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High-efficiency micro core–shell solar cell (μ-CSSC) arrays are fabricated from Si wafer by using traditional lithography and phosphorus diffusion. The p–n junction depth is around 450 nm, indicating that it forms core–shell structure in micropillars by using phosphorus diffusion. The μ-CSSC arrays have high minority carrier lifetime of 23 μs and long diffusion length of ∼150 μm. The best power efficiency of the μ-CSSC reaches to 9.2%. It is a convenient method for fabricating Si μ-CSSC arrays in wafer scale for future applications.

Schottky junction solar cells are assembled by directly coating graphene films on n-type silicon nanowire (SiNW) arrays. The graphene/SiNW junction shows enhanced light trapping and faster carrier transport compared to the graphene/planar Si structure. With chemical doping, the SiNW-based solar cells showed energy conversion efficiencies of up to 2.86% at AM1.5 condition, opening a possibility of using graphene/semiconductor nanostructures in photovoltaic application.

A novel method of combining photolithography, wet chemical etching and oxidation process was proposed to fabricate large area of silicon microwire (SiMW) arrays. The dimensions of the SiMWs can be easily controlled by photomask and etching conditions. Solar cells based on the heterojunction between SiMW and double-walled carbon nanotubes (DWNTs) were constructed. The initial test on the DWNT/SiMW shows efficiency (η) of 0.59%. By adding a few drops of HBr/B2 electrolyte, the efficiency was improved to 1.96% with Jsc=19.2 mA/cm2 and Voc=0.35 V, FF=29.2%, showing the potential of SiMWs in photovoltaic applications.

We report on high selectivity of microwave absorption by controlling the concentration of carbon nanotubes in polymer composites and matching the dielectric loss and magnetic loss through encapsulation of crystalline Fe nanorods inside nanotubes. The reflection loss reached more than 10 dB (> 90% absorption) by loading nanotubes at concentrations of 1 wt% to 10 wt% into the composites, and the frequencies corresponding to the maximum loss can be tailored throughout the range of 2 to 18 GHz by changing the concentration. A maximum absorption capability (75 dB x GHz) was observed at a CNT loading of about 4.5 wt%. The crystalline structure of encapsulated Fe nanorods can be modified to enhance the reflection loss. Control of absorption selectivity by modifying the structure and concentration of nanoscale fillers could facilitate potential higher-frequency applications (e.g., radar absorbing) of nanocomposites.

A hybrid solar cell model composed of a heterojunction cell and a photoelectrochemical (PEC) cell has been proposed and characterized. In the hybrid cell, a thin film of double-walled carbon nanotubes forms a heterojunction with the silicon nanowire (SiNW) array and also functions as the transparent counter electrode of the PEC cell. The cell performance can be readily tuned by controlling the SiNW density. Under AM 1.5G illumination, a power conversion efficiency of 1.29%, higher than those reported for SiNW array-based PEC cells, has been obtained.

Fe-filled thin-walled carbon nanotubes (CNTs) were synthesized by chemical vapor deposition. Dichlorobenzene/ferrocene solution was used both for carbon source as well as Fe source. Chlorine-contained precursor is in favor of the fabrication of thin-walled CNTs. The productive HCl in the reaction ambient could etch the CNT wall and growth front-end. Auger electron spectroscopy (AES) results indicated that the Cl atoms were almost entirely carried away by the carrier gas. Thermogravimetric analysis (TGA) showed that the filling rate of the Fe-filled thin-walled CNTs could be adjusted by controlling the flow rate of H2.

As the potential applications of carbon nanotubes in the field of electroluminescence, elements yttrium and europium were introduced to modify the emission properties of double-walled carbon nanotubes (DWNTs) to obtain higher efficacy and other properties. The light emission spectrum of the Y-Eu-doped DWNT filament is suppressed in the near-infrared range, while enhanced in the mid-infrared range. The doped DWNT filament can reach higher efficacy than that of the pure DWNT filament at the same input power and can work stably as long as 5000 h at 12 V. These filaments could be useful for the light sources with special functions, such as infrared light sources operated at low input power.

The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires. After annealing, the values increased to 291.0 Oe and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.

This study shows that S concentration in the Fe catalyst plays an important role in controlling the number of graphene layers during carbon nanotube (CNT) growth via chemical vapor deposition. Using different S concentrations, we have grown thin carbon nanotubes with from 1 to 5 layers. Single-walled carbon nanotubes growing from the active surface of an FeS–Fe eutectic were observed. A growth model basing on the HRTEM characterization and thermodynamic analysis is suggested in which the CNT nucleates and grows on the active surface area of the catalyst where S accumulates in the form of an FeS–Fe eutectic, and the S distribution on the catalyst particle surface determines the number of CNT layers.

A single-layer double-walled carbon nanotube (DWNT) membrane, with 100 cm2 in area, 50 nm in thickness, was spread by adding a few drops of ethanol (or acetone) on the purified DWNTs. Compared with acetone, ethanol is more efficient in spreading DWNT films. The spreading rate of DWNT membrane increases with the ethanol concentration, and it also first increases with temperature (below 60°C), then decreases as the temperature rises to above 60°C.

We have investigated vacuum brazing of CNTs with a eutectic alloy (Ag x Cu y ) doped with Ti. Bonding is confirmed to involve formation of covalent bonds between Ti and C atoms. The brazing in vacuum leads to the interdiffusion of Ti and C atoms and reaction at the joining interfaces. This joining process is promising for volume production with low cost and a low contact resistance.

We directly configured double-walled carbon nanotubes as energy conversion materials to fabricate thin-film solar cells, with nanotubes serving as both photogeneration sites and a charge carriers collecting/transport layer. The solar cells consist of a semitransparent thin film of nanotubes conformally coated on a n-type crystalline silicon substrate to create high-density p-n heterojunctions between nanotubes and n-Si to favor charge separation and extract electrons (through n-Si) and holes (through nanotubes). Initial tests have shown a power conversion efficiency of >1%, proving that DWNTs-on-Si is a potentially suitable configuration for making solar cells. Our devices are distinct from previously reported organic solar cells based on blends of polymers and nanomaterials, where conjugate polymers generate excitons and nanotubes only serve as a transport path.

Hybrid photoelectrochemistry and heterojunction solar cells made from carbon nanotubes and silicon nanowires show high energy conversion efficiencies of up to 6%.

Carbon nanotubes possess excellent electronic properties, and when self-assembled into thin films, they form conductive and transparent networks that are useful for many applications. Here, we synthesized large-area (100 cm2) spiderwebs consisting of interconnected single-walled nanotubes by floating catalyst chemical vapor deposition and a solvent-induced condensation process. These spiderwebs are sticky and robust, can be directly deposited or transferred to various materials and structures such as metal, paper, texture surface, and micro carbon fibers. The spiderwebs offer tunable transparency in the range up to 95%, and show enhanced conductivity compared with most of previous directly grown or post treatment films. Serving as transparent electrodes of solar cells, the nanotube spiderwebs can extract charge carriers from industrial semiconductors with a power conversion efficiency of 7.3% under AM 1.5 G, 100 mW cm−2 illumination.

High quality graphene sheets have been prepared by a facile liquid phase exfoliation of worm-like graphite (WEG). This approach combining with the advances in large scale industry manufacturing of WEG could potentially lead to the development of new and more effective graphene products.

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