Solar Cell Achieves 41.2% Efficiency at 744 Suns

A team of researchers from George Washington University, US Naval Research Laboratory, the University of Illinois Urbana-Champaign, Sotera Defense Solutions of Annapolis Junction, MD, USA, Semprius Inc, of Durham, NC, USA have worked together on developing a new high-efficiency solar cell prototype.

Researchers create 5-junction solar concentrator cell

Researchers create 5-junction solar concentrator cell

George Washington University researcher Matthew Lumb helped design and construct the prototype for the new solar cell.
The new prototype integrates multiple cells into a single device that Lumb says can capture almost all of the energy in the solar spectrum. The design has the potential to become the world’s most efficient, and like the most efficient solar cells, it uses lenses to focus sunlight on small area solar cells to produce electricity.

Cell Design Uses GaSb

The solar cell employs gallium antimonide (GaSb) substrates, which are usually found in photodetectors and infrared lasers. The design stacks a dual-junction GaSb solar cell with layers made up of a triple-junction GaAs solar cell. The fabrication technique uses a method called transfer printing for assembly of tiny, three-dimensional devices with a high degree of precision.

“Around 99 percent of the power contained in direct sunlight reaching the surface of Earth falls between wavelengths of 250 nanometers and 2,500 nanometers, but conventional materials for high-efficiency multi-junction solar cells cannot capture this entire spectral range,” Dr. Lumb said. “Our new device is able to unlock the energy stored in the long-wavelength photons, which are lost in conventional solar cells, and therefore provides a pathway to realizing the ultimate multi-junction solar cell.”

At a solar concentration of 744 suns, the new solar cell achieved 41.2% efficiency. If you take into account the measured transmission of the optics, the cell by itself has an implied efficiency of 44.5%.

While new design is very expensive to produce, the researchers wanted to demonstrate what was possible with the technology. Eventually, they hope to make it less expensive to produce.
Details of the findings were published in the journal Advanced Energy Materials.

Reference

M.P., Lumb et al, ‘GaSb-based Solar Cells for Full Solar Spectrum Energy Harvesting’, Advanced Energy Materials (2017); doi: 10.1002/aenm.201700345