Novel nanosized antenna arrays key to effective harvesting of solar energy

co-investigators. The collaboration also includes Penn State emeritus physics professors Paul Cutler and Nicholas Miskovsky, who are principal members of Scitech Associates.

“The solar power conversion device under development by this collaboration of two universities and an industry subcontractor has the potential to revolutionize green solar power technology by increasing efficiencies, reducing costs, and providing new economic opportunities,” Zimmerman says.

“Until the advent of selective atomic layer deposition (ALD), it has not been possible to fabricate practical and reproducible rectenna arrays that can harness solar energy from the infrared through the visible,” says Zimmerman. “ALD is a vitally important processing step, making the creation of these devices possible.

Ultimately, the fabrication, characterization, and modeling of the proposed rectenna arrays will lead to increased understanding of the physical processes underlying these devices, with the promise of greatly increasing the efficiency of solar power conversion technology.”

The atomic layer deposition process is favored by science and industry because it is simple, easily reproducible, and scalable for mass production. Willis says the chemical process is already used by companies such as Intel for microelectronics, and is particularly applicable for precise, homogenous coatings for nanostructures, nanowires, nanotubes, and for use in the next generation of high-performing semi-conductors and transistors.

Willis says the method being used to fabricate rectennas also can be applied to other areas, including enhancing current photovoltaics (the conversion of photo energy to electrical energy), thermoelectrics, infrared sensing and imaging, and chemical sensors.

A 2011 seed grant from UConn’s Center for Clean Energy Engineering allowed Willis to fabricate a prototype rectenna and gather preliminary data using ALD that was instrumental in securing the NSF grant, Willis says.

Over the next year, Willis and his collaborators in Pennsylvania plan to build prototype rectennas and begin testing their efficiency. Willis compares the process to tuning in a station on a radio.

“We’ve already made a first version of the device,” says Willis. “Now we’re looking for ways to modify the rectenna so it tunes into frequencies better. I compare it to the days when televisions relied on rabbit ear antennas for reception. Everything was a static blur until you moved the antenna around and saw the ghost of an image. Then you kept moving it around until the image was clearer. That’s what we’re looking for, that ghost of an image. Once we have that, we can work on making it more robust and repeatable.”

Willis says finding that magic point where a rectenna picks up maximum solar energy and rectifies it into electrical power will be the champagne-popping, “ah-ha” moment of the project.

“To capture the visible light frequencies, the rectenna have to get smaller than anything we’ve ever made before, so we’re really pushing the limits of what we can do,” says Willis. “And the tunnel junctions have to operate at the speed of visible light, so we’re pushing down to these really high speeds to the point where the question becomes ‘Can these devices really function at this level?’ Theoretically we know it is possible, but we won’t know for sure until we make and test this device.”