The new multijunction solar cell design has three subcells that each have different band gaps to absorb different parts of the solar spectrum. The scientists focused on improving the current match and the lattice match among the subcells to achieve the highest simulated efficiency for this type of solar cell to date. Credit: Marina S. Leite, et al. ©2013 American Institute of Physics

Multijunction solar cell could exceed 50% efficiency goal

February 20, 2013 by Lisa Zyga

(Phys.org)—Scientists have designed a new multijunction solar cell that, in simulations, can achieve an efficiency of 51.8%. This high performance exceeds the current goal of 50% efficiency in multijunction solar cell research as well as the current world record of 43.5% for a 3-junction solar cell.

The work was performed by a collaboration of researchers from the California Institute of Technology in Pasadena; the National Institute of Standards and Technology in Gaithersburg, Maryland; the University of Maryland in College Park; and Boeing-Spectrolab, Inc., in Sylmar, California. The team published a paper on their work in a recent issue of Applied Physics Letters.

As the researchers explain, multijunction solar cells are one of the most promising devices for efficiently converting sunlight into electricity. In multijunction solar cells, each junction or subcell absorbs and converts sunlight from a specific region of the spectrum. The subcells can be stacked on top of one another so that sunlight first strikes the highest bandgap subcell, which is tuned to light with the shortest wavelengths or highest energies. The longer wavelengths pass through the first subcell and strike the lower bandgap subcells.

This arrangement offers a significant advantage over single-junction solar cells, which have a maximum theoretical efficiency of only 34%. In theory, an “infinite-junction” solar cell has a maximum theoretical efficiency of almost 87%. But to approach this level, multijunction solar cells not only need multiple subcells, but optimal semiconductor materials for the subcells to provide a combination of band gaps that cover as much of the solar spectrum as possible.

Read more: Multijunction solar cell could exceed 50% efficiency goal — phys.org.

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