As reported in Compund Semiconductor: 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.
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.
"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.
Magnus Heurlin, Martin H. Magnusson, David Lindgren, Martin Ek, L. Reine Wallenberg, Knut Deppert & Lars Samuelson
Nature 492, 90–94
Semiconductor nanowires are key building blocks for the next generation of light-emitting diodes1, solar cells2 and batteries3.
To fabricate functional nanowire-based devices on an industrial scale
requires an efficient methodology that enables the mass production of
nanowires with perfect crystallinity, reproducible and controlled
dimensions and material composition, and low cost. So far there have
been no reports of reliable methods that can satisfy all of these
requirements. Here we show how aerotaxy, an aerosol-based growth method4,
can be used to grow nanowires continuously with controlled nanoscale
dimensions, a high degree of crystallinity and at a remarkable growth
rate. In our aerotaxy approach, catalytic size-selected Au aerosol
particles induce nucleation and growth of GaAs nanowires with a growth
rate of about 1 micrometre
per second, which is 20 to 1,000 times higher than previously reported
for traditional, substrate-based growth of nanowires made of group III–V
materials5, 6, 7.
We demonstrate that the method allows sensitive and reproducible
control of the nanowire dimensions and shape—and, thus, controlled
optical and electronic properties—through the variation of growth
temperature, time and Au particle size. Photoluminescence measurements
reveal that even as-grown nanowires have good optical properties and
excellent spectral uniformity. Detailed transmission electron microscopy
investigations show that our aerotaxy-grown nanowires form along one of
the four equivalent 111B
crystallographic directions in the zincblende unit cell, which is also
the preferred growth direction for III–V nanowires seeded by Au
particles on a single-crystal substrate. The reported continuous and
potentially high-throughput method can be expected substantially to
reduce the cost of producing high-quality nanowires and may enable the
low-cost fabrication of nanowire-based devices on an industrial scale.
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