A team comprised of the Fraunhofer Institute for Solar Energy Systems, Soitec, CEA-Leti and the Helmholtz Center, Berlin has just unveiled the world’s most efficient solar cell! Boasting an efficiency of 44.7%, the cell breaks the record set by Sharp just three months ago by 0.3%. The four-junction photovoltaic cell is not only dramatically more efficient than the theoretical 33.7% efficiency limit of conventional silicon-based solar PV, but it puts the team well on the road to reaching their goal of 50% efficiency by 2015.
Simply put, solar cell efficiency refers to how much energy from light—across the entire spectrum from ultraviolet to infrared—is converted into electricity. Greater efficiency in turn yields more cost-effective solar installations; using a smaller surface area, more electricity can be derived over the course of a given system’s lifespan. This efficiency is key to NREL’s goal of making large-scale solar energy systems cost-competitive with other energy sources by 2020, and key to making solar in general more affordable around the globe.
Soitec have been clear in their ambitions to create a solar cell with 50% efficiency, and working with their partners they have reached 44.7% remarkably quickly. With work beginning just a little over three years ago, the team unveiled a cell with 43.6% efficiency in May before attaining this most recent record.
Their four-junction “smart cell” design is the first of its kind used on earth—literally. According to Soitec, the “so-called III-V multi-junction solar cells” were originally developed for use in space. But in Soitec’s application “several cells made out of different III-V semiconductor materials are stacked on top of each other. The single subcells absorb different wavelength ranges of the solar spectrum.”
As for the rapid development of the cells since May of this year “a new procedure called wafer bonding plays a central role,” explains Frank Dimroth of Fraunhofer ISE. “With this technology, we are able to connect two semiconductor crystals, which otherwise cannot be grown on top of each other with high crystal quality. In this way we can produce the optimal semiconductor combination to create the highest efficiency solar cells.” The cells are then used in concentrator photovoltaics (CPVs), “a technology which achieves more than twice the efficiency of conventional PV power plants in sun-rich locations,” according to Soitec.
With this key record under their belt, the collaboration will continue their work to craft a cell with 50% efficiency by 2015.
Lead image © Fraunhofer ISE