Mitsubishi Electric Develops Practical-Use Multi-Crystalline Silicon Solar Cell with...

Mitsubishi Electric Develops Practical-Use Multi-Crystalline Silicon Solar Cell with World's Highest Conversion Efficiency Rate of 18.6%

TOKYO--(Business Wire)--
Mitsubishi Electric Corporation (President and CEO: Setsuhiro
Shimomura) announced today its achievement of a world record(1)
photoelectric conversion efficiency rate(2) of 18.6 percent(3) in a
150-millimeter square practical use multi-crystalline silicon solar
cell, an improvement of 0.6 percent over the company's previous
record(4).

Background and Purpose of Development

Production volumes of solar, or photovoltaic (PV), systems have
been increasing as they have garnered attention as a good source of
renewable energy, against the background of increased global
environmental awareness. While silicon is an essential component in
the wafers used to make solar cells, the supply of silicon has not
been able to keep up with demand. This is driving research into the
development of thinner wafers that not only use less silicon, but also
have improved efficiency and increased electrical output.

In a 150-millimeter square practical-use multi-crystalline silicon
solar cell, Mitsubishi Electric has achieved the world's highest
conversion efficiency rate of 18.6 percent by adding a low
reflectivity surface texture on the multi-crystalline silicon wafer,
by optimizing the p-n junction to increase electric current generation
and by developing a process to print electrodes on the surface of the
silicon (metallization) to reduce shade loss of front grid electrodes.
This technology contributes to higher efficiency in small
installations such as narrow roofs.

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
structure(5) 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 first(1) method(6) 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 junction(7). 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 highest(8) 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.

Patents

18 domestic and 7 international patents pending

Notes

1: As of March 19, 2008, based on Mitsubishi Electric's research.

2: Efficiency that solar light energy is converted to direct
current electrical energy.

3: Results from evaluation by the National Institute of Advanced
Industrial Science and Technology (AIST), a public standards
agency in Japan.

4: Photoelectric conversion efficiency rate of 18.0% for a
prototype, announced on May 31, 2007.

5: A hexagon structure with bowl-shaped concaves the size of
approximately 10 micrometers in diameter.

6: Partly using the results of the NEDO commissioned project, R&D
of Innovative Next Generation Photovoltaic System Technology.

7: Junction between positively charged n-type semiconductor and
negatively charged p-type semiconductor. The electric field
between the two types of semiconductors generates electricity when
light approaches.

8: PV-PN40G: 97.5%, as of March 19, 2008. Based on JIS C8961
regulated rated load efficiency.

About Mitsubishi Electric

With over 80 years of experience in providing reliable,
high-quality products to both corporate clients and general consumers
all over the world, Mitsubishi Electric Corporation (TOKYO:6503) is a
recognized world leader in the manufacture, marketing and sales of
electrical and electronic equipment used in information processing and
communications, space development and satellite communications,
consumer electronics, industrial technology, energy, transportation
and building equipment. The company recorded consolidated group sales
of 3,855.7 billion yen (US$ 32.7billion(9)) in the fiscal year ended
March 31, 2007. For more information visit
global.mitsubishielectric.com

(9) At an exchange rate of 118 yen to the US dollar, the rate
given by the Tokyo Foreign Exchange Market on March 31, 2007.

Mitsubishi Electric Corporation
Product Inquiries:
Ikumasa Kojima, +81-573-66-8019
Marketing Department, Nakatsugawa Works
Kojima.Ikumasa@ah.MitsubishiElectric.co.jp
here
Media Contact:
Yurika Fujimoto, +81-3-3218-3380
Public Relations Division
prd.gnews@nk.MitsubishiElectric.co.jp
here

Copyright Business Wire 2008