By Melissa Carney, Penn State
ALTOONA – Penn State Altoona is the lead institution in a collaborative research endeavor between Penn State; the University of Connecticut, Storrs; and Scitech Associates Holdings Inc., of State College, to study the physics of a device that could revolutionize green solar power technology.
On Nov. 1, the National Science Foundation awarded the two institutions a total of $650,000 in a three-year grant to perform “Electro-optical studies of nanoscale, geometrically-asymmetric tunnel junctions for collection and rectification of light from infrared through visible.”
At present, solar power technologies only use the infrared (IR) portion of the solar spectrum. The device to be developed by the Penn State Altoona and University of Connecticut collaborative team, based on patents held by Scitech Associates and University of Connecticut Professor of Chemical Engineering Brian Willis, would harness the visible part of the solar spectrum as well, a feat that has never been accomplished, allowing solar power technology to make a great leap forward.
The Altoona team consists of physics professors Gary Weisel, Brock Weiss and Darin Zimmerman. The collaboration also employs Penn State Emeritus Physics Professors Paul Cutler and Nicholas Miskovsky, who are the senior personnel of Scitech, and Willis.
The objective of the research project is to develop a “rectenna” device consisting of a nanosized antenna and an ultra-fast tunnel diode that simultaneously collects and rectifies solar radiation from infrared to visible. The manufacturing approach uses a chemical process called selective atomic layer deposition, a process originally developed by Willis, which is capable of fabricating arrays of thousands of nanoscopic, geometrically asymmetric tunnel junctions in a reproducible manner. An integrated program of device fabrication, characterization and numerical modeling will provide insight into device design aimed at creating larger arrays, to harness more power, and smaller junction gaps, to reach the visible spectrum.
Until the advent of selective atomic layer deposition, it has not been possible to fabricate practical and reproducible rectenna arrays that can harness solar energy from the infrared through the visible. The issue has been one of size – and size matters greatly in this case. To convert visible light into electricity, one needs to create large arrays of rectennas whose metallic electrodes are only a few nanometers apart, a distance that is about 30,000 times smaller than the diameter of a human hair. 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 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. The realization of high frequency rectification is also important for developing new technologies for IR sensing, imaging — including medical and chemical sensors — and for the transmission and reception of information. A large, diverse group of graduate, undergraduate and high school students will acquire extensive research experience and training. The four faculty members and two industry subcontractors have proven experience working with underrepresented groups including, women, minorities, and international colleagues and students.