A problem with the current generation of silicon solar cells is their relatively low efficiency at converting solar energy into electricity, said Vikram Dalal, an Iowa State University Anson Marston Distinguished Professor in Engineering, the Thomas M. Whitney Professor in Electrical and Computer Engineering and the director of Iowa State’s Microelectronics Research Center.
The best silicon solar cells in the laboratory are about 26% efficient while commercial cells are about 15%. That means bigger systems are necessary to produce a given amount of electricity, and bigger systems mean higher costs.
That has researchers looking for new ways to raise efficiency and decrease costs. One idea that could boost efficiency by as much as 50% is a tandem structure that stacks two kinds of cells on top of each other, each using different, complementary parts of the solar spectrum to produce power.