Solar cells with a more than 50% conversion efficiency may be a reality in the near future, thanks to new research from the US Naval Research Laboratory’s Electronics Technology and Science Division.
The solution to the old efficiency barrier is a newly-designed, triple-junction solar cell that has the potential to greatly exceed 50% conversion efficiency.
“This research has produced a novel, realistically achievable, lattice-matched, multi-junction solar cell design with the potential to break the 50 percent power conversion efficiency mark under concentrated illumination,” said Robert Walters, Ph.D., Naval Research Laboratory research physicist. “At present, the world record triple-junction solar cell efficiency is 44 percent under concentration and it is generally accepted that a major technology breakthrough will be required for the efficiency of these cells to increase much further.”
A ‘multi-junction solar cell’, is essentially, a solar cell where each specialized ‘junction’ is designed to very efficiently absorb and use different wavelength bands in the solar spectrum. Theoretically, it’s possible to create an ‘infinite-junction’ solar cell that could reach conversion efficiencies as high as 87 percent. But to do that, it’s necessary to create a semiconductor material system that is able to “attain a wide range of bandgaps and be grown with high crystalline quality.”
The new breakthrough that the researchers have made, is the identification of “InAlAsSb” quaternary alloys, “a high band gap material layer that can be grown lattice-matched” to the already useful “InP.”
With the material, the researchers were able to create a new solar cell design that they think will lead to power conversion efficiencies over 50%.
While this sounds like a great breakthrough, there is still a lot to be done before this leads to actual improved efficiency solar cells.