This is some more tweaking of
solar cell tech and should lead to further improvements in economics and
general efficiencies. Solar tech
continues to be stalled in much the same place it has held for a decade, in
spite of plenty of brave announcements by venture capitalists.
It needs either a breakthrough in
spectrum absorption and conversion or a significant drop in manufacturing
cost. At this late date I do not hold
out much optimism when it will all be scrap when they start shipping eight
times unity reactor from Rossi Focardi.
In the meantime we continue to
watch these efforts.
'Swiss cheese' design enables thin film silicon solar cells
with potential for higher efficiencies
by Staff Writers
This SEM micrograph shows the nanostructured ZnO layer, Swiss cheese
design for Micromorph solar cells.
Credit: Milan Vanecek, Institute
of Physics , Prague
A bold new design for thin film solar cells that requires significantly less silicon - and may boost their efficiency - is the result of an industry/academia collaboration between Oerlikon Solar in Switzerland and the Institute of Physics'photovoltaic group at the
One long-term option for low-cost, high-yield industrial production
of solarpanels from
abundant raw materials can be found in amorphous silicon solar cells and
microcrystalline silicon tandem cells (a.k.a. Micromorph)-providing an energy
payback within a year.
A drawback to these cells, however, is that the stable panel efficiency
is less than the efficiency of presently dominate crystalline wafer-based
silicon, explains Milan Vanecek, who heads the
photovoltaic group at the Institute of
Physics in Prague
"To make amorphous and microcrystalline silicon cells more stable
they're required to be very thin because of tight spacing between electrical
contacts, and the resulting optical absorption isn't sufficient," he
notes.
"They're basically planar devices. Amorphous silicon has a
thickness of 200 to 300 nanometers, while microcrystalline silicon is thicker
than 1 micrometer."
The team's new design focuses on optically thick cells that are
strongly absorbing, while the distance between the electrodes remains very
tight. They describe their design in the American Institute of Physics' journal
Applied Physics Letters.
"Our new 3D design of solar cells relies on the mature, robust
absorber deposition technology of plasma-enhanced chemical vapor deposition, which
is a technology already used for amorphous silicon-based electronics produced
for liquid crystal displays. We just added a new nanostructured substrate
for the deposition of the solar cell," Vanecek says.
This nanostructured substrate consists of an array of zinc oxide (ZnO)
nanocolumns or, alternatively, from a "Swiss cheese" honeycomb array
of micro-holes or nano-holes etched into the transparent conductive oxide layer
(ZnO) (See Figure).
"This latter approach proved successful for solar cell deposition,"
Vanecek elaborates.
"The potential of these efficiencies is estimated within the range
of present multicrystalline wafer solar cells, which dominate solar cell
industrial production. And the significantly lower cost of Micromorph panels,
with the same panel efficiency as multicrystalline silicon panels (12 to 16
percent), could boost its industrial-scale production."
The next step is a further optimization to continue improving
efficiency.
The article, "Nanostructured 3-dimensional thin film silicon solar
cells with very high efficiency potential," by Milan
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