Researchers at Northwestern University have recently broken through the difficulties of improving the photoelectric conversion efficiency of carbon nanotube solar cells in the past 10 years, increasing their conversion efficiency from 1% to more than 3%, and once again making carbon nanotube solar cells that have once been silent researched again. Entered people's field of vision. Related papers were published in the Nano Express newspaper.
Because it is lighter, thinner, and more flexible than traditional materials, carbon nanotubes are considered to be ideal materials for the manufacture of new types of solar cells as soon as they are available, but subsequent attempts have caused scientists to repeatedly suffer setbacks: regardless of the method used, carbon nanotube solar cells The photoelectric conversion efficiency is always around 1%. This figure is not only unable to compare with the current mainstream silicon solar cells, compared with other newly emerging new materials is not a star.
However, this new study will undoubtedly bring new hope to people. According to the report of the Physicist Organization Network on September 4 (Beijing time), the new technology developed by Mark Hansen, professor of materials engineering at Northwestern University, has improved the efficiency of carbon nanotube solar cells from 1% to 3%. It became the first carbon nanotube solar cell certified by the National Renewable Energy Laboratory.
Hansen said: "The conversion efficiency of carbon nanotube solar cells has been hovering around 1% in the past 10 years or even stabilizing, but we broke this stalemate. Although the absolute value is still not high, vertical comparison is still a Significantly improved."
Hansen’s trick is the chirality of carbon nanotubes, a phenomenon in which an object does not coincide with its mirror image, specifically the straight and curved carbon nanotubes. When carbon is curled into carbon nanotubes, there may be hundreds of different chiralities. In the past, researchers have tended to choose a specific type of chirality with good semiconductor performance and try to use them to make a complete solar panel. The problem is that the chirality of each carbon nanotube can only absorb light in a specific wavelength range, and such a solar cell cannot absorb most of the other wavelengths of light. Hanson's research team created a carbon nano-tube solar cell containing multiple types of chirality.
Experiments show that the new type of solar cell can absorb a wider range of wavelengths of sunlight than its predecessors. In addition, this new type of solar cell can even absorb sunlight of near-infrared wavelengths, which is currently not achievable by many advanced thin-film solar cells.
Although this is an important milestone for carbon nanotubes, this conversion efficiency is still relatively backward compared to other materials. Next, Hanson's research team will continue to improve the technology and create a multi-layered composite carbon nanotube solar cell. Each layer will be optimized according to a specific wavelength in the solar spectrum and will be able to Absorb more light. In addition, they may also add new materials such as organic or inorganic semiconductor materials to supplement carbon nanotubes.
Hansen said: “What we want to do is absorb as many photons as possible and convert it into electricity. In other words, we create a solar cell that can perfectly match the sunlight at multiple wavelengths at one time. The ultimate goal of this study."
Carbon nanotubes have good conductivity and high light absorption, which is why it is considered particularly suitable for making solar cells. However, this study has been in a very preliminary stage. The key question is whether people can find a suitable morphological process and then have an in-depth understanding of the principle of charge generation and separation in carbon nanotubes. Now that the conversion rate has broken the deadlock for 10 years, it will undoubtedly greatly enhance the confidence of the industry, but unless it can achieve a conversion rate of 10%, it will not be necessary for commercial production as a solar cell. (Reporter Wang Xiaolong)
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