news digest ♦ Solar
because, rather than creating large, expensive solar cells, you can use much smaller cells that produce just as much electricity by absorbing intensified solar energy from concentrating lenses. And concentrating lenses are relatively inexpensive,” Bedair continues.
This work is described in detail in the paper, “Effect of GaAs interfacial layer on the performance of high bandgap tunnel junctions for multijunction solar cells,” by Joshua P. Samberg et al published online on September 5th in Applied Physics Letters. DOI: 10.1063/1.4819917
Solar field on the roof of the Keystone Science Centre (Photo: NC State University)
Stacked solar cells consist of several solar cells that are stacked on top of one another. Stacked cells are currently the most efficient cells on the market, converting up to 45 percent of the solar energy they absorb into electricity.
But to be effective, solar cell designers need to ensure the connecting junctions between these stacked cells do not absorb any of the solar energy and do not siphon off the voltage the cells produce - effectively wasting that energy as heat.
“We have discovered that by inserting a very thin film of gallium arsenide into the connecting junction of stacked cells we can virtually eliminate voltage loss without blocking any of the solar energy,” says Salah Bedair, a professor of electrical engineering at NC State and senior author of a paper describing the work.
This work is important because photovoltaic energy companies are interested in using lenses to concentrate solar energy, from one sun (no lens) to 4,000 suns or more. But if the solar energy is significantly intensified - to 700 suns or more - the connecting junctions used in existing stacked cells begin losing voltage. And the more intense the solar energy, the more voltage those junctions lose - thereby reducing the conversion efficiency.
“Now we have created a connecting junction that loses almost no voltage, even when the stacked solar cell is exposed to 70,000 suns of solar energy,” Bedair says. “And that is more than sufficient for practical purposes, since concentrating lenses are unlikely to create more than 4,000 or 5,000 suns worth of energy. This discovery means that solar cell manufacturers can now create stacked cells that can handle these high-intensity solar energies without losing voltage at the connecting junctions, thus potentially improving conversion efficiency.”
“This should reduce overall costs for the energy industry 108
www.compoundsemiconductor.net October 2013
St. Petersburg researchers to be awarded for III-V solar cell developments
The two professors from the Russian university will be awarded for their semiconductor compounds with superior efficiencies and increased lifetime
Zhores I. Alferov, Nobel Laureate, professor and president of the St. Petersburg Academic University of the Russian Academy of Sciences, and Viacheslav M. Andreev, professor and head of the laboratory of the A.F. Ioffe Physico-Technical Institute in St. Petersburg, will receive the 2013 Karl Böer Solar Energy Medal of Merit.
The medal and a cash award of $60,000 is funded by the Karl W Böer Solar Energy Medal of Merit Trust. It is given every two years to an individual who has made significant pioneering contributions to the promotion of solar energy as an alternate source of energy through research, development or economic enterprise or to an individual who has made extraordinarily valuable and enduring contributions to the field of solar energy in other ways.
The award is given in honour of Karl Wolfgang Böer, a long-time University of Delaware faculty member, founder of UD’s Institute of Energy Conversion and a distinguished scientist in the field of solar cells.
George C. Hadjipanayis, executive director of the Karl W. Böer Solar Energy Medal of Merit Trust and the Richard B. Murray Professor of Physics and Astronomy, explains that the award is given to Alferov and Andreev “for their pioneering work in the design of new solar cells and concentrator modules based on III-V semiconductor compounds with superior efficiencies and increased lifetime.”
The recipient of the award is chosen by a panel of commissioners composed of scientists and presidents of several solar energy-related professional societies, a representative from the U.S. Department of Energy, a
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