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(1) Prevent the ballast from scattering under the subgrade to maintain the integrity of the ballast bed;
(2) Prevent subgrade soil from squeezing to both sides under load and strengthen the stability of subgrade
(3) Provide space for setting line signs and signal signs on both sides of the line;
It is used for railway staff to walk, avoid vehicles, and store materials, machines, tools, etc. on the upper part of the line for road maintenance.
A team led by researcher Li Qingwen from the Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences, has recently made significant progress in the development of nanotube array photovoltaic cells. The team used a carbon nanotube film directly drawn from a spinnable carbon nanotube array as a transparent electrode, achieving a photovoltaic efficiency of 10.5%. This breakthrough was published in a special issue of *Small*, marking an important step forward in the field of next-generation solar technology.
According to *Materials Views*, Schottky photovoltaic cells can be created by transferring a conductive film onto a silicon surface. When exposed to light, the device generates electron-hole pairs at the Schottky junction between the film and the silicon, enabling efficient photoelectric conversion. Compared to traditional silicon-based solar cells, this hybrid approach simplifies the manufacturing process, potentially leading to significant cost reductions. Among various materials, carbon nanotube films have gained attention due to their low surface resistance, tunable optical transmittance, and excellent environmental stability, making them ideal candidates for high-performance photovoltaic devices.
Li Qingwen explained that the uniform structure, transparency, and electrical properties of the nanotube arrays contributed to a smooth development process. The initial device efficiency reached around 6%, and through extensive experimentation, the team explored different types of carbon nanotubes. They found that double-walled carbon nanotubes outperformed multi-walled ones, and that the orientation of the nanotubes played a critical role in enhancing performance. The aligned structure helped create a larger contact area between the nanotubes and silicon, improving charge transport and overall efficiency.
To further improve the efficiency and stability of these devices, researchers need to better understand and control the interface between carbon nanotubes and silicon. If the bonding is purely physical, it may hinder the collection of photogenerated charges. Additionally, improving the quality and conductivity of the nanotubes—by reducing defects and achieving more controllable structures—can significantly enhance device performance.
Finally, Li Qingwen acknowledged the contributions of Dr. Jiangjiang Jiang, who conducted most of the experiments, as well as the support from Professors Zheng Xinhe and Sun Baoquan of Soochow University in optimizing the device structure and analyzing data. All authors participated in data interpretation, discussions, and the final revision of the paper.