New Method Improves Solar Energy Efficiency, Cuts Costs

Researchers have developed a method for improving the connections between stacked solar cells that allows for the greater overall efficiency of the solar energy devices.

Developed by scientists from North Carolina State University, the new technique allows these cells to operate at solar concentrations of 70,000 suns worth of energy while minimizing the amount of voltage lost as "wasted energy," or heat.

Stacked solar cells represent the most efficient cells on the market, converting up to 45 percent of the solar energy they absorb into electricity. However, in order to be effective, designers have to ensure that the connections between the cells do not absorb the solar energy, siphoning off the voltage produced by the cells.

"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," Salah Bedair, a professor of electrical engineering at NC State and senior author of a paper describing the work, explained in a statement.

The reason this is so important, the researchers explain, is because photovoltaic energy companies are looking to use lenses to concentrate solar energy to 4,000 suns or more; however, current connecting junctions start losing voltage at 700 suns. Furthermore, the more intense the solar energy, the more voltage the junctions lose.

"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 said.

As a result, Bedari explained, overall industry costs will likely see a reduction "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."