Optical rectifying antenna converts light directly to direct current

Recently, engineers at the Georgia Institute of Technology in the United States developed an optical rectifying antenna that converts light directly to direct current. The researchers believe that this result is expected to provide a new light detection technology that does not require refrigeration, and it can also convert waste heat into electricity, which will eventually become a new way of using solar energy.

The optical rectenna can operate at a temperature of 5°C to 77°C. It uses carbon nanotubes as an antenna to capture sunlight or other light sources. When light waves strike the nanotubes, the resulting oscillatory charge passes through the rectifier. The rectifier switches at a gigahertz frequency, producing tiny direct currents. Although the efficiency of current devices is only 1%, billions of rectennas are arrayed to generate powerful currents.

The rectenna was developed in the 1960s and 1970s. It typically operates in the wavelength range of about 10 microns. The new rectenna, which enters the visible range, requires the antenna and rectifier diode to be small enough to capture electromagnetic oscillations very quickly. Balatud Kola, an associate professor at George Woodruff’s School of Mechanical Engineering, explained: “A rectenna is essentially an antenna with a diode, but in the visible light range, it means using a nano-antenna with a metal—insulation—metal. Diodes. The closer the antenna is to the diode, the more efficient it is. So the ideal structure is to use the antenna as a metal in the diode - this is the structure we make."

According to the report of the physicist's organization network, researchers first produced vertically aligned carbon nanotube clusters on conductive substrates, and then used a variety of nano-manufacturing technologies to create metal-insulator-metal multilayer rectifiers. In operation, the oscillatory wave of light passes through the calcium-aluminum electrode and interacts with the nanotubes. The rectifier at the top of the nanotube can switch at femtosecond speed, allowing the electrons generated by the antenna to enter the electrode from only one direction.

Kola said that the current rectification antenna needs to improve efficiency, open carbon nanotubes to achieve multiple conductive channels, reduce resistance, etc. will eventually create efficiency is twice the cost of solar cells.

Researchers also hope to increase output power through optimization techniques. They believe that commercial valued rectennas may appear within a year. The relevant papers were published online on September 29th (Beijing time) in "Nature Nanotechnology". (Reporter Chang Lijun)