications of the PnP technique.

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Although lead halide perovskite (LHP) solar cells can be externally applied to water electrolysis for solar-to-hydrogen conversion, an LHP device with a monolithic configuration for photoelectrochemical (PEC) cells is more economically ideal for viable hydrogen production. To this end, the hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) catalyst attachment on the LHP solar cell terminals is a governing factor for high efficiency and stable operation. Herein, we report monolithic PEC cells with a double-cation perovskite solar cell connected to a robust 3D OER catalyst using conductive carbon powders for minimal ohmic contact loss. The monolithic PEC cell exhibits 0.56 V onset potential and a maximum photocurrent density of 24.26 mA/cm2 at 1.23 VRHE (reversible hydrogen electrode (RHE)) with a 9.16% applied bias photon-to-current efficiency. This result will stimulate commercial-level application of LHP-based PEC cells for solar water splitting as well as solar-to-fuel conversion with high efficiency.

Nanoarchitected materials are considered as a promising research field, deriving distinctive mechanical properties by combining nanomechanical size effects with conventional structural engineering. Despite the successful demonstration of the superiority and feasibility of nanoarchitected materials, scalable and facile fabrication techniques capable of macroscopically producing such materials at a low cost are required to take advantage of the nanoarchitected materials for specific applications. Unlike conventional techniques, proximity-field nanopatterning (PnP) is capable of simultaneously obtaining high spatial resolution and mass producibility in synthesizing such nanoarchitected materials in the form of an inch-scale film. Herein, we focus on the feasibility of using PnP as a scalable fabrication technique for three-dimensional nanostructures and the superiority of the resultant thin-shell oxide nanoarchitected materials for specific applications, such as lightweight structural materials, mechanically robust nanocomposites, and high-performance piezoelectric materials. This review will discuss and summarize the relevant results obtained for nanoarchitected materials synthesized by PnP and provide suggestions for future research directions for scalable manufacturing and application.

Emerging flexible optoelectronics requires a new type of protective material that is not only hard but also flexible. Organic–inorganic (O–I) hybrid materials have been used as a flexible cover window to increase wear resistance and polymer‐like flexibility. However, the hardness of O–I hybrid materials is much lower than that of metals and ceramics due to the low intrinsic hardness of the organic matrix and limited volume fraction of inorganic reinforcement. Herein, a new type of hybrid nanocomposite combining an O–I hybrid material with continuous and ordered 3D inorganic nanoshell as an additional reinforcement is proposed. The 3D alumina nanoshell uniformly embedded in the epoxy‐siloxane molecular hybrid (ESMH) enables a rule of mixture without a loss in flexibility. Two types of reinforcements comprising siloxane molecules and 3D alumina shell ensure a metal‐like hardness (1.3 GPa), which is significantly higher than that of the typical polymers and polymer nanocomposites. The 3D hybrid nanocomposite films show superb impact resistance due to the 3D alumina nanoshell that effectively suppresses crack propagation. Inch‐scale 3D hybrid nanocomposite films also endure 20 000 bending cycles without failure and maintain high transparency (>82.0% at 550 nm) in the visible regions.

Hydrogen is a promising future sustainable fuel candidate with boundless opportunities. Research into photoelectrochemical (PEC) water splitting based on a lead halide perovskite (LHP) has progressed significantly with the aim of more efficient solar hydrogen production. Herein, we unite a well-known photo-absorbing LHP with cost-effective water-splitting catalysts, and we introduce two types of monolithic LHP-based PEC devices that act as a photocathode and a photoanode for the hydrogen evolution reaction and oxygen evolution reaction, leading to efficient unbiased overall water splitting.Through the integration of these two monolithic LHP-based photoelectrodes, an unbiased solar-to-hydrogen conversion efficiency of 10.64% and a photocurrent density of 8.65 mA cm −2 are achieved.perovskite, photoelectrochemical cell, photoelectrode, unassisted | INTRODUCTIONPhotoelectrochemical (PEC) water splitting, 1 a promising artificial photosynthesis method, is a potential alternative technique for generating renewable fuel. Conventional PEC devices with metal oxides can generate renewable energy sources, such as hydrogen, from water splitting, which can alleviate CO 2 emissions from fossil fuels. However, most readily employed metal oxide-based PEC devices exhibit poor photocurrent density under 1 sun conditions and Carbon Energy.

The reaction kinetics at a triple‐phase boundary (TPB) involving Li+, e−, and O2 dominate their electrochemical performances in Li–O2 batteries. Early studies on catalytic activities at Li+/e−/O2 interfaces have enabled great progress in energy efficiency; however, localized TPBs within the cathode hamper innovations in battery performance toward commercialization. Here, the effects of homogenized TPBs on the reaction kinetics in air cathodes with structurally designed pore networks in terms of pore size, interconnectivity, and orderliness are explored. The diffusion fluxes of reactants are visualized by modeling, and the simulated map reveals evenly distributed reaction areas within the periodic open structure. The 3D air cathode provides highly active, homogeneous TPBs over a real electrode scale, thus simultaneously achieving large discharge capacity, unprecedented energy efficiency, and long cyclability via mechanical/electrochemical stress relaxation. Homogeneous TPBs by cathode structural engineering provide a new strategy for improving the reaction kinetics beyond controlling the intrinsic properties of the materials.

Obtaining a high resolution of a three-dimensional (3D) nanostructure is crucial in nanoengineering. For proximityfield nanopatterning (PnP), a type of nanostructure fabrication with a continuous transfer of interference, the geometry of the phase mask primarily determines the resolution of a fabricated nanostructure by modulating the phase shift of coherent lights. Currently, phase masks for PnP are limited to the intuitive design focusing on reducing zeroth (0th) order efficiency with a single variable design. Herein, the concurrent optimization method, using particle swarm optimization, calculates the optimum phase mask with an improved figure of merit for maximizing the electric field intensity contrast. For the high-contrast 3D nanopatterning, we inversely designed the desired electric-field intensity map and calculated the required phase mask. The calculated optimum phase mask for PnP fabricates the hexagonal nanochannel array with high uniformity in lattice and pore shape owing to its selective intensity control. In contrast to the minimized zeroth diffraction design, which cannot modify the intensity in a specific region, the inverse design can selectively maximize or minimize the intensity in the target regions. This concurrent optimization using the inverse design method increases the degree of freedom for the nanostructure of PnP, and it can fabricate the proper nanostructure applicable to various fields such as energy devices, structural materials, and semiconductor devices.