Sol Voltaics, based in Lund, Sweden, has announced that it has doubled the previously reported world-record for photovoltaic (PV) conversion efficiency using a GaAs nanowire array (NWA).
As independently verified by Fraunhofer-ISE, Sol Voltaics has demonstrated a 1-sun conversion efficiency of 15.3 percent in a GaAs NWA solar cell, representing a significant milestone towards providing the solar industry with an efficiency boosting tandem film.
This is the highest efficiency reported to date in a III-V NWA solar cell, and twice the prior record for GaAs NWA technology. Control of the high density of surface states of native GaAs is essential for PV applications, and these results, says Sol Voltaics, prove that it has has resolved this challenge in the growth of solar cell nanowires.
"The efficiency of our GaAs nanowires is a critical component of our low cost film. The use of III-V materials in the PV industry has always been a goal but the costs have been prohibitive. Using Sol Voltaic's Aerotaxy nanowire production methodology allows our III-V film to be produced at competitive cost at efficiencies that are industry changing," said Erik Smith, CEO of Sol Voltaics. "We look forward to working with industrial partners on the integration of our technology on to silicon cells so they may make the leap to 27 percent efficiency and beyond."
GaAs has been used in performance-category solar modules for years because of its high conversion efficiencies. The challenge has always been its high cost relative to other solar materials.
The low cost Aerotaxy process invented by Sol Voltaics' founder and Lund University professor Lars Samuelson, reduces the amount of GaAs and other expensive materials required to generate electricity. Nanowires are created by suspending active materials in gases intermingled in precisely controlled environment. The suspended materials bond to form larger, uniform structures: nanowires are literally grown in space.
Aerotaxy generates nanowires within milliseconds, according to the company, and can produce them on a continuous basis at comparatively low temperatures.
The finished nanowire film can be integrated into solar panels or stored indefinitely. A 2012 paper published in Nature details how Samuelson and his team manufactured GaAs nanowires with Aerotaxy.