Metamorphic multijunction solar cell

The National Renewable Energy Laboratory won one of R&D Magazine's R&D 100 Awards for its Metamorphic Multijunction Solar Cell, an ultra-light and flexible cell that converts solar energy with record efficiency.


The ultra-light, highly efficient solar cell was developed at NREL and is being commercialized by Emcore Corp.of Albuquerque, N.M., in partnership with the Air Force Research Laboratories Space Vehicles Directorate at
Kirtland Air Force Base in Albuquerque.

It represents a new class of solar cells with clear advantages in performance, engineering design, operation and cost. For decades, conventional cells have featured wafers of semiconducting materials with similar crystalline structure. Their performance and cost effectiveness is constrained by growing the cells in an upright configuration. Meanwhile, the cells are rigid, heavy and thick with a bottom layer made of germanium.
In the new method, the cell is grown upside down. These layers use high-energy materials with extremely high quality crystals, especially in the upper layers of the cell where most of the power is produced. Not all of the layers follow the lattice pattern of even atomic spacing. Instead, the cell includes a full range of atomic spacing, which allows for greater absorption and use of sunlight. The thick, rigid germanium layer is removed, reducing the cell's cost and 94% of its weight. By turning the conventional approach to cells on its head, the result is an ultra-light and flexible cell that also converts solar energy with record efficiency (40.8% under 326 suns concentration).