New high-efficiency concentrating carbon nanotube antenna

According to a recent report by the American Physicist Network, American researchers have used carbon nanotubes for the first time to create an "antenna" that captures and collects sunlight. The efficiency of collecting sunlight is 100 times that of ordinary photovoltaic cells. The new antenna It can be used in solar cells to improve its photoelectric conversion efficiency. New technologies are expected to enable researchers to develop smaller and more powerful solar arrays. The study was published online in the latest issue of the journal Nature Materials.

The research team led by Michael Strahano, an associate professor of chemistry at the Massachusetts Institute of Technology (MIT), said the new antenna can also be used in other areas where concentrating is needed, including for night vision or telescopes.

Solar panels generate electricity by converting photons into currents, and Strano's carbon nanotube antennas increase the number of photons that can be captured and convert the captured photons into energy "put" into the solar cell.

The new antenna is a fiber rope about 10 microns long and 4 microns thick, which contains about 30 million carbon nanotubes. These nanotubes have different electrical conductivity (band gap) and are distributed in the inner and outer layers of the fiber rope.

In any substance, electrons exist at different energy levels. When a photon hits the surface of the object, it excites the electron to a higher energy level. The Coulomb attraction interaction between the electrons that have obtained energy and the holes left after it reaches a new energy level will cause them to be spatially bound together under certain conditions. The resulting complex is called an exciton. . The difference in energy levels between holes and electrons is called the band gap.

The carbon nanotubes contained in the inner layer of the new antenna have a smaller band gap; the outer carbon nanotubes have a higher band gap. This is important because excitons may flow from a high energy band gap to a low energy band gap. This means that the excitons of the outer layer will flow to the inner layer. Therefore, when light illuminates the object, all excitons flow to the center of the fiber rope and gather there.

The Strano team said they would build such an antenna around a core of semiconductor material to assemble a solar cell. The interface between the semiconductor and the carbon nanotubes separates the electrons from the holes, and the electrons converge on one electrode, which is in contact with the internal semiconductor; the holes converge on the other electrode, which is in contact with the carbon nanotubes, so that the entire system Current will be generated. The efficiency of the solar cell depends mainly on the materials used for the electrodes.

Recently, scientists have developed carbon nanotubes with different properties, allowing the Strano team to control the properties of the different layers of the carbon nanotube fibers.

The Strano team is now looking for ways to reduce the energy loss of excitons through the fiber while allowing each photon to generate more excitons. At present, the energy loss rate of carbon nanotube antennas is 13%, but the new antenna that the research team is working on is only 1% of the energy loss rate target.