Single-walled nanotubes (SWNTs), which have a unique electronic structure, nanoscale diameter, high
curvature, and extra-large surface area, are considered promising reinforcement materials for the next generation
of high-performance structural and multifunctional composites. In the present study, force-field-based molecular
dynamics simulations are performed to study the interaction between polymers and SWNTs. The “wrapping”
of nanotubes by polymer chains was computed. The influence of temperature, nanotube radius, and chirality
on polymer adhesion was investigated. Furthermore, the “filling” of nanotubes by polymer chains was examined.
The results show that the interaction between the SWNT and the polymer is strongly influenced by the specific
monomer structure such as aromatic rings, which affect polymers' affinities for SWNTs significantly. The
attractive interaction between the simulated polymers and the SWNTs monotonically increases when the
SWNT radius is increased. The temperature influence is neglectable for polyethylene (PE) and polypropylene
(PP) but strong for polystyrene (PS) and polyaniline (PANI). Also, our simulations indicate that the adhesion
energy between the SWNT and the polymer strongly depends on the chirality. For SWNTs with similar
molecular weights, diameters, and lengths, the armchair nanotube may be the best nanotube type for
reinforcement. The simulations of filling reveal that molecules of PE, PP, and PS can fill into a (10, 10)
SWNT cavity due to the attractive van der Waals interactions. The possible extension of polymers into SWNT
cavities can be used to structurally bridge the SWNTs and polymers to significantly improve the load transfer
between them when SWNTs are used to produce nanocomposites.
Bulk-like molybdenum disulfide (MoS2) thin films were deposited on the surface of p-type Si substrates using dc magnetron sputtering technique and MoS2/Si p-n junctions were formed. The vibrating modes of E12g and A1g were observed from the Raman spectrum of the MoS2 films. The current density versus voltage (J-V) characteristics of the junction were investigated. A typical J-V rectifying effect with a turn-on voltage of 0.2 V was shown. In different voltage range, the electrical transporting of the junction was dominated by diffusion current and recombination current, respectively. Under the light illumination of 15 mW cm−2, the p-n junction exhibited obvious photovoltaic characteristics with a short-circuit current density of 3.2 mA cm−2 and open-circuit voltage of 0.14 V. The fill factor and energy conversion efficiency were 42.4% and 1.3%, respectively. According to the determination of the Fermi-energy level (∼4.65 eV) and energy-band gap (∼1.45 eV) of the MoS2 films by capacitance-voltage curve and ultraviolet-visible transmission spectra, the mechanisms of the electrical and photovoltaic characteristics were discussed in terms of the energy-band structure of the MoS2/Si p-n junctions. The results hold the promise for the integration of MoS2 thin films with commercially available Si-based electronics in high-efficient photovoltaic devices.
A solar cell based on the n-MoS2/i-SiO2/p-Si heterojunction is fabricated. The device exhibits a high power-conversion efficiency of 4.5% due to the incorporation of a nano-scale SiO2 buffer into the MoS2/Si interface. The present device architectures are envisaged as potentially valuable candidates for high-performance photovoltaic devices.
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