S. Korean scientists develop high efficiency thin-film solar cell

By Lee Joon-seung
SEOUL, June 29 (Yonhap) -- South Korean scientists on Monday said they have
developed a process to sharply increase efficiency of thin-film panchromatic
solar cells, an achievement that could lead to expansion of the use of clean and
reusable power.
The state-run Korea Institute of Science and Technology (KIST) team led by Park
Nam-gyu said they have been able to stack three different color layers on a
nanogranular titanium dioxide (TiO2) film.
This permits the newly developed dye sensitized solar cell (DSSC) panchromatic
film to absorb and convert all visible rays found in nature into power,
translating into more electricity.
Transparent, thin film solar cells are viewed as a next generation power source
since they are cheap to make, can be attached to any surface such as windows and
electronic devices, and are very light compared to conventional silicon-based
cells.
"By using the so-called chromatography principle, the team was able to
selectively coat yellow, red and green dyes onto the film," Nam said.
The solar cell researcher pointed out that in the past, such films could only be
made with one dye color which effectively limited efficiency to a maximum 11
percent. The 11 percent limit was attained by Nam's team last year.
Most commercial silicon-based solar cells used to make power have efficiency
rates of 20-24 percent, with numbers rising to 40 percent for satellites,
although these are very expensive to mass produce.
The new DSSC panchromatic films are only 20 nanometers thick and can
theoretically create 30 milliampere of electric current from a 1
square-centimeter surface. A nanometer is one-billionth of a meter.
This translates into an energy efficiency of around 15-16 percent.
The discovery, supported by the Ministry of Education, Science and Technology,
meanwhile, has been published in the latest issue of the Britain-based Nature
Materials journal, with foreign experts concurring that KIST researchers have
made a significant breakthrough in the future development of DSSC panchromatic
films.
yonngong@yna.co.kr
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