Right now up in space, satellites are using a solar technology pioneered and developed right here in the Research Triangle more than 30 years ago.

Satellites are powered by solar cells. But real estate on a satellite is a valuable commodity. It’s not practical to make them bigger just to put more solar cells on them.

Salah Bedair, a professor of electrical engineering at N.C. State University, came up with a way to stack them together and connect them them. His lab made the first stacked solar cell in 1979.

“We were the first to demonstrate that we can stack several solar cells together and improve the efficiency,” Bedair said.

In the 1970s, Bedair joined a research group at N.C. State researching ways to improve solar technology. The group submitted a proposal to the U.S. Department of Energy and the Air Force in 1977 seeking funding for the work. Sunlight is comprised of many colors. It’s not feasible to develop a single cell to absorb all light across the spectrum. Instead, individual cells absorb light from one particular color, Bedair explained. One cell absorbs blue light. Another absorbs green, and so on.

The idea was that stacking individual cells results in a solar cell that absorbs sunlight from across the light spectrum. The cells would be more efficient and they wouldn’t take up too much space. Bedair said that his role in the group was to do the experimental demonstration and prove the concept. He proved it. With the federal funding supporting the work over the course of seven to eight years, the group went on to improved improve the solar cell structures.

Over time, solar technologies have become more efficient. Bedair is still working on improving the stacked solar cell technology he helped develop. His most recent research involves improving the connecting junctions that link the solar cells in the stack. By reducing the voltage lost as heat, the new technology could make stacked solar cells even more efficient.

Background

Dr. Bedair’s biography as cited at NCSU:

“Dr. Bedair currently investigates semi-conductor materials and devices including novel growth techniques such as atomic layer epitaxy, laser-assisted diposition, molecular beam epitexy and chemical vapor diposition. He also studies optical, electrical and structural properties of semiconductors, epitaxial insulators and quantum well structures. Optical and microwave devices such as detectors, wave guides, solar cells, light emitting diodes, semiconductor light bulbs and modulation doped field effect transistors are currently considered in Dr. Bedair’s lab.”

Education

1960: BS in Electrical Engineering, Alexandria University
1965: MS in Nuclear Engineering, Univ. of Calif. Berkeley
1969″ PhD in Engineering Science, Univ. of Calif .Berkeley