Light-powered wireless manipulation of small objects in fluids has been of interest for biomedical and environmental applications. Although many techniques employing UV−vis−NIR light sources have been devised, new methods that hold greater penetrating power deep into medium are still in demand. Here, we develop a method to exploit X-rays to propel half-metal-coated Janus microparticles in aqueous solution. The Janus particles are simultaneously propelled and visualized in real-time by using a full-field transmission X-ray microscope. Our real-time observation discovers that the propulsive motion follows the bubble growth enhanced by water radiolysis near the particle surface under X-ray irradiation. We also show that the propulsion speed is remotely controlled by varying the radiation dose. We expect this work to open opportunities to employ light-powered micro/ nanomotors in opaque environments, potentially by combining with medical imaging or nondestructive testing.

Organic-inorganic metal halide perovskites, particularly CH 3 NH 3 PbX 3 (X = Cl, Br, and I), have recently emerged as a promising optoelectronic material [1] because of their excellent properties such as large optical absorption, long carrier diffusion length, high carrier mobility, and low-cost solution production process. [2][3][4][5][6] Over the past decade, there have been conducted substantial research to utilize perovskites for diverse applications as solar cells, [2,7,8] photodetectors, [9,10] light emitting diodes, [11,12] and lasers. [13,14] Most of the research has focused on the control over crystallinity or chemical composition in a thin film form, in result, making great advances in material performance. [15][16][17][18][19] Continuous demands on optoelectronic devices with high integration density and new functions have raised the need for nanostructured perovskites. [20] Especially, nanowires, 1D nanostructures with controlled diameters and lengths, are the basic building blocks for creating miniaturized devices. Techniques to fabricate perovskite nanowires mainly rely on i) vapor-phase deposition [21,22] or ii) solution-mediated crystallization. [14,[23][24][25][26] The former offers an excellent crystal quality but lacks the ability to precisely position individual nanowires. In the latter that is based on supersaturation of solutes, there have been several remarkable attempts to fabricate and align individual nanowires by confinement of solution inside templates, [23,24] nanoimprint molds, [25] or nanofluidic channels [26] under evaporation of solvent.Recently, some clever methods based on inkjet printing have been devised for patterning perovskite micro/nanostructures. [27,28] These attempts have enhanced the freedom of nanostructures design beyond straight nanowires, potentially enabling a high-level integration of perovskite circuitries and devices. However, the developed patterning techniques for perovskites are still limited to in-plane fabrication and alignment.Since its invention in the 1980s, 3D printing, known as additive manufacturing, has attracted great attention as a facile method to produce tangible freeform structures. Beyond simple prototyping, there have recently been enormous efforts to improve or diversify the properties of 3D printed objects-for their practical use-by engineering materials' crystallinity [29,30] or molecular orientation. [31][32][33] In this context, owing to their As competing with the established silicon technology, organic-inorganic metal halide perovskites are continually gaining ground in optoelectronics due to their excellent material properties and low-cost production. The ability to have control over their shape, as well as composition and crystallinity, is indispensable for practical materialization. Many sophisticated nanofabrication methods have been devised to shape perovskites; however, they are still limited to in-plane, low-aspect-ratio, and simple forms. This is in stark contrast with the demands of modern optoelectronics with freeform circui...

Inverted perovskite solar cells incorporating RF sputtered NiO thin films as a hole transport layer and window layer are demonstrated. The electrical and optical properties of the NiO thin films are engineered using varied sputtering conditions. The localized states within bandgap owing to its crystal disorder and nonstoichiometric features affect the transmittance and the optical bandgap of the NiO thin films which in turn influences the Jsc of the perovskite solar cells. In addition, the electrical properties of the NiO thin films can be also varied during sputtering condition affecting the concentration of nickel vacancies and the resulting hole concentration. The conductivity largely originates from the hole concentration relating to the density of states in the NiO thin films which influence the fill factor (FF) of the solar cells. The solar cells fabricated with the NiO thin films made at 4 Pa of deposition pressure show highest performance owing to excellent transmittance and wider bandgap along with moderate conductivity. With further optimization, the perovskite solar cells exhibit ~20 mA/cm2 of Jsc and a 12.4% PCE (11.3% of averaged PCE).

The photovoltaic performance of perovskite solar cells is highly dependent on the control of morphology and crystallization of perovskite film, which usually requires a controlled atmosphere. Therefore, fully ambient fabrication is a desired technology for the development of perovskite solar cells toward real production. Here, an air‐knife assisted recrystallization method is reported, based on a simple bath‐immersion to prepare high‐quality perovskite absorbers. The resulted film shows a strong crystallinity with pure domains and low trap‐state density, which contribute to the device performance and stability. The proposed method can operate in a wide process window, such as variable relative humidity and bath‐immersion conditions, demonstrating a power conversion efficiency over 19% and 27% under 1 sun and 500–2000 lux dim‐light illumination respectively, which is among the highest performance of ambient‐process perovskite solar cells.

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The ongoing energy crisis and global warming caused by the massive usage of fossil fuels and emission of CO2 into atmosphere continue to motivate researchers to investigate possible solutions. The conversion of CO2 into value-added solar fuels by photocatalysts has been suggested as an intriguing solution to simultaneously mitigate global warming and provide a source of energy in an environmentally friendly manner. There has been considerable effort for nearly four decades investigating the performance of CO2 conversion by photocatalysts, much of which has focused on structure or materials modification. In particular, the application of low-dimensional structures for photocatalysts is a promising pathway. Depending on the materials and fabrication methods, low-dimensional nanomaterials can be formed in zero dimensional structures such as quantum dots, one-dimensional structures such as nanowires, nanotubes, nanobelts, and nanorods, and two-dimensional structures such as nanosheets and thin films. These nanostructures increase the effective surface area and possess unique electrical and optical properties, including the quantum confinement effect in semiconductors or the localized surface plasmon resonance effect in noble metals at the nanoscale. These unique properties can play a vital role in enhancing the performance of photocatalytic CO2 conversion into solar fuels by engineering the nanostructures. In this review, we provide an overview of photocatalytic CO2 conversion and especially focus on nanostructured photocatalysts. The fundamental mechanism of photocatalytic CO2 conversion is discussed and recent progresses of low-dimensional photocatalysts for efficient conversion of CO2 into solar fuels are presented.