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Most
efficient photovoltaic cells-world record set by Mitsubishi
Electric
[March
20] Tokyo, Japan--Mitsubishi
Electric had developed a 150-millimeter square multi-crystalline
silicon solar cell boasting a photoelectric conversion efficiency
rate of 18.6 per cent, and set the world record for most efficient
photovoltaic cells.
Photo: LEFT-Newly developed PV cell:Lower
reflection and crystal grains can hardly be seen; RIGHT-Current
PV cell:Higher reflection and crystal grains can clearly be
seen. (enlarge
photo)
The new cell exploits a honeycomb
textured structure to reduce light reflectivity on the surface
of the cell and increase efficiency.
Such honeycomb structures have long been touted
by solar cell experts as a means of improving efficiency,
but Mitsubishi
claims to be the first to have developed a way of applying
the technology to a mass production line through a new fabrication
process combining laser patterning and wet etching.
Mitsubishi
Electric President and CEO Setsuhiro
Shimomura said that the new cells were also more efficient
in shaded conditions, making them better suited for use on
household roofs.
The company claims to have also improved the
cell's power generation efficiency through the use of a new
shallow, lightly doped emitter that increases light gain.
The announcement came as the company also pledged
to invest 7bn yen (£35m) as part of its plan to increase its
annual solar cell and panel production more than threefold
over the next four years to 500MW.
Main Features of the Newly Developed
PV Cell
1) World’s first developed with a low-reflective
honeycomb textured structure, with a view to using the technology
in next-generation high-efficient PV cells To create highly
efficient PV cells, it is necessary to reduce light reflectivity
on the surface. While a honeycomb-textured structure5 is recognized
as suitable for reducing surface reflectivity, it was a challenge
to develop a way to apply this technology in production lines.
Mitsubishi Electric has developed the world’s first1 method6
for fabricating a honeycomb structure on the surface of a
150-millimeter square multi-crystalline silicon by combining
laser patterning and wet etching.
2) Reduced emitter loss by optimizing the n-layer
in p-n junction Power generation also relies on the amount
of light that approaches the p-n junction7. A shallow, lightly
doped emitter (n-layer) increases light gain and improves
efficiency of power generation.
3) 25-percent reduced shade loss from front grid
electrodes and larger effective electrical output surface
area With modified screens and front metal electrodes, Mitsubishi
Electric reduced shading loss of front grid electrodes by
25 percent compared to previous cells.
Future Developments
Mitsubishi Electric will begin introducing this
multi-crystal silicon cell technology into its mass-produced
photovoltaic modules by fiscal 2011 (April 1, 2010-March 31,
2011).
Mitsubishi Electric also aims to increase output
of solar power generation systems by combining this technology
with its PV inverters, which have the industry’s highest8
energy conversion efficiency rate.
The company will promote these PV systems worldwide,
thus contributing to environmental preservation and achieving
a sustainable society. The company plans to make a presentation
of this achievement at “The 23rd European Photovoltaic Conference”
in September 2008 in Spain.
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