Structural and morphological dependence of carbon nanotube arrays on catalyst aggregation

<font face="times new roman,times" size="2">Catalyst aggregation affects the growth of carbon nanotube (CNT) arrays in terms of tubular structures, waviness, entanglement, lengths, and growth density etc., which are important issues for application developments. We present a systematic correlation between the aggregation of catalyst on the SiO2/Si substrate and the structure and morphology of CNT arrays. The thickness of the catalyst film has a direct effect on the areal density of the catalytic particles and then the alignment of the CNT array. Introducing alumina as buffer layer and annealing the catalyst film at low pressure are two effective approaches to downsize the catalyst particles and then the diameter, wall number of the CNTs. Both the size and areal density of the catalyst also change with the CNT growth in accordance with Ostwald ripening process, with the bottom of the CNT array varying from well-aligned to disordered and adhesion between catalyst particles and the substrate getting enhanced. Strategies including tuning the thickness of the catalyst film, changing buffer layer, controlling on the growth time and the system pressure were used to regulate the aggregation of the catalyst. CNT arrays from disordered to well-aligned, from multi-walled to few-walled and further to single-walled were reproducibly synthesized by chemical vapor deposition of acetylene.</font

Aligned Carbon Nanotubes for High-Efficiency Schottky Solar Cells

The development of low-cost and high-efficiency silicon Schottky solar cells has drawn considerable interest in recent years. A facial approach for the fabrication of carbon nanotubesilicon (CNTSi) Schottky solar cells by using aligned double-walled CNTs drawn from a CNT array is demonstrated. The aligned CNTs help to form high CNTSi junction density and provide efficient charge-transport paths. The power conversion efficiency (PCE) reaches 10.5%, which is higher than that of solar cells fabricated using pristine and random CNT networks. Furthermore, the cell fabrication is scalable, and the solar cells fabricated in one batch show very small PCE fluctuations

Twistable and Stretchable Sandwich Structured Fiber for Wearable Sensors and Supercapacitors

Twistable and stretchable fiber-based electrochemical devices having high performance are needed for future applications, including emerging wearable electronics. Weavable fiber redox supercapacitors and strain sensors are here introduced, which comprise a dielectric layer sandwiched between functionalized buckled carbon nanotube electrodes. On the macroscopic scale, the sandwiched core rubber of the fiber acts as a dielectric layer for capacitive strain sensing and as an elastomeric substrate that prevents electrical shorting and irreversible structural changes during severe mechanical deformations. On the microscopic scale, the buckled CNT electrodes effectively absorb tensile or shear stresses, providing an essentially constant electrical conductance. Consequently, the sandwich fibers provide the dual functions of (1) strain sensing, by generating approximately 115.7% and 26% capacitance changes during stretching (200%) and giant twist (1700 rad.m(-1) or 270 turns.m(-1)), respectively, and (2) electrochemical energy storage, providing high linear and areal capacitances (2.38 mF.cm(-1) and 11.88 mF.cm(-2)) and retention of more than 95% of initial energy storage capability under large mechanical deformations