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Photovoltaic (PV) cells are of immense interest due to their vast application potential in the fields of energy and communication. [1][2][3] The adoption of ideal photoactive material and the design of optimum device structure are critical to achieving low-cost, high-efficiency PV cells. The semiconducting single-walled carbon nanotubes (SWNTs) are potentially an attractive material for PV applications due to their many unique structural and electrical properties. They are almost defect free to greatly decrease carrier recombination, bear a wide range of direct bandgaps matching the solar spectrum, [4][5][6] and show strong photoabsorption [7][8][9][10] and photoresponse [11][12][13][14][15] from ultraviolet to infrared, and exhibit high carrier mobility [16] and reduced carrier transport scattering. [17,18] Indeed, previous studies had attempted to fabricate SWNT films into photoelectrochemical solar cells. [19] However, due to the inefficient separation and collection of photoexcited carriers and large intertube interaction, the maximum monochromatic incident photo-to-current conversion efficiency (IPCE) obtained for the cell is only 0.15%. Here, we report a novel approach that enables fabricating SWNT PV solar microcells with high power-conversion efficiency. In this cell, a directed array of monolayer SWNTs was nanowelded onto two asymmetrical metal electrodes with high and low work functions, respectively, resulting in a strong built-in electric field in SWNTs for efficient separation of photogenerated electron-hole pairs. Under solar illumination, the monolayer SWNT PV cell shows a power conversion efficiency of 0.80% and 0.31% at an illumination intensity of 8.8 W cm À2 and 100 mW cm À2 , respectively. Correspondingly, a remarkable efficiency of 12.6% and 5.1% was estimated based on the actual absorbed incident power. Our results demonstrate the exciting application potential of SWNTs for PV devices.A schematic diagram of our SWNT PV cell is shown in Figure 1a. In the experiment, Pd and Al metals, with a high and a low work function (F) of 5.1 eV and 4.1 eV, respectively, [20] were chosen as the drain and source contact electrodes. Using standard UV lithography and lift-off process, the two metals were patterned by the overlay on silicon wafers with a 500-nm thermally oxidized layer, forming the parallel electrode pairs. The electrodes were 150 nm in thickness, 40 mm in width, 50 mm in length, and separated by 500 nm. A 200-nm-thick Al electrode was sputtered on the back of Si substrate, through which a gate voltage was supplied to the Si substrate for modulating the SWNT-metal contact barrier. The SWNTs synthesized by the catalytic chemical vapor deposition (CVD) method with an average diameter of 0.9 nm (F % 4.5 eV, E g % 1.1 eV [21] ) were dispersed fully in chloroform and aligned onto the source and drain electrodes by an AC dielectrophoresis method to form the dispersed parallel SWNT bundle array. [22] Then, an ultrasonic nanowelding technique was applied to bond the SWNTs onto the metal electrodes. [...

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High strength and high ductility are often mutually exclusive properties for structural metallic materials. This is particularly important for aluminum (Al)-based alloys which are widely commercially employed. Here, we introduce a hierarchical nanostructured Al alloy with a structure of Al nanograins surrounded by nano-sized metallic glass (MG) shells. It achieves an ultrahigh yield strength of 1.2 GPa in tension (1.7 GPa in compression) along with 15% plasticity in tension (over 70% in compression). The nano-sized MG phase facilitates such ultrahigh strength by impeding dislocation gliding from one nanograin to another, while continuous generation-movement-annihilation of dislocations in the Al nanograins and the flow behavior of the nano-sized MG phase result in increased plasticity. This plastic deformation mechanism is also an efficient way to decrease grain size to sub-10 nm size for low melting temperature metals like Al, making this structural design one solution to the strength-plasticity trade-off.

Control of the architectures of three-dimensional (3D)-printed cellular parts to achieve electromagnetic interference (EMI) shielding protection is a challenging issue. In this paper, by combining FDM 3D-printing technology with hybridizing strategy, we successfully designed and fabricated high-performance polylactic acid nanocomposites incorporating graphene/carbon nanotube hybrids (PLA/GNPs/CNTs) and delicately controllable 3D-printed cellular parts. PLA/GNPs/CNTs nanocomposites prepared under the optimum conditions possessed the excellent comprehensive performance: Their tensile strength and Young’s modulus can achieve values 16.2 and 25.5% higher than those of pure PLA, respectively. The corresponding electrical conductivity can reach 82.0 S/m, and EMI shielding efficiency can achieve 36.8 dB, which is far beyond the commercial shielding standard (20 dB). In addition, the 3D-printed cellular parts were successfully fabricated with light weight and highly efficient EMI shielding property. Finally, a cellular factor (T cell) was innovatively adopted to quantitatively evaluate the relationship between cell structures and EMI shielding behaviors of 3D-printed cellular materials, indicating that the critical cell size of about 4.29 mm could be successfully fitted to maintain the suitable shielding efficiency in X-band frequency range. These related investigations provide a new theoretical mechanism for evaluating the EMI shielding performance of 3D-printed cellular materials and open up new spaces for construction of the lightweight and multifunctional cellular parts for EMI protection applications.